‘L’impossible équation des écologistes’

by Prof. Ch. Leclercq-Willain, 5 avril 2019 in ScienceClimatEnergie

Depuis plusieurs années un des combats mené par les écologistes dans différents pays européens (Allemagne, France, Belgique, ..) fut et reste celui du nucléaire mené actuellement en parallèle avec celui de la réduction des gaz à effet de serre (GES). Les « verts » allemands ont obtenu la fermeture de presque toutes les centrales nucléaires et l’Allemagne a toujours une exploitation importante de centrales gaz-charbon. L’Allemagne est ainsi le plus grand émetteur de CO2 en Europe. Il en est de même des pays de l’Est et de la Russie qui exploitent essentiellement des centrales gaz-charbon. En Belgique, la fermeture définitive des centrales nucléaires est prévue pour 2025.

What’s the worst case? Climate sensitivity

by Judith Curry, April 1, 2019 in WUWT

Are values of equilibrium climate sensitivity > 4.5 C plausible?

For background, see these previous posts on climate sensitivity [link]

Here are some possibilistic arguments related to climate sensitivity.  I don’t think the ECS example is the best one to illustrate these ideas [see previous post], and I probably won’t include this example in anything I try to publish on this topic (my draft paper is getting too long anyways).  But possibilistic thinking does point you in some different directions when pondering the upper bound of plausible ECS values.

5. Climate sensitivity

Equilibrium climate sensitivity (ECS) is defined as the amount of temperature change in response to a doubling of atmospheric CO2 concentrations, after the climate system has reached equilibrium. The issue with regards to ECS is not scenario discovery; rather, the challenge is to clarify the upper bounds of possible and plausible worst cases.

The IPCC assessments of ECS have focused on a ‘likely’ (> 66% probability) range, which has mostly been unchanged since Charney et al. (1979), to be between 1.5 and 4.5 oC. The IPCC AR4 (2007) did not provide any insight into a worst-case value of ECS, stating that values substantially higher than 4.5 oC cannot be excluded, with tail values in Figure 9.20 exceeding 10 oC. The IPCC AR5 (2013) more clearly defined the upper range, with a 10% probability of exceeding 6 oC.

Since the IPCC AR5, there has been considerable debate as to whether ECS is on the lower end of the likely range (e.g., < 3 oC) or the higher end of the likely range (for a summary, see Lewis and Curry, 2018). The analysis here bypasses that particular debate and focuses on the upper extreme values of ECS.