Question & Answer
From the Magazine: Saturday, October 14, 2006
To help elucidate the mysteries of climate change, Kenneth Green answers fourteen questions and separates hard fact from speculation.
1. What’s the truth: is the planet getting warmer?
Yes. We have been recording temperatures for only about 150 years, and the data are not completely reliable, but global average surface temperatures have increased by about 1.1 degrees Fahrenheit since the mid-19th century. The warming happened in two roughly equal phases, from 1910 to 1945, and then again from 1976 to the present.[i]
2. Why is the planet getting warmer? Is it a natural variation—a cycle like the Ice Ages—or something caused by humans?
From historical records and other kinds of evidence—such as geological changes caused by glaciers in ancient history or pre-history—we know that the climate is highly variable and that large natural changes can happen over short time periods. That could be happening now. On the other hand, some of the currently observed warming could be the result of human emissions of greenhouse gases. Because we know very little about the behavior of the climate more than 400 years ago, a simple analysis of historical climate can’t tell us whether observed warming is natural or not.[ii]
3. Then, why do some scientists blame human greenhouse gas emissions?
Some scientists, including those on the United Nations Intergovernmental Panel on Climate Change, conclude that since 1975, human activity has been the dominant factor influencing climate. This conclusion is based on computer models that forecast future trends based on a complex mix of factors that influence the climate. On the surface, this conclusion seems plausible as basic physics suggests that increased emissions of greenhouse gases—mainly carbon dioxide—by humans would trap more heat in the Earth’s atmosphere, a process called the “greenhouse effect.”
4. So, why are some scientists skeptical?
Because below the surface, things are more murky. Of the 12 phenomena the UN Climate Panel identified, as of 2001, that could either warm or cool the climate, only one is considered well understood: that is the heat–trapping effect of the greenhouse gases (see chart, page 94). Two other climate influences are given a “medium” level of understanding by the panel, and the other nine factors are understood “poorly.” In fact, some of the potential cooling forces and climate feedback mechanisms that are poorly understood may be large enough to offset the warming influence of the greenhouse gases. For example, research published in the August 4, 2006, issue of Science found that human-caused emissions of aerosol particles may increase cloud cover by up to 5 percent and that clouds have a cooling effect that may neutralize the warming that is caused by human-induced greenhouse gases. If that is true, then natural variation could be the best explanation for surface warming.[iii]
5. But what about the hockey stick? Doesn’t it prove that climate change is abnormal and caused by humans?
One bit of climate change debate that has received far more press attention than it deserves is a particular graph called the “hockey stick,” because of its appearance. The graph, originally published by a research group headed by Michael Mann at the University of Virginia, ostensibly estimates past temperatures in the Northern Hemisphere for the last 1,000 years by examining the changes in natural objects that are influenced by climate, such as tree rings and coral. The chart was featured prominently and repeatedly in the 2001 United Nations Climate Panel reports because it showed that recent climate change was an anomaly in a thousand-year-long context. The graph seems to show that only industrialization could be responsible for recent climate change. But a pair of Canadian researchers, Steve McIntyre and Ross McKitrick, found that methodological and statistical flaws in the Mann analysis had produced a chart that was highly misleading. The National Academy of Sciences set up a panel to review the hockey stick research and validated the criticisms.[iv] When they released their findings, panel members chided the UN Climate Panel for giving Mann’s research undue prominence in its landmark 2001 report.[v]
6. How warm is it likely to get?
No one can be sure
about the future, but that doesn’t stop people from trying to predict it.[vi]
The simplest way to project the future climate would be to make a linear
projection from what we’ve already seen. If human greenhouse gas emissions are
causing the majority of recent warming, and if the warming continues in a
linear fashion as suggested by the basic physics of the greenhouse effect, then
the average temperature could rise by about 2.7 degrees F by the year 2100.[vii]
