Global Climate Change and Human Causes

Ralph J. Cicerone

National Academy of Sciences

INTRODUCTION

Global climate change is a much discussed topic at the present time. This paper starts with a brief discussion about Earth’s climate and its energy budget from a planetary perspective. It then addresses the greenhouse effect caused by certain greenhouse gases. Current data on recent climate change are summarized, and the subject of carbon dioxide from fossil-fuel burning is discussed. Human causes, what we need to do about the situation, and first steps towards solutions are then considered. Throughout, the contributions of the space program to the study of global climate change and the mitigation of its effects will be addressed.

Earth’s Climate and Energy Budget

Figure 2.1 depicts the Sun shining down on Earth. The number 342 indicates the amount of power the planet receives—342 watts per square meter averaged over the planetary surface day and night and annually. About one third of this power is directly reflected back to space from white surfaces such as the tops of clouds and the snow surfaces at the poles. (Black surfaces and dark surfaces absorb, light surfaces reflect.) On balance then, 237 of the 342 watts per square meter are being absorbed in the form of visible sunlight (plus a tiny amount of ultraviolet sunlight and a little bit of infrared).

On a short time scale, say one year, the planet is not heating up, nor is it getting very cold. We are roughly in an energy balance, a fact that has been borne out by measurements from space platforms.

The problem is we are “roughly” in balance, not exactly in balance. We are warming up due to certain gases in the atmosphere that interfere with the balancing that would be caused by planetary radiation. The lower layers of Earth’s atmosphere are heating up, while the amount that continues to escape is almost in balance with what is coming in.

The Greenhouse Effect

Is the greenhouse effect real or merely an unproven idea? There is a lot of evidence to show that it is real and is operating.

For example, we are able to calculate the temperature of the surface of Mars. We could calculate it before it was actually measured by spacecraft. It is about 30°C below zero, varying a little during the day and night cycle. We could calculate the number correctly because there is no greenhouse effect on Mars. The atmosphere is too thin. The way we do such a calculation is to multiply the incoming sunlight (which at Earth-orbit distance is 342 watts per square meter as mentioned earlier) by 1 minus the reflectivity of the planet. If the planet were reflecting 100 percent of the incoming light, that would be zero; however, Mars only reflects about 30 percent. If you assume that nothing is changing with time, this is the equation you have to solve,

NOTE: Transcribed from a lecture presented at the University of New Hampshire, October 19, 2007.



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Global Climate Change and Human Causes Ralph J. Cicerone National Academy of Sciences INTRODUCTION heating up, nor is it getting very cold. We are roughly in an energy balance, a fact that has been borne out by Global climate change is a much discussed topic at the measurements from space platforms. present time. This paper starts with a brief discussion The problem is we are “roughly” in balance, not about Earth’s climate and its energy budget from a exactly in balance. We are warming up due to certain planetary perspective. It then addresses the greenhouse gases in the atmosphere that interfere with the balanc- effect caused by certain greenhouse gases. Current data ing that would be caused by planetary radiation. The on recent climate change are summarized, and the lower layers of Earth’s atmosphere are heating up, while subject of carbon dioxide from fossil-fuel burning is the amount that continues to escape is almost in bal- discussed. Human causes, what we need to do about ance with what is coming in. the situation, and first steps towards solutions are then considered. Throughout, the contributions of the space The Greenhouse Effect program to the study of global climate change and the mitigation of its effects will be addressed. Is the greenhouse effect real or merely an unproven idea? There is a lot of evidence to show that it is real Earth’s Climate and Energy Budget and is operating. For example, we are able to calculate the tempera- Figure 2.1 depicts the Sun shining down on Earth. ture of the surface of Mars. We could calculate it before The number 342 indicates the amount of power the it was actually measured by spacecraft. It is about 30°C planet receives—342 watts per square meter averaged below zero, varying a little during the day and night over the planetary surface day and night and annually. cycle. We could calculate the number correctly because About one third of this power is directly reflected back there is no greenhouse effect on Mars. The atmosphere to space from white surfaces such as the tops of clouds is too thin. The way we do such a calculation is to and the snow surfaces at the poles. (Black surfaces and multiply the incoming sunlight (which at Earth-orbit dark surfaces absorb, light surfaces reflect.) On bal- distance is 342 watts per square meter as mentioned ance then, 237 of the 342 watts per square meter are earlier) by 1 minus the reflectivity of the planet. If the being absorbed in the form of visible sunlight (plus a planet were reflecting 100 percent of the incoming tiny amount of ultraviolet sunlight and a little bit of light, that would be zero; however, Mars only reflects infrared). about 30 percent. If you assume that nothing is chang- On a short time scale, say one year, the planet is not ing with time, this is the equation you have to solve, NOTE: Transcribed from a lecture presented at the University of New Hampshire, October 19, 2007. 23

