Exam #4: Instructional Objectives

Compare a molecule of methane and carbon dioxide in terms of (a) ability to absorb infrared radiation and (b) average length of time they remain in the atmosphere.

(a) a methane molecule is 26 times more effective at infrared absorption than is a molecule of CO2 (b) destroyed on this timescale by chemical reactions. Carbon dioxide lasts much longer, and the mechanism of CO2 removal is more complex,

Describe what meta-analysis data say about (a) whether or not species are migrating toward cooler latitudes, and (b) whether or not events such as breeding, nesting, flowering, budburst, and ending migratory journeys are occurring earlier in the spring.

(a) species were moving northward at an average of about 6 km per decade, or upward in elevation at 6 m per decade. (b) Significant springtime events in the lives of species— breeding, nesting, flowering, budburst, ending migratory journeys— were happening earlier in some 62% of species studied; in one subset of 172 species, these spring events were advancing at the rate of 2.3 days per decade.

Describe the effect of global warming in the number of (a) extremely cold days during winter and (b) extremely hot days during summer

(a) studies point to a decrease in the number of extremely cold days over some regions, which may lengthen the growing season (the frost- free period) by as much as several weeks. (b)There's also evidence for increases in the number of extremely hot days and in heat waves during which well- above- average temperatures persist for days.

Use Figure 14.5 to describe whether there is a warming or a cooling trend, from 1980 to the present, in these layers of the atmosphere: (a) surface air, (b) troposphere, and (c) stratosphere.

(a) warming trend in surface air (b) warming trend in troposphere (c) cooling trend in stratosphere

Describe whether the strength of the evidence is strong or weak regarding the association between global warming and (a) hurricane strength, (b) precipitation intensity and short duration, (c) amount of precipitation

(a) weak association; the IPCC gives only low confidence that there has been a global increase in intense storm activity over the past century— although it finds such an increase virtually certain in the North Atlantic since 1970.shows that the rise in hurricane energy correlated closely with rising sea- surface temperatures through the late twentieth century, but that the correlation has broken down in recent years. (b) stronger association; precipitation is now falling in shorter, more intense events (c) strong toward increased precipitation. Over the past century, some time periods have seen more global precipitation and some less. Precipitation trends vary geographically as well, with dryer areas tending to get dryer and wetter areas wetter.

Describe positive and negative forcing in terms of (a) net energy inflow or outflow, and (b) cooling or warming.

(a)The forcing is considered positive if the imbalance results in a net energy inflow to the Earth system and negative if it results in a net outflow (b) A positive forcing results in warming and a negative forcing results in cooling.

Compare trees and crop plants in terms of (a) light reflectivity and (b) forcing effect.

(a)crop plants are generally more reflective than trees, (b)so replacing forests with cropland increases albedo and thus decreases the absorbed solar energy— a negative forcing

Describe the Younger Dryas events in terms of (a) what it was, (b) when did it happen, and (c) what was its likely cause.

(a)swung the Arctic back into ice- age conditions for some 1,500 years (b) starting about 12,000 years ago (c) from sudden changes in ocean circulation that occur when an influx of freshwater from melting ice alters the salinity, and hence the density, of ocean water

Describe the effect of global warming on (a) ocean acidity, (b) amount of carbonate available to marine organisms

(a)the uptake of anthropogenic carbon has already lowered the oceans' average pH by 0.1. With a doubling of atmospheric CO2, the oceans' pH could fall by another 0.3-0.4 units . Although the ocean would still be alkaline (pH > 7), at these lower pH levels, some species of high- latitude marine plankton may have trouble surviving. Because such organisms are at the base of marine food chains, the populations of larger marine species could suffer as well. (b)But carbonate is what marine organisms use to build shells and other structures, such as the rigid skeletons of corals. So adding CO2 to the oceans has the net effect of decreasing the amount of carbonate available to marine organisms.

Describe the effect of global warming on whether there will be more or less precipitation in (a) high latitudes, (b) rainy tropical regions, (c) in midlatitudes, and (d) dry tropical regions.

(more)precipitation and river flows are expected to increase at high latitudes and in some parts of the (rainy) tropics while decreasing at mid-latitudes and in dry tropical regions.

