There is not going to be the kind of large temperature rise that IPCC alarmists have predicted. The estimated modest rise of no more than 1 C will will actually do more good than harm. Matt Ridley, writing in the Wall Street Journal/Australian, has been talking to Nic Lewis, an expert reviewer of the leaked draft IPCC Scientific Report:
In short: we can now estimate, based on observations, how sensitive the temperature is to carbon dioxide. We do not need to rely heavily on unproven models. Comparing the trend in global temperature over the past 100-150 years with the change in "radiative forcing" (heating or cooling power) from carbon dioxide, aerosols and other sources, minus ocean heat uptake, can now give a good estimate of climate sensitivity.
The conclusion - taking the best observational estimates of the change in decadal-average global temperature between 1871-80 and 2002-11, and of the corresponding changes in forcing and ocean heat uptake - is this: a doubling of CO2 will lead to a warming of 1.6-1.7C.
This is much lower than the IPCC's current best estimate, 3C.
Lewis is an expert reviewer of the recently leaked draft of the IPCC's WG1 Scientific Report. The IPCC forbids him to quote from it, but he is privy to all the observational best estimates and uncertainty ranges the draft report gives. What he has told me is dynamite.
Given what we know now, there is almost no way the feared large temperature rise is going to happen. Lewis comments: "Taking the IPCC scenario that assumes a doubling of CO2, plus the equivalent of another 30 per cent rise from other greenhouse gases by 2100, we are likely to experience a further rise of no more than 1C."
A cumulative change of less than 2C by the end of this century will do no net harm. It will actually do net good - that much the IPCC scientists have already agreed upon in the last IPCC report. Rainfall will increase slightly; growing seasons will lengthen; Greenland's ice cap will melt only very slowly, and so on.
Some of the best recent observationally based research also points to climate sensitivity being about 1.6C for a doubling of CO2. An impressive study published this year by Magne Aldrin of the Norwegian Computing Centre and colleagues gives a most-likely estimate of 1.6C. Michael Ring and Michael Schlesinger of the University of Illinois, using the most trustworthy temperature record, also estimate 1.6C.
The big question is this: will the lead authors of the relevant chapter of the forthcoming IPCC scientific report acknowledge that the best observational evidence no longer supports the IPCC's existing 2-4.5C "likely" range for climate sensitivity? Sadly, this seems unlikely - given the organisation's record of replacing evidence-based policymaking with policy-based evidence-making, as well as the reluctance of academic scientists to accept that what they have been maintaining for many years is wrong.
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