March 11, 2004

Scorched Truth

Filed under: Climate Politics

The environmentalist organization Bluewater Network is taking credit for inspiring Senators John McCain (R-Ariz.) and Ernest Hollings (D-S.C.) to ask the U.S. General Accounting Office (GAO) to investigate potential impacts of climate change on public lands and waters.

Let’s hope the GAO gets it right, because the Bluewater Network report that purportedly prompted the Senators’ request is a bit off the mark, to say the least.

Bluewater Network is an environmental organization whose stated mission is to promote “critical policy changes in government and industry to reduce dependence on fossil fuels and eradicate other root causes of air and water pollution, global warming, and habitat destruction.” Its 2002 report entitled Scorched Earth examines the consequences of potential climate change on U S. public land and waters.

The fact is, Scorched Earth is just another in a long series of similar publications from environmental organizations that rely on extreme scenarios and misstated science to suggest that the climate and ecosystems of the United States will be rendered unrecognizable as a result of anthropogenic emissions of greenhouse gases.

The report’s Executive Summary contains a paragraph that epitomizes the doom-and-gloom predictions. Our rebuttal demonstrates how recent scientific findings counter those predictions and presents a more realistic (but admittedly far less dramatic) version of both the known, and potential, impacts of climate change. Here’s hoping the GAO finds inspiration here, and not in the same place McCain and Hollings did.

First, the “problem,” as characterized by Bluewater Network in Scorched Earth:

Over the past 100 years, emissions of greenhouse gas pollution have led to increased global temperatures of more than 1ºF, which is unprecedented in the past 1,000 years. Scientists worldwide predict that the pace of global climate change will accelerate over the next century and impact ecosystems with increasingly dramatic results. Average global temperatures could increase by up to 10.4ºF, a change unprecedented over the past 10,000 years. This temperature increase is projected to result in reduced water availability, increased catastrophic wildfires and storms, and habitat impacts that could wipe out entire species and ecosystems. Scientists predict a rise in sea level of up to 2.89 feet as a result of projected global temperature increases. Coupled with increasingly severe storm events, a sea- level rise of this magnitude will reshape coastlines and submerge low-elevation islands entirely in both the U.S. and abroad. These global climate change impacts will occur so rapidly that many plant and wildlife species will not survive.

“…increased global temperatures of more than 1ºF.”

Let’s start from the beginning. True, there has been a global temperature rise of about 1ºF in the past 100 years. But about half of that rise occurred prior to the mid-1940s—a period before there were large anthropogenic emissions of greenhouse gases. Between the mid-1940s and mid-1970s, global temperatures even declined somewhat, before beginning to rise again from the late-1970s to the present. A human fingerprint on the temperature increase during the past few decades is probable, because, as predicted by theory, the warming tends to take place in the coldest air of the winter, mainly in Siberia. But, this timing makes it inaccurate and misleading to state that the temperature rise that began more than 100 years ago has resulted from human-enhanced levels of greenhouse gases in the atmosphere.

“…scientists worldwide predict that the pace of global climate change will accelerate over the next century…”

The pace of global climate change is not widely forecast to accelerate during the next 100 years. Figure 1, taken from the UN Intergovernmental Panel on Climate Change’s 2001 Third Assessment Report (TAR), shows global temperature projections from a suite of different climate models. All the models were run with the same 1% per year increase in atmospheric carbon dioxide concentration. With few exceptions, these climate models all predict that global temperature rise will proceed at a constant (i.e., linear) rate, and not a rate that increases with time (i.e., accelerates). What’s more, the actual observed rate of increase of atmospheric CO2 concentration is less than one-half the value used in the simulations. Had the IPCC used the actual observed rate, then the rate of change of future global temperatures would be closer to the observed trend, given by the blue line that we have added to the U.N’s figure.

IPCC Temperature Projections

Figure 1. The global temperature change predicted by a suite of climate models for a 1% per year increase in atmospheric carbon dioxide levels (from the Third Assessment Report of the Intergovernmental Panel on Climate Change). The added blue line is the observed warming, which is clearly at the lower limit of the range.

“Average global temperatures could increase by up to 10.4ºF…”

The IPCC’s TAR gave the range of potential temperature rise by 2100 as 2.5ºF to 10.4ºF. Apparently Bluewater Network decided that it was better to leave off the lower end of that range and instead emphasize only the most extreme possibility. Was that because far less disastrous, and in many cases even beneficial, ecological impacts result from the small change at the low end of the range?

“a rise in sea level of up to 2.89 feet…”

The same holds true here. The IPCC TAR gives the range of sea-level rise by 2100 resulting from anthropogenic greenhouse gas increases as 0.30 to 2.89 feet. Again, Bluewater emphasizes only the highest end of the range. The low end of this range results in impacts no greater than those we observed during the 20th century, minor changes to which we fully adapted.

