Introduction to Global Climate Change

11 INTRODUCTION TO GLOBAL CLIMATE CHANGE

“Everybody talks about the weather, but nobody does anything about it.” This comment, attributed to Mark Twain in 1897, is no longer valid. Today, human activities infl uence climate, long- term trends in weather, on both local and global scales. Aver- age temperatures are rising. Storms and forest fi res seem to be increasing in severity (Figure 1.1). The vagaries of weather may obscure specifi c cause and effect relationships, but humans are defi nitely part of the problem. Humans are also part of the solution. To diminish the potential damage from climate change and the extreme weather events that result, governments have implemented policies that range from limiting carbon emissions to reinforcing levees. As the public has become more aware about this issue, their behaviors in matters ranging from recycling of materials to the purchase of refrigerators, vehicles, and windows, increasingly refl ects their concerns. On contentious issues such as global climate change, a broad understanding of the subject generally contributes to the quality of debate. This book considers the factors responsible for climate change; the geophysical, biological, eco- nomic, legal, and cultural consequences of such change; and 2 CHAPTER 1

FIGURE 1.1 Extreme weather Hurricane Katrina extends on August 28, 2005. (Imagery from the GOES-12 weather across the Gulf of Mexico as it approaches New Orleans satellite.)

various strategies to diminish some of the undesirable oping effective policies when the information available consequences. It compares methods that researchers in may be sparse and vague. different disciplines employ to evaluate past and future Most textbooks concentrate on a single discipline conditions, and it highlights the complexity of devel- (e.g., geophysics, biology, or economics) or subdisci- pline (e.g., glaciology, plant physiology, or mac- roeconomics); they introduce the major concepts and then apply them to several examples involving a variety of issues. This book, by con- trast, focuses on a single issue—global climate change—and relates concepts from a number of natural and social sciences to it. Nearly every- one will ﬁ nd certain topics from this wide spec- trum to be challenging; nonetheless, stretching to maintain flexibility becomes critical as one matures. Articles on environmental issues frequently evoke fear, uncertainty, and doubt (FUD) that further exploitation of natural resources might cause irrevocable damage. Excessive exposure to FUD, however, desensitizes the public to such issues (“crying wolf”) or, worse, elicits fatalistic despair. This book strives to present a more balanced per- FIGURE 1.2 “Doom and Gloom with Bloom” The author, spective and occasionally unbridled optimism, Arnold J. Bloom, is shown marching in Times Square, New York but will deserve the subtitle Doom and Gloom with City in this manipulated image. Bloom (Figure 1.2) if this attempt fails. This material cannot be copied, disseminated, or used in any way without the express written permission of the publisher. Copyright 2010 Sinauer Associates Inc. INTRODUCTION TO GLOBAL CLIMATE CHANGE 3

