In an article in the Guardian last month, I criticised an effort by a group of scientists and activists to cast aside the consensus view of thousands of scientists from the United Nations Intergovernmental Panel on Climate Change (IPCC). The group is organising an emergency summit on global warming in Copenhagen this month. The organiser calls the IPCC's work "wishy-washy" and says her conference is "not a regular scientific conference. This is a deliberate attempt to influence policy."

Vital decisions on climate change should not be based on the political activism of a few, but on the careful work by the IPCC. The IPCC works within a well-established, hugely respected framework that ensures all the scientific arguments are considered.

I pointed out that one conference participant, Stefan Rahmstorf, argues that sea level rises will be much higher than those anticipated by most researchers. Rahmstorf is a well-established, serious researcher on climate change who holds a minority view on the rise in the sea-level — the IPCC's estimate is an 18cm to 59cm rise by the end of the century. I mentioned him to make the point that meeting with like-minded colleagues does not somehow create a new global scientific consensus.

In his response, Rahmstorf labels me a "spin-doctor" who is "fooling the public". Often, such strong language can belie poor arguments. In this case, I believe that is the case.

In arguing that sea levels are rising much more than the consensus view of thousands of scientists, he makes a lot of the fact that the 1993-2003 sea level estimates were 50% higher than the IPCC's models expected, indicating that future sea level rises would also be higher. He fails to mention that the particular decade centred on 1998 has one of the highest sea level rises, which in the past has varied dramatically over decades. The decade before, the sea level was almost not rising or possibly even dropping (as one can see on p413 of IPCC's first report). One cannot pick the timeframes to fit the argument.

Rahmstorf denounces an article I wrote half a year ago where I pointed out that we only hear bad news on global warming. As an example, I wrote that we hear that sea levels are rising faster than expected, yet sea levels have actually risen less quickly than expected over past years. Rahmstorf is correct to note that the levels are no longer dropping — which they were from 2006 to early 2008, the data available at the time of my article — but curiously seems disinclined to explore why the rise over the past four years (2005-2008) has been half the previous rise at 1.6mm/year. The inescapable point is that sea levels are not escalating out of hand – if anything, they are doing the exact opposite right now.

And, as if underscoring the point of my previous article, Rahmstorf warns that Greenland may rapidly increase sea levels because ice tongues will melt, releasing glaciers behind them. In fact, as Science magazine wrote in January with the headline Galloping Glaciers of Greenland Have Reined Themselves In, the glaciers have slowed down again.

To many this may seem like a technical, obscure discussion. It is vitally important. Rahmstorf and his like-minded colleagues are setting out to convince decision-makers that their own minority views are more important than the mainstream perspective of the IPCC. They are, in my view, trying to replace science with politics – at a time when we need a lot more science and a lot less politics on climate change.

• Bjørn Lomborg, author of The Skeptical Environmentalist, is director of the Copenhagen Consensus Center and adjunct professor at the Copenhagen Business School.

Lomborg must be kidding

Stefan Rahmstorf



As a lead author of the last IPCC report, I find it gratifying that Bjørn Lomborg sings the praise of the "careful work" of the "hugely respected" IPCC.

Lomborg argues that 18 years could be too short for a robust trend comparison because of decadal variations in trend – but the 42-year period analysed by IPCC yields the same result. And it is telling that he then goes on to draw an "inescapable" conclusion about a slow-down of sea level rise from just four years of data. This is another well-worn debating trick: confuse the public about the underlying trend by focusing on short-term fluctuations. It's like claiming spring won't come if there is a brief cold snap in April.

Read Stefan Rahmstorf's response to Bjørn Lomborg and post your comments here