I’ve noticed a slight resurgence in those claiming to be lukewarmers and trying to argue that this is some kind of reasonable middle ground. I’ve written about lukewarmers before, but the basic issue with the lukewarmer argument is that they take something that is possible (low climate sensitivity) and argue that it is almost certain. The problem, quite obviously, is that arguing that something is likely, when it’s not, is not consistent with the available scientific evidence.
I think, however, that focusing on something like climate sensitivity somewhat misses a key point (intentionally possibly). The chance that climate sensitivity could be so low that we can continue to pump CO2 into the atmosphere, without any chance of the resulting changes leading to potentially damaging impacts, is almost certainly very small. Even if climate sensitivity is on the low side of the range, we can still pump enough CO2 into the atmosphere for the changes to be large and for the resulting impacts to be severe.
What I’m suggesting is that even lukewarmers (assuming that they would like to avoid changes that could have damaging impacts) should be willing to consider how we should be aiming to reduce our emissions. We can debate how best to go about reducing emissions, and how fast we should be aiming to do so, but the idea that we don’t need to do so is – I would argue – not even consistent with a reasonable lukewarmer position. Well, unless – as some suspect – lukewarmers are really just selecting their scientific position to suit their policy preferences.
I don’t know if I’ve expressed this as clearly as I might have, but what I’m really trying to suggest is that from a global warming perspective, the key factor (at least, the one over which we have some control) is our emissions. Is there a realistic scenario under which we can continue to pump CO2 into the atmosphere without producing impacts that are severely damaging? I would argue that the answer is no, even if you think that climate sensivity might be on the low side of the range.