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LONDON, (Reuters) – Adapting to the effects of  climate change such as floods and droughts is likely to cost two  to three times more than the United Nations estimates, a report  said yesterday ahead of a major U.N. summit in December.

The U.N. climate change secretariat, UNFCCC, puts the global  costs of adaptation, through measures such as building houses  higher to avoid flooding and limiting the spread of diseases, at  $40 billion to $170 billion a year until 2030.

The range is already so broad because of a large degree of  uncertainty over some of the costs.

The estimate has been used at U.N. climate meetings this  year in the run-up to the December summit in Copenhagen, whose  goal is a new international agreement on how to tackle global  warming, the study said.
“If governments are working with the wrong numbers, we could  end up with a false deal that fails to cover the costs of  adaptation to climate change,” said Camilla Toulmin, director of  the International Institute for Environment and Development.

It co-published the study with the Grantham Institute for  Climate Change at Imperial College London.

The report said UNFCCC had produced its numbers too quickly  — “in a matter of weeks” according to the lead author Martin  Parry — and covered the sectors it included only partially.

The authors took six months to update the U.N. estimate, and  had it reviewed by seven leading adaptation scientists,  including the lead authors of the original U.N. study. They did  not put a figure to their own estimate.

“Just looking in depth at the sectors the UNFCCC did study,  we estimate adaptation costs to be two to three times higher,  and when you include the sectors the UNFCCC left out the true  cost is probably much greater,” Parry said.