Climate Science Exam 1
Long Wave Radiation
...these materials give off long‐wave radiation in the form of thermal infrared radiation (or heat). Thus, gases, liquids, and solids in the atmosphere and on Earth's surface that are heated by the Sun radiate long‐wave infrared radiation.
Human Fingerprints on Climate
1. There is more industrial carbon in the atmosphere, and it is amplifying the greenhouse effect. 2. Less heat is escaping to space. 3. Oceans are warming from the top down. 4. Nights are warming faster than days. 5. More heat is returning to Earth's surface from the atmosphere. 6. Winter is warming faster than summer. 7. The stratosphere is cooling. 8. Physical laws of nature predict global warming consistent with observations.
Climate change is
A shift in the long-term average conditions for a location, region, or planet. Atmosphere changes (temperature...) • Hydrosphere changes (precipitation...) • Oceanic change (warming, SLR, acidification, circulation...) • Cryosphere change (glacier melt, sea ice change...) • Biosphere change (shifting species distribution, plants)
Weather
Day to day variability in atmospheric conditions.
Lutgens Ch. 2.
Earth has 2 principal motions: rotation and revolution. Rotation is the spinning of Earth about its axis. Revolution refers to the movement of Earth in its orbit around the Sun. Variation in solar energy: seasonal changes in the angle at which the Sun's rays strike the surface and the length of daylight. The variation of this angle of the Sun affects where on Earth the solar rays are most concentrated. Summer Solstice in NH: vertical rays of sun strike south latitude. Winter Solstice in NH: vertical rays of sun strike north latitude. Autumnal Equinox in NH: the vertical rays of sun strike the equator. Spring Equinox in NH: vertical rays of sun strike the equator. Energy is the ability to do work. Kinetic Energy: energy of motion. Potential Energy: energy with capability to do work. Heat is the transfer of energy into or out of an object because of temperature differences between that object and its surroundings. Mechanisms of energy transfer: 1. conduction: transfer of heat through matter by molecular activity 2. convection: transfer of heat by mass movement or circulation within a substance 3. radiation: the transfer mechanism by which solar energy reaches our planet. Radiation or electromagnetic radiation, (X-rays, visible light, heat waves, radio waves) travels as various size waves through the vacuum of space at 300,000 km per sec. Shorter wavelengths of radiation are associated with greater energy. The wave length of visible light ranges from (short, high energy) violet to (long, low energy) red. Most of the sun's energy is concentrated in the visible and near visible (infrared and ultraviolet) parts of the spectrum. Basic laws of radiation: 1. all objects emit radiant energy 2. hotter objects radiate more total energy per unit area than colder objects 3. the hotter the radiating body, the shorter is the wavelength of maximum radiation 4. objects that are good absorbers of radiation are also good emitters The perfect absorber and emitter is a blackbody. About 50% of solar energy that strikes the top of the atmosphere reaches Earth's surface. About 30% is reflected back to space. The remaining 20% of the energy is absorbed by clouds and atmospheric gases. The wavelength of the energy being transmitted as well as the nature of the absorbing or reflecting substances determines if solar radiation will be reflected or absorbed. The fraction of radiation reflected by a surface is called its albedo. Radiant energy that is absorbed, heats the Earth and is eventually reradiated skyward. Because the Earth is cooler than the Sun, its radiation is in the form of longwave infrared radiation, as opposed to the Sun's shortwave. The atmospheric gases (water and CO2) are more efficient absorbers of longwave radiation, so the atmosphere is heated from the ground up, therefore it gets cooler with increased altitude. Because of the annual balance between incoming and outgoing radiation (heat budget), Earth's average temperature remains relatively constant. Lower latitudes receive more solar radiation than is lost to space. Higher latitudes lose more heat through longwave radiation than is received. This energy imbalance between the latitudes drives the global winds and ocean currents and transfers surplus heat from the tropics to the poles. Radiation balance fluctuates with changes in cloud cover, atmosphere, and sun angle and length of daylight-- which migrates seasonally.
