GEOG 414 Mid Term

Hans Suess and Carbon-14 in CO2

- Austrian physicist, physical chemist, and geochemist -had a major role in climate science using radiocarbon (carbon -14, or 14 C). In the 1950s, a group at the University of Chicago headed by Willard Libby was using carbon -14 to date ancient materials. These materials were mainly archeological and anthropological, such as pottery and mummies. -He was responsible for developing radiocarbon dating techniques and contributed to knowledge of the elements and the evolution of the Solar System . Suess devised a plan to measure carbon isotopes in tree rings . He began to collect old trees with the assistance of staff from the National Park Service and the U.S . Department of Agriculture . Suess' main concern was studying how carbon moved through the environment . - Suess was the fi rst one to notice that tree rings had less carbon -14 than would have been present in natural carbon tree rings . The carbon in tree rings had to come from the burning of fossil fuels ; otherwise there would be more carbon -14 present. -Suess ' measurements of the distribution of carbon ions in the oceans resulted in the prediction that it could take 1,000 years for them to circulate both horizontally and vertically. - Hans Suess ' main contribution to climate change science was to determine that oceanic circulation took too long to distribute carbon ions and as a result the oceans would not absorb the amounts of carbon dioxide that mankind was putting into the atmosphere .

Gilbert Plass and Doubling of C02

- Canadian physicist who in the 1950s made predictions about the increase in atmospheric carbon dioxide levels in the twentieth century and its effect on the average Earth temperature that closely matches temperature measurements reported half a century later. - In 1953 as a result of his work on the effects of carbon dioxide from industrial sources as a greenhouse gas , he stated "At its present rate of increase, the carbon dioxide in the atmosphere will raise the Earth 's average temperature 1.5 °F every 100 years for centuries to come if man's industrial growth continues, the Earth's climate will continue to grow warmer." -Plass made use of early electronic computers and predicted that a doubling of carbon dioxide would cause a warming of Earth 's temperature by 3.6°C. He also predicted that carbon dioxide levels in 2000 would be 30% higher than in 1900 and that the planet would be about 1°C warmer in 2000 than in 1900. Intergovernmental Panel on Climate Change (IPCC ) 2007 Fourth Assessment Report estimated a climate sensitivity of 2-4.5°C for a doubling of carbon dioxide , a rise of 37% since pre-industrial times (from about 1750 AD) and a 1900-2000 warming of around 0.7°C

Carbon-14

- Carbon-14 originates in the upper atmosphere by bombardment of nitrogen by cosmic rays . Carbon-14 has a half-life of around 50,000 years, so the carbon -14 in fossil fuels has largely disappeared, as most fossil fuels are millions of years old. - There are three isotopes of carbon found in nature , carbon-12 ( 12 C) , carbon-13 ( 13 C), and carbon-14 ( 14 C). 14 C is radioactive carbon or radiocarbon . 12 C and 13 C are stable isotopes of carbon and radiocarbon is not measureable after around 50,000 years, so ancient deposits (more than 50,000 years old) contain no measureable amounts of 14 C .

Stefan Boltzmann Equation for a blackbody radiator

- E= (SB constant)*T^4 where -E = radiation emitted in Watts m^-2 -Stefan Boltzmann constant = 5.67 x 10^-8 Watts meter^-2 K^-4 -T = temperature (K)

Seasonal changes in albedo

- In the south polar region, the ice sheet over Antarctica remains intact through the year, but an extensive ring of sea ice surrounding Antarctica expands and contracts every year across an area of 16 million square kilometers. In contrast, the Arctic Ocean has a multiyear cover of sea ice that fluctuates much less in extent through the year, and the main seasonal albedo change in the northern hemisphere comes from the winter expansion and summer retreat of snow cover on Asia, Europe, and North America. Both of these changes in albedo play important roles in long-term climate change

Pacific/North American Pattern

- The Pacific/North American (PNA) pattern is the leading recurring mode of internal atmospheric variability over the North Pacific and the North American continent, especially during the cold season. It describes a quadripole pattern of mid-tropospheric height anomalies, with anomalies of similar sign located over the subtropical northeastern Pacific and northwestern North America and of the opposite sign centered over the Gulf of Alaska and the southeastern United States. The PNA pattern is associated with strong fluctuations in the strength and location of the East Asian jet stream. -The positive phase of the PNA pattern is associated with above average temperatures over the western and northwestern United States, and below average temperatures across the south-central and southeastern United States, including an enhanced occurrence of extreme cold temperatures -related to ENSO events and NAO variability

Electromagnetic radiation/waves

- The Sun , stars, Moon , and other planets radiate light which travels to Earth . This light is electromagnetic radiation which travels through space as either waves or photons . Electromagnetic waves are produced by the motion of electrically charged particles . These waves are called electromagnetic radiation because they radiate from electrically charged particles . They travel through outer space as well as through air and other substances. - Electromagnetic radiation , besides acting like waves , acts like a stream of particles that have no mass. The photons with the highest energy correspond to the shortest wavelengths . Electromagnetic radiation travels at the speed of light - Visible-light waves range in size from 0.4 to 0.7 m m (4,000-7,000 Å ), whereas an atom is only a few angstroms in size.

Roger Revelle and Ocean Chemistry

- U.S. scientist who made signi fi cant contributions to mankind's understanding of the oceans . He was an oceanographer and a major spokesman for science. He was one of the fi rst scientists to recognize the effects of rising levels of atmospheric carbon dioxide on the Earth 's surface temperature . He was a long-time member of Scripps Institute of Oceanography -Revelle became interested in the solubility of calcium carbonate and his interest in carbon dioxide in the atmosphere remained for the remainder of his life. In 1965, Revelle served as a member of the President's Science Advisory Committee on Environmental Pollution . The committee published the fi rst authoritative U.S. governmental report in which carbon dioxide was of fi cially recognized as a potential global problem.

Joseph Fourier and the Greenhouse Effect

- a French mathematician and physicist who had studied for the priesthood but never took his vows. Beginning with his work in the 1820s, scientists had understood that gases in the atmosphere might trap heat received from the Sun . Fourier realized that energy in the form of visible light from the Sun easily penetrates the atmosphere to reach the surface and heat it, but heat cannot so easily escape back into space . The air absorbs invisible heat rays (infrared radiation ) rising from the surface . The warmed air radiates some of the energy back down to the surface , helping it stay warm. This is the effect that would later be called the "greenhouse effect ." -laid the ground work for the blackbody radiation theory that showed that a bare, airless Earth at its distance from the Sun should be far colder than it actually is (about 30 degrees C colder)

Knut Angstrom's experiment

- asked his assistant to measure the passage of infrared radiation through a tube fi lled with carbon dioxide . The assistant reported that the amount of radiation hardly changed when he reduced the gas by a third. This meant that it took only a trace of the carbon dioxide gas to absorb the radiation. Adding more carbon dioxide made little difference and only a trace of it in the tube was blocking infrared radiation from getting through.

Proxy: ice cores

- ice cores can be used to estimate temperatures in times past. Using this method on tropical glaciers, Thompson and colleagues found a warming trend from 1700 to now, a cooler period from about 1400 to 1700, corresponding with the European Little Ice Age, and a slight warming centred at about 1100

Stratosphere

- much more stable layer almost completely separated from the turbulent storms and other processes so common in the troposphere. Only the largest storms penetrate the stratosphere, and only its lowermost layer. Large volcanic eruptions occasionally throw small particles up out of the troposphere and into the stratosphere. Because no rain or snow falls in most of this layer, it may take years for gravity to pull these particles back to Earth's surface. The stratosphere forms 19.9% of Earth's atmosphere; the troposphere and stratosphere together account for 99.9% of its mass. -The stratosphere is also important to Earth's climate because it contains small amounts of oxygen (O2) and ozone (O3), which block ultraviolet radiation arriving from the Sun. This shielding effect accounts for a small fraction of the 30% reduction in incoming heat energy from the Sun. It also greatly reduces the exposure of life-forms on Earth to the harmful effects of ultraviolet radiation, which can cause skin cancers and genetic mutations

Stable isotopes

-16O vs 18O, 12C vs 13C -most oxygen is 160 -plants preferentially take in 12C over 13C -there is 2% more 12C in fossil fuels bc fossil fuels come from dead plants/organisms -there isn't a lot of 14C left, bc it has decayed over millions of years -why can't we just plant a bunch of trees to counteract atmospheric CO2? (we need water and nutrients and space)

Climate change time line in media and science

-1800s-1940s: scientists figure out that adding CO2 to tatmosphere would cause global warming -1950s-1970s: scientists get concerned that we are adding CO2 to the atmosphere/causing warming -1980s-present: attempts to alert public/govt about climate change

Rain out effect

-18O is heavier and falls out first, gets more and more depleted as you move inland (more negative) -when you have a lot of ice, you have a lot of 16O in poles, because 18O depletes as you move inland and up to poles, and more 18O in oceans

1970s and cooling myth

-1973 Times article talking about global cooling (25 year period where temps were same/declining bc of pervasive idea of cooling) -85% of published papers were on warming vs. 15% on cooling

Layers of Earth's Atmosphere

-4 layers 1. Troposphere extends from the surface to between 8 and 18 kilometers 2. Stratosphere extends up to 50 km 3. Mesosphere 50-80 km 4. Thermosphere above 80 km -only the lowest 2 are critical in climate change

Atmospheric composition

-78% nitrogen, 21% O2, little bit of Argon, (O2 and N do not reradiate heat) -variable gases in the atmosphere: 1) water vapor 2) carbon dioxide 3) ozone

Where does CO2 go?

-8.9 Gt carbon from human activity/year -7.8 Gt fossil fuel emissions -1.1 Gt deforestation (mainly tropics) -3.6 Gt remains in atmosphere

Heat capacity and specific heat

-Absorption and storage of solar heat are strongly affected by the presence of liquid water because of its high heat capacity, a measure of the ability of a material to absorb heat. Heat energy is measured in units of calories (one calorie is the amount of heat required to raise the temperature of 1 gram of water by 1°C). Heat capacity is the product of the density (in g/cm3) of a heat-absorbing material and its specific heat, the number of calories absorbed as the temperature of 1 gram of this material increases by 1°C: heat capacity = density x specific heat -the specific heat of water is 1, higher by far than any of Earth's other surfaces -The ratios of the heat capacities of water:ice:air:land are 60:5:2:1. Much of the heat capacity of air is linked to the water vapor it contains. Likewise, much of the heat capacity of land is due to the small amount of water held in the soil.

