IPCC's climate-policy assumptions were justified

Sir

In the Commentary ‘Dangerous assumptions’ (Nature 452, 531–532; 2008), Pielke et al. suggest that the Intergovernmental Panel on Climate Change (IPCC) underestimates the challenge of global warming. I find their analysis misleading.

They criticize the IPCC for implicitly assuming that the challenge of reducing future emissions will mostly be met without climate policies. But the IPCC's Special Report on Emission Scenarios makes clear that, although the scenarios don't technically have climate policies, they can and do have energy-efficiency and decarbonization policies, which amount to the same thing (see IPCC reference emission scenario B1, which includes aggressive policies to help limit total global warming to about 2 °C). So advances towards reducing emissions are indeed policy-driven.

The authors also caution the IPCC against assuming that spontaneous advances in technological innovation will be instrumental in cutting future emissions. They claim that the IPCC is actually diverting attention away from policies that could stimulate technological innovation, pointing out that enormous advances in energy technology will be needed to stabilize atmospheric carbon dioxide to acceptable concentrations. This claim is unjustifiable: in fact, the IPCC report makes clear that we have the necessary technologies, or soon will, and focuses on creating the conditions for rapid technological deployment.

See also:

Long-range energy forecasts are no more than fairy tales

Energy assumptions were reasonable at the time, but not now

Future scenarios for emissions need continual adjustment

Climate policies will stimulate technology development

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Romm, J. IPCC's climate-policy assumptions were justified. Nature 453, 155 (2008). https://doi.org/10.1038/453155c

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