## Saturday, May 15, 2010

### Michael Mann on MWP spatial patterns

Michael Mann wrote an article about the Medieval Warm Period (MWP), as "it is sometimes called", and the Little Ice Age (LIA):
What we can learn from studying the last millennium (or so) (RealClimate)
Let me first start by saying that before science tries to learn something from the last millenium (to tell us about the future "climate change", which is the fashionable question that Mann is trying to promote), it may be a good idea to actually learn something about the last millenium.

But you know, paleoclimatology which used to be an academic subject about the truth concerning practically irrelevant questions has become an applied science: the main goal is how can we benefit from the answers, not necessarily true ones, to those questions. You know it's not about the truth at all: it's about something plausible.

But the TRF readers may be interested in the truth for its own sake. And as Mann's article clearly shows, pretty much nothing nontrivial has been learned about the spatial climate patterns in the last millenium, despite billions of dollars that are being invested into this discipline.

In particular, Mann discusses several rudimentary questions such as
1. Can climate models or proxies tell us more about the spatial patterns in the past?
2. Was the North Atlantic Oscillation during the MWP positive or negative?
3. Were El Ninos or La Ninas more frequent or less frequent than today?
4. And can we expect more frequent El Ninos or La Ninas in the next century because of that?
If you read his text, it's clear that the answers to all these - and many other - questions are pretty much completely unknown. The maximum he can do is to believe that the spatial patterns were such that they favored a warmer Eurasia during Medieval Warm Period and a colder Eurasia and North America during the Little Ice Age.

That's based on his wishful thinking, or more precisely a political bias, that these periods could have been some kind of regional flukes, after all. He has failed to "contain" the Medieval Warm Period when it comes to the magnitude of the temperature variations and its duration in time so now, he tells us, tries to "contain" it spatially.

Needless to say, there doesn't exist any reliable - and not even "potentially reliable" - evidence supporting such a regional character of the warm and cool periods. Even the climate models seem to be evenly split about this question (e.g. whether Eurasia was anomalously cool during LIA), Mann informs us. Of course, the hypothesis that the LIA and MWP were global in character is at least equally likely an explanation. After all, we have evidence about these phenomena from a pretty large fraction of the globe so even if they were regional, they were damn important even for the global averages.

It's also unclear whether we can learn more accurate information from the climate models or from the proxies. The reason is simple: none of them gives us any accurate enough data so that they would be worth talking about.

Concerning the last point, we learn that Michael Mann is a kind of heretic - to the extent that is still compatible with his membership in the leadership of the AGW Inquisition. While the IPCC's fourth report says that El Ninos will get more frequent, Michael Mann - by using a vague argument linking MWP, volcanos, and solar activity - expects that La Ninas could be more frequent, instead. It's very clear that the quality of such an argument is at the level of the blogosphere, and so are the corresponding papers, despite their attempts to visually look more serious.

So all of these regional patterns are pretty much unknown. You know, a believer in the abilities of the climate science to predict the future should worry about this ignorance because the regional trends may be very different in individual regions. Note that the warming trends on the hemispheres, and/or on the land vs ocean, often differ by a factor of 3 and sometimes in the sign, too. That's true even if you look at the last 50 years of data.

If the climate models and other arguments of the state-of-the-art climatology can tell us literally nothing about the patterns that appear in regions whose radii are as big as 3,000 km or so, why should we take seriously the predictions of these models and scenarios about the global mean temperature on Earth whose radius is 6,378 km, i.e. just a little bit bigger? Isn't it unlikely for a climate model to be completely useless up to 3,000 km and "suddenly" become very relevant when you get from 3,000 km to 6,000 km?

And why should we care about the global predictions if we know very well that the specific regional trends will be at least as important for the climate of any nation as the changes of the global averages?

#### 1 comment:

1. " I think that the CO2, being quickly distributed everywhere (and absorbing the nearly constant IR radiation through days, nights, and seasons), should have a nearly uniform warming impact on the Earth. "
I'm wondering about the effect of the oceans. Mass about 300-400 times the atmosphers mass, heat capacity much larger.
At least part of all this water has to warm with the atmosphere to reach a new equilibrium after warming by eg. doubling of CO2 concentrations.
Ocean currents will distribute the heat to large parts of all that water.