1995 This chapter recalls the last 70 years of research ) –1 300 1997 on global climate change. The next three chapters 1999 constitute a geophysical section that examines the 2001 month 2003 past, present, and future of Earth’s climate: Chap- 2005 ter 2 presents historical reconstructions of temper- 200 Typical ature and a few other indicators of climate, Chap- ter 3 details factors that influence climate, and Chapter 4 describes global climate models and the 100 changes they predict during the next century. Sub- Precipitation (mm sequent sections of the book introduce additional aspects about climate change: direct and indirect effects on organisms, mitigation strategies and the 0 economics thereof, international cooperation and Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month accords, and, fi nally, the interplay of culture and public opinion. The book strives to support every FIGURE 1.3 Precipitation (millimeters) in Davis, California statement with data in graphical or tabular form. Plotted are data for each month of every other year during the last The number of graphs and tables that results from decade and typical precipitation values (long-term averages). such an effort disrupts the continuity of the text and may overwhelm readers who are less quanti- tative in orientation. For this reason, some of this documentation is presented on the book’s web site, instrument that permitted precise, continuous record- www.sinauer.com/bloom, for readers who are ing of temperatures. Guy Stewart Callendar worked as more inquisitive and quantitatively inclined. a steam engineer for the British Electrical and Allied Industries Research Association, but he had inherited his father’s interest in temperature measurement and, Climate as a hobby, scrutinized weather records from around Long-term weather patterns, as mentioned in the previ- the world. ous section, characterize the climate. The weather page Callendar examined historical trends in global aver- in your local newspaper includes information on daily age temperatures by grouping temperature data from maximum and minimum temperatures; humidity; pre- the most reliable weather stations in given regions of cipitation; and wind speed and direction. Long-term the world and weighting the importance of each group averages of these measures defi ne the climate in your according to the geographic area represented by its sta- area. For example, a Mediterranean climate is charac- tions (Callendar 1938). He calculated 10-year moving terized by relatively hot, dry summers and cool, wet averages (the average of the values 5 years before and winters. In Davis, California, more than 80% of the rain- 5 years after a given date) to smooth out year-to-year fall occurs during the winter months (Figure 1.3), thus fluctuations (Figure 1.4). Callendar’s analysis sug- Davis is considered to have a Mediterranean climate. gested that world temperatures had increased by more “Climate is what we expect; weather is what we get,” than 0.2°C between 1890 and 1935. Based on crude is another statement attributed to Mark Twain. In other measurements of carbon dioxide (CO2) concentrations words, weather conditions are highly variable from in the atmosphere and a simplistic model, Callendar day to day or year to year. Over an 11-year period, total proposed that rising CO2 levels were responsible for precipitation during the month of December in Davis over half of this warming. ranged from 0 to 250 millimeters (see Figure 1.3). Con- The ideas of Callendar, an amateur encroaching sequently, predicting daily weather based on climatic on the domain of climatologists, licensed profession- trends over time is seldom worthwhile. Subtle changes als who focused on climate, were not well received in climate over a few decades are sometimes diffi cult to (Weart 2003). Most climatologists of the day believed discern from normal fl uctuations in weather. that temperature data, because they were so variable, The fi rst person to note the recent warming trend in could be statistically manipulated to support nearly Earth’s climate and associate it with fossil-fuel emis- any conclusion. For example, Helmut E. Landsberg sions was Guy Stewart Callendar (1898–1964). Callen- (1906–1985), perhaps the most renowned climatologist dar’s father, Hugh Longbourne Callendar, a professor of the twentieth century (Baer 1992), did not acknowl- of physics at the Imperial College of Science, London, edge any signifi cant historical changes in global aver- had developed the platinum resistance thermometer, an age temperatures and declared, “There is no scientifi c This material cannot be copied, disseminated, or used in any way without the express written permission of the publisher. Copyright 2010 Sinauer Associates Inc. 4 CHAPTER 1

FIGURE 1.4 A graph from Callendar’s 1938 publication This graph shows temperature patterns (°C) for various climatic zones and of Earth. Plotted here are 10-year running averages (the average of 5 years before the date and 5 years after) with respect to the average temperatures from 1901– 1930. (From Callendar 1938).

reason to believe that our climate will change radically small portion of the CO2 released from fossil-fuel burn- in the next few decades, hence we can safely accept the ing would dissolve in the oceans: the bulk would remain

past performance as an adequate guide for the future” in the atmosphere, and atmospheric CO2 concentrations (Landsberg 1946). would increase substantially. The larger scientific establishment also doubted By the mid-1950s, technological advances had

whether atmospheric CO2 concentrations had changed increased the precision of CO2 measurements ten- signiﬁ cantly (Weart 2003). Readings of CO2 concentra- fold. C. D. (Dave) Keeling (1928–2005), also of Scripps, tions would fluctuate with the winds because local obtained funds sufﬁ cient to equip two weather stations

sources that released CO2, such as nearby factories, and with instruments that monitored atmospheric CO2 with sinks that absorbed CO2, such as nearby forests, infl u- unprecedented accuracy. To minimize the infl uence of enced every sample. The consensus of the scientifi c local disturbances, he chose sites that were remote from