T.C. Chamberlain and the Ice Ages

-American geologist who is perhaps best known for his presentation of multiple working hypotheses. -developed planetismal hypothesis - In 1899, Chamberlin proposed that carbon dioxide in the atmosphere decreased during times of enhanced continental erosion, resulting in glaciation episodes during the last "ice age ." Enhanced erosion was due to higher standing mountains (due to mountain -building or orogenies ; or plate tectonics ) and increased chemical weathering . The oceanic record of strontium isotopes, preserved in marine sediment, supports his suggestion that glacial climates during the Phanerozoic are in part linked to increases in the rate of global chemical erosion relative to outgasing from Earth 's interior.

Proxy: Seashells

-Another kind of proxy for temperature lies in the composition of the shells of sea creatures such as corals and free-l oating plankton. From his analysis of sediments on the l oor of the Bermuda Rise in the north Atlantic Ocean - Around 3000 years ago, the data indicate that sea-surface temperatures were at least a degree warmer than at present, and the Mediaeval Warm Period (~1000 years ago) was as warm or warmer than today.

Albedo-temperature feedback

-Assume that climate abruptly cools, for any reason (perhaps a decrease in the output of the Sun). Part of the climate system's natural response to a cooling is an increase in the land area covered by snow and in the ocean area covered by sea ice. The expansion of these light, high-albedo surfaces will cause an increase in the percentage of incoming radiation reflected back out to space, and a decrease in the amount of heat absorbed at the surface. The loss of absorbed heat in these regions will in turn cause the local climate to cool by an additional amount beyond the initial cooling. This is an example of the concept of positive feedback, introduced in Chapter 1. The positive feedback process also works in the opposite direction: an initial warming will reduce the cover of snow and ice, increase the amount of heat absorbed by exposed land or water, and further warm climate. Climate scientists estimate that any initial climate change will be amplified by about 40% by this positive feedback effect. An initial cooling of 1°C would be amplified to a total cooling of 1.4°C by this process. -net effect is to increase Earth's overall sensitivity to climate changes. The greater the area on Earth covered by snow and ice, the more sensitive the planet as a whole becomes to imposed changes in climate. Because most of the regional albedo contrast on Earth is localized at the equatorward limit of snow and sea ice, the albedo-temperature feedback most strongly affects climate at higher latitudes near these limits.

Back radiation and longwave radiation

-Because Earth is continually receiving heat from the Sun but is also maintaining a constant (or very nearly constant) temperature through time, it must be losing an equal amount of heat (240 W/m2) back to space. This heat loss, called back radiation, occurs at wavelengths lying in the infrared part of the electromagnetic spectrum (see Figure 2-1). Because it occurs at longer wavelengths (5-20μm) than the incoming shortwave solar radiation, back radiation is also called longwave radiation. -Any object with a temperature above absolute zero (273°C, or 0K) contains some amount of heat that is constantly being radiated away toward cooler regions. -The amount of heat radiated by an object increases with its temperature. The radiation emitted is proportional to T 4, where T is the absolute temperature of the object in Kelvins. Objects with temperatures of 272°C (1K) emit at least a tiny bit of heat energy and so can technically be considered radiators

Guy Stewart Callendar and Rising Temperatures (Enhanced greenhouse effect/Callendar Effect)

-British engineer who was the fi rst scientist to study climate change in a systematic way. He was the first to connect rising carbon dioxide concentrations in the atmosphere to the increase in Earth 's temperature . He was aware of increasing carbon dioxide in the atmosphere as a result of burning fossil fuels and an increase in atmospheric temperature over the fi rst 40 years of the twentieth century , which he linked empirically. He used the term "enhanced greenhouse effect " to describe what was happening to Earth's climate . The enhanced greenhouse effect is also called the Callendar effect . -revived and reformulated the carbon dioxide theory by arguing that rising global temps and increased fossil fuel burning were closely linked -He argued that the rising carbon dioxide content of the atmosphere and the rising temperature were due to human activities , thus establishing the carbon dioxide theory of climate change in its recognizably modern form. He was the fi rst to establish the link between carbon dioxide and Earth 's temperature through his infrared trace gas expirments

Volcanic CO2 degassing

-CO2 fluxes from Earth, juvenile and metamorphic

Oxdized/reduced form of carbon

-CO2 is oxidized form of carbon -methane is the reduced form of carbon -the oxidation state is the measure of the surplus or defecit of electrons around the carbon -oxygen is a very greedy element for the two electrons that it requires to find its most stable electronic confguration -O2 is credited with stealing 2 electrons from it bond partner

Pre-Industrial CO2 levels vs current

-Carbon dioxide prior to the Industrial Revolution stood at an estimated 270-280 parts per million (ppm). Today (June 2012), it stands at over 396 ppm.

Impacts of clouds in climate system

-Clouds also contribute to the retention of heat within the climate system by trapping outgoing radiation from Earth's surface. This role in warming Earth's climate works exactly opposite to the impact of clouds in reflecting incoming solar radiation and cooling our climate. The relative strength of these two competing roles varies with region and season.

Positive NAO

-During a positive NAO there is a strengthening of the Icelandic low and Azores high. This strengthening results in an increased pressure gradient over the North Atlantic, which cause the westerlies to increase in strength. The increased westerlies allow cold air to drain off the North American continent rather than letting it build up and move south. Above average geopotential heights are observed over the eastern U.S., which correlates to above average temperatures The eastern U.S. often sees a wetter pattern with stronger storms during the winter season in this phase due to increased upper level winds Recent studies at the SCO indicate a decreased potential for wintry weather in NC due to the lack of cold air availability and above average temperatures associated with a positive NAO in this region

Greenhouse effect

-Earth's atmosphere contains greenhouse gases that absorb 95% of the longwave back radiation emitted from the surface, thus making it impossible for most heat to escape into space. The trapped radiation is retained within the climate system and reradiated down to Earth's surface. This extra heat retained by the greenhouse effect makes Earth's surface temperature 31°C warmer than it would otherwise be. -In effect, measurements made by satellites and space stations in outer space cannot detect the radiation emitted directly from the warmer surface of the Earth because of the muffling effect of the blanket of greenhouse gases and clouds. Instead, most of the heat actually radiated back to space is emitted from an average elevation of 5 kilometers, equivalent to the tops of many clouds—still well within the lowest layer of Earth's atmosphere

Electromagnetic radiation

-Earth's climate system is driven primarily by heat energy arriving from the Sun. Energy travels through space in the form of waves called electromagnetic radiation. These waves span many orders of magnitude in size, or wavelength, and this entire range of wave sizes is known as the electromagnetic spectrum

Recognizing El Niño

-El Niño can be seen in measurements of the sea surface temperature, -Normal conditions: the sea surface temperatures and the winds were near normal, with warm water in the Western Pacific Ocean -The winds in the Western Pacific are very weak (see the arrows pointing in the direction the wind is blowing towards), and the winds in the Eastern Pacific are blowing towards the west (towards Indonesia) -El Niño Conditions: warm water spreads from the western Pacific Ocean towards the east (in the direction of South America), the "cold tongue" has weakened, and the winds in the western Pacific, usually weak, are blowing strongly towards the east, pushing the warm water eastward.

General trends in El Niño and La Niña

-El Niño is an exaggeration of the usual seasonal warm cycle. whereas La Niña is an exaggeration of the usual seasonal cool cycle. -unusual for El Niños to occur in the rapid succession that they have

El Niño science

-El Niño is characterized by unusually warm ocean temperatures in the Equatorial Pacific, as opposed to La Niña, which is characterized by unusually cold ocean temperatures in the Equatorial Pacific. El Niño is an oscillation of the ocean-atmosphere system in the tropical Pacific having important consequences for weather around the globe. -Among these consequences are increased rainfall across the southern tier of the US and in Peru, which has caused destructive flooding, and drought in the West Pacific, sometimes associated with devastating brush fires in Australia. Observations of conditions in the tropical Pacific are considered essential for the prediction of short term (a few months to 1 year) climate variations. -The sea surface temperature is about 8ºC (14ºF) warmer off the coast of Asia than in the eastern Pacific, due to an upwelling of cold water from deeper levels in the east Pacific. The cooler water off South America is nutrient-rich, supporting high levels of primary productivity, diverse marine ecosystems, and major fisheries. Clouds and rainfall are found in rising air over the warmest water near Asia, whereas the east Pacific is relatively dry.

El Niño Southern Oscillation

-El Niño-Southern Oscillation (ENSO) is a main source of climate variability, with a two- to seven-year timescale, originating from coupled ocean-atmosphere interactions in the tropical Pacific. Major ENSO events affect weather patterns over many parts of the globe through atmospheric teleconnections. ENSO strongly affects precipitation and temperature in the United States with impacts being most pronounced during the cold season -A cooling trend of the tropical Pacific Ocean that resembles La Niña conditions contributed to drying in southwestern North America from 1979 to 200654 and is found to explain most of the decrease in heavy daily precipitation events in the southern United States from 1979 to 2013 -Eastern Pacific (EP) El Niño events affect winter temperatures primarily over the Great Lakes, Northeast, and Southwest, while Central Pacific (CP) events influence temperatures primarily over the northwestern and southeastern United States.56 The CP El Niño also enhances the drying effect, but weakens the wetting effect, typically produced by traditional EP El Niño events on U.S. winter precipitation

Typical El Niño Winters vs. La Niña Winter

-El Niño: Low pressure system from Alaska, Canada, Washington all across northern US Canadian boundary near Great Lakes -Drier in mid-east -Westerin South-West across to south-east -cooler in south-east -extended Pacific jet stream, amplified storm track -La Niña: Colder from Alaska down to northern US Canadian boundary -Wetter in Washington area -Wetter in Great Lakes area -Drier along south-west coast to South-east coast (high pressure system) -Variable Polar Jet Stream