Assuming humans completely stop adding carbon dioxide to the atmosphere today, use Figure 13.12 to estimate how much of it will remain in the atmosphere after about 50-100 years and after 1000 years

1. 1 fraction of CO2 will remain in the atmosphere after 50-100 years 2. 0.2 fraction of CO2 will remain in the atmosphere after 1000 years

List five independent pieces of evidence that point at humans as the cause of the increase in carbon dioxide concentration in the air

1. Because fossil fuels are commercial commodities, we have a good quantitative handle on the rate at which we burn them. The buildup of atmospheric CO2 is consistent with the emissions from fossil fuel combustion. 2. Carbon dioxide is a well- mixed greenhouse gas, but its concentration is marginally higher in the Northern Hemisphere, where most fossil fuel combustion takes place. 3. The ratio of the radioactive isotope carbon- 14 to carbon's common stable isotope, carbon- 12, in the atmosphere has been decreasing. Carbon- 14 is formed in the atmosphere by cosmic rays, and it's continually incorporated into living organisms. The result is a balance between uptake of C- 14 and its radioactive decay— a balance that maintains a steady ratio of C- 14 to C- 12 in living matter. Carbon- 14 uptake stops when organisms die, but radioactive decay continues. Thus long- dead matter is essentially devoid of C- 14. So the observed decrease in the ratio of C- 14 to C- 12 in Earth's atmosphere is consistent with the atmosphere being flooded with ancient carbon in which C- 14 had long since decayed. That ancient carbon is the carbon that was trapped underground in fossil fuels. 4. Additional isotopic evidence comes from a decline in the ratio of the stable isotope C- 13 to the more abundant C- 12 in the atmosphere. Because it's lighter, C- 12 participates more readily in chemical reactions, making it easier for photosynthetic organisms to take in carbon dioxide containing C- 12 than C- 13. Therefore the ratio of C- 13 to C- 12 is lower in plants than in the atmosphere. So the observed decline in the proportion of atmospheric C- 13 is indicative of plant- derived carbon entering the atmosphere. Again, that new atmospheric carbon is coming from fossil fuel combustion. 5. Finally, the concentration of atmospheric oxygen (O2) is dropping— not a lot, but measurably— and the rate of its decline is consistent with O2 joining with carbon to make CO2. Once again, that's an indication of fossil fuel combustion altering the composition of Earth's atmosphere.

Use Figure 13.5 to list the top three major sources of global anthropogenic carbon dioxide emissions in the early 21st century.

1. Coal - 37% 2. Oil- 29% 3. Natural gas- 16%

Use Figure 13.10 to list the top three reservoirs of carbon on Earth's systems (in Gigatons, or Gt).

1. Deep Ocean ( 38,000 Gt) 2. Soil (2,000 Gt) 3. Fossil fuel reserves (2,000 Gt)

Use Figure 14.8 to list four US cities that were covered by polar ice sheets almost two miles deep during the last ice age (25,000 years ago).

1. New York 2. Chicago 3. Bismarck 4. Seattle

Use Figure 13.10 to list the top two carbon flows (arrows) on Earth's systems (in Gigatons, or Gt).

1. Photosynethesis (123 Gt) 2. Air water exchange (78 Gt)

List eleven expected environmental consequences of global climate change

1. make Earth warmer. 2.It will also bring rising sea level, 3.altered precipitation patterns, 4.changes in soil moisture content, 5. increases in some extreme weather events, 6. more flooding and more drought, 7.alteration of natural climate cycles such as El Niño, 8.changes in species ranges and the composition of ecosystems, 9.advances of tropical diseases into formerly temperate regions, 10. in ocean circulation, 11.melting of Arctic permafrost

Describe four policies that Europe implemented and that have resulted in cutting their energy consumption and greenhouse emissions by half.

1.European countries have chosen high gasoline taxes to help curb consumption. 2.Even many smaller European cities have vibrant public transportation, and reliable, convenient rail systems link European communities. 3.Zoning regulations encourage city-, town-, and village- based development over suburban and exurban sprawl. 4. As a result of such tax, public transportation, and community development policies, Europeans have fewer cars per capita, and their cars are smaller and more fuel efficient

List three reasons why the public should trust climate models.

1.First, climate models are based on long- established scientific principles and measured properties of basic materials— science that governs the behavior of matter and energy in realms far beyond climate. 2.successfully reproduce present and past climates. 3. reproduce the geographical distribution of temperature changes, and they do an excellent job of describing the observed temperature structure throughout the atmosphere; they give reasonable agreement with observed variations in precipitation, cloudiness, and ice cover, and the ocean components of coupled models correctly follow the spread of anthropogenic trace chemicals throughout the oceans. Climate models also reproduce changes in patterns of natural climate variation.

