04/03/2009 7:04 pm
Warming is a global phenomenon: the entire planet is affected and not just one region or another. Given that all five of the world’s geographic zones are involved, its consequences vary greatly.Melting Ice and Sea Level
Global warming causes the glaciers to melt, thus making the level of the sea rise. This has increased by 3 mm per year since 1993; which may not sound like very much at first, but the mechanism is more complex than it seems. Indeed, the mechanical effect of the ocean’s expansion plays a large role in the phenomenon. Yet the melting of the Arctic, which is already well underway and could be finished by the end of the century, does not modify the level of the sea. It is like a floating ice-cube: it doesn’t make the glass overflow.
In Greenland, the melting, initially taken to be fairly moderate, caused a “flowing” of water making the glacier more “slippery” and more disposed to drown. The mechanism could therefore speed up considerably. If Greenland were to melt fully, it would bring about a rise of 6 to 7 metres in the level of the sea.
The situation in the Antarctic is likewise very complex. It is a huge continent and the situation on the West (beneath South America) is different to that on the East (beneath Australia). In the first case, there is clear melting, while in the second there is a slight increase in the quantity of ice! Furthermore with temperatures reaching as low as -70°C in the heart of the continent, it is not expected that it will melt completely. But if that were to happen, the sea level would rise by about 60 metres.
The rise of water levels poses a major problem because an important part of the world’s population lives on the coast. This is the case for the inhabitants of the micro-states in the Pacific; some of which, like Tuvalu, are immediately threatened. But it is also true for the inhabitants of large metropolis such as New York, London or Shanghai. [see Refugee pages].
The End of the Gulf Stream?
Climatic warming and the melting of the Arctic could modify the oceanic currents between the continents, and in particular the gulf stream. It is sometimes said that if this were to end, the climate could cool down in Europe. In reality, the conditions that would cause it to stop or even slow down are not fully known to us, nor is its exact impact on European climate. And in any event, Europe is continuing to warm up and will do so for the next few years.
Storms
After the 2003 heat-wave in Europe and hurricane Katrina in 2005 in the United States, scientists have been in great debate: does global warming encourage storms and extreme climatic changes? This is a rather technical point, and, of course, tornados and droughts occurred before the warming began. Today, researchers believe that the warming will bring about an increase in the intensity of tropical cyclones and the frequency of periods of extreme high temperatures.
Droughts
If it gets warmer one may imagine a dryer climate. Precipitation will probably diminish in subtropical zones. But the increase in temperature also encourages the evaporation of the oceans and thus precipitation towards the greater levels of latitude. But this precipitation will be more intense and violent; and water and will collect less in the ground.
The melting of the glaciers will also reduce flow of water into rivers across the planet; many zones will suffer from a decrease in their water resources.
Ecosystems
Whole ecosystems are threatened by global warming. In general, animal and plant species migrate towards the poles or else in altitude to find the temperatures to which they are accustomed. Thus, the spatial distribution of many trees is already moving towards the North of Europe. Nevertheless, this is not always possible. For example, in the Arctic: polar bears could disappear as they have nowhere to go. The Tundra and Boreal Forest are also threatened. Some animals that are dangerous to man and that are usually found only in tropical regions could reach more moderate regions. This is already the case of some mosquitoes that carry malaria or other sicknesses, like the West Nile Virus, that killed several hundred people in the US, and even in New York, in the last few years.
Oceans
Oceans will be affected in two ways. Firstly, global warming threatens coral reefs; and these are rich ecosystems. [See Coral Reef pages] Secondly, the more CO2 there is in the atmosphere, the more it is absorbed by the oceans; and CO2 acidifies the water. This acidification could endanger numerous organisms by preventing them, more specifically, from forming a skeleton. Plankton is especially sensitive to this phenomenon; and yet it is the basis of the marine food chain!
Positive
Some zones benefit from the warming; that is, if it is only slight: the farming production of North Canada, Russia and South America could increase.
The mine reserves that are present in the ground in those areas could also become more readily accessible. Furthermore, maritime transport could benefit from the melting of the Arctic: the North-West passage linking the Atlantic to the Pacific via the North of Canada, would be a short-cut compared to the Panama Canal. The North-East passage, above Siberia, could also become more practical.
Social Consequences
Warming will transform our society; modifying harvesting, forcing people to migrate. Flooding, storms and droughts will bring about their share of victims; infectious diseases could spread etc. Insurance companies were the first to try and evaluate how much all of this might cost (them). Others have followed suit and in 2006, the British government published a report directed by Nicholas Stern proposing a global evaluation. According to this study, if nothing were done, global warming could cost 5, 500 million euros in ten years! Taking the necessary measures to counter this phenomenon would cost 1% of the World GDP per year. That is 10 to 20 times less than not taking action!
Signaler un abus
