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geophysicists measure in 2007, a sharp increase of the greenhouse gas methane in the atmosphere. This could accelerate climate change.
The amount of the greenhouse gas Methane in the atmosphere rose significantly in 2007. According to a study by geophysicists from the Massachusetts Institute of Technology (MIT). It is based on data from air samples collected a global network of monitoring stations of the U.S. space agency NASA from 1997 to April 2008. Thus, the study authors, end a decade in which the concentration of the substance remained relatively stable. The sharp increase could accelerate global warming in the future.
By 1800, that is in pre-industrial times, the amount of methane was 700 parts per billion air particles (abbreviated ppb in English "parts per billion). Since then it has more than doubled. Between 1999 and 2006, the global average ppb 1773rd "Our measurements show that the concentration in the last year leapt by ten ppb to 1783 ppb," said study lead author Matt Rigby.
acts as a greenhouse gas methane 25 times stronger than carbon dioxide (CO2). Therefore, it is responsible for 20 percent of the previously measured and expected future global warming, although its concentration in the air by about a factor of less 4600 than that of CO2, the attribute that climatologists accounts for 60 percent of human-induced greenhouse effect. The colorless and odorless gas is produced in swamps, rice fields and in the digestive tract of cattle, but also in large quantities from coal mines and in Natural gas production released.
the other hand, it is of specific molecules - so-called hydroxyl radicals - are destroyed. They serve as a kind of detergent that cleans the atmosphere of pollutants. Once the atmospheric concentration of methane had remained constant as long, the researchers believed, between emissions and the reduction of methane had set a balance. The new measurements show that this balance is disturbed since the spring of 2007. This became more frequent in the aftermath of several million tons of additional methane in the atmosphere. "This is worrying because the stable level of half of the methane, the strong growth in CO2 emissions to compensate at least in part, "says Drew Shindell of the climatology of the Goddard Institute for Space Studies at NASA in New York. "The amount of methane continues to rise so much is this compensation effect is lost."
methane concentration increases everywhere
To the surprise of researchers found out that the methane concentration increased simultaneously in both hemispheres of the globe. Here, the main sources of gas are in the northern hemisphere. It usually takes about a year to have mixed by global air currents there with the Emissions of air so that a global mean adjusted. In the northern hemisphere, probably Swamps and wetlands in Siberia, the largest issuer. There was the unusually high temperatures in the past year, the activity of methane-producing bacteria considerably.
fits into this picture also an observation that scientists have made a Swedish-Russian expedition in mid-September on board the Jacob Smirnitskyi. The research ship sailed under the International Siberian Shelf Study 2008 "on the north coast of Russia along. Heading the sea seemed to boil over again, burst on the surface bubbles. Seismic and sonar measurements revealed that the gas in regular vents flowed upward - was apparently seine Freisetzung in der Tiefe recht schnell und ungezügelt.
Wo Methan aus dem Meeresboden blubbert
Bald hatte die Forschergruppe herausgefunden, was da in großen Mengen emporblubberte. Es war der Klimakiller Methan. In den nördlichen Schelfgebieten liegt er eigentlich als sogenanntes Gashydrat vor. Dieses Eis-Methan-Gemisch lagerte bislang sicher am Meeresgrund. Allein auf dem sibirischen Kontinentalschelf könnte es Vorkommen von 540 Milliarden Tonnen geben. Das Problem ist, dass der dauerhaft gefrorene Ozeanboden wegen der Erderwärmung aufzutauen droht. Dann wird das Hydrat instabil und zersetzt sich, dabei wird das Methan frei.
Apparently, this process has already begun. This is indicated not only the observations of the polar researchers on board the Jacob Smirnitskyi "out at several locations in the Laptev Sea - including a sea area near the Lena estuary - as well as in parts of the East Siberian Sea massively increased gas concentrations in water and air masses . Already in 2007 an international team of researchers had reported that North Siberian lakes emit 3.8 million tonnes of methane per year. This would increase to date in six to 40 million tons of estimated emissions from Arctic wetlands at ten to 63 percent.
If all stored in the Arctic methane into the air may, after Calculations Russian researcher twelvefold its concentration in the atmosphere. This would give a strong boost to global warming, which further methane from the Arctic Ocean could be free. A vicious circle arises, climatologists call it a "positive feedback". The decomposition of methane hydrates in the permafrost them is considered a so-called tipping points of 15, which could identify them before. Exceed the associated greenhouse processes these items could fall over the earth's climate.
atmosphere out of balance
go so far as the fears of the MIT researchers, however, not yet. Because of the fact that on der Nordhalbkugel der Erde eine mächtige Methanquelle zu geben scheint, auf der Südhalbkugel jedoch nicht, lenkte ihren Verdacht in eine andere Richtung: Möglicherweise nahm in der Atmosphäre die Menge des Waschmittels Hydroxyl ab, das Methan und andere Schadstoffe unschädlich macht, In diesem Fall wären, wie Modellrechnungen zeigen, die gemessenen Konzentrationen des Gases fast ganz ohne neue Emissionen zustande gekommen.
Auch sollte es auf der Nordhalbkugel in größeren Mengen vorliegen, weil sich dort durch Reaktionen mit anderen Luftschadstoffen mehr Hydroxyl verzehrt als im Süden. Folglich können die Methanmoleküle in der Nordhemisphäre länger in der Luft überleben. Zumindest teilweise, Sun geophysicist Rigby leave, the observed uneven distribution explained in that way.
do next step to find Rigby and his colleagues are now final, what could increase the concentration of methane in the atmosphere so much. "It could be a superposition of both effects," he says. Only then will we know whether it was a short-term anomaly or a permanent increase. Then I could also assess the danger to the climate through the gas threatens really
(Note, the blog-editor "The challenge for all - WWF Report: melts the ice,
then breaks off the Gulf Stream and then comes the next ice age).
From FOCUS editor Michael Odenwald
Photos: Marum University of Bremen / ddp, nasa
Copyright © 2008 by FOCUS Online GmbH
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