Radiative Equilibrium Science
Earth must radiate out to space 241.57 W/m2 of energy to keep the climate stable. Using the Stefan-Boltzmann Law we can calculate Earth's radiative equilibrium temperature, the temperature necessary to emit 241.57 W/m2. The law is expressed as the relationship I = σT4, which equates the radiant energy (I) to the fourth power of the temperature of a radiating body (T4) times a constant of proportionality (σ) equal to 5.67 × 10‐8. This can be reorganized as T = (I/σ)0.25 If Earth's surface temperature is in *equilibrium* with incoming solar radiation it must be a chilly −17.65 degrees Celsius But the 8real surface temperature is much warmer than the radiative equilibrium temperature*. This is because the temperature of Earth's surface is influenced by trapped radiation associated with certain gases in the atmosphere that absorb and then reradiate long‐wave infrared energy (greenhouse gases, effect). The difference between Earth's radiative equilibrium temperature (−17.65 degrees Celsius [0.23 degrees Fahrenheit]) and the actual surface temperature (about 14 degrees Celsius [57.2 degrees Fahrenheit]) is a good indicator of the *strength of the greenhouse effect*. If the planet had no atmosphere (or an atmosphere with no greenhouse gases), it's average surface temperature would be equal to the radiative equilibrium temperature. Of the 48 percent of solar radiation that is absorbed by Earth's surface, 25 percent is moved back into the atmosphere by evaporation, 6 percent as sensible heat moved by convection/conduction, and 17 percent by thermal infrared radiation. The atmosphere has already absorbed 23 percent of incoming energy and, with the contribution from the surface, now accounts for approximately 71 percent of incoming solar radiation. Because 29 percent of the Sun's radiation was initially reflected back to space, all (71% + 29% = 100%) of the 340.25 W/m2 (10.8 ft2) of incoming solar radiation is accounted for. The atmosphere radiates 59% of the incoming *solar radiation* back to space. This energy comes from a combination of sources: 23% comes from absorbed sunlight that is reradiated to space, 25% comes from surface heat delivered by *evaporation*, 6% from surface heat delivered by *convection/conduction*, and 5% from infrared radiation emitted by greenhouse gases. The remaining thermal infrared from the surface (12%) passes through the atmosphere and escapes out to space, and so it is not included in balancing the quantities (i.e. loss to space (59%) = gain from various sources (23% + 25% + 6% + 5%)) The equivalent of 54 percent of solar radiation resides in the atmosphere. However, satellite measurements indicate that the atmosphere radiates *thermal infrared energy* to space equivalent to 59 percent of the incoming solar radiation. Where does the roughly 5 percent difference come from? It comes from the natural greenhouse effect. The temperature of the surface becomes warmer than it would be if it were heated only by direct solar radiation. This additional heating of Earth's surface by the atmosphere is the natural greenhouse effect. The more greenhouse gases there are in the atmosphere, the more Earth's surface temperature will increase. The rising concentration of greenhouse gases in the atmosphere means that although Earth still absorbs about 71 percent of the incoming solar energy, an equivalent amount of heat is no longer leaving. This is called *Earth's energy imbalance.* The energy imbalance is the difference between the amount of solar energy absorbed by Earth and the amount of energy the planet radiates to space as heat. If the imbalance is positive, more energy coming in than going out, we can expect Earth to become warmer in the future—but cooler if the imbalance is negative. The exact amount of the current energy imbalance is hard to determine, but it appears to be approximately +0.58 ± 0.15 W/m2.
Climate
How the atmosphere "behaves" over an extended period of time (30+ years).
The human activity that cause global climate change
Human activities have indeed caused global changes in land use, air and water quality, and the abundance of natural resources Humans are causing the climate to change 170 times faster than natural forces.
A number of natural processes cause variability in Earth's climate—volcanic eruptions, the El Niño Southern Oscillation, variations in the Sun, changes in ocean circulation, and others.
In recent decades, their net effect has been to cool the climate and thus do not account for observed rapid warming.
Because it can reside in the atmosphere for more than 1,000 years, *carbon dioxide* is the most dangerous greenhouse gas.
It is released when we burn fossil fuels, sources of energy provided by burning fossil carbon, such as petroleum (fossil marine algae) and coal (fossil continental wetland plants). At higher levels of CO2 (450 to 600 ppm), sea‐level rise, changes in rainfall, severe weather events, and other consequences of global warming will come to permanently characterize the planet's surface. Carbon dioxide levels in the air have passed 400 ppm compared to a natural level of 280 ppm—an increase of over 40%. This is the highest level in millions of years. Release of planet‐warming carbon dioxide is ten times faster than the most rapid event in the past 66 million years, when an asteroid impact killed the dinosaurs
Latent Heat
Latent heat is energy released or absorbed in the atmosphere related to changes in phase between liquids, gases, and solids. Conversion from gas to liquid releases latent heat into the atmosphere.