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24 FORGING THE FUTURE OF SPACE SCIENCE 237 342 H2O, CO2, O3 105 68 390 FIGURE 2.1 Earth’s energy balance. SOURCE: Reprinted with permission from V. Ramanathan, 327 90 B.R. Barkstrom, and E.F. Harrison, Climate and the Earth’s radiation budget, Physics Today 16 169 42(5):22–33, 1989, with modifications. Copy- right 1989, American Institute of Physics. 2.1 from Presentation.eps bitmap image with some vector type which should provide the effective temperature of the Beginning in the fall of 1957, David Keeling planet. We get the right number for Mars. started measuring carbon dioxide in the air on the However, if we try the same calculation for Earth, it flanks of the Mauna Loa volcano on the big island of does not work. We would calculate that Earth’s surface Hawaii roughly once an hour, and he averaged the data is a subfreezing 18°C below zero on average and should every month. Keeling died about 3 years ago, but this be frozen into a solid block of ice. As far as we know, recording (Figure 2.2) is being carried on by hundreds that has never been true throughout geologic history, let of other people around the world. Each one of the black alone being correct now. The reason it is wrong is that dots in Figure 2.2 is the average of a month’s data. we have neglected the ability of the gases—notably wa- The average carbon dioxide amount started out ter vapor, carbon dioxide, ozone, and a few others—to around 312 parts per million (ppm), and by 2005 it assist in heating the surface of the planet. There is a was about 380 ppm. The most important thing that the level in our atmosphere at which the temperature is graph shows is that carbon dioxide in the atmosphere exactly −18°C, but not at the surface. That is because continues to increase rather smoothly. Superimposed of the greenhouse effect. on the long-term trend are the annual cycles, almost If we do the same calculation for Venus, we get like a sine wave. a really incorrect answer. We underestimate the tem- In either hemisphere, in the spring or summer perature of Venus by several hundred degrees. That the carbon dioxide amounts are lower. In the fall and is because the Venus atmosphere, as we have learned winter, they go up. The next spring and summer they from the space program, is very thick, very heavy, has come down a little bit, and again in the fall and winter, a much higher pressure than Earth’s, and is composed they go up. In the spring and summer photosynthesis largely of carbon dioxide. Some people attribute the is drawing carbon dioxide out of the air, and in the Venus situation as being due to a runaway greenhouse fall and winter the decay of annual plants, the decay effect. Venus is not that different in distance from the of organic matter in soils, and root respiration exude Sun than Earth, but its temperature is grossly different, carbon dioxide back into the atmosphere. In fact, the around 540°C. peak-to-peak amplitude of the depth of this oscil- This is powerful evidence that the greenhouse ef- lation tells us something about the total amount of fect is natural, real, and was operating before humans photosynthetic activity on the planet. This is where our were even here. oxygen comes from. There is a lot of geochemical and

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25 GLOBAL CLIMATE CHANGE AND HUMAN CAUSES bio-geochemical information contained in this graph. over the northern hemisphere, was about 20,000 years Many other scientists have been making such measure- ago. The previous one was about 140,000 or 150,000 ments for many years, using many different techniques. years ago. The temperature was low. In between those The numbers are right. They have been tested many glaciated periods, there are periods of interglacial times before. warming. We are in such a period now. Carbon dioxide is a strong greenhouse gas. In fact, On the upper curve is a carbon dioxide record. The we think it and water vapor are responsible for keeping ice cores that have been dated can be interrogated as Earth’s temperature above the subfreezing temperature to what the gases are inside, either by crushing the ice mentioned above. and extracting the gas under vacuum, or by melting it, For the last 20 years, scientists have been extracting which does not work quite as well if the gas is water- ice cores in Antarctica and Greenland, and by counting soluble. When the temperature was low in the previous layers and by other identifying information, they have ice age, carbon dioxide amounts were very low: on this created an historical record extending back 600,000 scale, about 180 ppm. years. From Dave Keeling’s curve (Figure 2.2) we are now The particular record in Figure 2.3 goes back more around 380 ppm. In the long ice-core record going back than 400,000 years. Today is time zero, and time goes over four planetary ice ages, we see that carbon dioxide back to the left. The lower curve is an approximation of was around 180 ppm during each of the cold times, what the temperature was like in the region where the and during the warm times over the last four glacial snow and ice formed, obtained from isotopes of water, cycles it was 280 ppm, 260 ppm, and 280 ppm—never hydrogen, and oxygen. 380 ppm. Glaciated periods can be seen in the past. The most Whatever is happening, Earth is now being pushed recent glacial period, when there was a great deal of ice into a regime where it has not been before at any time FIGURE 2.2 Atmospheric CO2 concentrations (ppmv), 1958–2004, derived from in situ air samples collected at Mauna Loa Obser- vatory, Hawaii. SOURCE: Courtesy of C.D. Keeling, T.P. Whorf, and the Carbon Dioxide Research Group at the Scripps Institution of Oceanography, University of California, La Jolla.