community was that nearly all the CO2 released from industrial and biological sources of CO2 and were sub- fossil-fuel burning would dissolve in the immense vol- ject to strong prevailing winds (Figure 1.5A). One site ume of Earth’s oceans, and thus atmospheric changes was at the South Pole and the other was on the Island would be negligible. of Hawaii, at the Mauna Loa Observatory atop the With the dawn of the nuclear age at the end of World northern ﬂ ank of the Mauna Loa volcano, at an eleva- War II, atmospheric and oceanic scientists became tion of 3,397 meters (Figures 1.5B and C). preoccupied with other products of human ingenu- Monitoring at the South Pole began in September ity, namely radioactive wastes. In 1954, fallout from 1957 and at Mauna Loa 6 months later. Concentrations

an American nuclear bomb test injured the crew of a of CO2 at the South Pole rose slowly, but steadily. The Japanese fi shing vessel. Later that year came the release CO2 measurements at Mauna Loa, however, oscillated of Gojira, the fi rst in a long series of horror movies to from month to month (Figure 1.6), raising doubts about feature Godzilla, a fictional monster created by an whether this instrument was performing properly (Keel- American nuclear bomb test. Anxiety was escalating. ing 1978). Fortunately, with more observations, Keeling 14 Would radioactive carbon dioxide ( CO2), which was realized that the oscillations at Mauna Loa refl ected the generated in the atmosphere during nuclear explo- annual cycle on nearby continents of relatively rapid

sions, dissolve in the oceans and widely contaminate plant photosynthesis in summer, which removes CO2 sea life and seafood? from the atmosphere, and relatively rapid biological

Roger Revelle (1909–1991) and Hans Suess (1909– respiration in winter, which releases CO2 to the atmo- 1993) of the Scripps Institution of Oceanography in sphere. Funding for the South Pole station ran out after 14 San Diego, California, analyzed the exchange of CO2 about 2 years, during which time data showed a rise between the atmosphere and the oceans. They published in CO2 concentrations from 311 ppm to 314 ppm (parts a seminal work in 1957 showing that only a thin, upper per million; 311 ppm = 0.0311%). The Mauna Loa station layer of seawater rapidly exchanged materials with the has provided a nearly continuous record of rising atmo-

atmosphere (Revelle and Suess 1957). These results had spheric CO2 concentrations from about 315 ppm in 1957 broad implications. On the positive side, contamination to about 386 ppm in 2009, an increase of about 20%. This of sea life from nuclear testing would be highly local- record has become known as the Keeling curve. ized; but on the negative side, the oceans would remove As evidence accumulated, the scientiﬁ c establish- 14 only a small portion of the CO2 being released into the ment became more receptive to the idea of global warm- atmosphere; most of the radioactive gas would remain ing and its relationship to atmospheric CO2 concentra- airborne. By analogy, these results indicated that only a tions (Figure 1.7). Even Landsberg, who by 1958 had

(A) (B) 90°N

60°N

30°N

0 Mauna Kea

30°S Hilo Kailua 60°S Mauna Loa Observatory 90°S 180° 120°W 60°W 060°E 120°E 180

0.0 1.3 2.7 3.5 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 >12.0 Average wind speed (m s–1) (C)

FIGURE 1.5 Sites to monitor atmospheric CO2 concentration (A) Average wind speeds (meters per second) at ground level around the globe. The black dotted oval on the left demarcates the Hawaiian Islands. (B) Satellite photo of Hawaii showing the location of the Mauna Loa Observatory. (C) The observatory in 1982 shown against the backdrop of the neighboring peak Mauna Kea.

become the director of the Ofﬁ ce of Climatology in the 400 U.S. Weather Bureau, shifted his stance on the subject: 320 For nearly a half century, a general warming trend 380 has been noted…For the moderate latitudes, 30° to 50°N in the area around the Atlantic, the natural 310 rise can be estimated at about 2°F (1.1°C) per 360 century …For the latest temperature change, there 19551960 1965 is an important contender as cause: atmospheric carbon dioxide. There are some interpretations 340

of historical and current observations pointing concentration (ppm) toward a gradual increase of this atmospheric 2 South Pole constituent…Carbon dioxide is an absorber of CO 320 Mauna Loa outgoing long-wave radiation, and hence has an inﬂ uence…often referred to as the ‘greenhouse effect’ (Landsberg 1958). 300 1955 1965 1975 1985 1995 2005 Year

FIGURE 1.6 Monthly average CO2 concen- Current State of Affairs tration (parts per million: 1 ppm means 1 microliter of CO2 is dissolved in each liter of total air; 1ppm = 0.001%) Disagreements still remain about the extent to which in the atmosphere at the South Pole and near the summit the recent warming in global temperatures deviates of Mauna Loa in Hawaii. The inset in the upper left shows from normal climatic cycles. Direct measurements of data from the ﬁ rst few years on an expanded scale.