Climate Change
Many studies indicate that the climate change observed during the 20th and early 21st centuries is due to a combination of changes in solar radiation, volcanic activity, land use, and increases in atmospheric greenhouse gases. Of these, greenhouse gases are the dominant long‐term influence, and they are causing the lower atmosphere, the air closest to Earth, to warm. This excess heat is causing dramatic changes in ecosystems, weather patterns, and other climate‐dependent aspects of Earth's surface
Global Warming
Overall, Earth's average surface temperature has increased approximately 1.0°C (1.8°F) since modern record‐keeping began in 1880 According to NASA, this change is driven by increased carbon dioxide and other greenhouse gas emissions into the atmosphere. However, mistaking short‐term climate variability (year‐to‐year changes in temperature) for long‐term trends (climate change) is a fundamental error. Overall, the global annual temperature has increased at an average rate of 0.07 degrees Celsius (0.13 degrees Fahrenheit) per decade since 1880 and at an average rate of 0.2 degrees Celsius (0.36 degrees Fahrenheit) per decade since 1970 (NOAA), the average surface temperature of the ocean and land combined has risen about 1.1 degrees Celsius (2.0 degrees Fahrenheit) over the past 136 years
Global warming
Refers specifically to the atmospheric response in terms of temperature increases due to the greenhouse effect.
Sensible Heat
Six percent of the heat leaving Earth's surface is carried by convection/conduction of sensible heat. Sensible heat is related to changes in temperature of a gas or object with no change in phase. In this case, convection is a rising current of warm air that forms because it is heated by coming in direct contact with the warm surface.
Fahrenheit and Celsius Equations
T(°F) = T(°C) × 1.8 + 32 T(°C) = (T(°F) - 32) / 1.8 A change of 1 degree Celsius (from 14 to 15) translates to a change of 1.8 degrees Fahrenheit.
What the Science Says
The global, long‐term, and unambiguous warming trend has continued during recent years. Since the last National Climate Assessment was published, 2014 became the warmest year on record globally; 2015 surpassed 2014 by a wide margin; and 2016 surpassed 2015. Sixteen of the warmest years on record for the globe occurred in the last 17 years (1998 was the exception). Since the early 1980s, annual average Arctic sea ice has decreased in extent between 3.5% to 4.1% per decade, has become thinner by between 4.3 and 7.5 ft, and is melting at least 15 more days each year. September sea ice extent has decreased between 10.7% and 15.9% per decade
Back Radiation
The heat radiated from greenhouse gases to the surface is called back radiation.
Emissions by Country
The top carbon dioxide emitters, in order, are China, the United States, the European Union, India, the Russian Federation, Japan, and Canada. These rankings include CO2 emissions from fossil fuel combustion, as well as cement manufacturing and gas flaring.
Radiative forcing
describes processes in Earth's climate system that cause an imbalance between the amount of sunlight entering the atmosphere and the amount of energy radiating to space. By 2015, the increase in radiative forcing since 1990 had increased 37 percent. Of the greenhouse gases analyzed by the IPCC, carbon dioxide accounts for the largest share of radiative forcing since 1990, and its contribution continues to grow at a steady rate. In fact, carbon dioxide alone accounts for 30 percent of the increase in radiative forcing since 1990.
Carbon Footprint
measure of the impact human activities have on the environment in terms of the amount of greenhouse gases produced, measured in units of carbon dioxide
The natural processes that cause global climate change include
plate tectonics, volcanic eruptions, extraterrestrial impacts, and variations in Earth's orbit (which we study in Chapter 4).
Stefan-Boltzmann Law
the amount of heat a surface radiates is proportional to the fourth power of its temperature. If temperature doubles, radiated energy increases by a factor of 16 (2 to the fourth power).
