sexta-feira, novembro 14, 2008

A “bomba” de metano

A imaginação dos alarmistas climáticos é fértil em arranjar motivos de alarme. Lançam uma atoarda, escrita ou falada, sem justificação plausível, com a maior das naturalidades. E os media aproveitam mais um furo jornalístico para atemorizar e desinformar a opinião pública.

Repete-se a atoarda e, a páginas tantas, até parece que se trata de uma verdade científica. Tem sido assim, tanto no que respeita ao Árctico como ao Antárctico.

A última moda é a da “bomba-com-retardador do metano existente no Árctico”. Como seria de esperar esta moda foi prontamente adoptada pelos alarmistas da nossa praça. Por exemplo, Carlos Pimenta, também conhecido como empresário da energia eólica, foi expedito a referir essa “ameaça” quando entrevistado no programa “A Voz do Cidadão”, de que já aqui demos conta.

O editor do MC aproveitou a recente publicação de um artigo sobre a matéria para consultar vários especialistas através de um forum internacional de que faz parte.

Eis pois esse artigo, no original, em inglês, tendo sido referenciadas, mediante numeração entre parêntesis rectos, as passagens que mereceram os comentários do meteorologista sueco Hans Jelbring apresentados na parte final.

Exclusive: The methane time bomb

By Steve Connor, Science Editor
Tuesday, 23 September 2008

Arctic scientists discover new global warming threat as melting permafrost releases millions of tons of a gas 20 times more damaging than carbon dioxide. [1]

Preliminary findings suggest that massive deposits of subsea methane are bubbling to the surface as the Arctic region becomes warmer and its ice retreats. [2]

The first evidence [3] that millions of tons of a greenhouse gas 20 times more potent than carbon dioxide [4] is being released into the atmosphere from beneath the Arctic seabed has been discovered by scientists. [5]

The Independent has been passed details of preliminary findings suggesting that massive deposits of sub-sea methane are bubbling to the surface as the Arctic region becomes warmer and its ice retreats.

Underground stores of methane are important because scientists believe their sudden release has in the past been responsible for rapid increases in global temperatures, dramatic changes to the climate, and even the mass extinction of species. [6]

Scientists aboard a research ship that has sailed the entire length of Russia's northern coast have discovered intense concentrations of methane – sometimes at up to 100 times background levels – over several areas covering thousands of square miles of the Siberian continental shelf. [7]

In the past few days, the researchers have seen areas of sea foaming with gas bubbling up through "methane chimneys" rising from the sea floor. They believe that the sub-sea layer of permafrost, which has acted like a "lid" to prevent the gas from escaping, has melted away to allow methane to rise from underground deposits formed before the last ice age. They have warned that this is likely to be linked with the rapid warming that the region has experienced in recent years. [8]

Methane is about 20 times more powerful [9] as a greenhouse gas than carbon dioxide and many scientists fear [10] that its release could accelerate global warming in a giant positive feedback [11] where more atmospheric methane causes higher temperatures, leading to further permafrost melting and the release of yet more methane.

The amount of methane stored beneath the Arctic is calculated to be greater than the total amount of carbon locked up in global coal reserves so there is intense interest in the stability of these deposits as the region warms at a faster rate than other places on earth. [12]

Orjan Gustafsson of Stockholm University in Sweden, one of the leaders of the expedition, described the scale of the methane emissions in an email exchange sent from the Russian research ship Jacob Smirnitskyi.

"We had a hectic finishing of the sampling programme yesterday and this past night," said Dr Gustafsson. "An extensive area of intense methane release was found. At earlier sites we had found elevated levels of dissolved methane. Yesterday, for the first time, we documented a field where the release was so intense that the methane did not have time to dissolve into the seawater but was rising as methane bubbles to the sea surface. These 'methane chimneys' were documented on echo sounder and with seismic [instruments]."