FIGURE 1.7 Rising temperatures A graph from Landsberg’s 1958 publication shows temperature patterns over nearly 50 years (°F and °C) for the summer (June–August) and winter (December–February) at Winthrup College, South Carolina. Dashed lines show the general temperature trend for the region. (From Landsberg 1958).

temperature have been available from weather sta- peratures from A.D. 1000 to 1900) was relatively straight, tions around the world only since 1861. To reconstruct whereas the “blade” (representing temperatures during temperature patterns before 1861 requires the use of the current century) was abruptly bent upward about proxy measures, measurements such as the width of 0.6°C (1.1°F). Mann and his colleagues proposed, as had tree rings that are strongly dependent on temperature Callendar and Landsberg several decades earlier, that

and can be dated with accuracy. Chapter 2 considers emissions of CO2 and other greenhouse gases from the different types of proxy measures. burning of fossil fuels were responsible for the dramatic In 1999, Michael Mann of Pennsylvania State Uni- warming trend (Mann et al. 1998). versity and his coworkers reconstructed the average By 2002, the political climate of the United States had annual temperatures in the Northern Hemisphere over changed, and fossil-fuel companies assumed a larger role the last 1000 years from a variety of direct measurements in governmental policies on energy. ExxonMobil, the larg- and proxy measures (Mann et al. 1999). The resulting est supplier of fossil fuels, distributed over $2 million per graph (Figure 1.8) became affectionately known as the year from 2000 through 2003 to organizations promoting “hockey stick” because the “shaft” (representing tem- the message that the scientific evidence linking global warming and fossil-fuel burning was unsound (McKib- ben et al. 2005; The Royal Society 2006). The “hockey stick” data became even more contentious, and the U.S. Con- 1.0 gress requested that the National Academy of Sciences, a body of prestigious scientists, verify Mann’s research. 0.5 Eight years after Mann and his coworkers published their 10-page article, the committee appointed by the National Academy released a 196-page report (National 0 Research Council 2006). This report upheld the major premise of the hockey stick: Global temperatures have

–0.5 warmed more than 0.6°C during the last century, and

Temperature change (°C) Temperature such changes are without precedent during the preced- ing 4 centuries and probably much longer. In particu- –1.0 lar, the year 2005 was the hottest on record, followed in 1000 1200 1400 1600 1800 2000 Year descending order by 2007, 1998, 2002, 2003, 2006, 2004, FIGURE 1.8 Temperature variation This data from the 2001, and 2008 (Goddard Institute for Space Studies 1999 publication of Mann et al. is dubbed the “hockey 2009). All indications are that this warming trend will stick.” It shows deviations of average annual temperatures continue and perhaps even accelerate. (°C) in the Northern Hemisphere from the long-term average About 130 stations around the world now monitor from 1902–1980 (temperature change). It is a composite atmospheric CO concentrations and have afﬁ rmed the estimate that the authors reconstructed from a variety of 2 sources. Gray shading indicates the extent of variation in the trends ﬁ rst observed in Keeling’s data from the South estimate, and the red line in the middle of the data represents Pole and Mauna Loa. Atmospheric concentrations of the long-term trends. (After Mann et al. 1999). CO2 have increased worldwide (Figure 1.9). Concen- This material cannot be copied, disseminated, or used in any way without the express written permission of the publisher. Copyright 2009 Sinauer Associates Inc. FIGURE 1.9 Global distribution of atmospheric CO This is a three-dimensional representation 390 2 of the latitudinal distribution of atmospheric CO2 )

–1 based on data from the Global Monitoring Division (GMD) cooperative air-sampling network. Notice that 380 the overall global trend is that CO2 concentrations are rising. CO2 concentration varies more during a year at higher latitudes because seasonal variation 370 is greater there. This concentration also varies more in the northern hemisphere because it has more land area than the southern hemisphere. Moreover, the 360 seasonal peak in concentration shifts with date from concentration (μmol mol