7. But Al Gore and others talk about huge increases of temperature, like 11 degrees. Why?
The UN Climate Panel, instead of using a straightforward linear model, projects future temperatures by feeding many assumptions about what the future will be like (economically, politically, technologically, etc.) into a computerized model of the climate. This approach produces a broad range of possible amounts of warming for 2100, from about 2.5 degrees F all the way up to 10.4 degrees F, but the exercise is highly imaginative. The input assumptions used in this process have been criticized,[viii] and high-end predictions are considered unlikely.[ix] Because of the inclusion of these high-end scenarios, the mid-range prediction of the UN Climate Panel is for an increase in global average temperatures of about 5 degrees F by the year 2100.[x]
8. Regardless of what’s causing it, what are the consequences of a 3-to-5-degree increase in the average temperature?
Nobody really knows because the computer models for predicting these consequences are the most limited of all. But from the most fundamental parts of climate theory, some changes are more likely than others: increased summertime highs, decreased wintertime lows, rising sea levels, more drought in some places and more rainfall in others, and yes, potentially more powerful (though not necessarily more frequent) storms.[xi] The likely consequences are far milder than the doomsday scenario some climate alarmists have put forward, but a warmer Earth is a challenge to be taken seriously.
9. Why not reduce our greenhouse gas emissions just in case?
Because regardless of
how nice it sounds, achieving major reductions in greenhouse gas emissions in
the near term is more a fantasy than a meaningful climate policy. People all
over the world want to live better. They want more food, more housing, more
medical care, more cars—and they want these improvements within their
lifetimes. Securing all of these benefits–especially at a time when three
billion people are joining the world economy, with the fall of communism and
the opening of India and
China—requires far more energy than can be produced in the next 50 years by such low-emission technologies as wind and solar power. At the national level, raising prices to reduce energy use—the most efficient way to limit emissions—would cause economic harm intolerable to people in most countries.[xii] Governments that restrict energy use or raise energy prices will render their national economies less competitive against countries that don’t. They will, inevitably, be forced to back away from the controls as companies flee to less-regulated places, taking good jobs with them.
Developing countries—including China and India, which are predicted to surpass the greenhouse gas emissions of developed countries by 2018—have refused to acquiesce to global greenhouse gas reduction schemes.[xiii] The reductions that developed countries could achieve by themselves would have little effect on the climate. To prevent such free-riding, a global climate regime would require establishing a global body with binding authority to set and enforce limits on the energy use of all countries—an unlikely event.
10. But what if we joined the international Kyoto treaty—wouldn’t that help?
The Kyoto Protocol, which the U.S. signed in 1997, has never—during either the Clinton or George W. Bush administrations—been submitted to the Senate for ratification. It called for U.S. emissions to be cut to 7 percent below 1990 levels. That may not sound like much, but, since energy use has risen significantly since 1990, the restriction would have meant reducing U.S. emissions by about 30 percent from “business as usual” by 2008-2012—a huge and costly reduction that many ratifying countries have missed spectacularly.[xiv] Even if Kyoto had worked all over the world, the treaty would have had an insignificant effect. Climate scientists supporting Kyoto acknowledge that the agreement, by 2100, would avert only 4 to 6 percent of the warming they attribute to human activity.[xv] The Energy Department during the Clinton administration estimated that meeting the requirements of Kyoto would reduce U.S. gross domestic product by 1 percent to 4 percent a year.[xvi] As a result, years of moderate growth could become no-growth or recessionary years.
11. Could we just adapt to the changes in climate?
Adaptation has been the neglected step-child in the climate policy debate for decades. Often derided by advocates of the Kyoto Protocol or other greenhouse-gas-reduction schemes as a “do-nothing” approach, it is anything but. In light of Kyoto’s failure, adaptation is beginning to get the kind of attention that it deserved all along. According to Frances Cairncross, the chairman of Britain’s Economic and Social Research Council, “Adaptation policies have had far less attention than mitigation, and that is a mistake…. We need to think now about policies that prepare for a hotter, drier world.”[xvii]
12. How might we adapt?
For the near-term, we could improve the resilience of infrastructure, including our power grid, our transportation system, our food supply, and protective structures such as seawalls (to guard against a rise in sea level from warmer water and melting ice caps). Governments will almost certainly get a better return investing in infrastructure protection than in greenhouse gas reduction schemes.
13. But what about protecting our environment, not just our buildings?
historically have done a better job protecting their ecosystems than poor
nations. So the smartest way to help the environment is to build strong
economies. That means free markets, enforceable property rights, and honest
governments based on the rule of law.
