green@work : Magazine : Back Issues : Sept/Oct 2003 : Global Warming

Global Warming: Fact or Fiction?
Is the threat of global warming and climate change real or simply an exaggerated claim? Two groups weigh in on the controversial and complex topic.

In July 2003, the Independent Institute, an Oakland, CA-based non-profit research and education organization, released a report entitled, New Perspectives in Climate Science: What the EPA Isn’t Telling Us. According to a news release issued when the report was published (see facing page), critical portions of science in many well-regarded climate change reports is “misleading,” including the 2001 National Assessment of Climate Change by the United Nations Intergovernmental Panel on Climate Change, the 2000 National Assessment of the U.S. Climate Change and the EPA’s 2001 Climate Action Report. The institute states that this is not an indictment of the individuals involved in creating the reports, “but is rather more symptomatic of the nature of science when funded by a government leviathan.”

In an effort to explore the claims made by the Independent Institute, green@work asked the Pew Center for Global Climate Change to comment on the report, specifically the four items highlighted in the news release that address the concept that the climate’s change is less than previously thought. Established in 1998 as a non-profit, non-partisan organization, the mission of the Pew Center on Global Climate Change is to provide credible information and innovative solutions in the effort to address global climate change. It brings together business leaders, policy makers, scientists and other experts to bring a new approach to a complex and often controversial issue, one that it says is based on sound science, straight talk and a belief that all parties involved can work together to protect the climate while sustaining economic growth.

Following are comments co-authored by Eileen Claussen, president of the Pew Center and president of Strategies for the Global Environment, along with Benjamin Preston, a senior research fellow with the Pew Center, which address specific items included in the Independent Institute’s report.

During the summer of 2003, while the Congress was actively engaged in debating various legislative proposals to address climate change, the Independent Institute released a brief report entitled New Perspectives in Climate Science: What the EPA Isn’t Telling Us. According to the press release issued by the Independent Institute, the new report highlights research provided by the Independent Institute’s panel on climate change. However, the assembled panel was comprised exclusively of individuals skeptical of the science of climate change, and the research that is presented within the report appears to have been selected to undermine the opinion of the mainstream scientific community: that human-induced climate change is a real phenomenon with real consequences. Here, we choose to concentrate on the four summary statements within the Independent Institute’s press release and examine the disparity between its view of science and that of the mainstream scientific community.

Independent Institute: Scientists established that the climate since the termination of the last glacial stage, some 12,000 years ago, has hardly been stable or constant, states the report. “Between four and seven thousand years ago, the earth’s mean surface temperature was some one to two degrees Celsius higher than it is today, for largely unknown reasons.” The Earth goes through periods of global warming, just as it does global cooling.

Comments: The global climate is variable over short- to long-time scales, and there have undoubtedly been periods in Earth’s history where the global climate was warmer or cooler than it currently is. Such variability does present a challenge for those attempting to identify trends in climate change and attributing those changes to specific sources. However, factors that influence climate are not mysterious, unknowable forces, and climate change observed over the 20th century is not simply the result of natural variability. Multiple studies over the past several years indicate that current temperatures in the Northern Hemisphere (for which the best data are available) as well as the rate at which they are increasing are greater than at any point in the past 1,000 to 2,000 years.

Although scientists are well aware of climate’s variability, they are also interested in assessing the extent to which these various natural and human factors can account for that variability. The two principle factors that ultimately determine the temperature of the Earth are the sun and the composition of the atmosphere. Variability in the orbit of the Earth around the sun or changes in the quantity and character of radiation emitted by the sun have a major influence on global climate. However, atmospheric composition is critical as well. Water vapor in the atmosphere, itself a greenhouse gas, keeps the planet approximately 60oF warmer on average than it would otherwise be. Other greenhouse gases from human activities compound this warming effect. Meanwhile aerosol particles that form in the atmosphere due to emissions of certain air pollutants from volcanoes and fossil fuel combustion can also reflect or absorb solar radiation to influence global climate.

Taking these factors into account, the United Nations’ Intergovernmental Panel on Climate Change (IPCC), along with dozens of independent studies, have come to similar conclusions: the variability observed in 20th-century climate cannot be explained without considering human emissions of greenhouse gases, and greenhouse gases are responsible for the majority of the warming observed in recent decades.