2 the northern hemisphere to southern hemisphere because photosynthesis, which absorbs CO , is CO 2 350 faster during the summertime of each hemisphere. 60°N0°N (From Dr. Pieter Tans and Thomas Conway, NOAA LatitudeLa ESRL GMD Global Carbon Cycle, Boulder, CO.) 0° 2006 60°S 2004 2000 2002 1996 1998 Year trations are lower in the summer, when plants incorpo- ure 3.13) and thus more terrestrial organisms that con- rate CO2 from the atmosphere into their organic carbon duct rapid photosynthesis and respiration. compounds via photosynthesis, and higher in the win- Global temperatures and atmospheric CO2 concen- ter, when biological respiration exceeds photosynthesis trations have tended to change in conjunction with and releases CO2 from organic carbon compounds. Sea- one another (i.e., show a positive correlation) both in sonal variation is greater in the Northern Hemisphere the current century and during the last 650,000 years than the Southern Hemisphere because the Northern (see Chapter 2). Admittedly, correlation does not imply Hemisphere has substantially more landmass (see Fig- causality (Box 1.1), but most in the scientiﬁ c commu-

BOX 1.1 Alternative explanations for global warming

The following examples about global warming dem- spoof, Connie M. Meskimen, a bankruptcy lawyer from onstrate that correlation does not imply causality. In a Arkansas, suggested that daylight savings time exacer- parody of scientiﬁ c method, Bobby Henderson—self- bates global warming by setting sunrise at an earlier hour described as an unemployed, amateur pirate with a (Figure B). Only a few scientists, however, have turned physics degree—found a negative correlation between to piracy or turned back their clocks prematurely. the number of pirates and global average temperature (Figure A) and advocates that people become pirates to stop global warming (Henderson 2006). In another

16 2000 1980 1940 You may have noticed that March of this year was particularly hot. As a 15 1920 matter of fact, I understand that it was the hottest March since the beginning 1880 of the last century. All of the trees were fully leafed out and legions of bugs 1820 1860 and snakes were crawling around during a time in Arkansas when, on a 14 normal year, we might see a snowflake or two. This should come as no surprise to any reasonable person. As you know, Daylight Saving Time started almost a month early this year. You would think that members of Congress would have considered the warming effect that an 13 extra hour of daylight would have on our climate. Or did they? Global average temperature (°C) Global average temperature 3500045000 2000015000 5000 400 17 Perhaps this is another plot by a liberal Congress to make us believe that Number of pirates (approximate) global warming is a real threat. Perhaps next time there should be serious studies performed before Congress passes laws with such far-reaching effects. Figure A Global average temperatures as a function of CONNIE M. MESKIMEN the number of pirates. This parodies standard presenta- tions of scientiﬁ c data. Notice that the labels on the x axis Figure B A tongue-in-cheek letter to an Arkan- are not consistent. (After Henderson 2006). sas newspaper.

