I notice The Global Warming Policy Foundation has a new report by Nic Lewis and Marcel Crok called Oversensitive : how the IPCC hid the good news on global warming (you can probably find it if you want to). I was going to write a post about this, but I notice that there’s a guest post by Piers Forster on Ed Hawkins’s blog that’s already commented on the GWPF report. I might just add two quick comments. One is that I’m still very surprised that there hasn’t been more mention of how the addition of a small amount of extra data significantly changed Lewis (2013)’s ECS estimate. Using data up until 1995, his method gives 2-3.6oC. Using data till 2001, it gives 1.0-2.2oC. I might be a little concerned about a method that seems that sensitive to small changes in data.
The report also includes the following statement
So, to conclude, we think that of the three main approaches for estimating ECS available today (instrumental observations, palaeoclimate observations, GCM simulations), instrumental estimates – in particular those based on warming over an extended period – are superior by far.
Really? Any mention of recent work suggesting that regional variations can make these energy budget constraints unreliable? Not that I could see.
If you want to read something that may be a somewhat better representation of the evidence, you could try reading the new report from the Royal Society and the US National Academy of Sciences called Climate Change : Evidence and Causes. Stoat already has a post that discusses this, so I won’t say much more about it.
I thought I’d finish this post with a video that I saw yesterday about abrupt climate change. If I quote from the Royal Society and NAS report, it says
Results from the best available climate models do not predict abrupt changes in such systems (often referred to as tipping points) in the near future. However, as warming increases, the possibilities of major abrupt change cannot be ruled out… Such high-risk changes are considered unlikely in this century, but are by definition hard to predict. Scientists are therefore continuing to study the possibility of such tipping points beyond which we risk large and abrupt changes.
So, we do not predict abrupt changes in the near future, but we can’t really rule them out. That sounds reasonable. In the video Richard Alley says
is it possible we’ve over-estimated the dangers? Sure. Is it possibly a little better? Sure. Is it possibly a little worse? Sure. Is it possible that CO2 breaks things that we really care about and things are a lot worse than we expect? Yes it is.
The uncertainties are mainly on the bad side.
And that’s a fundamental issue – in my opinion – with the Lewis and Crok report. They’re trying to argue that things will almost certainly be better than many estimates suggest. Could they be right? I hope so, but I would argue that some fairly basic physics suggests that they won’t be. That aside, how does it help policy makers by essentially suggesting that they ignore the possibility that things could be a lot worse than we expect? I don’t think it does. Optimism is a great quality. Blind optimism, on the other hand, can be rather dangerous if you’re ignoring potentially serious risks. There’s much more that probably could be said, but I’ll end there and let those who have more to say, do so through the comments.