THE world's most high-profile climate change sceptic is to declare that global warming is “undoubtedly one of the chief concerns facing the world today” and “a challenge humanity must confront”, in an apparent U-turn that will give a huge boost to the embattled environmental lobby.

Bjorn Lomborg, the self-styled “sceptical environmentalist” once compared to Adolf Hitler by the UN's climate chief, is famous for attacking climate scientists, campaigners, the media and others for exaggerating the rate of global warming and its effects on humans, and the costly waste of policies to stop the problem.

But in a new book to be published this month, Lomborg will call for tens of billions of dollars a year to be invested in tackling climate change. “Investing $100bn annually would mean that we could essentially resolve the climate change problem by the end of this century,” the book concludes.

Examining eight methods to reduce or stop global warming, Lomborg and his fellow economists recommend pouring money into researching and developing clean energy sources such as wind, wave, solar and nuclear power, and more work on climate engineering ideas such as “cloud whitening” to reflect the sun's heat back into the outer atmosphere.

In an interview with the Guardian , he said he would finance this investment through a tax on carbon emissions that would also raise $50bn to mitigate the effects of climate change, for example by building better sea defences, and $100bn for global healthcare.

His declaration about the importance of action on climate change comes at a crucial point in the debate, with international efforts to agree on a global deal on emissions stalled amid a resurgence in scepticism caused by rows over the reliability of the scientific evidence for global warming.

The fallout from those rows continued when Rajendra Pachauri, head of the UN Intergovernmental Panel on Climate Change, came under renewed pressure to step down after an independent review of the panel's work called for tighter term limits for its senior executives and greater transparency in its workings. The IPCC has come under fire in recent months following revelations of inaccuracies in the last assessment of global warming, provided to governments in 2007. The mistakes, including a claim that the Himalayan glaciers could melt by 2035, prompted the launch of a review of the IPCC's processes and procedures by the InterAcademy Council (IAC), an organisation of the world's science bodies.

The IAC said that the IPCC needed to be as transparent as possible in how it worked, how it selected people to participate in assessments and its choice of scientific information to assess.

Although Pachauri once compared Lomborg to Hitler, he has now given an unlikely endorsement to the new book, Smart Solutions to Climate Change . In a quote for the launch, Pachauri said: “This book provides not only a reservoir of information on the reality of human-induced climate change, but raises vital questions and examines viable options on what can be done.”

—The Guardian, London