nity agree that global temperatures are rising and that FIGURE 1.10 Dramatic changes in ice cover ▲ (A) Mt. Kilimanjaro on February 17, 1993 (top) and February human-generated emissions of CO2 and other greenhouse gases are contributing to this rise. Alternative 21, 2000 (bottom). Satellite images of the summit indicate the minimum amount of snow cover. (B) Outlines of the ice fi elds explanations for the current temperature trends con- near the summit of Mt. Kilimanjaro in 1912, 1953, 1976, fl ict with a growing body of evidence. Even organiza- 1989, and 2000. The inset illustrates the near-linear decrease tions with strong vested interests in fossil fuels have in ice area over time. (B after Thompson et al. 2002.) modifi ed their message. For instance, in 2005, ExxonMobil’s “Corporate Citi- zenship Report” acknowledged that “the accumulation of greenhouse gases in the Earth’s atmosphere poses 1.11). Sometime in the not-too-distant future, the Arc- risks that may prove signifi cant for society and ecosys- tic Ocean will have an ice-free season and realize the tems. We believe that these risks justify actions now, long-sought Northwest Passage, a sea route between but the selection of actions must consider the uncertain- the Atlantic Ocean and the Pacifi c Ocean through the ties that remain” (ExxonMobil 2005). The report pres- Canadian archipelago (see Chapter 4). This might prove ents ExxonMobil’s view of the uncertainties regarding to be a fi nancial windfall for Pat Broe, a Denver entre- the causes of global warming but then touts the $200 preneur who bought the port of Churchill on Hudson million that ExxonMobil had just bequeathed to the Bay at auction for $10 Canadian in 1997: An ice-free Global Climate and Energy Project at Stanford Univer- Northwest Passage could bring up to $100 million of sity in California as “the largest-ever privately funded shipping business to Churchill each year. research effort in low-greenhouse-gas energy.” Other fossil-fuel companies have taken similar approaches. In 2006, BP (formerly British Petroleum) In the Course of Human Events and Chevron announced plans to allocate $500 mil- The effects of climate have determined the outcome of lion and $400 million, respectively, for research on bio- many human endeavors. An appropriate ending to this fuels. All these companies now advertise their efforts in introduction is the famous fi gure drawn by Charles developing energy resources while minimizing envi- Joseph Minard (Figure 1.12), a testament to climate ronmental degradation. and the fate of empires (Tufte 2001). On June 24, 1812, Napoleon invaded Russia, crossing the Niemen River from Poland into Russia with 422,000 men. Six months Telltale Signs later, after experiencing temperatures as low as –38°C, Global warming has altered a broad range of geophys- Napoleon’s Grande Armeé departed Russia with a mere ical and biological phenomena. These phenomena 10,000 men. are the focus of several chapters in this book. Recent Climate again played a pivotal role in the disastrous changes in ice cover, however, are so visually striking German invasion of the Soviet Union in 1941. German as to warrant a place in this fi rst chapter. forces were trapped outside Moscow during the Rus- Mount Kilimanjaro reaches 5,895 meters above sea sian winter with inadequate shelter, clothing, fuel, and level in equatorial Tanzania. Not only is it the highest food. All in all, more than 4 million German and 8 mil- peak in Africa, it is also the only place on the conti- lion Soviet troops lost their lives on the Eastern Front. nent covered with snow year-round; hence its name, As these examples illustrate, insuffi cient consider- which translates as “Shining Mountain.” Satellite pho- ation of climate can have dire consequences. In 2007, tographs show the mountain in 1993 and 2000 (Figure military and spy agencies in the United States warned 1.10A). A compilation of maps outlining the ice fi elds that anticipated changes in the world’s climate pose a near the summit documents the changes over the last serious threat to the security of nations because of sub- century (Figure 1.10B). If the current rate of decline stantial shifts in the availability of natural resources and continues, the snows of Kilimanjaro will disappear the forced migration of millions of people (Mazzetti during the next few decades (Thompson et al. 2002). 2007). In their fourth assessment, the Intergovernmen- The far end of Earth provides another visual example tal Panel on Climate Change (IPCC), an organization of changes in ice cover over time. Since 1950, the Arctic established by the World Meteorological Organization has experienced an increase in average temperatures and United Nations, agreed that further global warming of about 2°C, more than twice that observed at lower is already unavoidable due to past human activities and latitudes (ACIA 2005). In response, the polar ice cap is a major international effort is required to mitigate the receding at a rate of around 10% per decade (Figure impacts (IPCC 2007a, 2000b,c).

(A) (B)

X 37°20’ E 12 2 ) R = 0.98 2

8 X

X 5000 4 X X Total area ice (km Total

0 1900 1950 2000 Year

5500

2000

1989 3°05’ S 1976

1953 (km) 1912 0 1 4500

This book outlines the causes and possible conse- cannot provide definitive answers to many of the quences of global climate change and then presents questions raised while considering the issue of global various strategies for addressing these possible con- climate change, but it can provide a broad context sequences. Climate change is a complex problem, from which readers may draw their own insights and probably one without a simple solution. This book conclusions.

