Arguments for or against doing things to slow climate change depend on what will happen if we don’t, a question the IPCC reports try to answer. That makes it important to know how reliable their predictions are. The scientific section of the latest report (IPCC AR6 WGI) runs to almost four thousand pages, largely of detailed analysis, depending on multiple scholarly articles for each step — Chapter 7, to pick one at random, has fifty editors and about nine hundred articles in its list of references. Someone with unlimited time, energy and expertise might be able to go through all of the calculations that produced the predictions in the reports in order to see if they were done correctly, but that is not a practical option, which raises the problem I mentioned in an
Any thoughts on the validity of using the IPC reports as predictions? I.e., if they are predictions of what would have happened otherwise in the absence of interventions, but there were interventions? ¯\_(ツ)_/¯?
Is there a reason you are just testing the buisness as usual scenario? My impression of IPCC reports is that is merely one scenario among many, and by no means the most likely.
Just to be silly about it, the simplest model I'd really try to fit to that data would be autoregression, a bit more comple, than linear but far more plausible as an underlying mechanism.
I think we’re going to learn a lot about how accurate the IPC reports are in the next few years if we have another El Nino event. Some people claim the last 3 years of La Nina have obscured the actual rise in temperature. I have no idea whether that’s true, but I suspect we will soon.
The IPCC should provide (maybe does, I don't know) a *median* of prediction, because (legitimate) climate change worries are about *tail risk*.
So, if reality diverges from the *mean*, that's not super concerning, given that understanding feedback-riddled climate systems is just really hard---I'd only care much if reality diverged significantly from the median prediction of what IPCC said were the best models... I do expect those to diverge as well though (due to bias at every level, since it's a hot-topic/politically-entangled issue).
Any thoughts on the validity of using the IPC reports as predictions? I.e., if they are predictions of what would have happened otherwise in the absence of interventions, but there were interventions? ¯\_(ツ)_/¯?
Is there a reason you are just testing the buisness as usual scenario? My impression of IPCC reports is that is merely one scenario among many, and by no means the most likely.
I'd be interested in pairing this with estimates of CO2 growth. I'm too lazy to do it myself.
Just to be silly about it, the simplest model I'd really try to fit to that data would be autoregression, a bit more comple, than linear but far more plausible as an underlying mechanism.
I think we’re going to learn a lot about how accurate the IPC reports are in the next few years if we have another El Nino event. Some people claim the last 3 years of La Nina have obscured the actual rise in temperature. I have no idea whether that’s true, but I suspect we will soon.
The IPCC should provide (maybe does, I don't know) a *median* of prediction, because (legitimate) climate change worries are about *tail risk*.
So, if reality diverges from the *mean*, that's not super concerning, given that understanding feedback-riddled climate systems is just really hard---I'd only care much if reality diverged significantly from the median prediction of what IPCC said were the best models... I do expect those to diverge as well though (due to bias at every level, since it's a hot-topic/politically-entangled issue).
Nice article.
"The solution is to test the model against data that not used" should be "data that were not used."
Thank you. It’s very strange that yours was the only article I’ve seen that assessed the predictions out of sample like this.