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26 FORGING THE FUTURE OF SPACE SCIENCE FIGURE 2.3 Antarctic ice core records. Temperature CO2 (upper) and CH4 (lower) time series (thousands of years before present) from the Vostok Antarctic ice core. SOURCE: J. Hansen and M. Sato, Greenhouse gas growth rates. Proceedings of the National Academy of Sciences 101(46):16109–16114, 2004. Copyright 2004 National Academy of Sciences, U.S.A. Original data from J.R. Petit, J. Jouzel, D. Raynald, N.I. Barkov, V.-M. Barnola, I. Basile, M. Bender, J. Chappellaz, M. Davisk, G. Delaygue, M. Delmotte, et 2.03 from presentation.eps al., Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica, Nature 399: 429 436, 1999. bitmap image where we have direct measurements. There is certainly ing curve) shown in Figure 2.2 superimposed on the evidence that hundreds of millions of years ago Earth geologic history. On the time scale shown, that is the was warmer, and we infer that there was a lot of carbon way carbon dioxide is behaving. dioxide. There is really no direct evidence of this, al- So where is the carbon dioxide coming from? Can though some people think there is indirect evidence. we really be sure that the increase of carbon dioxide In the case of methane, which is another very im- in the global atmosphere is due to fossil fuel burning? portant greenhouse gas, partly natural, it is the same We can, but we have to look at a lot of evidence, for story. When the temperature was low in the ice ages, example, the actual amounts. methane was at one-third parts per million. When it If you look in Figure 2.5 at the amount of carbon was warm, methane was at two-thirds parts per million. dioxide that is being discharged by fossil-fuel burning, One third, two thirds, one third, two thirds, and so plus a little bit generated during cement production, forth. Methane amounts are now five times higher than you can see that it has been growing very rapidly, such they were in low times, or about two and a half times that 100 years ago we were only discharging about higher than they were in the highest times geologically. 120th as much carbon dioxide, because we were not There is real evidence that these greenhouse gases have really using as much oil, petroleum, and so forth. Figure now entered into a realm of concentration where they 2.5 shows the current amount of carbon dioxide lost have not been for the last half million years. into the air from fossil-fuel burning to be about 7 bil- Figure 2.4 shows the same modern record (Keel- lion (7,000 million) metric tons (as carbon, including

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27 GLOBAL CLIMATE CHANGE AND HUMAN CAUSES FIGURE 2.4 Atmospheric CO2 concentrations (Keeling curve) Presentation.eps 2.4 Cicerone superimposed on the geologic history. Atmospheric Carbon Dioxide (Antarctic Record) Years before Present. SOURCE: Reprinted by permission from Macmillan Publishers Ltd: Nature (J.R. Petit, J. Jouzel, bitmap image D. Raynaud, N. I. Barkov, J. M. Barnola, I. Basile, M. Bender, J. Chappelaz, M. Davis, G. Delaygue, M Delmootte, V. M. Kotlyakov, M. Legrand, V. Y. Lipenkov, C. Lorius, L. Pepin, C. Ritz, E. Saltzman, and M. Stievenard, Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica, Nature 399, 429–436, 1999) Copyright 1999). Inset from C.D. Keeling and T.P. Whorf, Atmospheric carbon dioxide record from Mauna Loa (1957–2004), 2005, available at http://cdiac.ornl.gov/trends/co2/ graphics/ mlo145e_thrudc04.pdf, and earlier Keeling and Whorf CDIAC data sets. that due to the flaring of natural gas; the red curve). carbon dioxide—it is the loss of soil or organic matter Some of it is due to the direct burning of natural gas, when those tropical soils are exposed and are no longer some of it is due to the burning of petroleum, and some controlled by the roots. of it is due to the burning of coal and wood. Figure 2.6 shows carbon dioxide emissions from These numbers add up. In fact the amount of car- energy consumption in the United States, broken down bon dioxide that we measure increasing in the air every by source. The United States alone releases 6 to 7 bil- year is about 60 percent of this amount, rather than 100 lion tons of carbon dioxide a year. About 2.6 billion percent. Several other things are going on. Carbon di- tons comes from the burning of petroleum, about 1.2 oxide is being taken up by oceans and by plant growth. billion tons from the burning of natural gas, and a little Also, there is some carbon dioxide entering the air due over 2 billion tons from the burning of coal. On this to the decay of the biological material in an imbalanced scale, if you look at the contributions to carbon dioxide way, the tropical deforestation, for example. It is not just emission from other sources like hydroelectric plants, the burning of the plant material and wood that releases biomass, geothermal plants, and so on, they are virtu-

