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terça-feira, setembro 02, 2003

Lomborg por Lomborg

A propósito deste comentário do Cruzes Canhoto a esta notícia no Público :

Basically, there is no disagreement that the centuries before 1900 were much colder. This phenomenon is well known in history as the “Little Ice Age”

Likewise, the early part of Mann data indicates a slightly warmer climate, some periods of which could even be on par with the mean twentieth temperature. Again, there is no disagreement that the early part of the second millennium was warmer [than the Little Ice Age], a period known as the “Medieval Warm Period”.

[…] tree ring data […] are naturally limited to land data. Which means that they do not describe temperature of the more than 70% of the Earth’s surface covered by oceans.

Growth of trees are dependent on many other factors besides temperature […]

trees mainly grow in summer and during the day-time, which means that they do not realiably measure full, annual temperature.

Thus, the available data […] seem to indicate that there is considerable disagreement about the actual development in temperature.

Consequently, a recent status report concludes that “at present, it is debatable whether there is enough temperature proxy data to be representative of hemispheric, let alone global temperature”.

There is no doubt that the temperature of the late twentieth century is greater than many previous centuries, but this cannot be taken as a simple indication of overwhelming global warming as we are also coming out of a Little Ice Age.

The claim that the temperature is higher now than that at any time throughout the past 1000 years seems less well substantiated, as the data essentially exclude ocean temperatures, night temperatures and winter temperatures […]

Bjorn Lomborg in "The Skeptical Environmentalist".