Windy Weather

3 Feb 2013

At and which is being presented on sceptic sites as another blow to CAGW science - and see also and

Where do winds come from? The rotation of the planet whips them up? Turbulence in the atmosphere? In this paper we learn that trees fix carbon and produce oxygen but they suggest trees and vegetation also unleash forces powerful enough to drive global wind patterns. That is a big idea to take on board and the comments show that a lot of people are not convinced. However, this feature of the paper seems to have grown wings whereas what they were trying to concentrate on was that the impact of wind is a central part of the earth's climate system but is not part of the climate models. If wind is whipped up by trees, or the lack of trees, it will cause problems to the consensus theory - but how much a problem is something that might have been overstated. Sheil reckons bad science is protecting shoddy climate models - and we might all agree with that. The paper was controversial enough for the peer review process to stutter but the journal kept faith with scientific principles, it is alleged, Atmospheric Chemistry and Physics, being made of sterner stuff than the review process, published and be damned. 

According to Sheil, the theory explains declines in rainfall and rainfall reliability as a result of loss of forest cover - especially in subtropical regions. He says the forest in the Amazon is there not because there is a lot of rain, as such but because lots of rain has been attracted by the trees, the opposite way round. However, as pointed out, the Amazon, Congo and SE Asian rainforests are found beneath the Inter Tropical Convergence Zone while the mid latitude bands of forest are beneath the jet streams (or closely connected with them). Now, from a catastrophist point of view we may wonder, from this, why exactly did it get hot and dry in North Africa and Australia - what was the process. Clearly, they don't have enough rain to allow vegetation to grow apart from drought tolerant species. It is also a recognised factoid, true or false, that the weather across North Africa has become progressively hotter and drier. What caused the process of desertification to begin? We know North Africa was wetter and more luxuriant with an abundance of humans and animals up to around 4000BC - when it all started to go wrong. Well, it did actually start to go wrong around 6000BC - but perked up for a while. Was the desertification linked to a disappearance of vegetation, including trees? If so, did that have any bearing on landscape fires induced by cosmic encounters with little bits of comet or by any other catastrophic mechanism? If the disappearance was abrupt is this shown in the record (pollen analysis for example)? There is some indication of landscape fires across Europe around 4200BC - but Europe did not become a desert. Again, landscape fire may have been a feature at 3000 and 2300BC, and earlier, at 6000BC - and again we do not have deserts in Europe. We do instead have forest cover and the jet stream. North Africa and most of Australia is not in line with the jet stream and only its northern extremities come close to the Inter Tropical Convergence Zone. In spite of that dampener we still have to bear in mind that the monsoon system has shifted - leaving the Sahara increasingly in the Doldrums. The Sahara is also growing and this might be as a result of lack of vegetation - not enough rain falling as a result of wind systems altering. Again, these ideas are worth keeping an eye on as they may be an important factor to be weighed in the balance.