Independent Institute: Satellite records: Satellite data show a net global temperature trend of +0.06 degrees/decade, significantly less than forecast by climate models that are based on bad science. Annual satellite records show no significant change whatsoever.

Comments: Temperatures have been measured at weather stations at the Earth’s surface for approximately the past 150 years, yielding what is generally referred to as the surface temperature record. Surface temperatures have, in fact, increased significantly over the past century—a finding echoed by two separate reports by the U.S. National Academy of Sciences. In addition, temperature data for the troposphere (the lower layer of the atmosphere) have been obtained from weather balloons and orbiting satellites since the late 1970s, yielding what is referred to as the satellite record. Over the time period for which both surface and satellite data are available (1979 to present), surface temperatures have warmed faster than satellite temperatures. For example, the National Oceanographic and Atmospheric Administration reported warming of Earth’s surface temperatures between 1979 and 2002 of +0.29oF/decade. In contrast, satellite trends range from +0.06-0.21oF/decade (based upon two recent analyses of the same data). Due to uncertainties in both surface and satellite temperatures, it remains unclear just how much difference truly exists between the two records, although both records do show warming. However, the Independent Institute chooses to focus on the temperature trend that suggests the lowest possible rate of warming, suggesting that this is the single best indicator of global temperature.

The warming trends observed over the past few decades are indeed only a fraction of what is anticipated in the future. In 2001, the IPCC projected that surface temperatures would increase over the 21st century by an estimated two to 10oF, based upon future trends in greenhouse gas emissions. The Independent Institute’s report opted to choose the low-end of the range of warming indicated by the satellite record (+0.06oF/decade) as the best indicator of future warming, which translates into 21st-century warming of only about half a degree. Yet the Independent Institute’s analysis is problematic for two reasons. First, as noted above, there is uncertainty in the satellite temperature record and the satellite record may not be an accurate indicator of warming at the Earth’s surface where we live. Second, the assumption that future warming will be limited to historical rates is erroneous and scientifically untenable, because it ignores future patterns of global energy use and, thus, greenhouse gas emissions. The only way to ensure that the rate of future warming does not exceed that at present is to cap global greenhouse gas emissions at current levels, but even then greenhouse gases would continue to accumulate in the atmosphere, thus the warming would continue.

Independent Institute: EPA bias: The 2001 Climate Action Report, produced by the EPA to make projections and possible policy ideas, relies heavily on the 2000 National Assessment of global warming. The 2000 National Assessment is a Clinton Administration product that was based on bad science; it used models for climate projections that perform worse than a table of random numbers when applied to 10-year moving averages of U.S. temperatures since 1900.

Comments: The Climate Action Report (CAR), released in 2002 (not 2001), was an official communication from the U.S. Department of State to the United Nations’ Framework Convention on Climate Change. The CAR was intended to summarize the U.S. perspective on climate change, its implications for the United States, and the U.S. response. The U.S. National Assessment was a multi-year effort on behalf of the U.S. Global Change Research Program to assess the state of knowledge regarding the potential consequences of climate change to the nation. Although the Independent Institute’s report refers to this as a Clinton Administration document, the completion of such an assessment was mandated under the Global Change Act of 1990, passed during the first Bush Administration. Thus, when developing the chapter of the CAR regarding the potential consequences of climate change, its authors naturally went first to the National Assessment.

In addition to rejecting the results of the National Assessment as a Clinton Administration product, skeptics of climate change have raised questions about the two climate models used to project future changes in U.S. temperatures over the 21st century: the Canadian Climate Model and the United Kingdom Hadley model. The reference to these models “performing worse than a table of random numbers” is based upon statements by Patrick Michaels, the Virginia state climatologist and a senior fellow with the Cato Institute. This critique sounds quite damning, until one investigates what it actually means. Michaels’ implication that randomly selected numbers mimic reality better than climate models is a misleading exaggeration. Michaels calculated the long-term average temperature of the United States and then compared how closely annual temperatures from observations and the climate models matched this long-term average. Because climate varies from one year to the next, one would expect the temperature in any given year to be slightly higher or lower than the long-term average. Michaels found that observed temperatures tended to match the long-term average more closely than temperatures predicted by the Canadian and Hadley models. Michaels has used this to argue that the models are invalid, but this seems to be a case of Michaels placing unrealistic expectations on climate models and ignoring the big picture.

