Sorry, global warming has not been cancelled

The triumph of climate denialists in the Liberal Party and the recent unauthorised release of allegedly damaging emails from a British climate research group are being portrayed by some as the end of the global warming “conspiracy”.

However, the so-called scandal of the emails is a manufactured storm in a teacup. Anyway, the evidence for human-caused global warming is far more diverse and robust than denialists make out. In fact the latest evidence is even clearer, and more ominous. Denialist politicians are on the wrong side of history.

The hacking of the Climate Research Unit of the University of East Anglia and the selective release of allegedly damaging emails has generated a crescendo of outrage and righteousness among those who believe human-caused global warming to be a scientific conspiracy. The truth seems to be rather different. The scientists became suspicious they were being set up in a political sting operation. They were receiving seemingly excessive requests, from people they weren’t familiar with, not only for publicly-available data but for details of intermediate calculations, for computer code, even for computer code that would run on any platform. The full record of the emails is one of conscientious, very hard-working scientists trying to ensure the science wasn’t distorted by political interests.

Is the idea of a sting operation just another crazy conspiracy theory? Well no, it is well documented that ExxonMobil and other interests have been funding a systematic and sophisticated effort to create public doubt and confusion about the climate science. What is striking is how readily many people who call themselves sceptics have been willing to swallow without question the denialist interpretation spun from highly selected, out-of-context emails that were obtained illegally. And many people who claim scientists are conspiring on global warming just to obtain research money overlook the trillion-dollar incentives of fossil fuel companies to conspire to deny global warming.

The evidence for global warming does not depend on just one group, or just one kind of evidence. There are at least four groups in the world estimating global temperatures, two in the US, one (East Anglia) in Britain and one in Japan. Their estimates are combined in the image below, and they are consistent in their main features, and even consistent in many of their details. If the British group fudged their data, as alleged, it could not have been by much because they still got the same answer as the other groups. Temperatures rose strongly from 1900 to 1940. They fell a bit from 1940 to 1970, mainly because of an increase in human particulate pollution. Since 1970 temperatures have been rising more strongly.

Michael Schlesinger, University of Illinois
Trends in global temperature estimated by four different research groups are very similar, both in charting pronounced warming and a lot of short-term variability.
The groups are the National Oceanic and Atmospheric Administration, NASA, Britain’s Hadley Center and Climatic Research Unit (Univ. of East Anglia) and Japan’s meteorological agency.

The current rising trend cannot be explained without taking account of the effect of human emissions of greenhouse gases. Those who attack the computer models that demonstrate this overlook the fact that the general trend of global warming was predicted in the 1970s on the basis of much simpler models, and the world has been pretty much following those predictions, except things have recently begun to run much faster than previously projected.

There are fluctuations around these long-term trends because of various other effects. For example, the El Niño - La Niña cycle causes fluctuations over periods of a few years. This accounts for the slowing of the upward trend since about 2000, and even a brief recent reversal. Such brief reversals are not new or unexpected. They occurred in the early 1980s and early 1990s. As last year’s La Niña fades the warming resumes, and estimates for the 2009 mean are that it will indeed be warmer.

Senator Stephen Fielding has paraded a graph in front of Parliament House showing atmospheric carbon dioxide rising steadily since 1995 while the global temperature has fluctuated without rising steadily. The graph is also on his web site and is shown below. He claims this proves human emissions of greenhouse gases cannot be the cause of global warming. Senator Fielding is foolish to believe this simplistic interpretation, which comes from a noisy minority of scientists. Presumably the many other sceptics in the Parliament are guilty of the same folly.

This graph is misleading, because it begins only at 1995, when the temperature was relatively high, and because it excludes from view the earlier temporary pauses that make it obvious that the current pause in nothing unusual, and no reason to doubt the longer-term warming trend. The scientists who feed such misinformation to politicians are guilty of an elementary misinterpretation of a data series, and an elementary misunderstanding of the nature of climate. Climate is about long-term trends, not short-term fluctuations.