Fossil Fuels in climate change

-Fossil fuels are coal, natural gas , and petroleum - the main cause, by far, is the massive burning of fossil fuels since the Industrial Revolution and the mass production of the internal combustion engine that most use as a power source . These advances in the use of power have caused a steady and steadily increasing rise in the concentration of atmospheric carbon dioxide and the Earth continues to warm as a result - Fossil fuels are composed of hydrocarbons that have been buried in the Earth for millions of years. They form slowly and are not being replaced, and it is getting harder and more expensive to fi nd them and to economically bring them to market. For instance oil, new deposits of which used to be found by drilling on land , now is found by drilling in ocean waters (as in the Gulf of Mexico ). The fi rst oil well in the U.S. was in the State of Pennsylvania . The most recent new wells have been drilled off-shore and are being drilled in deeper and deeper waters as new deposits or reservoirs of oil continue to be discovered

Deforestation in climate change

-Humans have also been responsible for Earth's warming without realizing it by cutting down trees (deforestation ), the making of charcoal , and growing food, especially rice

Proxy: Varves

-In mountains of the near-Arctic, such as in Finland and Alaska, the spring thaw starts a rush of melt water down the valleys, which increases in the summer. The streams carry mud, silt and sand down the valley, leaving deposits on alluvial l ats where the valley slope is gentler. In places, such a stream may enter a lake, and the coarser sediment, mainly silt, is deposited over the lake l oor while some of the i ne clay remains suspended in the lake water. As autumn returns the stream l ow slackens and less and less sediment is brought into the lake, until by winter only a slow settling of clay is deposited on the lake floor. -Year by year, the layers of sediment accumulate: they are thicker, coarser and paler coloured at the bottom of each annual layer, and thinner, i ner and darker at the top. The layers themselves are quite thin, perhaps only a few millimetres thick; they are known as 'varves' -The thickness of an individual varve depends on that year's l ow of water, which in turn depends on the summer temperature; a warmer summer leads to more rapid melting and so more sediment than the average, and vice versa for a cooler than normal summer. Measurement of varve thickness over a long period can give an indication of the climate change for that period.

The Early Keeling Curve

-In the first part of the 20th century it was suspected that the concentration of atmospheric CO2 might be increasing in the atmosphere due to fossil fuel combustion. However there were relatively few measurements of this gas and the measurements varied widely. -Keeling project investigating the equilibria between carbonate in surface waters, limestone and atmospheric CO2. This involved the construction of a precision gas manometer to measure CO2 extracted from the air as well as acidified samples of water - he began to take air samples throughout the day and night and soon detected an intriguing diurnal pattern. The air contained more CO2 at night than during the day and after correcting for the effects of water vapor, had about the same amount of CO2 every afternoon, 310 ppm. He used stable isotope ratio mass spectrometry measurements of the CO2 he extracted to show that the 13C/12C ratio in CO2 at night was smaller than during the day and a function of plant respiration. - the CO2 concentration at Mauna Loa had risen by 1ppm in April 1958 to a maximum in May when it began to decline reaching a minimum in October. After this the concentration increased again and repeated the same seasonal pattern in 1959. In Dave Keeling's words "We were witnessing for the first time nature's withdrawing CO2 from the air for plant growth during summer and returning it each succeeding winter" -Dave Keeling's analytical skills and dedication had paid off with two dramatic discoveries: firstly, of the natural seasonal "breathing" of the planet and secondly, of the rise in atmospheric CO2 due to the combustion of fossil fuels by industry and to land use changes. Published in the 1960 Tellus Article, "The concentration and isotopic abundances of carbon dioxide in the atmosphere" (pdf), these significant findings marked the beginning of the now world famous "Keeling Curve" which extends for almost 5 decades and represents one of the most important geophysical records ever made.

John Tyndall and Thermal Radiation

-Irish physicist, mathematician, and mountaineer who began studying the radiative properties of various gases. He built the fi rst spectrophotometer which he used to measure the absorptive power of gases such as water vapor , carbon dioxide , ozone , and hydrocarbons . He was the first to show the vast differences between gases to absorb and transmit radiant heat - Tyndall showed that water vapor , carbon dioxide , and ozone were the best absorbers of thermal or heat radiation; they absorb much more strongly than the atmosphere itself -concluded that water vapor is the strongest absorber of radiant heat and that it is the most important gas in controlling the temp of the atmosphere -first scientist known who told his students why the sky is blue (because molecules in the atmosphere preferentially scatter the Sun's blue rays)

2 degree limit

-Limiting warming to no more than two degrees has become the de facto target for global climate policy. But there are serious questions about whether policymakers can keep temperature rise below the limit, and what happens if they don't. -In the 1970s, Yale professor William Nordhaus alluded to the danger of passing a threshold of two degrees in a pair of now famous papers, suggesting that warming of more than two degrees would push the climate beyond the limits humans were familiar with -1988 James Hansen testifies to Congress linking greenhouse gas emissions to rising temps, and the dangers associated with climate change -1990 Stockholm Environment Institute suggests 2 degrees above pre-industrial levels should be the maximum warming policymakers allow -etc. (review chart in CCretrospective reading)

Latitude impact on Earth's climate

-Many important characteristics of Earth's climate, such as the amount of incoming sunlight, vary with latitude. Incoming solar radiation is stronger at low latitudes, where sunlight is concentrated more nearly overhead, than at high latitudes, where the Sun's rays strike Earth at a more indirect angle and cover a wider area (Figure 2-4). As a result, larger amounts of solar radiation reach the same unit area of Earth's surface in the tropics than near the poles (Figure 2-5). -This unequal distribution of incoming solar radiation is aggravated by unequal absorption and reflection by Earth's surface at different latitudes. A smaller fraction of the incoming radiation is absorbed at higher latitudes than in the tropics mainly because (1) solar radiation arrives at a less direct angle (see Figure 2-4) and (2) snow and ice surfaces at high latitudes reflect more radiation (see Figure 2-5).

Absolute temperatures and relative anomalies

-Most of the images showing the transient changes in global mean temperatures (GMT) over the 20th Century and projections out to the 21st C, show temperature anomalies. An anomaly is the change in temperature relative to a baseline which usually the pre-industrial period, or a more recent climatology (1951-1980, or 1980-1999 etc.). With very few exceptions the changes are almost never shown in terms of absolute temperatures -The observed changes in global mean temperatures are more easily calculated in terms of anomalies (since anomalies have much greater spatial correlation than absolute temperatures). The details are described in the previous link, but the basic issue is that temperature anomalies have a much greater correlation scale (100's of miles) than absolute temperatures - i.e. if the monthly anomaly in upstate New York is a 2ºC, that is a good estimate for the anomaly from Ohio to Maine, and from Quebec to Maryland, while the absolute temperature would vary far more. That means you need fewer data points to make a good estimate of the global value. - people are often confused by the 'baseline period' for the anomalies. In general, the baseline is irrelevant to the long-term trends in the temperatures since it just moves the zero line up and down, without changing the shape of the curve. Because of recent warming, baselines closer to the present will have smaller anomalies (i.e. an anomaly based on the 1981-2010 climatology period will have more negative values than the same data aligned to the 1951-1980 period which will have smaller values than those aligned to 1851-1880 etc.). While the baselines must be coherent if you are comparing values from different datasets, the trends are unchanged by the baseline. -However, while we can conclude that using anomalies in global mean temperature is reasonable, that conclusion does not necessarily follow for more regional temperature diagnostics or for different variables. For instance, working in anomalies is not as useful for metrics that are bounded, like rainfall and sea ice extent changes

Types of teleconnections affecting US climate

-On intraseasonal to interannual time scales, the climate of the United States is strongly affected by modes of atmospheric circulation variability like the North Atlantic Oscillation (NAO)/Northern Annular Mode (NAM), North Pacific Oscillation (NPO), and Pacific/ North American Pattern (PNA) - These modes are closely linked to other atmospheric circulation phenomena like blocking and quasi-stationary wave patterns and jet streams that can lead to weather and climate extremes.10 On an interannual time scale, coupled atmosphere-ocean phenomena like El Niño-Southern Oscillation (ENSO) have a prominent effect.11 On longer time scales, U.S. climate anomalies are linked to slow variations of sea surface temperature related to the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO).

Reconstruction of all proxy temperatures

-On the basis of the historical records, the tree-ring measurements, varves, bore-hole temperatures and ice cores, several climate research groups have been able to reconstruct the global temperature changes over the past two millennia -It is particularly noticeable that the Mediaeval Warm Period, which in some earlier reconstructions was thought to have been as much as 2°C warmer than temperatures of the 20th century, is now thought to have been about much the same as the early 20th century and half a degree cooler than at the start of the 21st. -Every one shows the same thing; a gentle, if rather irregular decline all the time until about 1800, then a sharp upturn, becoming steeper. These recent results coni rm Michael Mann's 'Hockey Stick'.

Climate proxies: boreholes

-One of the more reliable temperature proxies comes from measuring the temperature down small boreholes into solid rock. The interior of the Earth is hot, but rocks are such good insulators that the Earth's surface temperature is set by the atmosphere. Down a borehole, the temperature slowly rises, at about 3°C per kilometre. If the surface temperature has been changing over a period of a few hundred years, that temperature rise is perturbed, and analysis can reveal the change in surface temperature. -The Earth retains the memory of its annual surface temperature history, down to a depth of about 150 metres, and long-term average temperatures can be reconstructed with coni dence as far back as 500 years and in some reconstructions for 20 000 years. -compared to the 1960-90 mean, current temperatures are about 1.5°C warmer than in the Little Ice Age, and more than half a degree warmer than during the Mediaeval Warming. Australian results indicate a cooling during the Little Ice Age of about half that experienced by the northern hemisphere

Cold PDO

-Opposite of the warm PDO, the expansive area of below average water temperatures off the coast of North America from Alaska to the equator signals the cold phase of the PDO. The area of warmer-than-average sea surface temperatures in the central Pacific are surrounded by below average temperatures near the North American continent. Expected impacts from a cold PDO and ENSO (La Nina) phase on the southeast include above average winter temperatures & below average winter precipitation.

Why is global circulation important in the context of global warming?