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28 FORGING THE FUTURE OF SPACE SCIENCE FIGURE 2.5 Global CO2 emissions from fossil fuel burning, cement production, and gas flaring for 1751–2002. SOURCE: Data 2.5 Cicerone Presentation.eps from the Carbon Dioxide Information Analysis Center, U.S. Department of Energy, Oak Ridge National Laboratory. bitmap image with vector grid lines added ally zero. It is primarily the fossil fuels that release the atmospheric measurements, and use other lines of evi- carbon dioxide in the very active burning from which dence like the isotopic content of the carbon and fossil we derive the energy, due to exothermic chemical reac- fuels compared to the isotopic content of the carbon tions. It is inherent in the process of extracting energy. dioxide, the spatial patterns, the geographical patterns, Figure 2.7 shows U.S. carbon dioxide emissions from the seasonal behavior, and so forth, you have very com- energy consumption by usage instead of source. pelling evidence that the carbon dioxide increase that When you go through all the numbers, compare we are seeing is caused by humans. Hydro (0) Biomass (0) Coal Geothermal (0) Petroleum 2.12 2.58 Wind (0) Solar (0) Nuclear (0) Coal 2.12 Natural Gas 1.18 Petroleum 2.58 Natural Gas 1.18 FIGURE 2.6 U.S. carbon dioxide emissions from energy consumption by source (in billion metric tons CO2). SOURCE: Data courtesy of the University of California, Lawrence Livermore National Laboratory and the Department of Energy. 2.06 from Presentation.eps

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29 GLOBAL CLIMATE CHANGE AND HUMAN CAUSES Aircraft 0.22 Freight/Other 0.48 Electricity Generation 2.32 Light-Duty Vehicles 1.07 Industrial Residential 1.21 0.36 Commercial 0.22 FIGURE 2.7 U.S. carbon dioxide emissions from energy consumption by usage (in billion metric tons CO2) SOURCE: Data courtesy of the University of California, Lawrence Livermore National Laboratory and the Department of Energy. 2.07 from Presentation.eps Similarly with methane. In Figure 2.8 the red part changes have not made much of a difference. The best of the pie chart represents annual methane release rates known number here is rather euphemistically called that are due to human activities. Some of them are “enteric fermentation.” That is basically belching and under human control, some of them are inadvertent. flatulence of cows. You might think that this is a wild The yellow part of the pie chart shows natural sources guess, but in fact it is the most well-known number on of methane. the chart because a typical cow loses about 10 percent There are some new entries here, but frankly the of its daily caloric intake every day due to methane loss. Gas Production Enteric Fermentation 45 Tg/yr (8.3%) 80 Tg/yr (14.8%) Coal Mining 35 Tg/yr (6.5%) Clathrate Decomposition Landfills 5? Tg/yr (0.9%) 40 Tg/yr (7.4%) Termites 40 Tg/yr (7.4%) Freshwaters 5 Tg/yr (0.9%) Biomass Burning 55 Tg/yr (10.2%) Wetlands 115 Tg/yr (21.3%) Boreal: 20-60 Tg/yr Rice Paddies Oceans 110 Tg/yr (18.5%) 10 Tg/yr (1.9%) Total = 540 Tg/yr FIGURE 2.8 Global methane release rates. SOURCE: R. Cicerone and R.S. Oremland, Biogeochemical aspects of atmospheric methane, Global Biogeochemical Cycles 2:299–328, from Presentation.eps 2.08 1988. Copyright 1988 American Geophysical Union.

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30 FORGING THE FUTURE OF SPACE SCIENCE 1.8 1.6 1.4 (Watts per square meter) 1.2 Radiative Forcing 1.0 0.8 0.6 FIGURE 2.9 Radiative forcing 0.4 from well-mixed greenhouse gases, 2004. SOURCE: Data 0.2 from NOAA ESRL Global Moni- toring Division. 0.0 CO2 CH4 N2O CFC12 CFC11 Other People have known this for 100 to 125 years, and they 2.09 from below. Methane contributes about 0.5 and tudes and Presentation.eps have tried to stop it by changing the cow’s diet. It turns nitrous oxide and a whole slew of other greenhouse out that the poorer the diet is, the higher the loss as gases add up to a little bit more than one percent of methane. Sheep are similar. the solar constant. The output of a star like our Sun So what does it all mean? As noted, we receive a does change over its lifetime, but not as much as one net of 237 watts per square meter of sunlight. What is percent per century. There is no theory or observations the effect of greenhouse gases in trapping energy near that suggest that the output of the Sun could change Earth’s surface? It turns out to be one percent. one percent in a hundred years. There are people who As shown in Figure 2.9, the added carbon dioxide wish it were so, and 10 or 15 years ago we thought that measured in the last 60 to 80 years is contributing about maybe the climate changes we were beginning to see 1.6 watts per square meter of extra energy trapped in could be blamed on the Sun, but there is evidence that Earth’s planetary boundary layer down at aircraft alti- refutes this assumption. .6 Temperature Anomaly(°C) .4 .2 FIGURE 2.10 Global temperature: Land- .0 ocean index from NASA Goddard Institute for Space Studies. SOURCE: Updated from J. Hansen, Mki. Sato, R. Ruedy, K. Lo, D.W. Lea, and M. Medina-Elizade, Global tem- -.2 perature change, Proceedings of the National Annual Mean Academy of Sciences 103:14288–14293, 5-year Mean doi:10.1073/pnas.0606291103, 2006. -.4 Copyright 2006 National Academy of Sci- ences, U.S.A. 1880 1900 1920 1940 1960 1980 2000 2.10 Fig.A2.eps

