Climatologists now require 20 to 30 years to even consider any climatic trend: Is that really honest, or is it just very convenient?
Guest essay by Stephane Rogeau of France
So that’s it: the 15+ years period of no temperature increase is, according to the IPCC, a non-event, barely worth mentioning in the Summary for Policy Makers (SPM). The explanation is simple: we are just witnessing short usual natural variations of the climate that are consistent with climate models. The question about whether those models had foreseen this so-called “hiatus” is just irrelevant: move along!
But let’s just imagine for a while that since around 2000, the world had seen a warming bigger than everything the IPCC had ever predicted. I mean a situation just opposite to what we have been experiencing until now with regard to model forecasts. What would have been the analysis proposed by the IPCC in its SPM report?
First possible analysis:
“The long-term climate model simulations show a trend in global-mean surface temperature from 1951 to 2012 that agrees with the observed trend (very high confidence). There are, however, differences between simulated and observed trends over periods as short as 10 to 15 years (e.g., 2000 to 2012). Due to natural variability, trends based on short records are very sensitive to the beginning and end dates and do not in general reflect long-term climate trends. As one example, the rate of warming over the past 12 years (2000–2012; 0.23 [+0.13 to +0.33] °C per decade), which begins after the effect of a strong El Niño disappeared, is bigger than the rate calculated since 1951 (1951–2012; 0.12 [0.08 to 0.14] °C per decade).
The observed extra increase in surface warming trend over the period 2000–2012, as compared to the period 1951–2012, is due in roughly equal measure to an increased trend in radiative forcing and a warming contribution from internal variability, which includes a possible redistribution of heat within the ocean.”
Second possible analysis:
“The rapid increase in surface warming during the last period of more than 12 years is a clear sign that, although climate models have gained in precision in their description of climate behavior, several factors had been under-estimated by the scientific community in the AR4. There is strong evidence that both lower and upper limits of the former estimation of transient climate response should be risen by as much as 1°C (very high confidence).
Projections for annual mean surface temperatures for the period 2081-2100 have therefore been reviewed to take into consideration the change in observed trend over the last period of 12 years. All different scenarios now show a very likely increase of global mean surface temperatures of more than 1.5°C by the end of the century, relative to 1985-2005, and up to 6°C in the RCP8.5 scenario.”
Let’s be honest: does anybody believe the IPCC would have chosen to write anything close to the first analysis?
Related: To the IPCC: Forget about “30 years”