Global and Seasonal thread summary and continuation

Okay, the “Globally and Seasonally averaged” thread has grown to over 500 comments and thus reached its point of diminishing return in terms of the time it would take to read it and the utility of doing so. And while on the one hand I don’t like to feed what is drifting towards to troll-like behaviour, the conversation continues and I don’t want to stifle it. It began with a comment of mine at Judith Curry’s blog about who is a denier and who is a sceptic. See the update in the original article for why Richard clearly falls out of the sceptic category.

So I am going to close that thread and move it over here by responding to Richard’s finally devoting some of his time to one of the main thrusts of the original post: why do his (alledged) findings disprove that CO2 plays any role in the current warming trend in globally and seasonally averaged temperatures?

Richard answers:

“How can more CO2 causing “global warming” make summer’s highest temps fall? How can it make extreme hot days FEWER? That’s the trend. AGW claims is that there will be more heat waves, not fewer.”

Of course this is not an answer. It is just a paraphrase of “because it must be”. It has come out in the discussion that when Richard talks about falling summer temperatures he is actually just plotting a single point for each year. Aside from how this must effect the statistical significance of his trend, there is a very legitimate question as to why should one prefer doing that to the normal practice of computing June-July-August average and calling this the summer temperature to be compared with December-January-February as the winter temperature? Do we learn more by looking at less data? I don’t see how. And does this (alledged) decline in summer maximum daily temperature really tell us that there are fewer heat waves?

What is a heat wave? Something like love, I know that, but how is it defined? According to the WMO, (paraphrase from Wikipedia), a heatwave is “when the daily maximum temperature of more than five consecutive days exceeds the average maximum temperature by 5 Celsius degrees”. So it is not hard to figure out from this that you can have a heat-wave, even a record setting heat wave, without out exceeding the single highest maximum temperature from the last year, or even any year in the instrumental record. You do not have to set a record high for every day, or any day for that matter, as achieving 5oC above the average meets the criterion.

He’s right that the climate models predict an increase in heat waves around the globe. And according to the IPCC an increase has been observed.

Since 1950, the number of heat waves has increased and widespread increases have occurred in the numbers of warm nights. The extent of regions affected by droughts has also increased as precipitation over land has marginally decreased while evaporation has increased due to warmer conditions

Richard goes on to disagree with these statements: “if global warming was driven by the sun, we should see summer warming faster than winter” and “greenhouse warming predicts nights should warm faster than days while solar warming is the other way around”. The latter statement was dismissed as “an assumption” the former rejected this way:

Not true. He is missing the fact that winds and frontal systems attempt to even out the planet’s temperature from the hotter regions to the colder regions. Since there is an upper ceiling on how hot the planet can get, it means that the winters would have to warm more beause the summers cannot get any hotter. Convection and systems circulation moves that summer air into the colder regions (summer in the south means winter in the north).

Aside from the irrelevance of some alledged “upper ceiling” (what is it and why? are we there already?), there is some seriously convoluted thinking here! Apparently there is this mechanism that redistributes heat around the globe if and only if that heat is the result of solar forcing. If we do observe that heat distribution (Richard’s claim) then it shows it can not be from CO2 forcing because…because…well, just because I guess.

Regardless of the existence of some mystical convection that only affects air warmed by a surface heated by direct sunlight and not heated by an enhanced greenhouse effect, AGW theories do in fact predict nights will warm faster than days, and winters will warm faster than summers. See these articles, here and here, from Skeptical Science. Once again, the observations match the expectations and CO2 fits the required mechanism whereas solar forcing does not.

Anyway, I don’t really expect much better from Richard in a new thread, but I am of the firm conviction that we can still learn from having these discussions.