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31 GLOBAL CLIMATE CHANGE AND HUMAN CAUSES The Warming of the Planet some of the open ocean regions, there is a very small, or zero, temperature increase because of the heat capacity So what is happening now? Since 1980, NASA has of water. What suggests that this phenomena is not been gathering temperature measurements (several natural is that warming is taking place everywhere at hundred million) from around the world going back the same time. to 1880. Historically, when we have temperature records In Figure 2.10 from the NASA Goddard Institute such as the Medieval warm period, or a mini ice age, for Space Studies, zero is not zero degrees, it is a refer- we have records from different places on Earth that are ence point—the average temperature all over the world contradictory, or nonexistent, because when it is cold from 1951 to 1980. Compared to that average, the pe- in one place, it is hot in another. In fact that is even riod of 70 years before 1951 was mostly colder, except true today in the United States on a single day. What is around 1940, and everything since has been warmer. happening now, though, is that the warming is taking In Figure 2.11 temperatures are measured over place everywhere at once. land and sea, averaged according to the size of the latitude belt, and presented as a global average. The The Rise in Sea Level urban-heat-island effect is removed. Many of the places where we have been measuring temperatures Another noted phenomenon is the rise in sea level. For have been surrounded by cities as time has developed. about 100 years, people have been measuring sea level Blacktop and human energy usage is making our cities rise carefully, but in a very primitive way—basically, hotter than the surrounding regions. What is interest- pounding stakes into the shoreline and recording ing is that now the temperature increase is seen almost mean sea level at many locations around the world. everywhere, although it is not uniform. In Figure 2.11 Figure 2.12 has been constructed over the last 100 the lower boundary is the South Pole and the upper years and shows sea level rise averaged over the ocean boundary the North Pole. basins of about 1.5 millimeters a year, which is about Note that you can see the outlines of continents 15 centimeters, or 6 inches, a century. in the heat pattern. The warming on this false-color Not all the ocean basins have behaved the same scale is largest in the high-latitude continental regions way, because there is geological heaving and rising go- like upper Siberia and the Arctic region. The warming ing on at the same time that has nothing to do with there is really pronounced compared to everywhere water-related sea level rise. The right-hand part of else, except down in the high southern latitudes. Over Figure 2.12 shows a red curve which is a new set of data FIGURE 2.11 Last 50 years surface tempera- ture change based on linear trends (degree C) SOURCE: J. Hansen, R. Ruedy, M. Sato, and K. Lo, NASA Goddard Institute for Space Studies, and Columbia University Earth Institute, New York, N.Y. 2.11 2005cal_fig3.eps type is outlined vector

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32 FORGING THE FUTURE OF SPACE SCIENCE determination of a trend that was underway. Sea level 35 is rising globally—that is for sure. 30 Sea Level Change (cm) 23 Annual Tide Gauge Records 25 Three Year Average Ice Cover Satellite Altimetry 20 15 Figure 2.14 is a visual representation of the change in 10 Northern Hemisphere sea ice between 1979 and 2003. It is evident that the ice cover in the Arctic region has 5 been reduced. Such measurements are now being made 0 from space. -5 One example of such a space-based data collection activity is the Gravity Recovery and Climate Experi- 1880 1900 1920 1940 1960 1980 2000 ment (GRACE) mission (Figure 2.15) involving two FIGURE 2.12 Recent sea level rise (1882–2005) based on satellites that very accurately measure the distance Permanent Service for Mean Sea Level (PSMSL) tide gauge data 2.12 recentsealevel.eps from 23 sites selected by Douglas (1997). SOURCE: Created by between each other using a K-band interferometry, as Robert A. Rohde, University of California, Berkeley. Courtesy of shown in Figure 2.15. They also make use of Global Global Warming Art, available at http://www.globalwarmin- Positioning System signals for accurate position loca- gart.com/wiki/File:Recent_Sea_Level_Rise_png. tion. If there is any minor perturbation to Earth’s gravi- tational field due to a “mass anomaly,” such as a large mountain or a big piece of ice, the leading satellite feels collected by satellite-born altimeters on two spacecraft, the gravitational anomaly sooner and starts to separate TOPEX and Jason, looking down at Earth. Figure 2.13 in distance a little bit from the trailing one. By carefully is the detailed record of what the satellite data show. measuring the variations in distance between the two Satellite measurements are probably more accurate satellites and when they occur, over a period of months and are global, with proper averaging over all the ocean it is possible to infer changes in the mass of the ice. In basins. They show a rate of sea level rise double that the case of Greenland, after taking measurements for which had been measured earlier—3 millimeters per several years, it was possible to put together Figure 2.16 year rather than 1.5. No one is sure yet whether this showing the ice mass loss. represents an acceleration of the rise of sea level over These results in Figure 2.16 compare very well the last 15 years, or whether it is just a more accurate FIGURE 2.13 1992–2006 sea level rise observed by satellite altimetry SOURCE: Eric Leuliette, University of Colorado, Boulder available at http://sealevel.colo- rado.edu; updated from Leuliette, E. W, R.S. Nerem, and G. T. Mitchum, 2004, Calibration of TOPEX/Poseidon and Jason altimeter data to construct a continuous record of mean sea level change, Marine Geodesy 27(1-2):79–94. 2.13 from Presentation.eps bitmap image

