ANOMALIES AND REFUTATIONS

The science of global warming has progressed through tackling anomalies cited by skeptics. Critics of global warming made attempts to discredit the methodology of climatologist Michael Mann’s famous “Hockey stick” graph (first published in Nature in 1998). Mann’s graph showed average global temperatures over the last 1,000 years, with little variation for the first 900 and a sharp rise in the last century. After more than a dozen replication studies, some using different statistical techniques and different combinations of proxy records (indirect measures of past temperatures such as ice cores or tree rings), Mann’s results were vindicated. A report in 2006 by the U.S. National Academy of Sciences, National Research Council, supported much of Mann’s image of global warming history. “There is sufficient evidence from the tree rings, boreholes, retreating glaciers and other ‘proxies’ of past surface temperatures to say with a high level of confidence that the last few decades of the twentieth century were warmer than any comparable period for the last 400 years.” For periods before 1600, the 2006 report found there was not enough reliable data to be sure but the committee found the “Mann team’s conclusion that warming in the last few decades of the twentieth century was unprecedented over the last 1,000 years to be plausible” (National Academy of Science press release 2006).

Measurements from satellites and balloons in the lower troposphere have until recently indicated cooling, which contradicted measurements from the surface and the upper troposphere. In August 2005 a publication in Science of the findings of three independent studies described their measurements as “nails in the coffin” of the skeptics’ case. These showed that faulty data, which failed to allow for satellite drift, lay behind the apparent anomaly.

Another anomaly was that observed temperature rises were in fact less than the modelling of CO2 impacts predicted. This is now explained by evidence on the temporary masking properties of aerosols, from rising pollution and a cyclical upward swing of volcanic eruptions since 1960.

Critics of global warming have been disarmed and discredited. Media investigations and social research have increasingly highlighted the industry funding of skeptics and their think tanks, and the political pressures on government scientists to keep silent. Estimates of the catastrophic costs of action on emissions have also been contradicted most dramatically by the British Stern Report in October 2006. Many companies have been abandoning the skeptical business coalitions. The Australian Business Round Table on Climate Change estimated in 2005 that the cost to gross domestic product of strong early action would be minimal and would create jobs.