Global Ecological Problems and Issues

The most frightening possibility is the so called runaway greenhouse effect. This far the oceans, soils, peat lands and forests of the Earth have absorbed a significant part of all the greenhouse gas emissions. This has slowed down the warming process. But many scientists are afraid, that if the climate warms too much, the global warming starts to feed itself.

According to Peter Cox and other researchers of the Hadley Centre for Climate Prediction and Research plants should first absorb more carbon dioxide from the atmosphere. However, when it gets hotter, the level of carbon dioxide absorbed by the trees and other plants is likely to level out, while the amount produced by the micro‑organisms decomposing organic matter would increase exponentially. According to the models constructed by Cox and his co‑workers the biosphere will rapidly shift, around the year 2050, from absorbing a little carbon dioxide to belching huge amounts of the gas. This would accelerate the warming, and the more the climate would warm up, the more carbon dioxide would be released from the soils. Such a vicious circle could rapidly add at least two centigrades to the expected global warming.

Methane clathrates are ice‑like solids in which methane molecules have been trapped inside cages that consist of ice. They were first discovered by Russian scientists from the permafrost, but it is now known that they also occur in the offshore areas, in the sediments of the continental slopes. Very little is known about these deposits. According to the lowest estimates there should be about 10 000 billion tons of methane in the offshore clathrate deposits and about 400 billion tons under the permafrost. This is 2000 times more than the current amount of methane in the atmosphere. Other studies have concluded that the clathrate deposits could be one thousand times larger and contain up to 10 000 000 billion tons of methane. Moreover, the up to two kilometres thick mud layers of the actual sea bottom have been estimated to contain a further 15 000 000 billion tons of organic carbon.

The clathrate deposits remain stable only in near‑freezing temperatures. If the waters along the continental slopes warm up, increasing amounts of methane should be released into the atmosphere, which could create another viscious circle with a nightmarish quality. It has not been possible to quantify the size of the potential emissions. However, Russian scientists have already reported about major methane eruptions in the Sea of Okhotsk, near the island of Sakhalin.

Other studies have linked the eight‑degree warming at the end of the late Paleocene, 55 million years ago, to offshore methane eruptions. Fossil evidence suggests that land and sea temperatures rose sharply during this period. Many species of single‑celled organisms dwelling in the seafloor sediment became extinct. At the same time there was a notable increase in the light carbon 12 isotope in the preserved shells of the creatures that survived the heat spell. According to many scientists, methane clathrates are the most likely source for the light carbon.

Researchers of the Tromsö University of Norway have found 700 metres wide and 30 metres deep craters created by violent methane eruptions from the bottom of the Barents Sea. Moreover, in 1998 Russian researchers from the Shirshov Institute of Oceanology found unstable hydrate fields off the West coast of Norway. It seems that they were the cause of the so called Storrega submarine landslide, in which 5600 cubic kilometres of sediments slid 800 kilometres down the continental slope, about 8000 years ago. If the oceans become much warmer, other clathrate deposits might become destabilized and create huge tsunamis, thus devastating coastal areas.

The floating ice around the North Pole currently covers about 15 square kilometres in the winter and 7‑8 million square kilometres during the summer. These vast expanses of drifting ice form an effective reflector that reflects up to 98 per cent of the Sun's radiation back towards the space. Open sea is much darker and absorbs more radiation. If the area covered by the ice starts to diminish, the warming of the northern areas will accelerate.

There is a number of other potentially serious feedback loops. If the climate heats by a few degrees, the methane production of the peat bogs might multiply. If the circulatory system of the oceans is disrupted, it will remove less carbon dioxide from the atmosphere and bring back less nutrients from the deeper layers of the ocean. The less nutrients there are, the less plankton is produced. This could affect the climate by several different ways. Certain forms of plankton produce large amounts of a substance called DMS (dimethylsulphide) as a by-product of their metabolism. DMS aerosols are often the most important source of cloud‑condensation nuclei over the ocean, so reduced production of DMS could reduce the cloud cover and accelerate the warming.

The runaway greenhouse effect might actually start as a local or regional phenomenon, quickly spreading to become a global disaster. Some regions are likely to experience much more than the average amount of warming, while others could actually cool by a few centigrade due to the shadowing impact of sulfur aerosols, soot particles and other pollutants. The vicious circle could be initiated for example by the rapid destabilization of a single large methane clathrate deposit. This could happen for instance in the northern sea of Japan, which may already have warmed by three centigrades.

The third report of the Intergovernmental Panel on Climate Change warned, in 2001, that methane emissions could increase by fifty per cent during the next fifty years, while the concentration of smog chemicals such as carbon monoxide, nitrogen oxides and ozone could double or triple. IPCC said that this could be potentially dangerous, because future emissions of these pollutants might actually overwhelm the oxidative capacity of the whole atmosphere.

Even before, in 1993, Sasha Madronic of the US government's National Center for Atmospheric Research in Boulder, Colorado, had warned that the atmosphere's hydroxyl chemistry is potentially unstable and carries the seeds for runaway reactions that could create a collapse in the hydroxyl levels. If the amount of pollutants increases too much, the atmosphere will start losing hydroxyl. After the chemistry has been tipped off balance, the remaining hydroxyl ions will be able to clean out only a rapidly diminishing amount of the new emissions entering the atmosphere. In such a situation the amount of pollutants remaining in the air would increase with an almost exponential rate, and the whole Earth would quickly become engulfed in huge clouds of smog.

As far as we know, the depletion of the atmosphere's hydroxyl content could be a real possibility if the carbon monoxide, ozone and nitrogen oxide emissions from cars, factories and thermal power plants and the methane emissions from various different sources continue to increase with the present speed, and if the global warming will cause vast forest and peat fires on different continents.

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