-Polar jet streams are looping down causing latitudinal variation in temperatures -impacts weather patterns (intensity/energy of hurricanes, temp variations, more intense wildfires) -biodiversity is affected, habitats move up latitudinally -groundwater/stream recharge

Incoming solar radiation

-Radiation from the Sun arrives at the top of Earth's atmosphere with an average energy of 1368 watts per square meter (W/m2). These watts are the same units of energy used to measure the brightness (or more accurately the power) of a household light bulb. If Earth were a flat, one-sided disk directly facing the Sun, and if it had no atmosphere, 1368 W/m2 of solar radiation would fall evenly across its entire surface -But Earth is a three-dimensional sphere, not a flat disk. A sphere has a surface area of 4πr 2 (r being its radius) that is exactly four times larger than the surface area of a flat one-sided disk (πr 2). Because the same amount of incoming radiation must be distributed across this larger surface area, the average radiation received per unit of surface area on a sphere is only onequarter as strong (1368/4 = 342 W/m2) -The 342 W/m2 of solar energy arrives at the top of the atmosphere, mainly in the form of visible radiation. About 70% of this shortwave radiation passes through Earth's atmosphere and enters the climate system (Figure 2-3). The other 30% is sent directly back out into space after reflection (or scattering) by clouds dust, and the more reflective regions at Earth's surface. As a result, the average amount of solar energy retained by Earth is 240 W/m2 (0.7 342 W/m2). -Of the 70% of solar radiation that is retained within the climate system, about two-thirds is absorbed at Earth's surface and about one-third by clouds and water vapor in the atmosphere (see Figure 2-3). This absorbed radiation heats Earth and its lower atmosphere and provides energy that drives the climate system.

Tier-one insights into climate change

-Some aspects of anthropogenic climate change are now certain or near certain3 : atmospheric carbon dioxide and methane levels are increasing, both due to human activity; these increases have caused warming over the past half century and will cause further warming in the future. Warming will cause sea-level rise via thermal expansion and ice sheet melting, and future storms are likely to be associated with greater precipitation and more flooding as the moisture-holding capacity of the atmosphere increases. These are the tier-one insights of climate change science -uncertainties increase about impacts as questions become regionally focused

Ekman Spiral

-The Ekman spiral is a structure of currents or winds near a horizontal boundary in which the flow direction rotates as one moves away from the boundary.

Keeling Curve applied to the past and future

-The Mauna Loa record can now be placed in the context of the variations in CO2 over the past 400,000 years, based on reconstructions from polar ice cores. During ice ages, the CO2 levels were around 200 ppm, and during the warmer interglacial periods, the levels were around 280 ppm. The levels in 2005 were around 378 ppm. -Looking ahead, if the rate of fossil-fuel burning continues to rise on a business-as-usual trajectory, such that humanity exhausts the reserves over the next few centuries, CO2 will continue to rise to levels of order 1500 ppm. The atmosphere will not return to pre-industrial levels even tens of thousands of years into the future. Unless serious efforts are made to reduce the dependence on fossil fuels, it is clear that we are on a threshold of a new era of geologic history, one with climate very different from that of our ancestors.

Atlantic Multidecadal Variability/Atlantic Multidecadal Oscillation

-The North Atlantic Ocean region exhibits coherent multidecadal variability that exerts measurable impacts on regional climate for variables such as U.S. precipitation and Atlantic hurricane activity -This observed Atlantic multidecadal variability, or AMV, is generally understood to be driven by a combination of internal and external factors -AMV manifests in SST variability and patterns as well as synoptic-scale variability of atmospheric conditions. The internal part of the observed AMV is often referred to as the Atlantic Multidecadal Oscillation (AMO) and is putatively driven by changes in the strength of the Atlantic Meridional Overturning Circulation - It is important to understand the distinction between the AMO, which is often assumed to be natural (because of its putative relationship with natural AMOC variability), and AMV, which simply represents the observed multidecadal variability as a whole.

North Atlantic Oscillation

-The North Atlantic Oscillation (NAO) consists of two pressure centers in the North Atlantic: one is an area of low pressure typically located near Iceland, and the other an area of high pressure over the Azores (an island chain located in the eastern Atlantic Ocean). It is important to note that these two locations are most commonly used to measure the NAO, but studies have found that the pressure centers move around on a seasonal basis, and other locations have also been used for measuring this index. Fluctuations in the strength of these features significantly alters the alignment of the jet stream, especially over the eastern U.S., and ultimately affects temperature and precipitation distributions in this area. It is also important to note that the AO and NAO are two separate indices that are ultimately describing the same phenomenon of varying pressure gradients in the northern latitudes and the resultant effects on temperature and storm tracks across the continent.

North Pacific Oscillation

-The North Pacific Oscillation (NPO) is a recurring mode of variability in the extratropical North Pacific region and is characterized by a north-south seesaw in sea level pressure. Effects of NPO on U.S. hydroclimate and marginal ice zone extent in the arctic seas have been reported -The NPO is linked to tropical sea surface temperature variability. Specifically, NPO contributes to the excitation of ENSO events via the "Seasonal Footprinting Mechanism".95, 96 In turn, warm events in the central tropical Pacific Ocean are suggested to force an NPOlike circulation pattern

Pacific Decadal Oscillation

-The Pacific Decadal Oscillation (PDO) is a pattern of Pacific climate variability similar to ENSO in character, but which varies over a much longer time scale. The PDO can remain in the same phase for 20 to 30 years, while ENSO cycles typically only last 6 to 18 months. The PDO, like ENSO, consists of a warm and cool phase which alters upper level atmospheric winds. Shifts in the PDO phase can have significant implications for global climate, affecting Pacific and Atlantic hurricane activity, droughts and flooding around the Pacific basin, the productivity of marine ecosystems, and global land temperature patterns. Experts also believe the PDO can intensify or diminish the impacts of ENSO according to its phase. If both ENSO and the PDO are in the same phase, it is believed that El Niño/La Nina impacts may be magnified. Conversely, if ENSO and the PDO are out of phase, it has been proposed that they may offset one another, preventing "true" ENSO impacts from occurring.

Pacific Decadal Oscillation/Interdecadal Pacific Oscillation

-The Pacific Decadal Oscillation (PDO) was first introduced by Mantua et al. 1997123 as the leading empirical orthogonal function of North Pacific (20°-70°N) monthly averaged sea surface temperature anomalies - Interdecadal Pacific Oscillation (IPO) refers to the same phenomenon and is based on Pacific-wide sea surface temperatures -PDO/IPO lacks a characteristic timescale and represents a combination of physical processes that span the tropics and extratropics, including both remote tropical forcing and local North Pacific atmosphere-ocean interactions.14 Consequently, PDO-related variations in temperature and precipitation in the United States are very similar to (and indeed may be caused by) variations associated with ENSO and the strength of the Aleutian low (North Pacific Index, NPI)

Pacific/North American (PNA)

-The Pacific/North American teleconnection pattern (PNA) is one of the most recognized, influential climate patterns in the Northern Hemisphere mid-latitudes beyond the tropics. It consists of anomalies in the geopotential height fields (typically at 700 or 500mb) observed over the western and eastern United States. It is important to note that the PNA has been found to be strongly influenced by the El Niño-Southern Oscillation (ENSO) phenomenon. The positive phase of the PNA pattern tends to be associated with Pacific warm episodes (El Niño), and the negative phase tends to be associated with Pacific cold episodes (La Niña).

Warm PDO

-The broad area of above average water temperatures off the coast of North America from Alaska to the equator is a classic feature of the warm phase of the Pacific Decadal Oscillation (PDO). The warm waters wrap in a horseshoe shape around a core of cooler-than-average water. Impacts from the PDO depend in part on how it is aligned with the ENSO cycle; if the cycles are in opposite phases, then effects will be weakened. However, when both the PDO and ENSO are in the warm phase, meaning ENSO would be in the El Niño phase, expected impacts on the southeast include below average winter temperatures & above average winter precipitation.

La Niña conditions

-The cold tongue (blue) is cooler than usual by about 3° Centigrade (5.4° Fahrenheit). The cold La Niña events sometimes (but not always) follow El Niño events.

Southern Oscillation Index

-The fluctuations in ocean temperatures during El Niño and La Niña are accompanied by even larger-scale fluctuations in air pressure known as the Southern Oscillation. The negative phase of the Southern Oscillation occurs during El Niño episodes, and refers to the situation when abnormally high air pressure covers Indonesia and the western tropical Pacific and abnormally low air pressure covers the eastern tropical Pacific. In contrast, the positive phase of the Southern Oscillation occurs during La Niña episodes, and refers to the situation when abnormally low air pressure covers Indonesia and the western tropical Pacific and abnormally high air pressure covers the eastern tropical Pacific. -The Southern Oscillation Index (SOI) is one measure of the large-scale fluctuations in air pressure occurring between the western and eastern tropical Pacific (i.e., the state of the Southern Oscillation) during El Niño and La Niña episodes. Traditionally, this index has been calculated based on the differences in air pressure anomaly between Tahiti and Darwin, Australia. In general, smoothed time series of the SOI correspond very well with changes in ocean temperatures across the eastern tropical Pacific.

Earth's main storage tanks of solar heat

-The low-latitude oceans are Earth's main storage tanks of solar heat. Sunlight penetrates into and directly heats the upper tens of meters of the ocean, especially in the tropics, where the radiation arrives from a Sun high in the sky. Equally important, winds blowing across the ocean's surface stir the upper layers and rapidly mix solar heat as deep as 100 meters (Figure 2-9). In contrast, even though tropical and subtropical landmasses generally become very hot under the strong Sun, they are not capable of storing much heat because heat is conducted down into soil or rock at very slow rates

Negative PNA

-The negative phase features troughing and below normal geopotential heights over the western U.S. and ridging with above normal geopotential heights over the eastern U.S. The result is below average temperatures for the western U.S., and above average temperatures over the eastern U.S. Research indicates that a negative PNA typically results in a reduced potential for winter weather in NC

Negative vs. Positive phase of SOI

-The negative phase of the SOI represents below-normal air pressure at Tahiti and above-normal air pressure at Darwin. Prolonged periods of negative SOI values coincide with abnormally warm ocean waters across the eastern tropical Pacific typical of El Niño episodes. Prolonged periods of positive SOI values coincide with abnormally cold ocean waters across the eastern tropical Pacific typical of La Niña episodes -ENSO has period of about four years (2-7 years), but there have been a lot of El Niños from 80s to 90s

Albedo

-The percentage of incoming radiation that is reflected rather than absorbed by a particular surface is referred to as its albedo (Table 2-1). Snow and ice surfaces at high latitudes have albedos ranging from 60% to 90%, with larger values typical of freshly formed snow and ice, and somewhat lower values for snow or ice that contain dirt or are partly covered by pools of melted water. In contrast, snow-free land surfaces have much lower albedos (15-30%) and ice-free water reflects even less of the incoming radiation (below 5% when the Sun is overhead). The albedo of any surface also varies with the angle at which incoming solar radiation arrives. For example, water reflects less than 5% of the radiation it receives from an overhead Sun, but a far higher fraction of the radiation from a Sun lying low in the sky (Figure 2-6). This same tendency holds true for the other surfaces. Because 70% of Earth's surface is low-albedo water, Earth's surface has an average albedo near 10%. These factors combine to make Earth's surface more reflective near the poles than in the tropics.

