I had some further thoughts about the subject of the last post. Here they are.
In the last post I mentioned that a change in either the mean value or the variance of a probability distribution will greatly affect the probability of extreme events. I also mentioned that a change in variance has a more profound impact on the likelihood of extremes than a change in mean value.
One of the analogies sometimes used to explain the impact of global warming on the weather is that we’re “loading the dice.” Perhaps a better desrciption is that we’re changing the dice.
We’ve occasionally looked at temperature time series from NCDC (National Climate Data Center) for USA48 (the 48 states of the continental USA excluding Alaska). But in addition to data for individual states, NCDC also offers data for each individual climate division within each state. The temperature data, for example, can be found here.
Segmenting USA48 by division rather than state will give us a much more detailed geographical picture of climate change in the mainland U.S. Let’s take a look at some of the things the data have to say.
It’s getting tiresome.
There’s a new post on WUWT about how
“Authors Steirou and Koutsoyiannis, after taking homogenization errors into account find global warming over the past century was only about one-half [0.42°C] of that claimed by the IPCC [0.7-0.8°C].”
Anthony Watts was so excited he felt the need to alert Richard Muller to this result. The blog post leads to the usual frenzy of accusations that the global temperature estimates are a fraud. There’s much talk of how the entire global warming during the last 100 years is only 0.4C, and half of that must be natural, leaving a mere 0.2C (at most) attributable to humankind, so they’ve been right all along that we’re not changing the climate in any dangerous way. There are even some bizarre statements like one reader concluding “that is fully consistent with what we’ve said all along, that incresed water vapor is a negative, not positive feedback…” How water vapor got into the discussion, I don’t know.
What’s lacking is the faintest glimmer of actual skepticism about this claim.
Anthony Watts has a post titled “Coldest July in history for Anchorage?” This happened less than a day after I said this:
One of Anthony Watts’ favorite comments is along the lines of “coldest March in 40 years!!!” He rarely (if ever) says “coldest March ever.”
Is this my come-uppance?
The subject came up — yet again — whether or not there is a “pause” in global warming recently. Specifically:
Re looking at global warming over the last 15 years. I know it breaks all the “statistical” rules, but just simply eyeballing the graph of (annual average) temperatures shows a distinct change in the trend of global temperatures after 1998. In order to avoid a charge of “cherry picking” I could have said 10 years since 2002 – but to me the break in the trend is pretty clear.
We’ve often dealt with this subject, but since it’s so common, and seems to come from real skeptics as well as fake ones, we’ll address it once again. In depth.
I received a rather lengthy comment from “TLM” on this post. My reply is too long for an in-line response, so here it is.
NOTE: see the UPDATE at the end of the post.
Jeff Masters at Wunderblog (part of Weather Underground) reported that for the lower-48 states of the USA, every one of the last 13 months was in the top third of its historical distribution. He calculated the odds of that happening by random chance, in an unchanging climate, being only 1/3 to the 13th power, or a mere 1 chance out of about 1.6 million. Pretty small odds.