THREAD on the climate sensitivity (& carbon budgets)...
After decades of research, the equilibrium climate sensitivity has remained fairly close to 3°C for a doubling of pre-industrial CO₂ concentrations.
carbonbrief.org/explainer-how-…
After decades of research, the equilibrium climate sensitivity has remained fairly close to 3°C for a doubling of pre-industrial CO₂ concentrations.
carbonbrief.org/explainer-how-…
The range has remained stubbornly wide (1.5°C-4.5°C), despite many individual studies claiming to narrow it (particularly recent instrumental-based methods). Though, @AndrewDessler could argue that in the 1970's the range was underestimated & today it is overestimated (maybe).
Most methods have a similar range, but instrumental methods are certainly lower. Many reasons why the instrumental record may be low (aerosols, variability, temperature estimates, ocean heat content, etc, etc).
I have a few purely statistical issues with instrumental estimates:
1. If the ECS is a (useful) state variable, then it should be robust to data
2. With ~200 years of data, you are smoking something if you can estimate equilibrium >1000+ years ahead. (link.springer.com/article/10.100…)
1. If the ECS is a (useful) state variable, then it should be robust to data
2. With ~200 years of data, you are smoking something if you can estimate equilibrium >1000+ years ahead. (link.springer.com/article/10.100…)
Does the sensitivity matter?
To me, it is analogous (& very related) to carbon budgets. Since I think carbon budgets are not that useful for policy (other than an elevator pitch), you can infer what I think of the policy utility of the ECS rdcu.be/OfDv
To me, it is analogous (& very related) to carbon budgets. Since I think carbon budgets are not that useful for policy (other than an elevator pitch), you can infer what I think of the policy utility of the ECS rdcu.be/OfDv
There is a close link between the uncertainty range on the ECS & the range on the carbon budget, and related methods & concepts, so unsurprising people working on ECS also like delving into carbon budgets... cicero.oslo.no/no/posts/klima…
Just as with carbon budgets, loads of interesting scientific questions with ECS. But, when a variable has irreducible uncertainties, & each new estimate makes front page news, you are giving policy makers justification for inaction (@Oliver_Geden) nature.com/articles/s4156…
By all means, do more research on ECS & carbon budgets, but don't assume interesting science means policy relevance. Way too much focus on variable (magic) numbers diverts attention from the real game -> mitigation!
Hats off, again, to @hausfath @CarbonBrief for another great, and extremely useful, post carbonbrief.org/explainer-how-…