Positive PNA

-The positive phase consists of above normal geopotential heights over the western U.S. and below normal geopotential heights over the eastern U.S. This correlates to ridging over the western U.S., and deep troughing over the east. The net result of the height field pattern in this phase is that it forces cold air residing in Canada to plunge southeastward, which results in below normal temperatures over the eastern U.S. and above normal temperatures over the western U.S. Research indicates that a positive PNA, especially during an El Niño year, produces an above average number of winter weather events in NC.

Paris Climate Agreement

-The signatories aimed "to strengthen the global response to the threat of climate change, in the context of sustainable development and efforts to eradicate poverty" and contained three key provisions: 1) Holding the increase in the global average temperature to well below 2 °C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5 °C above pre-industrial levels, recognizing that this would significantly reduce the risks and impacts of climate change 2) Increasing the ability to adapt to the adverse impacts of climate change and foster climate resilience and low greenhouse gas emissions development, in a manner that does not threaten food production 3) Making finance flows consistent with a pathway towards low greenhouse gas emissions and climate-resilient development. -Rich countries must provide 100 bill dollars from 2020 as a floor -developed countries must continue to take the lead in the reduction of greenhouse gases -developing nations are encourage to enhance their efforts and move over time to cuts -voluntary, all nations come under the agreement

Oceans and Atmosphere: Large Scale Circulation and Climate Variability

-The tropics have expanded poleward by about 70 to 200 miles in each hemisphere over the period 1979-2009, with an accompanying shift of the subtropical dry zones, midlatitude jets, and storm tracks (medium to high confidence). Human activities have played a role in this change (medium confidence), although confidence is presently low regarding the magnitude of the human contribution relative to natural variability -Recurring patterns of variability in large-scale atmospheric circulation (such as the North Atlantic Oscillation and Northern Annular Mode) and the atmosphere-ocean system (such as El Niño-Southern Oscillation) cause year-to-year variations in U.S. temperatures and precipitation (high confidence). Changes in the occurrence of these patterns or their properties have contributed to recent U.S. temperature and precipitation trends (medium confidence), although confidence is low regarding the size of the role of human activities in these changes

Troposphere

-The troposphere is both the layer within which we live and the layer within which most of Earth's weather happens. Storm systems that produce clouds and rainfall or snowfall are almost entirely confined to this layer. Dust or soot particles that are lifted by strong winds from Earth's surface into the lower parts of this layer are quickly removed by precipitation every few days or weeks. The troposphere is also the main layer within which we measure Earth's climate and its changes, particularly those at Earth's surface. As we will see later, about 80% of the gases that form Earth's atmosphere are contained within the troposphere.

Earth's atmosphere composition

-The two main gases in Earth's atmosphere are N2 (nitrogen) at 78% of the total and O2 (oxygen) at 21%, but neither is a greenhouse gas because neither traps outgoing radiation. In contrast, the three most important greenhouse gases form very small fractions of the atmosphere. Water vapor (H2 Ov ) averages less than 1% of a dry atmosphere, but it can range to above 3% in the moist tropics. Carbon dioxide (CO2) and methane (CH4) occur in much smaller concentrations of 0.035% and 0.00018%, but they are also important greenhouse gases.

Affect of teleconnections on climate responses

-These modes of variability can affect the local-to-regional climate response to external forcing in various ways. The climate response may be altered by the forced response of these existing, recurring modes of variability.15 Further, the structure and strength of regional temperature and precipitation impacts of these recurring modes of variability may be modified due to a change in the background climate.16 Modes of internal variability of the climate system also contribute to observed decadal and multidecadal temperature and precipitation trends on local to regional scales, masking possible systematic changes due to an anthropogenic influence

Charles Keeling and CO2

-U.S. chemist who came to Scripps -He was the fi rst scientist to con fi rm the increase of carbon dioxide in the atmosphere by very precise measurements that produced data which resulted in what is now called the Keeling Curve (Fig. 1.2). Prior to the work of Keeling, no one had quanti fi ed that carbon dioxide was steadily increasing in atmospheric concentration and his measurements became a milestone in historical climate change science. -Keeling discovered that the atmosphere breathes in an annual cycle that re fl ects the in fl uences of photosynthesis , respiration , and atmospheric mixing. -Mauna Loa volcano location for Scripps site - Keeling also noted a seasonal variation in his CO 2 measurements. In the summer months the CO 2 readings would decrease due to plants taking CO 2 out of the atmosphere and using CO 2 in photosynthesis . In winter the CO 2 readings would increase due to plants dying or going dormant and giving up their CO 2 to the atmosphere .

Taking Earth's temperature

-Urban heat islands aren't a viable source for taking heat measurements -satellite data is a good way to take climate measurements (there's limitation though, orbits decay)

Computer models: 1960s & 1980s

-WWII: short-term weather prediction -1960s: GCMs -Syukuro Manabe makes first 3D model of the atmosphere -model resolution through time: different in scale/resolution from 1990-2007 b/c of rapid improvements in computing power

Ozone hole

-a hole located in the southern hemisphere over Antarctica -in this region, during winter time it gets cold enough that an unusual form of cloud occurs in the stratosphere, comprised of frozen particles of nitric acid -the frozen nitric acid clouds convert the chlorine from the breakdown of freons into a very reactive form that doesn't just deplete ozone by a small amount, but consumes it entirely within that air mass

Scattering

-a lot of energy just gets diffused/scattered around

Syukuro Manabe and Climate Modeling

-a meteorologist at the Geophysical Fluid Dynamics Laboratory (GFDL) of NOAA located at Princeton University in the U.S -began work on some of the earliest attempts to model the atmosphericoceanic system to be able to solve some of the problems of climate science. In the 1960s, Manabe and his research team developed a radiative-convective model of the atmosphere and modeled greenhouse gases such as water vapor , carbon dioxide , and ozone . This was the beginning of long-term research on climate change and global warming . In the late 1960s he began to develop a general circulation model (GCM) of the atmosphere -ocean -land system. Suki Manabe pioneered the use of computers to simulate global climate change and natural climate variations.

Ferrel cell

-a midlatitude mean atmospheric circulation cell -in this cell, the air flows poleward and eastward near the surface and equatorward and westward at higher levels

Ozone

-a reactive oxygen molecule comprised of three oxygen atoms -ozone in the stratosphere is produced as O2 molecules which are zapped by energetic UV-C light, breaking apart into two very reactive O2 atoms -each of these may find another O2 molecule and join it to form O3, aka ozone -ozone absorbs UV light called UV-B that is less energetic but more abundant than the UV-C require to break up an O2 molecule -stratospheric ozone filters UV-B radiation that might otherwise reach the surface, causing skin cancers and sunburn

Urey reaction

-a two directional equation that is really important to Earth's climate

Insolation imbalance

-air flows from high to low pressure (leads to differential energy/heating which means differential pressure which prompts circulation)

Polar cell

-air rises, diverges, and travels toward the poles -once over the poles, the air sinks, forming the polar highs -at the surface, air diverges outward from the polar highs -surface winds in the polar cell are easterly (poor easterlies)

William Ruddiman and Paleoclimate

-best known for proposing that humans began to affect carbon dioxide and methane concentrations in the atmosphere as early as 10,000 years prior to the present (2012) by deforestation and the beginnings of agriculture . - strong proponent of the Anthropocene designation beginning 8,000 years BC when humans began to change the composition of the atmosphere with early agricultural practices .

Biological pump

-biology in the ocean acts to decrease the CO2 concentration of surface waters by converting CO2 into organic carbon via photosynthesis -dead phytoplankton sink from surface waters exporting their carbon to the deep sea -this process is termed the biological pump -if all the life in the ocean were killed, if the biological pump had stopped, then the CO2 concentration in the atmosphere would rise

humic acids

-carbon chemistry is kept highly organized within living things, but after life is finished with it, carbon left in soils, sediments, and rocks forms itself into an indescribable goo called humic acids aka kerogen

Terrestrial carbon sink

-carbon uptake by the terrestrial biosphere on land is difficult to measure -the distribution of carbon on land compared to in the ocean is very spotty -most of the carbon on land is in the soil rather than in the trees -in soil, the amount of carbon depends on the recent history of the land: fires, agriculture, erosion, etc. -the land is playing two roles in the carbon budget story, one as a visible deforestation source and another as a potential invisible carbon uptake sink

Global pressure: January vs July

-changes of pressure bc of subsolar point (most intense point of radiation) changes

Urban Heat Island effect

-cities tend to be warmer than the surrounding countryside -why? because of radiation effects-->cities are designed to get rid of water, have low albedoes bc of dark surfaces

Northern Annular Mode/Arctic Oscillation (NAM/AO)

-closely related to the NAO -It describes a similar out-of-phase pressure variation between mid- and high latitudes but on a hemispheric rather than regional scale.77, 78 The time series of the NAO and NAM/AO are highly correlated, with persistent NAO and NAM/AO events being indistinguishable.

Hadley cell, Ferrell cell and Polar cell

-contributors to regional climate trends from changes in large-scale latitudinal circulation -these cells determine the location of subtropical dry zones and midlatitude jet streams -cells are expected to shift poleward during warmer periods, which could result in poleward shifts in precip patterns, affecting natural ecosystems, agriculture, and water resources -A high pressure band is located at about 30° N/S latitude, leading to dry/hot weather due to descending air motion (subtropical dry zones are indicated in orange in the schematic views). Expanding tropics (indicted by orange arrows) are associated with a poleward shift of the subtropical dry zones. A low pressure band is found at 50°-60° N/S, with rainy and stormy weather in relation to the polar jet stream bands of strong westerly wind in the upper levels of the atmosphere.