Albedo
Bright white snow and sea ice reflect a significant portion of the incoming light, reducing the potential solar heating. Such differences in reflectiveness are known as Earth's albedo. Earth's surface has both high albedo regions such as glaciers and sea ice and low albedo regions such as oceans and other dark surfaces, the amount of reflected and absorbed sunlight varies from place to place
Can we trust Climate Scientists?
A study of 120 research articles published in the field of climate research between 1997 and 2013 found that climate researchers do not conceal uncomfortable facts that could potentially disprove climate change. Study authors concluded, "It was gratifying to see that the scientific method is robust. It is important to show that we can trust the results of climate research, even if more work is needed about how those results are reported."
If global warming continues at its current rate
Earth will be increasingly characterized by more abnormally hot days and nights; fewer cold days and nights; more frequent and severe droughts, hurricanes, and cold‐season storms; a decrease in glaciers and ice sheets; erosion and flooding of coastal areas; and other effects capable of displacing large portions of the human population.
Water Vapor
Is about 60% of the trapped heat in Earth's greenhouse. Water vapor is responsible for 1 out of 200 molecules in the greenhouse. The atmosphere can only hold so much water vapor normally because eventually, the water vapor will turn into rain; however, if the world is heated up by other causes like carbon dioxide levels, this can increase the amount of water held in the atmosphere and trap more heat in a feedback loop. Water vapor only amplifies these temperature changes caused by other greenhouse gasses; independently of these, it cannot increase anything.
Keeling Curve
Keeling's measurements collected at Mauna Loa show a steady increase in mean atmospheric carbon dioxide concentration from about 315 parts per million (ppm) in 1958 to 411 ppm as of June 2018. Now the longest continuous record of atmospheric carbon dioxide in the world, the Keeling Curve, has become an iconic symbol of both the value of long‐term monitoring of natural systems and the powerful impact human activities have had on the planet. The seasonal concentration of carbon dioxide in the atmosphere rises in the winter and falls in the summer. This is because of photosynthesis where plants accumulate carbon in the spring and summer when they're active and release carbon back to the air in the fall and winter.
Greenhouse Gas Specifics
*Methane* is the second most prevalent greenhouse gas emitted by human activities. In 2014, CH4 accounted for about 11% of all U.S. greenhouse gas emissions from human activities. Methane is 25 times more potent as a greenhouse gas than carbon dioxide, but there is far less of it in the atmosphere and it is measured in parts per billion. When related climate effects are considered, methane's overall climate impact is less than half that of carbon dioxide; thus, methane is second only to carbon dioxide as a cause of global warming. The role of *ozone* is complicated. There is "good ozone" in the upper atmosphere that blocks the Sun's harmful UV radiation and does not play a role in climate change. There is "bad ozone" at ground level that damages people's lungs and contributes to smog. There is also mid‐altitude ozone that acts as a greenhouse gas. Greenhouse ozone, also known as tropospheric ozone, is on the rise because cars and coal‐fired power plants release air pollutants that react with oxygen to produce more tropospheric ozone. In 2014, *nitrous oxide (N2O)* accounted for about 6 percent of all U.S. greenhouse gas emissions from human activities. The compound is emitted when people add nitrogen to soil by synthetic fertilizers. Agricultural soil management is the largest source of N2O emissions in the United States, accounting for about 79 percent of total U.S. emissions. Nitrous oxide is also emitted during the breakdown of nitrogen in livestock manure and urine, which contributes 4 percent of emissions. because *chlorofluorocarbons destroy ozone*, stratospheric ozone had been declining at a rate of about 4 percent per decade until the 1980's when they became outlawed by international treaty. At the same time, a much stronger, but seasonal decrease in ozone over Earth's poles has opened an "ozone hole" over the Antarctic. *Water vapor* (a gas) is a key component of both processes. It is the most abundant and powerful greenhouse gas and an important link between Earth's surface and its atmosphere. The concentration of water in the atmosphere is constantly changing, controlled by the balance between evaporation and precipitation (rain and snowfall) Water vapor constitutes as much as 2 percent of the atmosphere and accounts for the largest percentage of the natural greenhouse effect. Human activity does not significantly affect water vapor concentrations except in local circumstances (such as irrigating fields or building reservoirs in arid areas). However, as global warming increases the average temperature of the troposphere, the rate of evaporation increases; hence, the amount of water vapor increases in a warmer atmosphere—a powerful positive feedback effect.84 Increases in other heat‐trapping gases, such as carbon dioxide, lead to more heating and thus more water vapor (increased water vapor in the atmosphere has already been observed Soot may be responsible for 25 percent of observed global warming over the past century
