News that Vancouver didn’t have enough snow for the Winter Olympics led millions of global warming sceptics to change their mind. OK, it didn’t. Yet anecdotes dominate the debate on both sides and carry more weight in shaping public opinion than the scientific process.
This is in line with media coverage of science in general, which often tends to highlight the silly and the sensational. The latest sensations concern stolen e-mails that are supposed to prove that scientists tried to cover up evidence against global warming, and false predictions that the Himalaya’s glaciers would disappear by 2035.
Let’s start with the e-mails. The main scientific issue is how data from different sources and time periods are used to calculate temperature trends and project what might happen in the future. This work is summarised in the famous “hockey stick” graph, showing a long period of relative stability ending in a sudden upturn coinciding with the industrial age.
The graph is based on work by Michael Mann and was published in the 2001 IPCC report. In one e-mail, Mann’s colleague Phil Jones, director of the Climatic Research Unit at East Anglia University, writes about using “Mike’s Nature [journal] trick… to hide the decline”.
This has been presented as proof that Mann was falsifying his analyses to hide the fact that global warming was no longer happening, and indeed that temperatures were declining. For example, writing in the Washington Post last December, Sarah Palin claimed that “leading climate “experts” deliberately destroyed records” and “manipulated data to “hide the decline” in global temperatures”.
Replying to Palin, Mann pointed out that the e-mail in question was written in 1999, just after the warmest year ever recorded (1998) to that date: “It could not possibly have referred to the claim that global temperatures have declined over this decade – a claim that is false (the current decade, as has been recently reported, will go down as the warmest on record).”
“Trick” in the context means a solution to a methodological problem – how to integrate long-term and recent data. There was nothing underhand about it. The two data sets were clearly labelled and could be downloaded by anybody wanting to check the method.
In 2006, Gerald R. North, Chairman of the National Academy of Sciences Committee on Surface Temperature Reconstructions, testified before the House of Representatives on the work of Mann and others studying climate records. The 12 members of North’s committee had expertise in a range of fields including climate modelling, statistics, climate change and variability. As well as an in-depth review of the literature, they organised a workshop with speakers from all sides of the debate.
They have disagreements with some aspects of Mann’s work, as you would expect in any scientific debate, but find that Mann’s conclusion — that the late 20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1000 years — “…has subsequently been supported by an array of evidence that includes both additional large-scale surface temperature reconstructions and pronounced changes in a variety of local proxy indicators, such as melting on icecaps and the retreat of glaciers around the world, which in many cases appear to be unprecedented during at least the last 2000 years.”
That brings us to the glaciers story. The prediction that the glaciers in the Himalayas would melt by 2035 is wrong and should have been verified before being quoted in the part of the IPCC report that deals with climate change impacts, adaptation and vulnerability. However, one mistaken prediction does not invalidate the data on whether the amount of snow and ice on Earth is decreasing:
“Observations show a global-scale decline of snow and ice over many years, especially since 1980 and increasing during the past decade, despite growth in some places and little change in others. Most mountain glaciers are getting smaller. Snow cover is retreating earlier in the spring. Sea ice in the Arctic is shrinking in all seasons, most dramatically in summer. Reductions are reported in permafrost, seasonally frozen ground and river and lake ice. Important coastal regions of the ice sheets on Greenland and West Antarctica, and the glaciers of the Antarctic Peninsula, are thinning and contributing to sea level rise. The total contribution of glacier, ice cap and ice sheet melt to sea level rise is estimated as 1.2 ± 0.4 mm yr–1 for the period 1993 to 2003.”
Of course, a single blog post cannot cover all the questions raised by these stories. Some people do not believe climate change is happening, others argue that it is real, but mainly a natural phenomenon. The OECD does not agree with these points of view. The link below provides some of the Organisation’s contributions to the debate.
OECD work on climate change
US National Academy of Sciences climate change web site
UK Royal Society Preventing dangerous climate change