Cretaceous period & Early Eocene optimum

-creatceous period was when dinos ruled the Earth, and during early eocene optimum which followed, apparently needed more CO2 in their atmosphere in order to balance the degassing and weathering CO2 fluxes at that time -the breathing of rocks, via silicate weathering thermostats, takes place on timescales of millions of years

Carbon balance

-degassing vs weathering -volcanoes are a source of carbon degassing (they release 0.1 Pg) -there's almost no limit to what carbon can form, but when they come together they form a really tight bond that doesn't break down, but instead liquifies across time to create oil/fossil fuels

History of burning coal

-early man in Europe was burning coal. It is known that coal was used during the Bronze Age , more than 4,000 years ago. Today (June 2012), coal burning is the greatest source of carbon dioxide (CO 2 ) in the atmosphere where it stays for a long time (perhaps for thousands of years) and continues to contribute to global warming .

Arrhenius and CO2

-fi rst person to investigate what the effect of doubling atmospheric carbon dioxide would have on global climate . Arrhenius was a Swedish scientist and one of the founders of physical chemistry . He was apparently one of the fi rst to discuss quantifying carbon dioxide in the atmosphere . He was the fi rst to predict that emissions of carbon dioxide from the burning of fossil fuels and other combustion processes would cause global warming -Arrhenius was the fi rst to predict that emissions of carbon dioxide from the burning of fossil fuels and other combustion processes would cause global warming -showed that the Arctic region would experience an increase in temperature of about 8 or 9 degrees C if CO2 increased 2.5-3 times its value

Sedimentary rocks

-former ocean sediments that are currently on land -life on earth has built up a sizable pool of carbon in the reduced form in ocean sediments and sedimentary rocks

Photosynthesis

-forward direction of reaction done by plants -energy comes from sunlight, photosynthesis cannot proceed without energy from light

Stomata

-gases are exchanged with the outside atmosphere through adjustable vents called stomata -when the leaf needs CO2 for photsynthesis, the stomata open -the cost of opening stomata is loss of water

Net radiation

-generally more radiation at the equator, less at the poles -radiation imbalance from equator to poles, but radiation/energy is distributed via winds and ocean currents

Methane

-greenhouse gas 20 times more powerful per molecule than CO2 at current concentrations -methane has natural sources as well as additional anthropogenic sources to the atmosphere -once released back into the atmosphere, methane reacts slowly with activated oxygen compounds to oxidize back to CO2 -the reactive O2 compounds are produced by sunlight -in the absence of sunlight methane and 02 gas coexist in ice core bubbles for hundreds of thousands of years with no reaction, put in the sunlight they slowly burn up

Planetismal hypothesis

-had at its center the idea that smaller objects (planetesimals) collided with each other in the early stages of the Solar System and formed the planets by accretion (growing together and becoming larger).

Lithospheric and solar changes effect on past climate

-have big impacts on large time scales (millions of years, but not important on our timescales) -climate has changed in the past b/c of changes in atmospheric composition, tectonic changes, etc. -variations in atmospheric composition: changes in aerosols, dust, water vapor, cloud cover all change atmospheric composition which changes albedo/radiative forcing -Tectonic and land surface changes: if you have a completely changed how win circulated around that area

Polar amplification

-higher latitudes warm (Arctic) more than low latitudes

Residence time

-how long the average Carbon atom stays in the atmosphere

Organic carbon

-hydrocarbons and carbohydrates together form organic carbon

Atlantic Multidecadal Oscillation (AMO)

-identified as a coherent mode of natural variability occurring in the North Atlantic Ocean with an estimated period of 60-80 years. It is based upon the average anomalies of sea surface temperatures (SST) in the North Atlantic basin, typically over 0- 80N -The Atlantic Multidecadal Oscillation (AMO) is a near-global scale mode of observed multidecadal climate variability with alternating warm and cool phases over large parts of the Northern Hemisphere. Many prominent examples of regional multidecadal climate variability have been related to the AMO, such as North Eastern Brazilian and African Sahel rainfall, Atlantic hurricanes and North American and European summer climate. These SST variations have been called the 'Atlantic Multidecadal Oscillation' (AMO) and are part of a coherent temperature variation across much of the Northern Hemisphere • The SST-based AMO index provides a simple, concise way to describe multidecadal climate variability in the North Atlantic • Associated with important climate impacts, such as the multidecadal variability of Atlantic Hurricane activity, North American and European summer climate, northern hemispheric mean surface temperature, and Arctic sea ice anomalies • The AMO pattern is robust across different datasets

Acidic

-if a solution has a high concentration of hydrogen ions, we will call it acidic -hydrogen ions are very reactive -a strongly acidic solution can burn your skin or clothes by chemical reaction with hydrogen ions

IPCC

-improved resolution -improved number of contributors -always the same result -25 years of activity -increasing complexity via improved resolution -gaining confidence in each report

Soil carbon pool

-it turns out that there is more carbon in soils than there is in the living biosphere -larger than the terrestrial biosphere carbon pool by a factor of about two -largely dead carbon, decomposing leaves and other plant material -the amount of carbon stored in soils is highly variable from place to place, depending on the climate, the forestry, and the history of the land. Desert do not have much carbon in their soils whereas grasslands tend to have quite a bit. -there is more soil carbon in colder climates htan in warmer climates because organic carbon decomposes more quickly when it is warm. -farming tends to decrease the amount of carbon in soils, but no-till helps avoid this problem

Relationship of the jet stream/Polar vortex to climate change

-jet stream, polar vortex caused by pressure differences between higher and lower latitudes keeps arctic air at higher latitudes -as climate warms, allows arctic air to sweep down into other places -higher latitudes warm faster than lower latitudes

Juvenile carbon and metamorphic decarbonation

-juvenile: some of the carbon degassing from Earth may be juvenile carbon, which has spent that last 4.5 billion years of the Earth history bound up in the deep Earth only to emerge now. -metamorphic: when silicate rocks are produced from sedimentary rocks, deep in the Earth's interior where it is hot. Chemical reaction. This direction is generally favored at high temps, Co2 released by metamorphic reactions may find its way to the surface in volcanic gases or in hot water springs at the bottom of the ocean.

Sedimentary rock carbon pool

-lager than the ocean, land, or atmospheric pools -carbon exists in the form of limestones (CaCO3), and to a lesser extent as organic carbon -these carbon reservoirs together contain about 500 times as much carbon as the atmopshere and the landscape combined. -Most organic carbon in sedimentary rocks is in a form called kerogen. -Kerogen is useless as a fossil fuel because it is dilute, usually less than 1% by weight of sedimentary rocks, and because it is in a solid form making it difficult to extract.

Land warming vs ocean warming

-land warms more than the ocean in the sense that you see more drastic temp changes inland (continentality) vs marine effect (ocean temps more stable) -global mean precip increases as world warms

Synoptic climate

-large scale climate change patterns

Ocean carbon reservoir

-larger than either the land surface or the atmosphere -ocean's carbon is dead, and oxidized: energetically dead and biologically dead -the sum of all forms of carbon in the ocean is dissolved inorganic carbon -the ocean dissolved inorganic carbon pool is larger than the atmospheric pool by a factor of about 50. There is also dissolved organic carbon in the ocean: dead, scrambled molecules similar to soil organic carbon, the total amount of carbon in the ocean that lives is small, only about a Gton

Carbohydrates

-life is comprised of carbon largely in the intermediate oxidation state called carbohydrates

Hadley cell

-low-latitude air moves toward the equator -due to solar heating, air near the equator rises vertically and moves poleward in the upper atmosphere -subtropical high pressure belth -confine the intertropical convergence zone which is an area of intense heating and rising air

Ocean circulation

-mixing zone=top 2% of the ocean where atmosphere and ocean can really mix -major ocean surface currents: all of the circular current patterns around the ocean are called gyres -gyres are offset by winds a little bit bc of the Coriolis effect, winds drag the gyres right or left

Carbon Cycle in Oceans

-more carbon fluxes twd the surface -takes in 78.4 Pg, degasses 80 Pg

inorganic carbon

-most carbon on earth is oxidized carbon, also called inorganic carbon, in CaCO3 (limestone) rocks or dissolved in the oceans

Upwelling

-moves cold water along West Coast North America -Gulf Stream moves warm water up to Northern Europe -upwelling causing transport of cold water at South America's southern tip

General Circulation Model

-multi-columnar projection of the astmospheric heat transfers, momentum, etc.

Warming papers: Ocean pH

-ocean acidification causes hardship for calcium shells (calcium carbonate naturally dissolves CO2 but CO2 is being added to the oceans faster than Calcium carbonate can naturally dissolve it) -2000s impacts: CO2 dissolving in water dissolves to a weak acid (affects how sound travels in ocean, coral skeleton forming, etc.) -rates of change are very fast -tripling of acidity in oceans by 2100

Hydrocarbons

-oil and natural gas -some biomolecules are hydrocarbons such as fats

Eccentricity

-orbital cycle involving how elliptical the orbit of the Earth is, also called its eccentricity -at present, the Earth's orbital path is nearly circular -the eccentricity of the orbit has cycles of 100,000 to 400,000 years -the strongest climate impact of eccentricity is to determine the strength of the precessional forcing -when eccentricity is low, the orbit is circular, and the 20,000 year waves in the precession cycle vanish

Paleoclimate in past and future climate projections

-palaeoclimate research can present the same information as an experiential suite of observations and associated narratives -Primarily, Earth history shows us that climate can change. We live during a particularly protracted period of climate stability — the Holocene — that has allowed civilization to thrive. Even on those relatively modest timescales of thousands of years, the concept of climate change has become embedded in our mythology and culture, from biblical floods to Dutch paintings of frozen canals -Crucially, our proxies for past carbon dioxide and temperature, despite their uncertainties and eccentricities, nearly universally show that when concentrations of carbon dioxide in the atmosphere were high, our planet was hot. Importantly, warming occurred in a manner consistent with climate models1,2 (although models appear to underestimate polar warming6 ), suggesting that to the first order, we understand the processes that govern Earth's temperature.

