segunda-feira, 30 de abril de 2007

"Is Global Warming a Sin?" ALEXANDER COCKBURN

O cepticismo à esquerda.

"(...)As Hertzberg readily acknowledges, the carbon dioxide content of the atmosphere has increased about 21 per cent in the past century. The world has also been getting just a little bit warmer. The not very reliable data on the world's average temperature (which omit most of the world's oceans and remote regions, while over-representing urban areas) show about a 0.5Co increase in average temperature between 1880 and 1980, and it's still rising, more sharply in the polar regions than elsewhere. But is CO2, at 380 parts per million in the atmosphere, playing a significant role in retaining the 94 per cent of solar radiation that's absorbed in the atmosphere, as against water vapor, also a powerful heat absorber, whose content in humid tropical atmosphere, can be as high as 2 per cent, the equivalent of 20,000 ppm. As Hertzberg says, water in the form of oceans, clouds, snow, ice cover and vapor "is overwhelming in the radiative and energy balance between the earth and the sun Carbon dioxide and the greenhouse gases are, by comparison, the equivalent of a few farts in a hurricane." And water is exactly that component of the earth's heat balance that the global warming computer models fail to account for.

It's a notorious inconvenience for the Greenhousers that data also show carbon dioxide concentrations from the Eocene period, 20 million years before Henry Ford trundled his first model T out of the shop, 300-400 per cent higher than current concentrations. The Greenhousers deal with other difficulties like the medieval warming period's higher-than-today's temperatures by straightforward chicanery, misrepresenting tree-ring data (themselves an unreliable guide) and claiming the warming was a local, insignificant European affair.

We're warmer now, because today's world is in the thaw following the last Ice Age. Ice ages correlate with changes in the solar heat we receive, all due to predictable changes in the earth's elliptic orbit round the sun, and in the earth's tilt. As Hertzberg explains, the cyclical heat effect of all of these variables was worked out in great detail between 1915 and 1940 by the Serbian physicist, Milutin Milankovitch, one of the giants of 20th-century astrophysics. In past postglacial cycles, as now, the earth's orbit and tilt gives us more and longer summer days between the equinoxes.


It looks like Poseidon should go hunting for carbon credits. Trouble is, the human carbon footprint is of zero consequence amid these huge forces and volumes, and that's not even to mention the role of the giant reactor beneath our feet: the earth's increasingly hot molten core."

Sem comentários:

Enviar um comentário