At some locations, methane concentrations reached 100 times background levels. These anomalies have been seen in the East Siberian Sea and the Laptev Sea, covering several tens of thousands of square kilometres, amounting to millions of tons of methane, said Dr Gustafsson. "This may be of the same magnitude as presently estimated from the global ocean," he said. "Nobody knows how many more such areas exist on the extensive East Siberian continental shelves. [13]

"The conventional thought has been that the permafrost 'lid' on the sub-sea sediments on the Siberian shelf should cap and hold the massive reservoirs of shallow methane deposits in place. The growing evidence for release of methane in this inaccessible region may suggest that the permafrost lid is starting to get perforated and thus leak methane... The permafrost now has small holes. We have found elevated levels of methane above the water surface and even more in the water just below. It is obvious that the source is the seabed." [14]

The preliminary findings of the International Siberian Shelf Study 2008, being prepared for publication by the American Geophysical Union, are being overseen by Igor Semiletov of the Far-Eastern branch of the Russian Academy of Sciences. Since 1994, he has led about 10 expeditions in the Laptev Sea but during the 1990s he did not detect any elevated levels of methane. However, since 2003 he reported a rising number of methane "hotspots", which have now been confirmed using more sensitive instruments on board the Jacob Smirnitskyi.

Dr. Semiletov has suggested several possible reasons why methane is now being released from the Arctic, including the rising volume of relatively warmer water being discharged from Siberia's rivers due to the melting of the permafrost on the land. [15]

The Arctic region as a whole has seen a 4 ºC rise in average temperatures [16] over recent decades and a dramatic decline in the area of the Arctic Ocean covered by summer sea ice. Many scientists fear [17] that the loss of sea ice could accelerate the warming trend because open ocean soaks up more heat [18] from the sun than the reflective surface of an ice-covered sea. [19]

Eis agora os comentários do meteorologista sueco Hans Jelbring :

[1] - This “new” time bomb is released every winter with maximum emissions during winter time (dec-mars). There is nothing new and the release rate is stabilizing or diminishing since about 1999.

[2] - It does not depend on any ice retreat and why should it? Subsea temperature will be about the same, regardless of a diminishing ice cover.

[3] - It takes ignorance to claim this.

[4] - This is relating to calculations from James Hansen that has been approved by IPCC. I have seen the figure 20-40 times as potent by ppmv that is. There exists no verification of this statement. Only modeling based of a number of different assumptions.

[5] - It can be mentioned that the existence of enormous amounts of clathrates (methane ice that can be stable up to +5 ºC) have been known for decades and has been used in scare mongering, too.

[6] - There are spikes in methane and carbon dioxide during certain periods and especially during warming periods. It is quite natural that decomposition of organic matter produce CO2, methane and CO. The biota in northern Canada and Siberia accumulate during normal conditions and a faster decomposition will occur during warmer periods (See attachment).

[7] - This should be expected.

[8] - The northern hemisphere has warmed more than the southern one lately. There is a passage in my thesis treating the reason which I called subsidence energy. Air masses is brought from the SH occasionally from dec-mars via air from SH. The energy does not go in the opposite direction and the amplitude is quasi cyclic. There is probably a connection with the production rate of Mobile Polar Highs and the path they move.

[9] - Unverified assumption and it does not matter anyway since greenhouse gases do little to increase temperature.

[10] - Those who do not consider facts.

[11] - Fantasy construction with no verification in sight.

[12] - The amount means that the clathrates have come back in a new disguise. They are stable some hundreds meters below the ocean floor. This issue has been treated carefully although “blow ups” have been found relating to earth quakes or land slates (along coastal areas).

[13] - Well, the emissions into the atmosphere are known since at least +20 years in many locations. This is one reason why NH polar areas have 10 % higher concentrations than SH locations.

[14] - Measurement in Barrow shows that the emissions are not continuous but very varying from time to time with occasional outbreaks. Wetlands are also a source.

[15] - As I already said, the overall methane emission has stabilized or is declining whatever they have found.

[16] - Come on! Warm winters, that dominate the increase, are still far below 0 ºC and the sea along the coast is frozen.

[17] - Fantastic reference!

[18] - Correct, but solar irradiation has hard to enter the sea when the incidence angle is small and there are few sunny days up there.

[19] - This is the type of “scientific” articles I am so tired of reading.

Fonte: The Independent.