Describe two reasons why accurately predicting future climates is not possible.

1.First, we don't know enough about every detail of the climate system— the myriad feedbacks, the surprising nonlinear effects, the behavior of clouds, and the complex interactions of land, sea, air, ice, and biosphere— to make precise predictions of what will happen when and where. 2.Second, we can't predict future human behavior, yet humans are now major players in the global climate system

List four negative effects of Arctic sea ice loss.

1.Loss of sea ice affects the local ecology and, in particular, endangers wildlife such as polar bears and seals; this, in turn, affects indigenous peoples of the Arctic. 2.increased precipitation 3.changes in the ozone hole 4. change in wind patterns over the Southern Ocean.

Describe four infrared-altering geoengineering technologies

1.One widely discussed approach is to fertilize the oceans with iron, a nutrient that currently restricts the growth of plankton. More plankton performing photosynthesis would increase the downward flux of carbon from atmosphere to oceans, helping counter the upward flux from fossil fuel combustion. 2. using chemical reactions to capture atmospheric carbon dioxide, perhaps with "artificial trees" that expose their reactive "leaves" to the air, or 3.altering ocean chemistry so that the oceans absorb more CO2. 4.Simpler CO2-absorption technologies range from planting more natural trees to grinding up rocks and spreading them over vast land areas to accelerate the natural weathering process that, on the longest timescales, takes CO2 from the atmosphere.

Explain two reasons why models can develop projection of future climate but not actual predictions.

1.That's partly because climate models advancing decades and centuries into the future can't claim the precision of tomorrow's weather prediction. 2. It's also because future climate depends on factors that are unpredictable, such as volcanic eruptions and human behavior.

Describe four factors that make measuring sea level difficult

1.The sea surface is rarely smooth, 2. and it's subject to tidal variations. 3.Even weather affects sea level, 4.as the sea rises beneath regions of low atmospheric pressure

List three factors that make cities generally warmer than rural areas.

1.Urban energy use 2.albedo changes 3.more black pavement, fewer plants) make cities warmer than the surrounding countryside.

Use Figure 14.1 to describe three distinct temperature trends in different eras, starting in 1910

1.an obvious rise beginning around 1910 and ending around 1945, 2. a steady or slightly declining temperature from 1945 to about 1975, 3.) a steep rise beginning in the mid- 1970s and continuing to the present.

List five insect-borne tropical diseases that are becoming more common in temperate (mid-latitude) regions due to climate change.

1.malaria, 2.Lyme disease, 3.West Nile virus, 4. Zika virus, 5.dengue fever

List two main factors that contribute to sea level rise

1.melting of ice 2. the thermal expansion of water; The ocean acts like a giant thermometer as its water increases in volume, and its level therefore rises, with increasing temperature

Use Figure 14.3 to describe whether there is greater warming (a) over land or sea, (b) in the Northern or Southern Hemisphere, and (c) in the Arctic or Antarctic latitudes.

1.note the greater warming over land 2.in the northern hemisphere, 3.and especially at arctic latitudes.

Describe two ways in which humans alter the hydrologic cycle

1.our depletion of groundwater moves water from natural underground aquifers to the oceans. 2.Dams and agricultural irrigation have the opposite effect, blocking the natural flow of water to the oceans and instead sending much of it to the atmosphere via evapotranspiration.

Describe three impacts of a 1-2 meter rise in sea level on human society.

1.would submerge some 16% of the country's land and displace 17 million people. In addition, an overall sea- level rise would add to the highest tides and storm surges, increasing the risk of flooding over much greater areas. Globally, such flooding could affect hundreds of millions of people. 2.leads to reduced agricultural productivity and exacerbates the growing scarcity of freshwater resources 3.may inundate estuaries, where, as we saw in Chapter 8's discussion of tidal energy, the interplay of saltwater and freshwater helps to nourish rich ecosystems that act as the nurseries for much of the world's marine life.

State the approximate year that scientist use as a baseline for calculating global average temperatures based on sufficient reliable thermometer-based temperature measurements.

1850 - Although the mercury thermometer was invented in the early eighteenth century, records of direct temperature measurements before about 1850 are simply too sparse for us to compute a meaningful global average from them. And even when we do have enough data, combining those temperature measurements requires care.