“…increasingly severe storm events…”

A common environmentalist promise, but yet another that is unfounded. On March 3, 2004, Sen. McCain called a meeting of the full Committee on Commerce, Science, and Transportation to hear testimony on the impacts of climate change. The scientists testifying before the committee were carefully selected to present a single side of the issue—that global warming was a threat so dangerous as to require urgent attention. When Sen. Frank Lautenberg (D-N.J.) directly asked witness Jerry Mahlman from the National Center for Atmospheric Research about how increasingly severe storms would impact the New Jersey coastline, even Mahlman testified that the projections of increasingly severe extratropical storms were “unfounded.”

“…many plant and wildlife species will not survive…”

Plants and animals in the United States have been subjected to wide natural fluctuations of temperature during the past 100 years, and undoubtedly for many centuries before recordkeeping began. Figure 2 shows the U. S. annual average temperature history since 1895, as kept by the National Climatic Data Center. In 1917, average temperature came in just under 51ºF. Just four years later, in 1921, the average temperature was 54.5ºF—more than 3.5º warmer. Massive extinctions did not result. The varied terrain and climate of the United States provides for the existence of a great many microclimatic niches, and the species that inhabit them are well adapted to rather large climate variations. That is not to say that a changing climate, in whatever direction, might not lead to species range shifts and in some cases even species loss. But as Figure 2 shows, U.S. flora and fauna are accustomed to adapting to fluctuations in climate, both long- and short-term.

US Temperatures

Figure 2. Average annual temperature history of the United States, 1895-2003, according to the National Climatic Data Center.

The Executive Summary of Bluewater Network’s Scorched Earth is accurate in one respect: It correctly characterizes the misconceptions contained throughout its 52 pages. So much for the publication said to have inspired McCain and Hollings’s GAO request. Of course, as the investigative arm of Congress, the GAO need not follow Scorched Earth’s lead. With any luck, the GAO will look to our pages, and the science on which they are based, for inspiration. In addition, we would like to direct their attention to two things:

1) The availability of a true picture of temperature change.

A scientific consensus has emerged as to what the rate of temperature change will be in the coming century—and it is at low end of the 1.4ºC to 5.8ºC range of the IPCC TAR. That consensus is well represented by the work of two prominent scientists who are often considered to represent opposite poles of informed opinion about climate change. In recent scientific papers, Patrick Michaels (2001) and James Hansen (2001)— both of whom have been intensely studying this issue for many years—have concluded that the most likely rate of temperature rise during the next 50 years as a result of anthropogenic emissions will be about 0.75ºC plus or minus about 0.25ºC. Both researchers reached their conclusions independently after careful study of a wide variety of actual observations (rather than sole reliance on climate model output). Each goes on to suggest that the rate of warming in the second half of the 21st century may even be lower. Why? Among the many reasons is that global per capita emissions of carbon dioxide peaked in the mid-1980s and has declined significantly since then, indicating that the world’s energy efficiency is increasing.

The impact of a temperature rise of this modest degree on America’s public lands and waters will be far beneath the dire consequences Bluewater Network has foretold, and in some cases will likely lead to beneficial responses.

2) Already, climate change has led to a better environment for plant life.

Consider the work of Ramakrishna Nemani and colleagues, who studied two decades’ worth of satellite observations of large-scale plant growth patterns across the world. The team reports a remarkable enhancement of global vegetation during that time. Nemani concludes the enhanced growth resulted from a combination of two major influences: the increased fertilization effect from growing concentrations of atmospheric carbon dioxide and the patterns of change in the earth’s climate during the study period. That finding is strong evidence of a global-scale benefit of greenhouse gas enhancement—and stands in stark contrast to a picture of ecological destruction. For the plant life that constitutes a vital part of America’s public lands and waters, greenhouse gas enhancement has proven beneficial. Again, this is information that Bluewater Network has left out of its commentary.

To produce an accurate report, it is imperative that the GAO look to these and other actual observations of the impacts of climate change, how plants and animals (including humans) have adapted to those impacts, and how climate change may proceed into the future. It is not appropriate to rely heavily on modeled projections of what the climate is supposed to look like. Depending too completely on climate models will simply lead to another scientifically indefensible fiasco. Recall the U. S. National Assessment on Climate Change—the last large-scale effort to describe the potential impacts of climate change on the United States. The modeling science underlying that report was so bad that the Office of Science and Technology Policy (OSTP) ruled that it failed to meet Federal Data Quality Act standards, implying that its contents would not hold up to careful scientific scrutiny (See for more details). The GAO should be careful to avoid a repeat.


Bluewater Network, 2002. Scorched Earth: Global climate change impacts on public lands and waters.

Hansen, J.E., and M. Sato, 2001. Trends of measured climate forcing agents. Proceedings of the National Academy of Sciences, 98, 14778–14783.

Intergovernmental Panel on Climate Change, 2001. Climate Change 2001: The Scientific Basis. Houghton, J.T., et al. (eds.), Cambridge University Press, Cambridge, U.K., 881pp.

Michaels, P.J., et al., 2001. Revised 21st century temperature projections. Climate Research, 23, 1–9.

Nemani, R.R., et al., 2003. Climate-driven increases in global terrestrial net primary production from 1982 to 1999. Science, 300, 1560–1563.

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