Anonymous
CO2 has zero effect on anything claimed by alarmists. Just ask scientists.
I have extensively documented (from peer review) how extreme weather has globally declined/stabilized over the decades, some since 1850. This includes tornadoes, hurricanes, cyclones, flooding, droughts, fires, hail, etc.
I have also documented how food production has increased, polar bears increased (since 1960), and that we have more trees than 35 years ago.
Elizabeth
Yes, but there are two parts to their study.
The first part examines CO2 concentrations similar to what the IPCC examines ... a doubling of CO2 beyond pre industrial levels of 278 ppm. Our current CO2 levels are just over 400 ppm so still a bit to go ... but the point is they find that temperatures rise.
What they then find is that at concentrations of 4 times that pre industrial level, climate sensitivity drops to zero. We can keep adding CO2 but it doesn't increase the global average temperature. The reason for this is that cloud formation now causes cooling in cycles.
But what they are actually showing is massive variabilty at those concentrations (Fig. 2, in their paper). Sometimes it gets much cooler due to this formation of clouds. It also implies that it gets much warmer in between those cycles leading to the average temperature flattening out.
Skeptics will be all over this like flies on poo, whereas the paper is worrying because it implies much greater swings in temperature at high CO2 concentrations. The other thing I'd point out before the skeptics get their claws into it is that this paper discusses a model that projects out well into the future yet still draws the same conclusion (the planet will warm) in the shorter term. If they have issues with warming, they can't claim this paper supports their view. If they have issues with short term models, they can't claim this paper confirms their opinion since it is a long term model ... they can't whinge about the models they don't like but accept the less certain model they do!
JimZ
If you decrease the sensitivity to zero, that means that adding CO2 won't have an effect if I understand it correctly. I'm not an expert. but clearly the more CO2 we add, the less new effect it will have. I have read it argued before that much of the added sensitivity is already insignificant since the existing CO2 already absorbs most of the available spectrum. You certainly won't hear alarmists suggest that. I think it is true of methane since water vapor absorbs the spectrum that methane would if it increased in concentration and water vapor is thousands of times more concentrated. For me the jury is still out and I'm waiting to be convinced either way.
skeptik
Not really, no.
That's not even what the study is examining, and it certainly isn't what it claims.
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This is the graph from your own article.
Do you think it looks like they're saying it's cooler at higher CO2 levels?