01 February 2011

Question Place

Finally back and in some shape to answer questions and perhaps even do something useful with suggestions, so bring 'em on and let's have some fun!


jg said...

I've been trying to get better handle on how to compare warming during the Eemian to that of the holocene and to expected warming of the next centuries.
I was surprised to learn how little total insolation changes over thousands of years (e.g. less than a watt per meter). So, whereas doubling of CO2 can be simplified as an additional 4 watts per square meter, it's hard to compare this to the increase insolation at high northern latitudes.
I've read in Nature that the warming from insolation is comparable to the warming expected from anthropogenic CO2, but I would like to investigate this myself (well, with your help).

Jesús R. said...

I've been reading Lindzen's recent digression and I think I can see its flaws. However, there are some things that have me puzzled:

1. He says: "there have been previous periods that appear to have been warmer than the present despite CO2 levels being lower than they are now".

I know about the contrary: previous periods cooler with more CO2 (the faint young Sun paradox), but not the other way around. Do you know what period he may be referring to?

2. In the tropics, in case of disagreement between temperature measurement at the surface and at the upper troposphere, he suggests that observations in the upper troposphere are more reliable:

"It is well known that above about 2 km altitude, the tropical temperatures are pretty homogeneous in the horizontal so that sampling is not a problem. Below two km (roughly the height of what is referred to as the trade wind inversion), there is much more horizontal variability, and, therefore, there is a profound sampling problem. Under the circumstances, it is reasonable to conclude that the problem resides in the surface data, and that the actual trend at the surface is about 60% too large".

That seems just the contrary of what peer review papers found. I don't know much about this, but Lindzen's suggestion seems really difficult to believe, since observations diverge so much in Santer et al 2008's figure 6.

3. He says that "Lindzen and Choi (2009) contained a number of errors; however, as shown in a paper currently under review, these errors were not relevant to the main conclusion".

If I recall correctly, the main conclusion of the critics was that AMIP models aren't suitable to estimate the climate sensibility of the fully coupled climate system, and that CMIP models were much closer to what models predict. So I cannot imagine what the main conclusion is that Lindzen considers still remains.

As a last remark, there are some parts of conspiracy theory, accusations and even insults that I find simply shameful for Lindzen: "Such hysteria simply represents the scientific illiteracy of much of the public, the susceptibility of the public to the substitution of repetition for truth, and the exploitation of these weaknesses by politicians, environmental promoters [...] That the data should always need correcting to agree with models is totally implausible and indicative of a certain corruption within the climate science community".


*I've also posted this in RealClimate.

Nick Barnes said...

Please do a post on Weddell polynyas, in particular on the 1970s giant polynya: whether or not it was a figment of ESMR's imagination, if not what might have caused it, and thence to speculate on whether and when we might see one again, etc.

Robert Grumbine said...

Wow! I should be more careful of what I ask for. Some nontrivial questions here. Nontrivial meaning that it'll take some time to answer well, but also that it will be good to have the answers.

jg and Jesús: Your questions are somewhat related. Particularly the first of Jesús'. The Eemian was the last interglacial before this one. It was warmer than we are today, though CO2 was not as high.

One quick note is, today's climate is not fully adjusted to today's CO2 levels. Some parts of the climate system respond pretty rapidly, but that's 20-30 years. And some parts are slow, such as the ice shelves and ice sheets, which take hundreds to thousands of years. So, when you (or Lindzen) goes to compare today's climate to the Eemian, it is not straightforward to do so.

Thanks for the reminder. I have a couple of posts in mind, and perhaps will turn this in to a project for readers and me to carry out collectively. Some parts seem to lend themselves to that.

Jesús R. said...

Great, Robert, thanks for your answer!

I've been thinking about my second question (re. the tropical tropospheric hot sopt), and I think that temperatures there may be all the homogeneous that Lindzen wants, but if you don't have a good observational mechanism, you won't know what that temeprature is. The problem with radiosondes seems to be that non climatic bias have been discovered (mainly due to changes in the instruments, location of the stations...) and those are difficult to correct. This seems to be a work in progress indeed. That's why they differ so much in Santer et al's Figure 6.

Allen & Sherwood 2008 is worth a look too, since they develop an alternative independent method to derive temperatures there.