Pack-rat middens as proxies

-pee in their nests, but good for climate bc uric acid crystallizes and preserves everything in their nests

Carbon cycle on short time scales: plants

-photosynthesis and respiration -plants lock away some CO2 for themselves, but when they die, the decompose and rerelease CO2 -photosynthesis: taking in a little less than 119 Pg, degasses 119 Pg -more forests in Eastern US than a few decades ago

Precession

-precession of the seasons or sometimes precession of equinoxes -the axis rotation of the Earth spins around like a wobbling top, completing the entire circle in 20,000 years -most of the solar heat influx variability at high latitudes derives from precession, and nearly all of the variability in the tropics comes from precession -precession has an effect on cliamte because the Earth's orbit is not circular but elliptical -where we are in the precession cycle at present, the Earth is closest to the Sun during winter in the northern hemisphere -the seasonal cycle of solar heat flux in the northern hemisphere is weakened by this orientation, because the Earth is close to the Sun when the northern hemisphere is tilted away from the Sun. The seasonal cycle of solar heating is stronger in the southern hemisphere now because the Earth is close to the Sun and tilted toward the Sun at the same time. It is the tilt of the Earth that causes the Earth's seasons, the precession cycle merely modifies the seasons somewhat.

Temperature proxy summary

-proxies estimate global temps over the past 2000 years -slow and steady temperature fall until ~1800 -climate was following Milankovic cycle expectation

Teleconnections

-recurring, persistent, large-scale patterns of pressure and circulation -anomalies that span vast geography -identified using statistical correlations -cyclical, happens over long time scales (are distant) -in terms of 10-50 year time scales you have climate changes not related to GHGs, but other climate variability factors -pressure systems provide a lot of noise that makes it difficult to pinpoint climate change indicators -teleconnections interact with a lot of other factors of climate systems (precip, etc.)

Land use

-release 1.1 Gt of carbon into atmosphere

Fossil fuels and cement production

-release 7.8 Gt carbon into atmosphere

What happens to outgoing longwave radiation

-returned to space -latent/sensible heat transfer -absorbed and re-radiated (counter radiation/back radiation)

CO2 fertilization

-rising CO2 in the atmosphere may also directly encourage plants to grow faster by a process known as CO2 fertilization -if CO2 concentrations are higher in the outside atmosphere, plants can get the CO2 they need without opening their stomata as much or as often, being stingier with their water.

Weathering

-sedimentary rocks produced from silicate rocks is weathering -a silicate rock weathers by dissolving its calcium and silica into river water ultimately to be delivered to the ocean -occurs under relatively cold, wet conditions of the surface of the Earth -if weathering were allowed to continue to its equilibrium, it would pull nearly all of the CO2 out of the atmosphere

Energy balance

-shortwave radiation is coming in is n the form of (visible light) but is not enough to power the earth, so Earth bottom up heating occurs -there is counter radiation happening on Earth +SW (insolation) - SW (reflection) - LW (infrared) + LW (infrared) = Net Radiaton

Silicate rock, magma, lava

-silicate: rock formed at a high temp. Formed by cooling and freezing melted rock. -Lava: found at the Earth's surface -magma: found in Earth's subsurface

Carbon dioxide levels

-slight decline for 1000 years, average has been 280 ppm pre-Industrial -sharp increase from 1800 -temperature and CO2 were linked over this period, as they were over past ages

Hockey stick

-slow temp fall for 1800 years, sharp rise since -recent temp rise is beyond all previous experience -today's climate change has no parallel in the past 2000 years

Le Chatelier's principle

-states that an addition or removal of a chemical on one side of the chemical equilibrium will cause the reaction to run in the opposite direction to compensate for the change. Take some of something out, the equilibrium will put some of the something back. Add more of something, the equilibrium will remove some of the something.

Reservoirs

-stocks or pools where carbon is stored on Earth -the bigger the reservoir of Carbon, the slower the flux of carbon in and out

Ocean acidification

-term used to describe significant changes to the chemistry of the ocean. It occurs when carbon dioxide gas (or CO2) is absorbed by the ocean and reacts with seawater to produce acid.

North Atlantic Oscillation (NAO)

-the leading recurring mode of variability in the extratropical North Atlantic region, describes an opposing pattern of sea level pressure between the Atlantic subtropical high and the Iceland/Arctic low. Variations in the NAO are accompanied by changes in the location and intensity of the Atlantic midlatitude storm track and blocking activity that affect climate over the North Atlantic and surrounding continents. -A negative NAO phase is related to anomalously cold conditions and an enhanced number of cold outbreaks in the eastern United States, while a strong positive phase of the NAO tends to be associated with above-normal temperatures in this region -The positive phase of the NAO is associated with increased precipitation frequency and positive daily rainfall anomalies, including extreme daily precipitation anomalies in the northeastern United States -The NAO's influence on the ocean occurs through changes in heat content, gyre circulations, mixed layer depth, salinity, high-latitude deep water formation, and sea ice cover

Trade winds in normal, non-El Niño conditions

-the trade winds blow to the west along the equator from South America towards Asia in the tropical Pacific Ocean. These winds pile up warm surface water off Asia, so that the sea surface is about 1/2 meter (1 1/2 feet) higher at Indonesia than at Ecuador in South America.

Buffer

-the CO2 concentration of seawater is buffered by its pH chemistry. Another way of saying this is that the seawater has greater capacity to hold carbon than it would if CO2 were not buffered.

Petagram

-the SI unit for measuring Carbon -One Petagram = 1 Gigatonne Gt aka one quadrillion grams 10^15 grams

Obliquity

-the angle of the pole of rotation, relative to the plane of Earth's orbit -the Earth rotates, making day and night, on a rotation axis of the north and south poles -this rotational axis is not perpendicular to the plane of Earth's orbit around the Sun, but is tilted somewhat -the angle of tilt is currently 23.5 degrees, but it varies between 22-25 degrees every 41,000 years -the impact of obliquity on the solar heating flux is stronger in high latitudes

Proxy: tree rings

-the annual growth rates of trees, particularly those growing in cold climates, can be estimated from the thickness and density of their annual growth rings. Provided it has enough water, a tree's growth rate depends on the hours of sunshine it receives in the summer and on the temperature. Other things that can af ect the climate are also recorded in tree rings, such as El Niño and La Niña events. By sampling trees from places where the main factor af ecting growth is in temperature (mainly near-Arctic locations), most of the other things that af ect tree growth can be separated out, allowing a connection to be made between tree-ring width and local summer temperature. This connection is quite clear during the i rst half of the 20th century, but there is divergence between tree-ring deduced temperatures and thermometer records after about 1960 One explanation for the divergence is that later 20th-century air pollution has dimmed the Sun enough to reduce tree growth, and so makes it look as though the temperature has fallen. Another is that moisture stress, possibly associated with increasing temperatures, has caused a change

Respiration

-the backward direction of the photosynthesis chemical reaction -we consume the products of photosynthesis and breathe oxygen to harvest the energy originally from sunlight, exhaling CO2 and water vapor

Glacial/interglacial cycles

-the clearest example of the power of the ocean to affect CO2 in the atmosphere is the glacial/interglacial cycles -the geologic record of the last 500 million years shows Earth going into an ice age every 150 million years or so -we are in an ice age now, and have been for about 2 million years -during an ice age, the amount of ice, and the climate of the Earth, fluctuate rhythmically between glacial states and interglacial states

James Hansen and Temperature Analysis

-the director of the Goddard Institute of Space Studies (GISS ) at Columbia University -He began studying the atmosphere of Venus and later applied his work to the Earth's atmosphere . He developed radiative transfer models to better understand the effects of aerosols and trace gases on Earth's climate . Hansen 's development and use of global climate models has contributed to the further understanding of the Earth's climate - In 1987, Hansen and one of his colleagues (S. Lebedeff ) devised a method of obtaining a global average temperature . This method continues to be used by GISS and agencies in other countries to arrive at an annual average global temperature .

Carbon on earth take home points

-the most stable form of carbon on Earth is oxidize as CO2 or CaCO3 -photosynthesis stores energy from the Sun by producing organic carbon which also serves as a building scaffolding for the machinery of life -there is less carbon in the atmosphere than there is in other carbon reservoirs on Earth such as the terrestrial biosphere and the oceans -these other reservoirs tug on atmospheric CO2, seasonally for the land and on 100,000 year glacial/interglacial cycles from the ocean -the weathering of igneous rocks on land controls the pCO2 of the atmosphere on million year timescales. This silicate thermostat stabilizes climate -the thermostat is broken on Venus, because there is no water left, and on Mars, because there is no active volcanism left

Carbon cycle take home points

-the ozone hole is not global warming, they are different issues -methane has a short lifetime in the atmosphere -CO2 has a long lifetime in the atmosphere. Stabilizing CO2 in the atmosphere at some "safe level" will require major new energy initiative

Thermocline

-the shallower ocean has other water masses and circulation modes -the zone of the ocean separating the warm from the cold is the thermocline -thermocline waters may be exposed to the atmosphere in winter, when the sea surface waters are cold -thermocline waters ventilate to the atmosphere on timescales of decades

Trade Winds during El Niño

-the trade winds relax in the central and western Pacific leading to a flattening of the thermocline (blue band) due to a depression of the thermocline in the eastern Pacific, and an elevation of the thermocline in the west. - reduced the efficiency of upwelling to cool the surface and cut off the supply of nutrient rich thermocline water to the euphotic zone. The result was a rise in sea surface temperature and a Winds and temperature from the surface down to 200m deep on the Equator at 110ºW, showing neutral conditions (left) and strong El Nino conditions (right). "Central Pacific" El Niño, 2009-2010. The strongest "Central Pacific El Niño in the past 3 decades, with maximum warming in the central equatorial Pacific, vs the classic El Niño (like 1997-1998), with maximum warming in the eastern equatorial Pacific. See YouTube video. drastic decline in primary productivity, the latter of which adversely affected higher trophic levels of the food chain, including commercial fisheries in this region -The weakening of easterly tradewinds during El Niño is evident in this figure as well. Rainfall follows the warm water eastward, with associated flooding in Peru and drought in Indonesia and Australia. The eastward displacement of the atmospheric heat source overlaying the warmest water results in large changes in the global atmospheric circulation, which in turn force changes in weather in regions far removed from the tropical Pacific

Manabe and Wetherald

-their 1975 estimate of the warming from a doubling of CO2 was the first such estimate to be based on completely sound and quantitatively accurate implementations of radiative and convective physics; stood the test of time -misrepresented the entire atmosphere as a single (Earth's surface temp is not uniform, need to see geographical distribution of climate change) -many climate impacts descend fro rainfall changes, changes in the hydrological cycle need to be characterized

Terrestrial biosphere

-there are two forms of carbon that we associate with the landscape that we live in -the actual living carbon, trees and camels and all the rest of it, is called the terrestrial biosphere -there is about 500 Gton C in the terrestrial biosphere, similar in size to the atmosphere

Wavelength and frequency

-trough to trough -how often wavelength goes trough to trough -gamma rays, x-rays, UV, visible light, radio (longest to shortest)

Ocean carbon sink

-uptake of fossil fuel CO2 by the oceans -the ocean sink depends on ocean circulation, and on the chemical forms that dissolved CO2 takes in seawater the densest water at the sea surface is in the Antarctic and North Atlantic because it is very cold there.