Compare the scientific consensus of the Intergovernmental Panel on Climate Change (IPCC) about whether humans were responsible for climate change in their 1995 and 2013 reports.

1995, the scientists and policymakers writing the IPCC's Second Assessment Report cautiously noted "a discernible human influence on climate." In its 2013 Fifth Assessment Report, the IPCC was still clearer: "Evidence for human influence has grown since AR4 [the IPCC's 2007 Fourth Assessment Report]. It is extremely likely that human influence has been the dominant cause of the observed warming since the mid- 20th century."

Describe to what extent the U.S. Department of Defense and the Pentagon are considering the effects of climate change.

A 2015 report by the U.S. Department of Defense identified climate change as a national security concern and cautioned that it has the potential to exacerbate political instability around the globe, while a 2016 Pentagon directive ordered military leaders to account for climate change in virtually all military activities.

Use Box 15.2, to explain why small changes to mean temperatures can increase the chance of extreme events.

A slight change in the mean value— for example, a degree or so of global warming— can nevertheless cause large changes in the probability of rare extreme values. Figure 15.13 shows why. The figure depicts two hypothetical temperature distributions with slightly different means. The probability of a given temperature occurring is proportional to the height of the curve at that temperature, and the probability of temperatures in a given range depends on the area under the curve in that range. A slight increase in the mean has little effect on the distribution of the more probable values near the mean, but it substantially raises the curve at the right- hand end of the distribution.

Explain two advantages and one disadvantage of high-resolution climate models

Advantages: can simulate regional variations in climate and is able to describe small- scale features of oceanic and atmospheric circulation. Disadvantages: But high resolution comes at a price (costly)

Explain why aerosols are not well understood as greenhouse gases.

Aerosol forcing is further complicated by the presence of different types of aerosols that provide positive or negative contributions to the overall aerosol forcing equation.

Use Box 14. 1 and Figure 14.2 to describe the data agreement in temperature anomaly of three independent climate research groups, the Climatic Research Unit of the University of East Anglia (CRU), the NASA's Goddard Institute for Space Studies (GISS), and NOAA's National Climatic Data Center (NCDC)

Although the three graphs aren't identical, they show remarkable agreement both in overall trends and in many details. All have a strong peak in 1998—probably the result of an intense El Niño that year. 1998 stood as the warmest year into the early 2000s, when 2005 edged it out in all three datasets. 2010 then brought a new record. The years 2014, 2015, and 2016 all set global temperature records— an unprecedented three years in a row of record- breaking warming. In addition, 2016 saw the 3 warmest months in the entire industrial- era temperature record, part of a streak of 16 consecutive months that set new month- specific records.

Describe the current rate of increase in (a) carbon dioxide concentration (in ppm/year), and (b) global average temperature (in °C/decade).

Atmospheric CO2 is currently increasing at more than 2 ppm each year, and the global average temperature is rising at about 0.2°C per decade.

Use Figure 14.1 to describe whether most temperatures before and after 1975 were at average (anomaly = 0), below average (negative anomaly) or above average (positive anomaly)

Before 1975 most temperatures were below average (negative anomaly). After 1975 most temperatures were above average (positive anomaly).

List an aerosol that has a warming effect, especially when it fall on snow and melts it.

Black carbon absorbs sunlight and contributes to warming— an effect that's significant when it falls on snow

Use Figure 13.9a to describe the change in carbon dioxide concentration over the past 1000 years

Carbon dioxide concentration over the past thousand years shows a sharp rise that coincides with the industrial era: by 2015 the concentration had passed 400 ppm.

Use Figure 15.16 to describe the effect of climate change on the volume flow of the Atlantic Meridional Overturning Circulation (AMOC) from 2000-2100.

Climate change has a large impact on the volume flow of AMOC; from 2000-2100 the graph showed a rapid decline average flow of the aMOC today is some 15-20 Sv, so the decline shown here represents a reduction of about 50%.

Describe the "caution" the author provides regarding the paradox of energy intensity and energy consumption.

