Too much can be made about mistakes in US surface-temperature data from the Goddard Institute for Space Studies (GISS). Too little can be made about them, too.
Conservative commentators overreacted to revelations that GISS had erred in ways that stoked alarm about global warming. GISS is run by James Hansen, one of the first scientists to issue warnings about human contributions to observed warming and a longstanding ally of Al Gore in the former vice-president’s crusade for aggressive response. When a Canadian mathematician pressed for and won a downward correction to GISS temperature data, bloggers and radio talk-show hosts pounced. One of them, Rush Limbaugh, called the correction evidence that “this whole global warming thing is a scientific hoax.”
That’s an overstatement. But so, evidently, was Gore’s claim in his award-winning scare movie, “An Inconvenient Truth,” that 9 of the 10 hottest years in US history have occurred since 1995.
Restated data
The inconvenient Canadian, Steven McIntyre, found errors in GISS temperatures for the US after January 2000. This month, the agency restated the data to show an overall decrease of 0.15º C. After the change it no longer can be claimed that 1998 was the hottest year in the US temperature record. That distinction now goes to 1934. Several other 10 hottest years receded in history after the adjustment.
The shift undercuts alarmist talking points more than it does the proposition that Earth’s surface has warmed in the past century. While US temperature readings are among the best available, they represent a small part of the global whole. Hansen has pointed out that the change is barely distinguishable in global data, which show warming. McIntyre and others nevertheless are pressing their scrutiny of US temperature data and what US problems might mean to observations elsewhere.
Without question, potential lapses in the quality of temperature data deserve attention. Chances are low, however, that whatever new errors might come to light will show Earth to have been cooling. Even if that happened, no one would believe it. Young energy consumers and voters have been taught that their parents overheated the planet by driving to work and that anyone with doubts must be under an evil spell cast by oil companies.
In any event, it’s no hoax that carbon dioxide of human origin is accumulating in the atmosphere. The central issue of the brittle global warming debate should be the extent to which the gas accumulation causes the temperature rise. Serious scientists can be found on both sides of the question. The unfortunate habit of politics is to note the coincidence of CO2 and temperature gains, to assume causation, and to insist that people do anything imaginable to halt the trend, starting now.
In fact, the CO2 and temperature records don’t correlate perfectly; in the US, the correlation is worse now than it was before the GISS changes. Timing discrepancies have long been a source for doubt-Gore and his fans call it denial-about the ability of people to affect global temperature by cutting CO2 emissions.
Other questions remain. By how much can people hope to alter global temperature with behavior changes, for example, when they account for only 1% of atmospheric CO2, which itself represents no more than 0.04% of the atmosphere and is not, contrary to popular opinion, the most potent greenhouse gas? Hansen and others answer in part by postulating a cascade of self-amplifying catastrophes that will occur if the CO2 concentration reaches an imminent “tipping point.” Maybe they’re right.
One scenario
Their gloomy scenario, however, is just one among a range of scientifically defensible possibilities-not all of them dire-about a complex system that so far has been mercilessly unpredictable. So maybe Hansen and his allies aren’t right.
At best, this setback to the Hansen-Gore foreboding, however minor, should moderate the zealotry that has closed the global warming debate to questions that need answers. If so, it will have served human interests. Meanwhile, oil and gas companies should keep finding ways to cut the CO2 emitted by their work.