The critical question is whether or not these climate models produce reasonable estimates of long-term climate trends, to which the answer is yes. As the authors of the National Assessment have commented repeatedly, including testimony before the U.S. Congress, the models do a reasonable job of reproducing 20th-century climate when they incorporate basic factors such as solar variability, greenhouse gases and aerosols. Furthermore, their projections for 21st-century climate are consistent with the suite of climate models currently in use around the world. For example, when used in the National Assessment, the Hadley and Canadian models projected 21st-century global warming of 5oF and 8oF, respectively. As mentioned earlier, IPCC’s range for future global warming is 2oF to 10oF. Given that both the estimates produced for the National Assessment fall within the range produced by the IPCC (and other scientists), the argument that they are unreasonable is without merit.

Furthermore, the Canadian model (which has received the brunt of the criticism for producing “alarming” scenarios of future warming) projects warming of nearly identical magnitude to the climate model utilized by NASA’s Geophysical Fluid Dynamics Laboratory (GFDL). The fact that GFDL was recently selected by the Bush Administration to be one of two premier modeling centers in the United States for studying climate change indicates that the Canadian model is neither an outlier nor is its performance in simulating future climate inherently flawed.

Independent Institute: Global warming and urban mortality: Examining the relationships between warming and mortality in 28 U.S. cities, heat-related mortality declined in 22 of the 28 cities. In the 1980s, many cities (especially in the southern United States) experienced no excess mortality, an effect that spread northward across interior cities in the 1990s.

Comments: The decrease in heat-related mortality in some southern cities over the past two decades can largely be attributed to human actions to limit exposure to high temperatures, not the least of which is the use of air conditioning (as the Independent Institute report itself acknowledges). This also explains lower rates of heat-related mortality in southern cities relative to northern cities. The use of air conditioning has proliferated more rapidly through southern cities because of higher average summer temperatures. Northern cities as a whole have been slower to adopt such measures and, thus, are at a greater risk of heat-related mortality during extreme events. For example, the 1995 heat wave in Chicago, IL, resulted in an estimated 700 excess deaths. Similarly, this summer’s heat wave in Europe is currently believed to have caused approximately 11,000 excess deaths in France, where summer temperatures are typically mild. Thus, even wealthy, developed countries are vulnerable to the effects of climate, particularly when they are caught off-guard by sudden, extreme events. Such extreme temperature events are projected to become more common as a result of climate change, and thus the Independent Institute report again errs by assuming that the past is an accurate indicator of what’s to come in the future.

The Independent Institute report faults the National Assessment and the IPCC with presenting overly alarming discussions of the potential for increased heat-related mortality. In truth, both reports were actually optimistic about the ability for the United States, at least, to adapt to potential adverse health effects of climate change. For example, relatively simple technologies such as air conditioning, combined with early-warning systems and health communication were acknowledged as potential measures to reduce the risk associated with heat-related mortality. But ironically, increased use of such technologies increases energy use, which drives up energy costs as well as greenhouse gas emissions that contribute to global warming. Furthermore, there will always be populations at risk, such as the poor, the elderly and those that work or recreate outdoors. If one looks beyond the borders of the United States, it’s obvious that implementing even rudimentary preventive measures remains a challenge, particularly for developing countries. Thus, the good news is that actions can be taken to protect human health, but effort must be exerted to ensure that they are taken and that such protections are equitably distributed—and that such actions themselves do not lead to greater environmental consequences over time.

As the United States and the world move forward in addressing the challenge of climate change, it is important that we remain committed to conducting research to improve our understanding. However, there are a number of aspects of climate change that we know with a high degree of confidence: the world is warming; humans are increasing the concentrations of greenhouse gases in the atmosphere; continued emissions of such gases will contribute to future changes in the global climate; and such changes will have consequences for the world’s natural and societal systems. There are additional details about which we remain uncertain, however; even a small magnitude of warming can have serious implications for the global environment. Furthermore, the effects of climate change could turn out to be worse than currently projected. Given what we already know about human contributions to global climate change and the risk of increasingly severe consequences in the future, we have ample information upon which to act to address this challenge.