Energy intensity is not a direct indicator of energy consumption. We can make refrigerators more efficient, but if we become so affluent that we put two or three refrigerators in each home, then we defeat those gains. We can make cars twice as efficient, but if we drive them twice as far, then we've gained nothing

Use Figure 14.1 to describe the size of the error bars (estimated uncertainty) and what this means for reaching conclusions about the overall temperature anomaly trend

Error bars show approximate uncertainty at four different times. For the first few decades shown, the estimated uncertainty is on the order of ±0.2° C— a little larger than typical year- to- year fluctuations. By 1950, with an increase in the number of reporting stations and their global distribution , the uncertainty drops to roughly ±0.05°C. Although these uncertainties are significant, they're far smaller than the overall trends, which means we can have considerable confidence that those trends are real features of Earth's recent climate history

Explain why the atmospheric cooling effect of sulfate aerosols is not enough to cancel out the warming effect of carbon dioxide

First, the overall aerosol forcing simply isn't great enough to counteract greenhouse warming. Second, sulfate aerosols have relatively short atmospheric lifetimes, so they don't get well mixed, and thus their climatic effect tends to be localized. Direct forcing by sulfate aerosols may indeed cause cooling in regions downwind of heavily industrialized areas, but this effect can't compensate globally for greenhouse gas warming.

Use Box 15.1 to list what is the world's most sophisticated climate model that you can consult.

HadGEM3—for Hadley Centre Global Environment Model 3—is the Hadley Centre's state- of- the- art climate model

Describe two factors that make scientists think that the actual Earth's climate short-term sensitivity can be more than 4.5 °C

However, the statistical distribution of possible climate sensitivities has a longer "tail" at the high end, so there's a significant chance that the actual sensitivity is higher than 4.5°C. Furthermore, these values don't account for very long- term processes such as the melting of large ice sheets, and when these processes are taken into account, the climate sensitivity over thousands of years could be even higher

Use Figure 15.9 to indicate the expected carbon dioxide concentration by 2100 if we keep a "business as usual" scenario of fossil fuel use.

If we keep the business as usual scenario of fossil fuel the excepted carbon dioxide concentration by 2100 is 1,200 ppm

Describe the contribution of scientists Paul Crutzen, Mario Molina, and F. Sherwood Rowland to science.

In 1974, however, chemists Paul Crutzen, Mario Molina, and F. Sherwood Rowland showed that CFCs rising into the stratosphere would decompose under the influence of solar ultraviolet, and that the chlorine freed by this decomposition would destroy ozone without itself being used up.

Describe the global average temperature goal of the 2015 international Paris Agreement.

In the words of the Paris Agreement, the goal of the parties is to "strengthen the global response to the threat of climate change" by "holding the increase in the global average temperature to well below 2°C above pre- industrial levels and pursuing 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."

Describe the purpose of the international agreement known as the Montreal Protocol of 1987

It required a gradual phaseout in the production and use of CFCs and other ozone- depleting substances.

Explain why it is difficult to take the planet's temperature.

It's not easy to take a planet's temperature, even when we live on it. Temperature varies with geographical position, with altitude and ocean depth, and with time. Air, water, and land temperatures are generally different. So there are many measures of Earth's temperature.

Use Box 13.1 to describe the purpose of the IPCC (Intergovernmental Panel on Climate Change).

Its purpose is to assess our scientific knowledge of climate change, the impacts of that change on human and natural systems, and the steps we might take to adapt to climate change or to mitigate its effects

Use Table 15.1 to list the ice sources has the largest potential sea-level rise and the one that has smallest potential sea-level rise.

Largest potential sea-level rise: Antarctica (62 m) Smallest potential sea-level rise: Mountain glaciers (0.24 m)

Describe the current status of mountain glaciers and polar ice compared with several decades ago

Mountain glaciers are shrinking across the globe, with many exhibiting dramatic reductions (Fig. 14.11). A few glaciers are growing, but that's because glacial behavior is governed by a balance between snowfall and melting Polar ice is also shrinking: Both the Arctic's floating sea ice and the continental ice sheets of Greenland and Antarctica are melting.

Compare the greenhouse gas emissions of grass-fed beef and regular beef.

No matter how they're fed, cattle are going to produce methane and manure. You might cut down a little on emissions from energy use, but again, that's a small fraction of beef- associated emissions

Use Table 13.1 to list the gas with the highest global warming potential over a short time scale (20 years) and the gas with the highest global warming potential over a long time scale (100 years).

Over a short time scale (20 years) - CFC- 11 (CCl3F) (Trichlorofluoromethane) Over a long time scale (100 years)- CF4 (Carbon tetrafluoride

Use Figure 14.7 to state when was the last time that the average temperature was as warm as the present, and what happened in between these eras.

