Forcings – Hansen et al 2000 v UNIPCC 2007

Two months ago I did an analysis of aerosols in the UNIPCC AR4 report, observing that

  1. That the IPCC can’t add up.
  2. The figures appear contrived to show that only CO2 was the problem.

Anthony Watts has a posting today “Shocker: The Hansen/GISS team paper that says: “we argue that rapid warming in recent decades has been driven mainly by non-CO2 greenhouse gases“. This is based on the James Hansen (and others) paper analysing natural forcings, with the following graphic.

Hansen et al Figure 1: Estimated climate forcings between 1850 and 2000.

I thought that I would do a quick the comparison between what the IPCC were saying in 2007, with what Hansen et al. were saying in 2000.

According to the UNIPCC

  1. Hansen underestimated CO2 component.
  2. Hansen overestimated the CH4 component.
  3. Hansen overestimated the impact of the sun.

However, Hanson could counter that the UNIPCC have completely forgotten about the impact of volcanoes.

It could be completely coincidental, that further analysis by climate scientists gives a greater role to CO2, and therefore even stronger justification for constraining CO2 emissions. However, although they became more certain on positive forcings, they are less certain than Hansen on aerosols. It gives even greater credence to the cynical view that the climate science community are exaggerating the influence of anthropogenic forcings on climate. Given the billions of dollars annually being poured into research one could reasonably expect a reduction in the uncertainties over time.

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