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33 GLOBAL CLIMATE CHANGE AND HUMAN CAUSES FIGURE 2.14 Northern Hemisphere sea ice extent (1979 versus 2003) Left: Sea ice minimum extent for 1979. Right: Sea ice mini- 2.14 sea ice collage.eps mum extent for 2003. SOURCE: NASA Goddard Space Flight Center Scientific Visualization Studio. with those generated by other satellite missions using GRACE mission, you get roughly the same number. different measurement techniques. One such technique A big ice-mass loss is taking place. Unfortunately the involves a radar altimeter looking down at the ice, satellite record is only 3 or 4 years long at this point. which enables the mapping of the height of the ice. By Similar results have been noted over Antarctica, but mapping the height of the ice and the way it is shrink- not in all parts. ing in height, you can calculate how much ice mass has Throughout the Cold War, the United States been lost. When compared to what is measured by the and Russia (the former Soviet Union) were operat- GPS Satellites K-band ranging measures Ground-based distance change between satellites GPS Receiver Mass anomaly of interest FIGURE 2.15 GRACE mission concept. SOURCE: Courtesy of NASA. 2.15 from Presentation.eps

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34 FORGING THE FUTURE OF SPACE SCIENCE FIGURE 2.17 Recent analyses of satellite measurements do 2.17 from Presentation.eps not indicate a long-term trend in solar irradiance (the amount of bitmap image energy received by the Sun). SOURCE: Courtesy of Physikalisch- FIGURE 2.16 Greenland Grace monthly mass solutions. Meteorologisches Observatorium Davos—World Radiation SOURCE: Reprinted by permission from Macmillan Publishers Center (http://www.pmodwrc.ch), updated from C. Fröhlich, Ltd: Nature (I. Velicogna and J. Wahr, Acceleration of Greenland Solar irradiance variability since 1978: Revision of the PMOD ice mass loss in spring 2004, Nature 443:329–331), Copyright composite during solar cycle 21, Space Science Reviews 125(1- 2006. 4):53–65, 2006. ing nuclear-powered submarines under the ice caps It was not that many years ago that people were throughout the Arctic. It was very much in their inter- theorizing that climatic changes that we were seeing est to measure how thick the ice was above their heads were due to the Sun. It is not possible to do that any- if they ever had to surface. A lot of these data have now more. We now have measurements that show that is been declassified. They show that the thickness of the not the case. The evidence is very strong that what we sea ice over the Arctic has decreased roughly 40 percent are seeing is a human effect. in the last 40 years. Figure 2.18 displays the result of a set of cal- Referring now to Figure 2.10, there is something unusual about the last 30 years. The warming is now be- ing observed everywhere. It is really difficult to find any temperature station in the last 30 years that is showing anything other than warming. Furthermore, the rate of change is faster than anything that has been measured before. It is also beyond the rate of variability that can be generated in a first principles fluid dynamical model of Earth’s oceans and atmosphere. Another distinction about the last 30 years is that it is the first period in human history in which it has been possible to measure the output of the Sun with enough precision to be able to say whether the Sun is getting warmer, giving us more heat or less. Figure 2.17 is a graph by Claus Frohlich and Judith FIGURE 2.18 C omputed and observed temperatures. Lean. They have merged measurements of the output SOURCE: P.A. Stott, S.F.B. Tett, G.S. Jones, M.R. A llen, J.F.B. Mitchell, and G.J. Jenkins, External control of of the Sun made by three different satellites over a 22- 20th century temperature by natural and anthropogenic year period. The output is changing, up and down, by f orcings, S cience 2 90(5499):2133–2137, doi:10.1126/ a tenth of a percent, roughly like a solar cycle. It is not science.290.5499.2133, 2000. Reprinted with permission trending upward. from AAAS.