Roughly 130,000 years ago, Earth also saw a short (10,000 years or so) spell of warmer- than- normal temperatures. Between these brief, warm interglacials is a much longer ice ageshows two warm interglacials separated by an ice age lasting roughly 100,000 years. This pattern of ice ages and interglacials persists for nearly a million years into the past.

Use Figure 14.12b to describe by how much the extent of summertime Arctic sea ice has declined since 1979

Shows a plot of the decline over time. sea- ice extent has declined by nearly 50% since 1980, and the decline has accelerated in recent years.

Explain three reasons why simpler climate models are sometimes preferable to large-scale models.

Simpler models, 1. run quickly 2. allow researchers to carry out numerous experiments with different initial conditions, assumptions about greenhouse gas emissions, and other parameters. 3.And because simpler models involve fewer details, it's often easier to interpret the results or focus on a particular physical process of interest.

Use Figure 13.8 to describe the change in the concentration of carbon dioxide since 1750 to the present.

Since 1750 it showed a gradual increase up until around 1975 the concentration of carbon dioxide skyrocketed. . in 2015 the annual average Co2 concentration exceeded 400 ppm for the first time.

Describe a species that will struggle to move poleward fast enough because climate change is happening too rapidly.

Some species, especially trees, may not be able to move poleward fast enough to match the changing climate. Thus they may die off at the warmer end of their range without having had time to advance and populate newly suitable poleward regions. The result could be a decline in some forest ecosystems, including animal species that require particular forest types.

List six expected impacts of global warming on society.

Some, such as increased disease and mortality rates among the elderly and the urban poor, will result directly from increased temperatures— especially from extreme heat waves, whose probability will increase disproportionately, as described in Box 15.2. Demand for air conditioning will stress already frail electrical infrastructures, reducing their reliability and increasing brownouts as well as fuel consumption. And tropical diseases may spread to higher latitudes.

Explain the difference between equilibrium and transient responses in climate sensitivity.

Sometimes climate sensitivity is qualified by whether it describes the immediate response— sometimes called the transient response— or the long- term equilibrium response

Describe a possible nonlinear consequence if freshwater from melting Arctic ice shuts off the ocean current system

Such an event could be caused by a decrease in ocean salinity and density-driven by an infusion of fresh water from melting Arctic ice. Ironically, the now- benign climate of Britain might rapidly cool in response to a warming-induced ice melt

List one weather formation that is caused by sulfate and other aerosols.

Sulfate and other aerosols act as nuclei on which atmospheric water vapor condenses, forming clouds

Use Figure 14.9 to describe the correlation between carbon dioxide and temperature anomaly over the last 150,000 years.

Temperature and atmospheric CO2 show a tight correlation through the last ice- age cycle, as evident in this record from the Vostok ice core in antarctica. This correlation involves complex feedbacks between temperature and CO2 concentration. Both plots stop before the industrial era.

Explain two reasons why it is better to use temperature anomalies to track global warming compared with absolute temperatures.

That's partly because temperature changes are well correlated over large distances, but absolute temperatures aren't. It's also because two thermometers that might not agree perfectly on the actual temperature will nevertheless give the same response to a given temperature change.

Describe six factors that make it hard to pinpoint the overall effect of clouds on climate computer models

The details depend: 1. on the type of cloud 2.its three- dimensional shape 3. whether it's made of water droplets or ice crystals, 4.the size of the droplets or crystals, 5. the cloud's altitude 6. and a host of other factors such as their geographical and temporal distribution

Use Figure 14.15 to compare the effect of "Natural only" climate forcing (light gray) and "Natural + manmade" climate forcing (dark gray) in the observed temperature (black line).

The effect of "Natural only" climate forcing (light gray) is typically at or significantly below the observed temperature (black line). The only time it was higher than the observed temperature was around 1910. While "Natural + manmade" climate forcing (dark gray) was either at or above the observed temperature, with the only time being significantly below was around 1905.

Use Figure 15.14 to describe the trend in sea level rise from current levels to the year 2100

The general trend is that it sea level will steadily rise, RCP2.6 continues to rise throughout the remainder of the graph while RCP8.5 dramatically increases from the year 2040 on

Describe the benefit of the Gulf Stream to Europe.

The water's warmth tends to decrease its density, whereas the high salt concentration tends to increase it. As the Gulf Stream flows northward and cools, its density therefore increases,cool the climate of northwestern Europe.

Describe how political negotiations watered down the 1997 Kyoto Protocol mandate for industrialized nations to reduce greenhouse gas emissions by 2012.

