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From [1] >kapitza 19 days ago [-] >This is slightly misleading. What we've understood for a century is the thermal forcing due to CO2, which is a logarithmic
by jamez1 10y ago
From [1]
>kapitza 19 days ago [-]
>This is slightly misleading. What we've understood for a century is the thermal forcing due to CO2, which is a logarithmic function of the CO2 concentration (ie, forcing == O(log n) in CO2 concentration).
What we don't understand (unless we decide GCMs are predictive and can be validated) is the impact of a given thermal forcing on planetary temperature. This is the "climate sensitivity." Unfortunately, this is the number we actually care about.
If climate sensitivity is low (negative feedback), Earth is thermally buffered and we have to worry less. If climate sensitivity is high (positive feedback), the opposite.
(Note also that Arrhenius, the discoverer of this effect, and pretty much everyone through the '60s, assumed that global warming was a positive side effect of burning fossil fuel, just from the preindustrial assumption that warm winters and high crop yields are good for humanity.)
- snowwrestler 10y agoKapitza is agreeing with me, although he/she might not realize it. Climate sensitivity is just shorthand for the question of how harmful global warming is going to be. The concept concedes the correctness of the simple model I outline. As it should, because basic physics would have to be wrong for the simple model to be wrong.
- gmmeyer 10y agoThere can be a debate about how much global warming would happen or even, potentially, whether or not there are highly complex forces at work that could potentially cause it to be null. And, there's also the potential question of how much the climate would change given a certain amount of increased energy in the system (global warming just means that there's increased energy in the system). However, it seems like, from the measurements we have seen, there is quite a bit of warming from this and that the climate change is likely to be severe. We're already seeing quite a lot of it and we'll almost certainly see a lot more. So, sure, there are questions about how bad it'll be. But those questions are just: will this be bad or really bad. They're not: is global warming occurring or not?