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35 GLOBAL CLIMATE CHANGE AND HUMAN CAUSES culations done 5 or 6 years ago by Peter Stott and from 1970 to today, and then projected into the future. colleagues, where they tried to assimilate data into a Currently we are at about 412 quadrillion Btu. That global average temperature record. Globally averaged number has virtually doubled in 35 years—from 207 temperature is not the most important indicator of to 412 Btu (35 years at a 2 percent per year growth climate variability, but it is the easiest to measure and rate). Projecting ahead to the next 20 years, there is understand and the easiest to calculate. another 50-percent increase. This is thought to be a If you look at either natural or human activity rather conservative projection. (Probably 80 or 85 per- (“anthropogenic”) separately, the calculations do not cent of the carbon dioxide build up in the atmosphere represent what actually has been happening, but if you is due to fossil fuel usage. Fifteen to twenty percent is look at the two together (“all forcings”) you get a pretty due to tropical deforestation and loss of organic matter good simulation of what has been measured. As the from soil.) calculations in Figure 2.18 project into the future, based Another interesting feature, aside from raw growth mostly on fossil-fuel energy usage, they indicate a con- in demand, is where the growth is occurring. The dark tinued global warming. This is why people are getting blue part of the histogram in Figure 2.19 is from mature seriously concerned about the melting and breaking of market economies like the United States, Western Eu- ice formations over Antarctica and Greenland. When rope, and Japan. The red part is from so called “transi- ice formations on land melt, the water goes into the tion economies.” These are a little bit harder to define. ocean, adding to sea level rise. The brown part accounts for emerging economies like One other kind of evidence of ice changes has to China and India and a few other places in Asia. This do with seismic activity and cracks inside the ice, which is where the significant growth has come from in the is being recorded by seismic instruments. The level of last 10 years. that activity has multiplied in the last 5 years. It can be seen immediately that if we are going to try to solve this problem, either with technology or moderating demand and improving efficiency, we have What Do We Do? Where Is It All Coming From? a double challenge on our hands. We have to deal with What Is Going to Happen? what is happening currently and also with aspirations Figure 2.19 comes from the Energy Information for economic development, which is strongly linked Agency, which has compiled data of total world- to energy use in the emerging economies. This is one marketed energy consumption, by types of economy of the reasons why it has been difficult to obtain an international agreement on what to do. What do we need to do? Most people would say we need a dual strategy. We have to maximize energy Quadrillion Btu 1,000 efficiency and minimize energy use. We have to develop History Projections new sources of clean energy—where “clean” means not 800 just lower carbon dioxide emission, but lower emis- Emerging Economies 645 sions of mercury, sulfur, and black carbon and soot (the Transitional Economies 598 553 600 things that are making cities in developing countries so Mature Market Economies 504 unhealthy). This is the challenge. 412 348 366 400 There is some good news; in fact, there is a lot 285 310 243 of good news. Figure 2.20 shows the electricity con- 207 200 sumption per person in the United States and in California. 0 California’s electricity use per person has flattened 70 75 80 85 90 95 02 10 15 20 25 19 19 19 19 19 19 20 20 20 20 20 out over the last 30 years, while in the rest of the United States it has continued to go up. This has happened for FIGURE 2.19 World marketed energy consumption by region, several reasons. First, California instituted statewide 1970–2025. SOURCE:EIA 0484(2005).eps 2.19 Courtesy of Energy Information Admin- regulations on insulation in appliances and homes istration, U.S. Department of Energy.

