At first glance Andrew Bolt's 4th point criticising Al Gore's An Inconvenient Truth seems at if it could be reasonable, but that's why we check his facts:
4: Gore shows a series of slides of vanishing lakes (like Lake Chad) and snow fields (like Mt Kilimanjaro's) and blames global warming for it all.
In fact, Lake Chad is so shallow it nearly dried out as far back as 1908, and again in 1984. So many more people depend on it now that the water pumped out for irrigation has quadrupled in 25 years. No wonder it's drying.
And Mt Kilimanjaro was losing its snows more than a century ago, not because of global warming, but, says a 2004 study in Nature, largely because deforestation has cut the moisture in the air.
And that worrying picture Gore shows of vanishing glaciers in the Himalayas? Newcastle University researchers last month said some glaciers there are now getting bigger again.
Regarding the Lake Chad thing, it is not clear what his criticism or point is, so it is hard to answer. His logic seems to be floundering. Global warming theory does not discount the causes of previous droughts or other manifestations of AGW. Human irrigation demands AND reduced rainfall has resulted in the lake surface area decreasing from 25,000 km2 in 1963 to 1,350 km2 today according to modelling studies.
It's not EITHER OR.
Bolt's claim about Mt Kilimanjaro's snows dissappearing largely because of deforestation not global warming is either disingenious or ignorant. One of the causes of global warming is deforestation. Forests are important elements in the carbon-cycle; one of the most obvious roles they play is that they 'fix' or 'sink' the carbon-dioxide by taking it out the atmosphere during photosynthesis. In this way they moderate our climate.
Growing glaciers? The University of Newcastle study findings don't challenge global warming theory. In fact they confirm them: :::[Newcastle University Press Release: Mountain climate change trends could predict water resources]
Date released: 24 August 2006
New research into climate change in the Western Himalaya and the surrounding Karakoram and Hindu Kush mountains could explain why many glaciers there are growing and not melting.
The findings suggest this area, known as the Upper Indus Basin, could be reacting differently to global warming, the phenomenon blamed for causing glaciers in the Eastern Himalaya, Nepal and India, to melt and shrink.
What gets me about Bolt, is that it is so easy to check the facts, yet he doesn't.
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