These mandates applied only to the most industrialized countries ( so- called Annex 1 countries), and the protocol counted not only actual emissions reductions, but also market- based emissions trading and technology transfer to less developed countries. Furthermore, the Kyoto emissions limits were set by negotiations among participating countries, which resulted in less ambitious limits as each country tried to ensure that its limits would be relatively easy to reach. Some 37 countries agreed to undertake the Kyoto emissions reductions. The United States, at the time the world's foremost emitter of greenhouse gases, signed the agreement, but it was not ratified in the U.S. Senate. When George W. Bush assumed the presidency in 2001, he canceled the United States' involvement in the Kyoto Protocol. Because China wasn't an Annex 1 country under the protocol, that left the world's two leading emitters out of the agreement

Explain why scientists are particularly concerned with the West Antarctic Ice Shelf.

This alone alone could raise sea level by about 3 meters, or 10 feet. This amount would be enough to flood many coastal cities, and it would significantly reduce the land area of low- lying regions

Use Example 13.1 to estimate the effect on Earth's average temperature can change with a 5 W/m2 forcing.

Thus the temperature goes up about 1 K, or 1°C.

Explain the effects of ozone in the troposphere and the stratosphere

Tropospheric ozone, which results from photochemical reactions involving air pollutants, is both a noxious, toxic pollutant and a greenhouse gas. Stratospheric ozone is a different story altogether. It forms naturally from the action of solar ultraviolet radiation on oxygen in the upper atmosphere. By absorbing ultraviolet, stratospheric ozone protects us surface dwellers from this harmful radiation.

Describe the "deep decarbonization" strategy to cut greenhouse gas emissions.

Unlike the wedge approach, deep decarbonization tailors its recommendations to individual countries and mixes policy considerations with technological ones. A main goal of deep decarbonization is to decouple countries' economic activity from their carbon emissions, lowering per capita emissions in the most developed countries to below about 2 tonnes per person while maintaining or enhancing GDP.

Describe why scientists need to apply mathematical corrections to raw air temperature data recorded from early weather stations.

Urban energy use and albedo changes (e.g., more black pavement, fewer plants) make cities warmer than the surrounding countryside. As cities grow, the locations of weather stations on their outskirts become increasingly urbanized, which means the stations begin to record higher temperatures. Absent any real global temperature change, this urban heat island effect would produce a warming trend in temperature records from urban weather stations.

Use Figure 14.6 to describe the overall temperature anomaly trends over the past millennium

a gradual decline in temperature over the first 900 years, followed by a sharp upturn from 1900 to the present

Describe one disadvantages of sunlight-reducing geoengineering technologies.

advantage: aim to restore balance by reducing incoming solar energy to counter the effect of greenhouse gases in blocking outgoing infrared. Disadvantage: inject sulfur dioxide into the stratosphere. Like SO2 emitted by coal burning, the injected SO2 would react with other components of the atmosphere to create highly reflective sulfate aerosols, which would reflect sunlight back to space. Therefore, the addition of these particles would result in a negative forcing and thus produce a cooling effect.

List three proxies that are used a as "stand in" for temperature values before 1850.

are tree rings, 1.whose width and density reflect climate conditions on a year- to- year basis; lake sediments, 2.whose thickness and composition reflect the thermal energy available to produce snowmelt streams that carry sediments into lakes; coral reef bleaching, 3.which occurs when coral organisms are stressed by rising temperatures; and isotope ratios (see Box 14.2).

Describe the climate of roughly the past 10,000 years and why these conditions were essential for human civilization.

climate of roughly the past 10,000 years has been substantially more stable than that of the last ice age and the beginning of the current interglacial. This is not to say that there hasn't been significant variation, but that variation has been relatively gradual and modest. This stable period coincides with the development of agriculture, and many would argue that a stable climate was essential for this major advance in human civilization.

Describe whether the impacts of climate change will affect developed or developing countries the most.

developing countries will be more impacted by climate change Low- lying coastal regions, for example, will suffer more from sea- level rise; continental interiors will see more drought; and high latitudes will warm disproportionately. That's because wealthier countries will be better able to adapt to and counter deleterious effects. Wealthy countries can build protective seawalls to ward off the rising oceans; they can engineer massive water projects to ensure continuing supplies of freshwater; they can outbid poorer countries if declines in domestic agriculture require increased food imports; their advanced health care systems can better cope with spreading tropical diseases; and their robust economies can speed recovery from extreme weather events

Use Figure 14.4 to describe the change in the ocean heat content since 1970

has been increasing (Fig. 14.4), an indication that the oceans are absorbing some of the energy trapped by greenhouse gases.

