(Caveat here is that I understand much less climate science than I would like, and there are gaps in my knowledge that someone who recently took a few undergrad classes on climate science can fill).
The equilibrium climate sensitivity (ECS) refers to the equilibrium change in global mean near-surface air temperature that would result from a sustained doubling of the atmospheric equivalent CO2 concentration (ΔT2×).
I think the best way to make sense of that is to think of temperature as proportional to log concentration.
(My actual original source is neither, but from an extended discussion with someone else who’s much more knowledgeable about climate science than I am, but also not a real expert)
I skimmed your linked article and I don’t really understand the discrepancy. I could think of some possible reasons (eg, there’s the trivial sense in which all differentiable functions are locally linear) but I’m not confident in them so I’ll sleep on this and see if maybe someone else could comment on it in the meantime.
In the current regime (i.e. for increases of less than ~4 degrees C), warming is roughly linear with cumulative carbon emissions (which is different from CO2 concentrations). Atmospheric forcing (the net energy flux at the top of the atmosphere due to changes in CO2 concentrations) is roughly logarithmic with CO2 concentrations.
How temperatures will change with cumulative carbon emissions at temperatures exceeding ~4 degrees C above pre-industrial is unknown, but will probably be somewhere between super-linear and logarithmic depending on what sorts of feedback mechanisms we end up seeing. I discuss this briefly in at this point in this talk: https://youtu.be/xsQgDwXmsyg?t=520
For #6, what is your source that temperature increases are proportional to log(CO2 ppm)? This paper indicates that it’s a simple proportional relationship, no log: https://iopscience.iop.org/article/10.1088/1748-9326/11/5/055006#erlaa23b8f1
(Caveat here is that I understand much less climate science than I would like, and there are gaps in my knowledge that someone who recently took a few undergrad classes on climate science can fill).
https://www.ipcc-data.org/guidelines/pages/reporting.html says it’s logarithmic.
I think this is widely known in the field, for example see here: https://en.wikipedia.org/wiki/Climate_sensitivity#Equilibrium_climate_sensitivity
I think the best way to make sense of that is to think of temperature as proportional to log concentration.
(My actual original source is neither, but from an extended discussion with someone else who’s much more knowledgeable about climate science than I am, but also not a real expert)
I skimmed your linked article and I don’t really understand the discrepancy. I could think of some possible reasons (eg, there’s the trivial sense in which all differentiable functions are locally linear) but I’m not confident in them so I’ll sleep on this and see if maybe someone else could comment on it in the meantime.
In the current regime (i.e. for increases of less than ~4 degrees C), warming is roughly linear with cumulative carbon emissions (which is different from CO2 concentrations). Atmospheric forcing (the net energy flux at the top of the atmosphere due to changes in CO2 concentrations) is roughly logarithmic with CO2 concentrations.
How temperatures will change with cumulative carbon emissions at temperatures exceeding ~4 degrees C above pre-industrial is unknown, but will probably be somewhere between super-linear and logarithmic depending on what sorts of feedback mechanisms we end up seeing. I discuss this briefly in at this point in this talk: https://youtu.be/xsQgDwXmsyg?t=520