White House Edits Climate Change—Why?

"Bush Aide Softened Greenhouse Gas Links to Global Warming," reads a front page headline in today's New York Times. Ah, the stupidity!

In other climate change news, eleven national academies of science, including the US National Academy of Sciences, issued a joint statement yesterday declaring, "Climate change is real." The statement also declares, "There is now strong evidence that significant global warming is occurring." The statement cites the Intergovernmental Panel on Climate Change's 2001 projections that average global surface temperatures will increase to between 1.4 and 5.8 degrees centigrade above 1990 levels by 2100. The joint statement also cites IPCC estimates that thermal expansion and glacial melting will increase sea levels by between 0.1 and 0.9 meters by 2100.

The statement then goes on to recommend various policy responses including "acknowledge that the threat of climate change is clear and increasing." OK, there is man-made global warming. Now what? Just how big the threat is is what matters for selecting appropriate policies. If the temperature increase is at the lower end of the IPCC range (and satellite data since 1978 that find the global average trend is an increase of 0.09 degrees centigrade per decade suggests that it may be), then the urgency to adopt drastic and costly remedies will be a lot less.

After all, the average surface temperatures rose by about 0.6 degrees centigrade (+0.2 or -0.2 degrees) and sea level rose by about 0.2 meters in the 20th century without provoking global ecological and economic catastrophe.

The joint statement also advises world leaders to "launch an international study to explore scientifically-informed targets for atmospheric greenhouse gas concentrations, and their associated emissions scenarios, that will enable nations to avoid impacts deemed unacceptable."

The crucial issue that the national academies statement is addressing is that so far there is no good scientific basis for defining what in fact constitutes "dangerous anthropogenic interference with the climate." Clearly a lot more scientific research on this question needs to be done.

The joint academy statement also calls on world leaders to "identify cost-effective steps that can be taken now to contribute to substantial and long-term reduction in net global greenhouse gas emissions."

Sounds great, right? However, there is more than one way to achieve long-term reduction in greenhouse gas concentrations. The world could start on a long slow path to reductions by beginning cuts now, or the world could continue on a path of rapid technological and economic growth and make steep cuts later to achieve the same eventual concentrations of greenhouse gases.

There good reasons to question the reductions now versus reductions later strategy, according to a 2000 Resources for the Future study which concluded, "According to the estimates in most I[ntegrated] A[ssessment] models, the costs of sharply reducing GHG concentrations today are too high relative to the modest benefits the reductions are projected to bring." So which is better? Which is more cost-effective? That's not science; that's politics and economics.

By adding greenhouse gases to the atmosphere (chiefly carbon dioxide from burning fossil fuels), humanity is increasing global temperatures. How much? Uncertain. How dangerous? Uncertain. How best to handle it? Uncertain.

Given these uncertainties, White House functionaries had no need to exaggerate. Shame on them.