Use Figure 15.12 to indicate in what region the increase in global surface air temperature is expected to be the greatest.

increases are greatest in the arctic

Describe how the sun's energy output is expected to change over billions of years and whether this change will be relevant or not over decades or centuries of human history

it has been increasing and will continue to do so. That long-term trend has significant climate implications over the lifetime of our planet, but it's irrelevant on scales of decades to centuries.

Describe what date range is used to obtain the average temperature used as a reference for describing temperature anomalies, and what a positive and a negative anomaly mean.

it's the average temperature for the period from 1961 to 1990. A negative anomaly indicates a global temperature below this average, and a positive anomaly indicates a higher temperature.

State Earth's climate short-term sensitivity range, in °C, if atmospheric carbon dioxide concentrations double from 280 ppm to 560 ppm.

likely increase by somewhere between 1.5° C and 4.5°C once the climate came to equilibrium after a doubling of CO2 from its preindustrial 280 ppm.

Use Figure 13.4 to classify the climate forcings since 1750 as (a) positive/warming, (b) negative/cooling, (c) strong (magnitude is more than one), and (d) weak (magnitude is less than one).

positive/ warming

Describe the "wedge" approach to cut greenhouse gas emissions.

relies on greater energy efficiency, nonfossil energy sources for electric power generation and industry, and switching to carbon- free electricity, hydrogen, or biofuels for transportation

Use Figure 15.7 to predict the global temperature increase 70 years from now, assuming carbon dioxide concentration will increase by 1% yearly.

results from 35 climate models in the CMIp5 project, showing response to a 1% per year increase in atmospheric CO2, resulting in a CO2 doubling at about 70 years. shows a range of temperature increases from about 1°C to 2.5°C, with the mean just below 2°C.

Use Figure 15.11 to compare temperature increases under both "business as usual" (RCP8.5) and "decreasing carbon dioxide" (RCP2.6).

shows projected temperature rises through the twenty- first century for RCP2.6 and RCP8.5, including the range of values in each ensemble of model runs. only rpC2.6 holds the global temperature increase to the widely accepted goal of less than 2°C above the preindustrial level (which is at about −1°C on this graph). The two begin to split at the year 2025 where RCP8.5 is much higher than RCP2.6 throughout the remainder of the graph

Use the inset in Figure 13.8 to explain why the small graph that shows carbon dioxide concentration since 1960 has a vertical zigzag pattern.

shows, they track the seasonal variations in CO2 each year, which reflect the increased uptake of CO2 by trees and plants during the Northern Hemisphere's growing season and the corresponding reduction of this uptake during winter.

Use Figure 15.8 to describe what happens to the temperature change if carbon dioxide concentration increases from 450 to 1000 ppm over the next 300 years.

shows, we can expect correspondingly greater temperature increases in the current century, with still higher equilibrium values several centuries hence.

State about what percentage of the world's species risk extinction due to climate change under a "business-as usual" (RCP8.5) scenario.

some 16% of the world's species risk extinction due to climate change under the business- as- usual RCP8.5 scenario.

Compare the energy for each passenger-mile used by commercial airplanes in the 1970s and today.

the U.S. airline fleet today uses only about one- third of the energy it did in 1970 per passenger per mile flown

Use Figure 13.9b to describe the change in carbon dioxide concentration over the past half million years.

the industrial- era rise is even more dramatic on a longer timescale. Clearly, earth has not seen anything close to today's Co2 levels in at least a half million years. the regular patterns in (b) correspond to ice ages and interglacial warm periods

Describe an essential tool scientists use to quantitatively explore the physical, chemical, geological, and biological processes that affect climate

to work out how those altered processes affect the entire Earth system. This is a job for large- scale computer models, which even today are challenged to handle every conceivable process of importance to Earth's climate.

Contrast food pre-production and post-production activities, and which of them produce greenhouse gas emissions

we use energy in pre- production activities, such as making fertilizers, animal feed, and pesticides, as well as in post- production food processing, storage, transport, refrigeration, retailing, preparation, and waste disposal. All these energy uses result in greenhouse gas emissions. But the impact of these emissions is dwarfed by emissions from agriculture itself