Weirding Humans

16 Mar 2017

At https://phys.org/print408702531.html ... we have a strange paper here - but useful in the sense it provides another dimension to what is normally pushed our way. It concerns the drying up of the Sahara desert. Were humans to blame?

Humans may of course be responsible for overgrazing, which is one of the charges laid at their feet, but the idea they can change the climate by such activities appears to be on the extreme side of the argument. However, it is after all, climate science, and any half cocked idea is grist for the mill. Climate science appears to be able to throw up some ideas that are totally contrary to what the rest of climate science is saying - but don't knock it as it all helps to have an open mind on the issue. The article is published in Frontiers in Earth Science (and the subject matter is certainly at the frontier). One statement stands out - in East Asia (China to everybody else) Neolithic people changed the landscape so profoundly that monsoon rains stopped penetrating so far inland (the NW zone which regularly experiences fall offs in monsoon rains when the climate is cool). Tilling fields is somehow able to cause the monsoon track to shift, we are told. Not only that, he follows this with - 'evidence of human driven ecological and climate change has been documented in Europe, N America and New Zealand ...'. Really. He then turns his attention to the dessication of the Sahara which most climate scientists attribute to a shift in the monsoon track. In this instance it is overgrazing that is said to shift the monsoon rain path. Who knew that a few herds of cattle could affect the atmosphere. In his view overgrazing triggered the albedo effect - lack of vegetation causing more sunlight to bounce off the ground (back up to the atmosphere). So, can overgrazing cause a desert to form? There is evidence that this has actually happened when herds have been allowed to overgraze causing the desert to grow at the fringe. Overgarazing can indeed cause the area of desert to expand. What he is saying is a trifle different. The desert was formed in the first place by overgrazing.

Another bit told us about all the water in the Sahara during the early Holocene, lakes and rivers running through a landscape that was green. This all came to an end around 6200BC (see earlier piece) followed by several hundred years of dry arid conditions. It was in the aftermath of this event, with much less greenery to go around, that cattle raising tribes appeared in the Sahara. In other words, the decline had already set in. As an earth scientist he must know that periods of arid weather came and went on other occasions too - at 4350, 3200, and 2300BC. These were not brought on by grazing animals - they involved a cooling of the global climate. They arrived suddenly and dissipated slowly. He says that scientists should seek to find out why the lakes dried up and what humans were doing when the lakes were there - in order to find out why it happened. The answer to that is provided by archaeology. They were fishing. Looking to catch their dinners.

The article really is all about CAGW alarmism and has nothing to do with serious science. Most of the facts he gripes about are already known and published. It is mischief making. It serves to to show up the anti human dimension of CAGW - too many humans spoils the broth. Weirding human activity is all about scaring the impressionable.