Wednesday 06 Oct 2021 | 22:44 | SYDNEY
Wednesday 06 Oct 2021 | 22:44 | SYDNEY

Reader riposte: What the IPCC says


Sam Roggeveen


15 August 2008 11:17

Jim Manzi, who authored the piece that started our climate change thread (and who blogs at The American Scene) responds to Dominic Meagher's critique of his article:

I would like to make a few quick comments in response to Mr Meagher’s letter:

  1. He may be well aware of the facts of the properties of CO2, and of the purpose and stature of the IPCC, but I did not want to assume that all readers had this knowledge.
  2. The IPCC projects a 2.8C increase in global temperatures by 2095 as a result of the A1B SRES scenario, often used as a reference case scenario, as per table SPM.3 in this IPCC Summary for Policymakers (see p.13). In the same table you will find also a range of six marker scenarios that are between 1.4C to 4C. The straight average of these scenarios is also 2.8C warming by 2095. This is why I used 3C as warming 'under a reasonable scenario' by 2100. I think this is a fair representation of the IPCC scenario-based projection results. 
  3. The IPCC estimates that warming of 4C should reduce global economic output by 1- 5% (see p.17). 
  4. The reason I was careful not to make a more precise statement about when in the 22nd century we would reach 4C of warming if we had reached 3C of warming by 2100 is precisely because of the non-linearity of climate response.