Guest Post by Ira Glickstein.
The graphic from RealClimate asks “How well did Hansen et al (1988) do?” They compare actual temperature measurements through 2012 (GISTEMP and HadCRUT4) with Hansen’s 1988 Scenarios “A”, “B”, and “C”. The answer (see my annotations) is “Are you kidding?”
The three scenarios and their predictions are defined by Hansen 1988 as follows
“Scenario A assumes continued exponential trace gas growth, …” Hansen’s predicted temperature increase, from 1988 to 2012, is 0.9 ⁰C, OVER FOUR TIMES HIGHER than the actual increase of 0.22 ⁰C.
“scenario B assumes a reduced linear growth of trace gases, …” Hansen’s predicted temperature increase, from 1988 to 2012, is 0.75 ⁰C, OVER THREE TIMES HIGHER than the actual increase of 0.22 ⁰C.
“scenario C assumes a rapid curtailment of trace gas emissions such that the net climate forcing ceases to increase after the year 2000.” Hansen’s predicted temperature increase, from 1988 to 2012, is 0.29 ⁰C, ONLY 31% HIGHER than the actual increase of 0.22 ⁰C.
So, only Scenario C, which “assumes a rapid curtailment of trace gas emissions” comes close to the truth.
THERE HAS BEEN NO ACTUAL “CURTAILMENT OF TRACE GAS EMISSIONS”
As everyone knows, the Mauna Loa measurements of atmospheric CO2 proves that there has NOT BEEN ANY CURTAILMENT of trace gas emissions. Indeed, the rapid increase of CO2 continues unabated.
What does RealClimate make of this situation?
“… while this simulation was not perfect, it has shown skill in that it has out-performed any reasonable naive hypothesis that people put forward in 1988 (the most obvious being a forecast of no-change). … The conclusion is the same as in each of the past few years; the models are on the low side of some changes, and on the high side of others, but despite short-term ups and downs, global warming continues much as predicted.”
Move along, folks, nothing to see here, everything is OK, “global warming continues much as predicted.”
Hansen 1988 is the keystone of the entire CAGW Enterprise, the theory that Anthropogenic (human-caused) Global Warming will lead to a near-term Climate Catastrophe. RealClimate, the leading Warmist website, should be congratulated for publishing a graphic that so clearly debunks CAGW and calls into question all the Climate models put forth by the official Climate Team (the “hockey team”).
Hansen’s 1988 models are based on a Climate Sensitivity (predicted temperature increase given a doubling of CO2) of 4.2 ⁰C. The actual CO2 increase since 1988 is somewhere between Hansen’s Scenario A (“continued exponential trace gas growth”) and Scenario B (“reduced linear growth of trace gases”), so, based on the failure of Scenarios A and B, namely their being high by a factor of three or four, it would be reasonable to assume that Climate Sensitivity is closer to 1 ⁰C than 4 ⁰C.
As for RealClimate’s conclusion that Hansen’s simulation “out-performed any reasonable naive hypothesis that people put forward in 1988 (the most obvious being a forecast of no-change)”, they are WRONG. Even a “naive” prediction of no change would have been closer to the truth (low by 0.22 ⁰C) than Hansen’s Scenarios A (high by +0.68 ⁰C) and B (high by 0.53 ⁰C)!