"A new, lower estimate of climate sensitivity".

The main points highlighted in “A new, lower estimate of climate sensitivity” from World Climate Report, November, 2011.  are given below:

• A proposed paper in Science magazine concludes that the climate sensitivity or the extent to which earth’s average temperature will rise as a result of a doubling of the atmospheric concentration of CO₂ with a 66% probability lies in the range 1.7°C to 2.6°C, with a median value of 2.3°C.

• This is lower than the estimates of the climate sensitivity given by the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4), in which the likely range is given as 2.0°C to 4.5°C, with a best estimate of 3.0°C.

• The results from the new analysis largely eliminate the “fat tail” or very large climate sensitivities as a realistic possibility.

• The authors find only “vanishing probabilities” for a climate sensitivity value greater than 3.2°C and values greater than 6.0°C are “implausible.”

• The IPCC assessment of the literature routinely includes studies concluding that there is a greater than a 10% possibility that the true climate sensitivity exceeds 6°C and some which find that there is a greater than 5% possibility that it exceeds 10°C.

• The new paper, from a team of researchers from Oregon State University, states that combining results from extensive sea and land surface temperature reconstructions models there is lower probability of imminent extreme climatic change than previously thought.

• The paper states that the possibility of climate sensitivity being in the 1°C to 2°C range is not minimal.

• Growing number of papers published in recent years employing investigations of the earth’s paleoclimate behavior have reached somewhat similar conclusions.

• These findings also impact strongly on projected economic losses due to climate change.

• According to a researcher the paper is a useful antidote to the exaggerated uncertainty estimates that have been prevalent over recent years.

• The IPCC could consider including findings of such papers in its Fifth Assessment Report.

Posted By:  

Ramesh Kumar Jalan, Ph.D.

Resource Person & Moderator

Climate Change Community, Solution Exchange,

United Nations Development Programme

New Delhi, India