Cooling Overheated Global Warming Rhetoric

Brief Analyses | Global Warming

No. 345
Wednesday, December 20, 2000
by H. Sterling Burnett

The November 2000 negotiations at the Hague, Netherlands, on implementing the 1997 Kyoto Protocol on climate change took place against a backdrop of lobbying by environmental non-governmental organizations (NGOs). These NGOs used selective science and inaccurate news reports to demand that the United States accede to international demands for drastic, immediate action to reduce greenhouse gas emissions. However, a closer look at the evidence shows that they downplayed uncertainties in the studies that they cited, and ignored other studies that cast doubts on the need for immediate emission cuts.

Proxies For Past Temperature: Longer Measurements Are Better Than Shorter Ones

In the July 14 issue of Science, Dr. Thomas Crowley of Texas A & M University concluded that the 20th century has been the warmest century of the past 1,000 years and that greenhouse gas emissions from human energy use are responsible for as much as 75 percent of this warming. Crowley used data from tree rings and ice core boreholes to construct estimates of temperature trends, saying that previous studies using such data were hampered by "inadequate lengths of the time series being evaluated." Crowley attempted to control for solar and volcanic activity to separate "natural" climate variability from human-induced temperature variations.

A thousand years is a blip in geologic time. Looking at temperature records over even longer periods might lead one to quite different conclusions. In an analysis published by the National Center for Policy Analysis on August 31, 2000, Dr. David Deming of the University of Oklahoma points out that Earth's average temperature was higher than at present for more than 7,500 of the past 10,000 years [see the figure] . Indeed, borehole measurements indicate Earth was as much as 1.5 degrees Fahrenheit warmer for 5,000 of those years. This was during a time of lower greenhouse gas levels and when human actions could have had only a minuscule effect on temperature trends.

Regional Climate Predictions: How Not To Do Global Warming Modeling

The draft report of the "National Assessment on the Regional Impacts of Climate Change in the United States" issued by the Clinton Administration in June 2000 used selected computer models to estimate future regional climate trends under conditions of higher greenhouse gas levels.

However, the National Academy of Sciences, the United Nations Intergovernmental Panel on Climate Change (IPCC) and the Pew Center on Global Climate Change have all stated that climate models cannot produce meaningful regional predictions. The U.S. Environmental Protection Agency concurred, stating, ". . . complicated computer models . . . are still not accurate enough to provide reliable forecasts of . . . the direction, let alone the magnitude or timing, of the seasonal or even annual changes . .."

In addition, the National Assessment relied on two computer models - developed by the Canadian Centre and the United Kingdom's Hadley Centre - which repeatedly disagreed. For instance:

  • For the Southeastern U.S., the Canadian model forecasted less precipitation during the coming century than at present, while the Hadley model predicted more.
  • For the Midwest, the Canadian model predicted an increase in the frequency and severity of droughts, while the Hadley model forecasted fewer and less severe droughts.
  • The Canadian model predicted that water levels in the Great Lakes would fall by approximately five feet, while the Hadley model predicted increased Great Lakes levels of about one foot.

The most troubling portion of the National Assessment was its overview, which made claims unsupported by the underlying research. For instance, the lead authors of the Health Section said, "Many statements in the Overview Document have a rather extreme/alarmist tone and do not appear to fairly reflect the scientific literature, the historical record, or the output of the extant models." The overview also misrepresented the scientific findings concerning links between global warming and hurricane activity. A scientist involved with that portion of the assessment said, "I am concerned that sections where hurricanes are discussed are too often giving the impression . . .that hurricanes will be an ever growing menace in a generally warmer, wetter climate. . . . [F]or the present, the science does not support this view."

Trouble at the North Pole or Trouble with the Facts?

A story in the August 19, 2000, New York Times reported that for the first time in 50 million years the ice pack at the North Pole had melted. Harvard University oceanographer James J. McCarthy, a prominent member of the IPCC, observed open water at the North Pole while exploring the Arctic ecosystem on an educational cruise last summer. He and others pointed to this "discovery" as more evidence of the effects of human-caused climate change.

However, scientists more familiar with the Arctic's climate history and geological record report, and the IPCC's own temperature records indicate, that rather than being unprecedented, open water at the North Pole is fairly common. During the summer at any one time, more than 10 percent of the Arctic Ocean is free of ice and it is not rare that the North Pole is part of that 10 percent.

This evidence prompted the Times to retract its original story. In its August 29 edition, the Times admitted that it had misstated the true condition of polar ice and that Dr. McCarthy "would not argue with critics who said that open water at the pole was not unpre-cedented."

Ignoring Criticisms Of Current Climate Change Claims

Those advocating U.S. action to implement the Kyoto accord and reduce greenhouse gas emissions have also ignored new findings that would undercut support for such actions. For example:

  • Researchers discovered (July 28, 2000 Science) a previously unknown greenhouse gas that traps heat more effectively than any previously recognized greenhouse gas - 18,000 times more effectively than CO2 pound for pound. Scientists have yet to identify its source - they assume it is human activities - but it has not been accounted for in the models used to simulate present, past and future climate.
  • Scientists at the European Space Agency, using satellite and other astronomical data, have shown that the computer models used to predict global warming have severely underestimated the sun's impact on current warming. The sun's energy output has surged in the past 100 years, with a correspondingly large increase in ultraviolet light. In addition, its magnetic field has doubled. Neither of these factors has been accurately modeled. If this research proves correct, then reducing energy use to cut greenhouse gas emissions will have no effect on future warming.
  • In another recent report, NASA's Dr. James Hansen, who brought the term "global warming" to the general public's attention for the first time in 1988 Senate testimony, argued that urban air pollutants and greenhouse gases other than CO2 are the main sources of human-caused warming. Until this report, Hansen for nearly 20 years had maintained that CO2 emissions from fossil fuel use were the primary cause of global warming.


Though no final agreement was reached at the Hague conference, the negotiations will serve as starting point from which the next presidential administration will begin future climate change negotiations. The incoming President should realize, however, that although global warming is a serious issue, our knowledge of its causes and consequences is far too speculative to justify precipitous action intended to prevent it.

H. Sterling Burnett is a senior policy analyst with the National Center for Policy Analysis.

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