14. Is there anything else, besides reducing emissions or strengthening infrastructure, that we might do?
Yes. We could pull
greenhouse gases back out of the air after they are emitted. Trees turn carbon
dioxide into oxygen and stable carbon compounds, so we could plant more
forests. We might also store CO2 underground or in the oceans. Research is
Kenneth Green is a resident scholar at the American Enterprise Institute. He has served as an expert reviewer for the United Nations Intergovernmental Panel on Climate Change, and has studied climate science and policy for over 15 years, working at California’s Reason Foundation, then at Canada’s Fraser Institute. He holds a doctorate in environmental science and engineering from the University of California at Los Angeles.
[i] United Nations Intergovernmental Panel on Climate Change. Climate Change 2001, The Scientific Basis, Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Available at . The United Nations has circulated a draft copy of the forthcoming Fourth Assessment Report in which some values differ from the Third Assessment Report. Out of respect for the citation restrictions that the UN placed on the draft report, it will not be cited here.
[ii] National Academy of Sciences, Surface Temperature Reconstructions for the Last 2,000 Years (National Academy Press, 2006). Available from the National Academies at
[iii] Yoram J. Kaufman and Ilan Koren, “Smoke and Pollution Aerosol Effect on Cloud Cover,” Science 313 (2006).
[iv] National Academy of Sciences, Surface Temperature Reconstructions.
[v] Kurt Cuffey and Gerald North, “Surface Temperature Reconstructions for the Last 2,000 Years,” press conference via webcast:
[vi] Hadley Centre for Climate Prediction and Research, Met Office, “Climate Change Projections,” available at .
[vii] The warming rate from 1975 to 2000 was about 0.27 °F/decade.
[viii] Ian Castles, “IPCC Emissions Scenarios: The Case for a Review,” in IPCC Issues: A Swag of Documents (2003). Available at
[ix] Mort Webster, et al., “Uncertainty Analysis of Climate Change and Policy Response,” MIT Joint Program on the Science and Policy of Global Change, Report No. 95 (December 2002). Available at:
[x] United Nations Intergovernmental Panel on Climate Change. Climate Change 2001: The Scientific Basis.
[xi] R. A. Pielke Jr., et al., “Hurricanes and Global Warming,” bulletin of the American Meteorological Society, November 2005. Available on the author’s website at
[xii] As Stephen P. A. Brown, director of Energy Economics and Microeconomic Policy Analysis at the Federal Reserve Bank of Dallas, puts it: “Higher crude oil prices squeeze refiner’s margins, and higher prices for petroleum products such as gasoline, diesel and jet fuel raise costs for the transportation sector. Higher domestic natural gas prices put considerable pressure on the U.S. petrochemicals industry—which has to compete against foreign competitors that use crude oil or lower-priced foreign sources of natural gas. It also raises costs for petrochemicals users. Higher natural gas prices also hurts [sic] domestic fertilizer producers, and makes crop production more costly.” Stephen P. A. Brown, “Energy Prices and the Economy,” February 2004. Available at .
[xiii] Energy Information Association, “Greenhouse Gases, Climate, and Energy,” Chapter 1. Last Modified April 2, 2004. Available at http://www.eia.doe.gov/oiaf/1605/ggccebro/chapter1.html.
[xiv] AFX News, “Canada, Japan, Europe failing on Kyoto greenhouse gas targets—UN,” November 18, 2005. Available at http://www.forbes.com/finance/feeds/afx/2005/11/18/afx2345473.html.
[xv] Tom L. Wigley, “The Kyoto Protocol: CO2, CH4 and climate implications,” Geophysical Research Letters, Vol. 25 (1998).
[xvi] Energy Information Administration, “Impacts of the Kyoto Protocol on U.S. Energy Markets and Economic Activity,” Table ES-1. Report # SR-OIAF/98-03, October 1998. Available at
[xvii] Roger Highfield, “Kyoto isn’t working, prepare for climate change, say scientists,” The London Telegraph, September 4, 2006. Available at
[xviii] U.S. Climate Change Technology Program, “Technology Options for the Near and Long Term,” November, 2003. Available at
[xix] U.S. Department of Energy, “Carbon Sequestration R&D Overview” (Washington, D.C.). Available at (accessed September 13, 2006).
[xx] Office of Science, “Carbon Sequestration Focus Areas.” Available at (accessed September 14, 2006).