Category Archives: Technology and Society

Judith Curry

She is a heretic, who has been cast out of the tribe:

In the run-up to the Paris conference, said Curry, much ink has been spilled over whether the individual emissions pledges made so far by more than 150 countries — their ‘intentional nationally determined contributions’, to borrow the jargon — will be enough to stop the planet from crossing the ‘dangerous’ threshold of becoming 2°C hotter than in pre-industrial times. Much of the conference will consist of attempts to make these targets legally binding. This debate will be conducted on the basis that there is a known, mechanistic relationship between the concentration of carbon dioxide in the atmosphere and how world average temperatures will rise.

Unfortunately, as Curry has shown, there isn’t. Any such projection is meaningless, unless it accounts for natural variability and gives a value for ‘climate sensitivity’ —i.e., how much hotter the world will get if the level of CO2 doubles. Until 2007, the UN Intergovernmental Panel on Climate Change (IPCC) gave a ‘best estimate’ of 3°C. But in its latest, 2013 report, the IPCC abandoned this, because the uncertainties are so great. Its ‘likely’ range is now vast — 1.5°C to 4.5°C.

This isn’t all. According to Curry, the claims being made by policymakers suggest they are still making new policy from the old, now discarded assumptions. Recent research suggests the climate sensitivity is significantly less than 3˚C. ‘There’s growing evidence that climate sensitivity is at the lower end of the spectrum, yet this has been totally ignored in the policy debate,’ Curry told me. ‘Even if the sensitivity is 2.5˚C, not 3˚C, that makes a substantial difference as to how fast we might get to a world that’s 2˚C warmer. A sensitivity of 2.5˚C makes it much less likely we will see 2˚C warming during the 21st century. There are so many uncertainties, but the policy people say the target is fixed. And if you question this, you will be slagged off as a denier.’

This is religion, not science.