FIGURE 1.11 Minimum amount of Arctic sea ice in by NASA satellites at the end of the Arctic summer. 1979 (left) and 2007 (right). This is based on data collected

Moscowa R. 100,000

Moscow 127,000 Chjat 100,000 100,000

22,000 50,000

6,000 33,000 Mojaisk Polotsk Tarutino Gloubokoe

Niemen R. 175,000 Malojaroslavetz 422,000 Vitebsk

400,000

145,000 Dorogobongr Wirma 87,000 Kovno Vilna Smolensk 96,000

30,000 55,000 Berizina R. Orscha

Smorgoni 37,000

Botr 24,000

8,000 4,000 20,000 10,000 12,000 28,000Studianka Molodeczno

Minsk 50,000 Mohilow Temp. (°C) 0° 0° Oct. 24 0° Oct. 18 –11° Nov. 14 –14° Nov. 20 –20° –25° Nov. 28 –26° Nov. 14 –30° Dec. 1 –40° –33° Dec. 7 –38° Dec. 6

FIGURE 1.12 A map of Napoleon’s invasion of reﬂ ects the size of the French army at various locations. The Russia in 1812 The tan band depicts the French army’s branch points indicate where some troops separated during crossing the Niemen River into Russia and advancing the advance and later rejoined the retreat. Temperatures east toward Moscow; the black band depicts the army’s (°C) in red are linked to the path of retreat. westward retreat from Moscow. The thickness of the bands

Summary Review Questions Climate refers to the general weather patterns in a par- 1. Over the last century, global average temperatures ticular location. Long-term changes in such patterns are have often diffi cult to differentiate from the large fl uctuations (a) cooled about 0.1°C. in weather that normally occur. Nonetheless, long-term (b) not changed signifi cantly. measurements of temperatures from around the world (c) warmed about 0.1°C. indicate that Earth is warmer today than it has been for (d) warmed about 0.6°C. several centuries. This warming has been associated (e) warmed about 6.0°C. with human activities, especially the release of carbon dioxide from the burning of fossil fuels. Although a 2. Atmospheric CO2 concentrations were about small portion of this carbon dioxide dissolves into the _____ ppm in 1957 and about _____ ppm in 2009. oceans, the vast majority remains airborne and increases (a) 200 atmospheric carbon dioxide concentrations. (b) 270 Global warming has produced noticeable changes in (c) 315 a broad range of phenomena including the disappear- (d) 386 ing snows of Kilimanjaro and a decrease in the extent (e) 550 of the polar ice caps. Such changes are likely to infl u- ence the fate of human civilizations.

3. Which of the following researchers made major Suggested Readings contributions to our understanding about climate trends? (Select one or several.) National Research Council. 2006. Surface Temperature (a) Guy Stewart Callendar Reconstructions for the Last 2,000 Years. The National (b) C. D. Keeling Academies Press, Washington, D.C., http://www.nap. (c) Roger Revelle edu/catalog/11676.html. (d) Pat Broe The National Academy of Sciences has a mandate (e) Charles Joseph Minard from the U.S. Congress to advise the federal govern- ment on scientiﬁ c and technical matters. The Acad- 4. Most of the carbon dioxide released from the emy appointed a committee of twelve distinguished burning of fossil fuels scholars to prepare this report on global temperature changes over the past two millennia. (a) dissolves in the oceans. (b) remains in the atmosphere. Weart, S. R. 2003. The Discovery of Global Warming. Harvard (c) is consumed by animals via respiration. University Press, Cambridge, Mass. (d) becomes radioactive. A fascinating account about the history of research (e) freezes and becomes dry ice. on climate change. Dr. Weart regularly updates the version available for free at http://www.aip.org/history/ climate/. 5. Evidence of current global temperature trends include (select one or several) (a) the disappearance of year-round snow in Africa. (b) Napoleon’s successful invasion of Russia. (c) the Northwest Passage through the Canadian archipelago. (d) the proliferation of movies featuring Godzilla. (e) the extension of daylight savings time.

This material cannot be copied, disseminated, or used in any way without the express written permission of the publisher. Copyright 2010 Sinauer Associates Inc. This material cannot be copied, disseminated, or used in any way without the express written permission of the publisher. Copyright 2010 Sinauer Associates Inc.