segunda-feira, setembro 22, 2008

"A Realimentação Positiva" ou "O Tiro pela Culatra" ou "O Não-Linear do Milénio"

Hundreds of methane 'plumes' discovered
Half of Europe's frogs face extinction
Permafrost carbon estimates doubled A new study by a team of international scientists has revealed the amount of carbon frozen in the world's permafrost is double what was previously thought. The three-year study concluded that the amount of carbon locked up in the world's permafrost is at least 1,500 billion tonnes more than double previous estimates and the equivalent of twice the current amount of Co2 in the world's atmosphere. Permafrost is frozen soil found at high latitudes, close to the north or south poles, and contains the remains of plants and animals which due to the extreme cold do not decompose, trapping carbon in the soil. This is the most accurate assessment yet of the amount of carbon contained in worldwide permafrost but the actual amount may well be higher, says CSIRO scientist and study team member Dr Pep Canadell. "We are now in the ballpark of what probably is there, there is still a big issue and that is the depth, our database goes down to three metres for much of the permafrost ... but we know that the depths can be much greater," he said. The level of carbon contained in the world's permafrost is of particular significance to climate change as once the carbon it contains begins to be released there is no way to stop it. This could lead to a large amount of extra carbon dioxide and methane being released into the atmosphere and potentially speeding up warming, a process some climate scientists refer to as a tipping point, Dr Canadell says. "Technically, we call it the climate carbon feedback and permafrost is a beautiful one and we know that some of these processes can potentially be irreversible," he said. "Irreversible doesn't mean that all the carbon is going to go into the atmosphere right away, but it means that when it starts it's fundamentally impossible to stop. "It may take a few hundred years to melt and to release a substantial amount of carbon but there is nothing that humans can do once these things start." Dr Canadell likened the process to a massive compost pile which once started generates its own heat that would continue even if temperatures were to fall. "This is like a big compost pile, so when you start the decomposition of the compost pile, it is self heating," he said. "It's hot when you touch it so there is a point where you no longer need the external temperature driving that melting and decomposition, because the microbial community is self-generating enough heat to continue melting." The findings have been published in the latest edition of the scientific journal, Bioscience.

terça-feira, setembro 09, 2008

Depois da Tailândia