Bjørn Lomborg, the author of ‘The Skeptical Environmentalist’, now believes reaching an agreement at Copenhagen is vital. His Copenhagen Consensus has published a paper calling for geo-engineering measures, such as deflecting sunlight from the face of the earth, to be considered. Lomborg answers readers’ questions below.

Update: Thanks to everyone who participated. We are no longer taking new questions.

Questions are in bold:

Don’t you think that by placing too much emphasis on techniques such as geo-engineering, we risk relying too heavily on highly risky scientific endeavours (more risky for the environment, I would argue, than reducing carbon emissions) with climatic effects that we still understand relatively poorly?
Jeremy Whipp (by email)

BL: You’re quite right that there should be an informed, ethical discussion about climate engineering. And I should underline the point that the research paper we released last week – on the costs and benefits of different climate engineering solutions – is just one out of a series of papers that the Copenhagen Consensus Center is releasing this month. In each paper, different climate economists look at the costs and benefits of different responses to global warming, whether it’s cutting carbon, methane or black carbon, planting more forests, etc.

To answer your question: there are risks to be considered, but we shouldn’t kid ourselves that other possible solutions to global warming – like the one we focus most on, carbon cuts – are risk-free. Think about what happened with bio-fuels – and think, also, about the possible impacts on free trade. And also consider the boondoggle that politicians are likely to make – the Waxman-Markey Bill was 1400 pages long, gives pay-offs to everyone imaginable, but does virtually nothing to actually reduce temperatures.

Are there any new pieces of evidence available now, that made you change your mind, which were not available when you wrote your earlier books? Or are you simply interpreting the same data differently?

Do you believe that the analyses and recommendations of the UN climate panel adequately represent the consensus among leading climate researchers? – Nicolay Worren, Oslo (by email)

BL: In both my first Danish book in 1998 and the English version of The Skeptical Environmentalist in 2001, I stressed that man-made global warming exists. In Cool It, I wrote: “global warming is real and man-made. It will have a serious impact on humans and the environment toward the end of this century”. What I have also consistently argued is that there are other global challenges that we must also address, and that some of the extreme suggestions about global warming are overblown. My view is that the careful research of the United Nations panel of climate change scientists, the IPCC, is the best guide to what we can expect from global warming. The IPCC’s report writing process is robust and custom-made to weather criticism.