Water vapor feedback

-water vapor, Earth's major greenhouse gas, varies in concentration from 0.2% in very dry air to over 3% in humid tropical air. This strong dependence on temperature produces an important positive feedback in the climate system called water vapor feedback. Assume that climate warms for any reason. A warmer atmosphere can hold more water vapor, and the increased greenhouse gas traps more heat. This large greenhouse effect in turn further warms Earth, amplifying the initial warming through a positive feedback loop. The same positive feedback process works when the climate cools: initial cooling reduces the amount of water vapor held in the atmosphere and produces additional cooling because of the reduced greenhouse effect. It is estimated that direct positive feedback from water vapor can triple the size of an initial climate change. This estimate is based on the action of water vapor in a clear sky; it ignores the more complicated effects that occur when water vapor condenses and forms clouds.

Wein's Law

-wavelength max = a/T where -wavelength max: wavelength of maximum emission (um) - a = Wen's constant (2898 um K) -T = temperature (K)

Last Glacial Maximum

-we are currently in an interglacial state, having been for 10,000 years -during the Last Glacial Maximum, global temp was 5-6 K colder than today and much of North America and Northern Europe were covered with a massive dome of ice, like what currently exists in Greenland

Reflection

-we depend on albedo to reflect back radiation

Rocks as carbon reservoirs

-we talk about atmospheric carbon concentrations bc our life spans are short, so we're interested in the fast flux of the atmosphere -rock carbon cycle fluctuates on timescale of thousands to millions of years -rock weathering is a carbon sink (pulls in carbon that was degassed) --weathering takes CO2 out of the atmosphere and breaks it down into sedimentary layers, but can also release CO2 by creating silicate rocks during rock cycle -increased plants (which produce weak acids) all lead to increase chemical weathering (decreased temp = decrease CO2, inc temp = increase CO2)

Weather vs climate

-weather is the instantaneous, here and now -longer term patterns on 30 year units are climate

Arguments for leaving fossil fuels in ground as they are now

1. Humans may need them later 2. Burning them is causing the planet to warm

Negative NAO

A negative NAO indicates weakening of both the Icelandic low and Azores high, which decreases the pressure gradient across the North Atlantic. This decreased pressure gradient results in a slackening of the westerlies. The decrease in the westerlies allows cold air to build up over Canada, and this combined with below average heights (troughing) over the eastern U.S. gives the cold air a greater chance to move south and affect the eastern United States. Below average geopotential heights are often observed over the eastern U.S. during the negative phase of the NAO, which correlates to below average temperatures The eastern U.S. typically receives colder, drier air masses during the winter season in this phase Recent studies at the SCO indicate an increased potential for wintry weather in NC due to the position and availability of cold air, and a more favorable upper level pattern conducive to coastal storm tracks

Shortwave radiation

The energy that drives Earth's climate system occupies only a narrow part of this spectrum. Much of the incoming radiation energy from the Sun consists of visible light at wavelengths between 0.4 and 0.7 μm (1 μm, or micrometer = 1 millionth of a meter), sometimes referred to as shortwave radiation. Some ultraviolet radiation from the Sun also enters Earth's atmosphere, but radiation at still shorter wavelengths (X rays and gamma rays, measured in nanometers, or billionths of a meter) does not affect climate.

Key limitations of AMO

• Instrumental SST data are short in length compared to the multidecadal timescale of the AMO • The SST-based AMO index does not directly capture aspects of the AMO related to coherent variations in salinity, subsurface temperature and ocean-driven turbulent heat fluxes • Quantifying the relative importance of large scale ocean circulation (especially AMOC) vs. external radiative forcing in causing the AMO is challenging

The Hiatus

-average global temps hit a record high in 1998 due to a spectacular example of the El Niño phenomenom in 1997 -then global temps stalled in winter 1998 -reasons for hiatus: natural variability of teleconnections, radiative forcing via unexpected increase in stratospheric aerosol particles (volcanoes and water vapor content), and transient climate response (magintude of the temperature response to CO2 conentrations) -individual factors don't have significant contributions, it's the collective -PDO flip cycles every 15-30 years, with variation -ultimately there really hasn't been a hiatus

Why does Earth not act as a black body?

-because of greenhouse gas effect (anthropogenic component of GHG negatively enhances natural GHG effect)

Tracing CO2 to fossil fuel emission via isotopes

-isotopes: atom with different number of neutrons, some lighter some heavier

Absorption

-plants are really good at taking this shortwave radaton n and convertng t

Radioactive isotopes

-14C-->14N -14C half life of 5730 years

Volcanoes affect on world climate

-Ben Franklin observes in 1784 that during the summer of 1783, the climate was abnormally cold, both in Europe and back in the U.S. The ground froze early, the first snow stayed on the ground without melting, the winter was more severe than usual -result of volcanic activity - An enormous eruption of the Laki fissure system (a chain of volcanoes in which the lava erupts through a crack in the ground instead of from a single point) in Iceland caused the disruptions. The Laki eruptions produced about 14 cubic kilometers of basalt (thin, black, fluid lava) during more than eight months of activity. More importantly in terms of global climate, however, the Laki event also produced an ash cloud that may have reached up into the stratosphere. This cloud caused a dense haze across Europe that dimmed the sun, perhaps as far west as Siberia. In addition to ash, the eruptive cloud consisted primarily of vast quantities of sulfur dioxide (SO2), hydrogen chloride (HCl), and hydrogen fluoride gases (HF). The gases combined with water in the atmosphere to produce acid rain, destroying crops and killing livestock. The effects, of course, were most severe in Iceland; ultimately, more than 75 percent of Iceland¿s livestock and 25 percent of its human population died from famine or the toxic impact of the Laki eruption clouds. Consequences were also felt far beyond Iceland. Temperature data from the U.S. indicate that record lows occurred during the winter of 1783-1784. In fact, the temperature decreased about one degree Celsius in the Northern Hemisphere overall. That may not sound like much, but it had enormous effects in terms of food supplies and the survival of people across the Northern Hemisphere -volcanic eruptions produce major quantities of carbon dioxide (CO2), a gas known to contribute to the greenhouse effect. Such greenhouse gases trap heat radiated off of the surface of the earth forming a type of insulation around the planet. The greenhouse effect is essential for our survival because t maintains the temperature of our planet within a habitable range. Nevertheless, there is growing concern that our production of gases such as CO2 from the burning of fossil fuels may be pushing the system a little too far, resulting in excessive warming on a global scale. There is no doubt that volcanic eruptions add CO2 to the atmosphere, but compared to the quantity produced by human activities, their impact is virtually trivial: volcanic eruptions produce about 110 million tons of CO2 each year, whereas human activities contribute almost 10,000 times that quantity. - the more substantive climatic effect from volcanoes results from the production of atmospheric haze. Large eruption columns inject ash particles and sulfur-rich gases into the troposphere and stratosphere and these clouds can circle the globe within weeks of the volcanic activity. The small ash particles decrease the amount of sunlight reaching the surface of the earth and lower average global temperatures. The sulfurous gases combine with water in the atmosphere to form acidic aerosols that also absorb incoming solar radiation and scatter it back out into space. The ash and aerosol clouds from large volcanic eruptions spread quickly through the atmosphere -Major volcanic eruptions have additional climatic effects beyond global temperature decreases and acid rain. Ash and aerosol particles suspended in the atmosphere scatter light of red wavelengths, often resulting in brilliantly colored sunsets and sunrises around the world. -sulfates released from eruptions cause cooling

Claret Conglomerate

-The Claret Conglomerate (Fig. 1) was deposited during a warming event known as the Palaeocene-Eocene Thermal Maximum (PETM), which occurred about 56 million years ago7 . The evidence for an increase in carbon dioxide concentrations — a pronounced shift in the carbon isotopic composition of the atmosphere — is among the strongest in all of Earth's history -We know that the carbon dioxide increase at the PETM caused the oceans to become more acidic — a direct chemical consequence of adding more carbonic acid to the oceans10. The Palaeocene and Eocene were also characterized by a lack of extensive continental ice and much higher sea level— evidence that Greenland and Antarctic ice sheets would eventually melt at elevated CO2 levels, and that in an essentially ice-free world the sea level can be 70 metres or more above today's levels, -The PETM Claret Conglomerate is evidence for more extreme rainfall. But it is more difficult to ascertain if it is evidence for a wetter climate in Spain or perhaps a drier climate with more intense and episodic events7 . The same question can be asked of the change in clay assemblages deposited in marine sediments during the PETM or the widespread increase in sedimentation rates in marginal marine settings11. -Other proxies, such as the hydrogen isotopic ratio of leaf waxes, suggest an increase in moisture transport to the poles12. Collectively, these data indicate that global warming caused a significant reorganization of the global hydrological cycle with significant meteorological change in many locations. That is a simple and powerful narrative, regardless of the uncertainty associated with the details -The PETM also allows us to explore the potential consequences for ecosystems. On land, floristic changes were widespread13, accompanied by soil faunal14 and mammalian dwarfism15. Soils, especially in continental interiors, became more barren. This could have been due to increased erosion or increased oxidation of organic matter under hotter and wetter conditions16. These changes on land appear to have profoundly affected the oceans. Intense storm events stripped soil from the land and delivered nutrients to the coastal seas, burying some ecosystems while providing nutrients for others

Flux

-transfer of C from one reservoir to another -source = increase in Pg of Carbon going out -sink = decrease of Pg Carbon going in

Satellite data

-one form of remote sensing (any sensing/data collection not involving physical collection of data) -MODIS is a satellite that offers satellite images every 1-2 days