We climate scientists are not ecofanatics

In the UK only about 26 per cent of the population believe the scientific consensus that climate change is happening and is man-made. Many feel they are being steamrollered into believing something false or flakey that will make them poorer or stop them flying.

Given this dangerous mood of scepticism, it is no surprise that the IPCC — the body that represents the integrity of climate-change scientists across the world — is being attacked.

Let’s be honest, sometimes the Intergovernmental Panel on Climate Change does get it wrong. It was an error to include a poorly sourced claim in its 2007 report about the rate at which Himalayan glaciers are melting; but this mistake was marginal — it did not influence any of the IPCC’s main conclusions or appear in the summaries of the report. The great body of the IPCC’s work represents science at its best — and it needs defending from its detractors.

The IPCC is not a self-selected group of scientists with a political agenda. It was founded in 1988 by the World Meteorological Organisation and the UN Environment Programme with a mandate to produce accurate, balanced assessments about human-induced climate change.

I was chairman or co-chairman of the Science Working Group from 1988–2002, through the first three IPCC reports. About 70 scientists from around the world attended the first meeting of the group near Oxford early in 1989. We had no preconceived agenda regarding our conclusions. In fact, a number of attendees argued that not enough was known about human-induced climate change to produce any significant report. However, we agreed that we would identify carefully what we knew with reasonable certainty, estimate the uncertainties and distinguish it from what we were much more uncertain about. This doesn’t exactly mark us out as a bunch of ecofanatics.

The IPCC is too big an organisation to be captured by an ideological cabal or fall foul of group-think. It draws in scientists from every discipline from many different nations. Climatologists from Benin rub shoulders with scientists from the West, and from Saudi Arabia and other petrol-states for whom belief in global warming is against their immediate interests.

The IPCC process also makes it impossible for green propaganda to be slipped in. The IPCC has published four reports — in 1990, 1995, 2001 and 2007. Each contains three volumes covering science, impacts and mitigation; in 2007 each volume was about 1,000 pages long. Their main content is a detailed review of thousands of peer-reviewed scientific papers. But a report from Greenpeace or any other campaigning body would not be included because the science would not be considered robust enough.

Each chapter of an IPCC report goes through three reviews. The first is by expert scientists. The second involves a wider international community of climate scientists and others with an interest (including industrial and green NGOs) and the third is by national governments. Report summaries are scrutinised sentence by sentence at an IPCC plenary meeting over three or four days. These scientific meetings can become intense. I recall one that got bogged down over whether the words “appreciable human impact” were justified by the evidence. We clapped with relief when we agreed on “discernible human impact”.

A further myth is that the IPCC is alarmist. In truth, it’s far easier to find what now looks like excessive caution in IPCC reports. For instance, the 1990 report stated that increases in greenhouse gases were causing global warming but added that, because of natural climate variability, this warming could not be clearly detected in the observed record. As warming has continued at about the rate projected by the reports, each subsequent report has in general shown increasing confidence in its conclusions. Let me give you another example: the 2007 report declined to estimate the possible effect of accelerated melting of ice caps, as it considered no reliable estimates were available at that time.

A third myth is that the IPCC has refused to recognise that there has been no significant increase in global average temperature in the past decade or so. Sceptics cite this as evidence against human-induced global warming. But the level of natural year-to-year variability in the temperature record shows that a decade is too short a time to establish a change in the long-term trend. It is also known that a substantial part of the recent variability is down to the El Niño-Southern Oscillation, a massive climate pattern in the Pacific. The Pacific sector has certainly been cooler than elsewhere during the past decade.

Perhaps there is a criticism that can be made of IPCC scientists: they have been too slow publicly to defend their integrity. They have not been willing or able to hit the airwaves or make their case in newspapers. But scientists are now faced by powerful lobbies who are working to distort and discredit the science behind climate change. We scientists have facts on our sides — we must not be afraid to deploy them.

Sir John Houghton, former chief executive at the Met Office.