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36 FORGING THE FUTURE OF SPACE SCIENCE kWh 14,000 12,000 12,000 U.S. 10,000 8,000 8,000 KWh 7,000 6,000 California 4,000 Art Rosenfeld at Lawrence Berkeley Lab turns his attention 2,000 to the energy problem 0 1990 1992 1994 1996 1998 2000 1960 1962 1964 1966 1968 1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 FIGURE 2.20 Electricity consumption/person in the U.S. and California. SOURCE: Adapted from Commissioner Art Rosenfeld, “Sus- tainable Development, Step 1: Reduce Worldwide Energy Intensity by 2% Per Year,” presentation at the Global Energy International Prize Presentation and Symposium, University of California at2.20 1.2-Chu.eps 2003. Courtesy California Energy Commission. Berkeley, November 19, and made it easier to buy energy-efficient appliances. Carrying out the same exercise in other states, you get Second, California adopted a pricing strategy whereby basically the same graph with more scatter. you pay more for electricity if it is used at peak demand No matter how you look at it, these changes are hours and less if you use it during off-peak hours. already happening, and in the future are going to be That saved a lot of money in terms of transmission significant. One way to rate the changes in importance lines—power plants that did not have to be built, and is whether or not they are reversible. so on. California also de-coupled the profits of utilities Back in the 1950s, 1960s, and 1970s, the biggest from the amount they were selling. Some of this was use of electricity in the home was the refrigerator. If you done through legal intervention and some through assume that there was basically one refrigerator in every regulation. house, Figure 2.22 shows the way household refrigera- During a congressional hearing last year where tor electricity consumption was going. In that period this author testified, the question was asked, “What’s refrigerators were getting bigger. Then California the big deal about 2 degrees temperature change?” An- instituted some standards on efficiency of appliances other witness said, “I can not even feel it. I can not tell and forced the manufacturers to start building better the difference between 72 degrees and 74.” By way of refrigerators, and the refrigerator electricity consump- response, it is worth referring to Figure 2.21, which is tion in California started going down. At the same based on data from the California Energy Commission time, the refrigerators were still getting bigger. In fact, for the summer of 2004. If the data are broken down what limits the size of a household refrigerator today into the number of days in the summer when the tem- is the width of the kitchen door! perature was 75°F, 80°F, 85°F, and so on, and the total But there is a mysterious “vampire” that has come electricity use for each temperature is plotted, the result into the situation. The lower curve in Figure 2.22 is a straight line. Every 2 degrees increase in summer shows the typical usage in a California household of daytime temperature costs 1.2 Gigawatts of electricity! “vampire electricity”—the electricity needed to operate

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37 GLOBAL CLIMATE CHANGE AND HUMAN CAUSES 50,000 Peak Electricity Demand (MW) y = 610.72x - 15120 45,000 R2 = 0.8484 40,000 35,000 30,000 25,000 75 80 85 90 95 100 Average Maximum Daily Temperature (F) FIGURE 2.21 Peak electricity demand in the CallSO area as a function of maximum daily temperature: June–September 2004. NOTE: CalISO = California Independent System Operator, a not-for-profit public-benefit corporation charged with operating the ma- jority of California’s high voltage power grid. SOURCE: California Climate Change Center, Climate Change and Electricity Demand 2.21 CEC-500-2005-201-SF.eps in California, White Paper CEC-500-2005-201-SF, February 2006. Courtesy California Energy Commission. 2000 Estimated Standby 1800 Average Energy Use per Unit Sold (kWh per year) Power (per house) 1600 1400 Refrigerator Use per 1978 Cal Standard Unit 1200 1987 Cal Standard 1000 1980 Cal Standard 800 1990 Federal 600 Standard 400 1993 Federal Standard 2001 Federal 200 Standard 0 2005 2003 2009 2007 2001 1999 1969 1989 1993 1983 1985 1967 1963 1965 1953 1977 1987 1995 1955 1949 1959 1991 1973 1979 1957 1997 1975 1981 1961 1971 1947 1951 FIGURE 2.22 United States refrigerator use (actual) and estimated household standby use v. time. SOURCE: Commissioner Art 2.22 1.2-Chu.eps Rosenfeld, “Sustainable Development, Step 1: Reduce Worldwide Energy Intensity by 2% Per Year,” presentation at the Global Energy International Prize Presentation and Symposium, University of California at Berkeley, November 19, 2003. Courtesy California Energy Commission.

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38 FORGING THE FUTURE OF SPACE SCIENCE appliances (TVs, computers, video recorders, and so on) national security. We could decrease local air pollution in the stand-by mode. We have got to do something and increase our national competitiveness. (On average, about the way many of these electronic appliances are manufacturing in Germany and Japan currently uses designed, because they have now surpassed what used about 60 percent as much energy per unit produced to be the biggest consumer of electricity in a typical as we do. At times of high-energy prices, that cost of household! We can do this. It is not that difficult. manufacturing is a significant part of the cost of unit What else can we do? Energy efficiency has to be production.) We could encourage the development of the first step. Even if you do not think that climate new products for global markets. change is serious, or you did not want to bet that cli- Americans are supposed to be the innovators. We mate change is going to be serious, you would still have are supposed to know how to create whole new indus- good reasons to do this because of all the things that tries. We could be grabbing these markets and helping energy efficiency would do. the world at the same time, if we would only get seri- First of all, it could decrease U.S. dependency ous about energy efficiency and create a whole new on foreign oil. Just driving our cars and trucks in the generation of energy-efficient products. All this, while United States today, we are using 6 million barrels of also slowing down the increases of carbon dioxide and oil per day more than we are producing. At $50 a barrel, methane in the atmosphere. Energy efficiency seems this accounts for about $200 billion of our trade deficit. to be a no-brainer. This trade deficit means that we are dependent for the There are lots of other things we can be doing. operation of our country’s entire economy on parts of However, it is going to take a combination of citizen the world that do not particularly like us. We should action, governmental action, and business leadership. clearly decrease our dependency and thus improve our

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