Greenhouse Gases
Carbon dioxide (CO2) Methane (CH4) Ozone (O3) Nitrous oxide (N2O) Chlorofluorocarbons (CFCs) Water vapor (H2O). Carbon dioxide, methane, nitrous oxide, and fluorinated gases (F‐gases) are the key greenhouse gases emitted by human activities. Carbon dioxide is released to the atmosphere by burning oil and coal for energy and by deforestation. Methane is released through concentrated animal feeding operations, waste management, and biomass burning. Nitrous oxide is released when we use fertilizers and burn biomass. Fluorinated gases are used in refrigeration and a variety of consumer products. All these gases are collecting in the atmosphere in ever‐greater quantities, and the heat they trap is changing the climate. Water vapor, the most powerful greenhouse gas, plays a significant role in the difference between nighttime and daytime temperatures. You get much larger daily temperature shifts in regions that are very dry (e.g., Arizona, where the daily range between maximum and minimum temperatures can be 27 degrees Celsius [50 degrees Fahrenheit] or more) than in regions near the ocean (e.g., Hawaii where the daily range is only about 8 degrees Celsius [15 degrees Fahrenheit]). This is because the atmosphere in areas with high humidity continues to radiate heat throughout the night, whereas in dry areas this is not the case (a) The primary greenhouse gases emitted globally include carbon dioxide from fossil fuels, industrial processes, forestry, and other land uses; methane; nitrous oxide; and the fluorinated gases. (b) The primary economic activities that lead to greenhouse gas production include electricity and heat production (25%), industrial activities (21%), agriculture, forestry, and other land uses (24%), transportation (14%), energy generation in buildings (6%), and other forms of energy uses (10%) such as fuel extraction and processing. There are four ways *human activity is known to have caused the observed rapid increase in atmospheric CO2* over the last few centuries. Various national statistics are collected that account for fossil fuel consumption, combined with knowledge of how much atmospheric CO2 is produced per unit of fossil fuel (e.g. gallons of gasoline). These are tracked by various entities and provide reproducible datasets. By examining the ratio of various carbon isotopes in the atmosphere. The burning of long‐buried fossil fuels releases CO2 containing carbon of different isotopic ratios to those of living plants, enabling distinction between natural and human‐caused contributions to CO2 concentration. Higher atmospheric CO2 concentrations in the northern hemisphere, where most of the world's population lives (and emissions originate from), compared to the southern hemisphere. This difference has increased as anthropogenic emissions have increased. Atmospheric O2 levels are decreasing in Earth's atmosphere as it reacts with the carbon in fossil fuels to form CO2
Radiative Equilibrium
Earth's planetary temperature will on its own shift toward a state called the radiative equilibrium. The basic principle underlying this is the Stefan-Boltzmann Law (described more on the next page), which dictates that the hotter an object is, the more radiation it emits... powerfully leading to an equilibrium state. As the energy absorbed by Earth's surface causes the temperature to rise, a rapidly increasing amount of heat is radiated to space, counteracting the surface warming. The amount of heat lost to space is large compared to the smaller increase in surface temperature, a process referred to as radiative cooling. Earth's surface temperature is about 14°C (58°F) on average—more than 30°C warmer than it would be if there were no natural greenhouse effect. With a temperature of 5,500 degrees Celsius (10,000 degrees Fahrenheit), the surface of the Sun radiates energy in the visible and near infrared portion of the electromagnetic spectrum (Figure 2.1). The hotter something is, the shorter its peak wavelength of radiated energy is. The average intensity of solar energy reaching the top of the atmosphere is about 1,361 W/m2. The amount of sunlight arriving at the top of Earth's atmosphere is only one‐fourth of the total solar energy, or approximately 340.25 W/m2 averaged over the entire planet. The net heating is the difference between the amount of incoming sunlight and the amount of heat radiated by Earth back to space. In the tropics, there is a net energy surplus because the amount of sunlight absorbed is larger than the amount of heat radiated. In the polar regions, however, there is an annual energy deficit because the amount of heat radiated to space is larger than the amount of absorbed sunlight (owing to the albedo). 48 percent of incoming sunlight passes through the atmosphere and is absorbed by dark surface environments such as the ocean and other water bodies, rock, and soil.
