Following the comparison of the latest global temperature data with the first IPCC predictions made 21 years ago in 1990 here, I received some valid criticism and suggestions. One in particular was that I should have used the latest report since advances in climate science have improved model predictions since 1990. I now need to admit that I was mistaken about the 2007 report, because in fact it does contain short to medium term predictions for global surface temperatures based on different CIESIN CO2 emission scenarios. Until 2025, the only scenario which differs significantly from the others is the one labelled “committed” where somehow the world is able to stabilise emissions at 2000 values. I have now overlaid the up to date HADCRUT & UAH data with smoothed trend fits on exactly the same prediction graph that appears in the 2007 report . You can check that the data overlay is precise since the black dots on the blue HADCrut curve are actually plotted on the 2007 IPCC graph and match exactly values I am using.
The blue lines are HADCrut and the green line is UAH. Since 2000 there has been an apparent divergence of the data from the model predictions, and the data now lie below the “Commitment” curve which assumed that CO2 emissions were frozen at 2000 values.
It was pointed out by John M Reynolds that in the HADCrut 160 year time series there is evidence for a 60 year temperature oscillation (see previous post) which he associates with a natural oscillation in the oceans. This would imply we could be entering a downturn cycle in temperatures for about another 30 years, overlaid over a long term warming trend due to increasing CO2 levels.