Met Office Fails To Acknowledge Their Climate Model Is Overly Sensitive
The Met Office has responded to David Rose’s latest contribution to the debate. In Rose’s article there is a box about Nic Lewis’ rather technical critique of the Met Office report on the pause, about which I blogged the other day. In their reply the Met Office notes that it “will require time to provide as helpful a response [to Nic Lewis] as possible, so further comment will be released in due course. But right after that they claim:
The article states that the Met Office’s ‘flagship’ model (referring to our Earth System Model known as HadGEM2-ES) is too sensitive to greenhouse gases and therefore overestimates the possible temperature changes we may see by 2100.
There is no scientific evidence to support this claim. It is indeed the case that HadGEM2-ES is among the most sensitive models used by the IPCC (something the Met Office itself has discussed in a science paper published early this year), but it lies within the accepted range of climate sensitivity highlighted by the IPCC.
Equally when HadGEM2-ES is evaluated against many aspects of the observed climate, including those that are critical for determining the climate sensitivity, it has proved to be amongst the most skilful models in the world.
The information that the HadGEM2 model is too sensitive came from Nic lewis’ article. The red bar in the figure below is the ECS of HadGEM2. It’s clearly obvious that it’s higher than the ECS of all other models and even higher than the 95% upper range of the CMIP5 models.
Nic Lewis replied to the Met Office as follows:
I would like to comment on the statements:
“The article states that the Met Office’s ‘flagship’ model (referring to our Earth System Model known as HadGEM2-ES) is too sensitive to greenhouse gases…”
and (referring to the sensitivity of HadGEM2-ES):
“it lies within the accepted range of climate sensitivity highlighted by the IPCC.”
Table 1 in Forster et al, 2013 ( Evaluating adjusted forcing and model spread for historical and future scenarios in the CMIP5 generation of climate models. J. Geophys. Res., doi:10.1002/jgrd.50174) gives the equilibrium climate sensitivity (ECS) of HadGEM2-ES as 4.59°C.
The IPCC stated in its 4th Assessment Report (WG1: Box 10.2): “we conclude that the global mean equilibrium warming for doubling CO2, or ‘equilibrium climate sensitivity’, is likely to lie in the range 2°C to 4.5°C.” It gave no other range for ECS in that report, nor has it as yet changed that range.
I therefore fail to understand how the Met Office can claim that HadGEM2-ES lies within the accepted range of climate sensitivity highlighted by the IPCC.