Effects of Global Warming
Storms that are provided with more moisture produce more‐extreme precipitation events. Warmer air also results in greater evaporation that dries Earth's surface, increasing the intensity and duration of drought. Global warming is producing a world that is drier, yet, ironically, prone to greater flooding. Greenland is losing ~286 billion tons of ice annually, Antarctica is losing ~159 tons, and alpine glaciers are losing over 200 billion tons of ice annually Arctic sea ice is shrinking because of global warming. Winter Arctic sea ice was the lowest on record in 2017. The global percentage of land area in drought has increased about 10%. The global occurrence of extreme rainfall has increased 12%. Heavy downpours are more intense and frequent. Extreme weather events are more frequent. Climate‐related local extinctions have already occurred in hundreds of species, including 47% of 976 species surveyed. Plant and animal extinctions, already widespread, are projected to increase from twofold to fivefold in the coming decades. Rising CO2 decreases the nutrient and protein content of wheat, leading to a 15% decline in yield by mid‐century. By 2050, climate change will lead to per‐person reductions of 3% in global food availability, 4% in fruit and vegetable consumption, and 0.7% in red meat consumption. These changes will be associated with 529,000 climate‐related deaths worldwide. The world's oceans have warmed at twice the rate of previous decades and the extra heat has reached deeper waters. Today, global mean sea level is rising three times faster than it was in the 20th century. Average pH of ocean water fell from 8.21 to 8.10, a 30% increase in acidity. Ocean water is more acidic from dissolved CO2, which is negatively affecting marine organisms Air temperatures have risen and, as a result, heat waves and drought are more common. Storms have increased in frequency and intensity, seasons have shifted, and the ranges of plant and animal life have moved. The glaciers are melting, global sea level is rising and accelerating, and the temperature of the oceans has increased.
Kyoto Protocol and Paris Agreement
The Kyoto Protocol required that by 2012, industrialized countries such as the United States reduce their carbon dioxide emissions to 7 percent below the levels measured in 1990 and by 20 percent by 2020. As the leading developed nation, the United States has historically produced the bulk of the world's carbon dioxide emissions. Then, in 2007, China's output surpassed that of the United States. Today, powerful economic growth in India is rapidly escalating emission production there as well. The Paris Agreement lays out global commitments on climate change reduction measures from 2020. The agreement entered into force with the joining of at least 55 countries that together represent at least 55 percent of global greenhouse gas emissions. On April 22, 2016 (Earth Day), 174 countries signed the agreement in New York. The expected primary result of the agreement is to limit global warming to less than 2 degrees Celsius (3.6 degrees Fahrenheit), compared to preindustrial levels, and to reach zero net anthropogenic greenhouse gas emissions during the second half of the 21st century. 1. Governments of the world need to end the practice of subsidizing the production of fossil fuels. These subsidies often take the form of tax relief for oil and coal companies and outright investments by nations in producing fossil fuels. Experts have estimated that over $600 billion in subsidies is provided every year to offset expenses in producing carbon fuels. 2. Put a global tax on carbon pollution. By taxing carbon, we would be charging those who use carbon fuels for the damage they do to the environment and the threats to public health and safety, a justifiable cost that will decrease the use of fossil fuels and increase the production of clean energies. 3. Invest in greener technologies that can take the place of dirty carbon energy.
Feedbacks
Water Vapor Feedback: As the temperature of the atmosphere rises, more water is evaporated and the total concentration of water vapor increases. Hence, it accumulates in the atmosphere as a positive feedback to the warming caused by other gases, principally carbon dioxide. A climate forcing can trigger feedbacks that intensify (*positive feedback*) or weaken (*negative feedback*) the original forcing. An example of a feedback is when global warming causes the loss of ice at the poles, which reduces Earth's albedo, causing less reflection of incident solar radiation, leading to more absorption by the atmosphere and surface, causing further warming that leads to more ice loss. A tipping point 68 occurs when a positive feedback cannot be recovered, implying that human efforts to decrease greenhouse gas emissions might not be sufficient to stop the warming (permafrost melting and releasing methane)..
