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The earth is running a temperature The earth's climate has always varied. Many factors influence our climate, such as solar radiation, weather systems, greenhouse gases, particles and aerosols, the earth's rotation around the sun, snow coverage and sea currents. Greenhouse gases have also always influenced our climate; without them, the earth would be uninhabitable, with an average temperature of -19 °C. With every year that passes, the scientific evidence becomes clearer that mankind's emissions of greenhouse gases – mainly carbon dioxide, nitrous oxide and methane – are strengthening the greenhouse effect. This has already lead to an increase in the earth's average temperature of around 0.6 °C during the 20th century. Such rapid changes threaten the conditions for all life on earth. There are signs that we could, for example, suffer sudden changes in the earth's climate system and the collapse of whole ecosystems. In recent times a number of positive feedback systems have been discovered which can lead to an acceleration in the temperature increase; one such system is reduced albedo due to melting glaciers. The emissions of greenhouse gases are currently increasing in line with, or even faster than, the most negative scenario predictions; developments are heading in completely the wrong direction. It is therefore one of mankind's biggest challenges to prevent continued increases in the earth's average temperature. (figuren finns på engelska på http://www.pnas.org/content/104/24/10288.full) Figure: Actual emissions of carbon dioxide compared with scenarios, from Raupach et al. (2007) Emissions of carbon dioxide are the most significant cause of the climate change problem. Each year, around 25 billion tonnes of carbon dioxide are emitted, just by burning fossil fuels. A further 6 billion tonnes are released by deforestation. This has lead to a rise in the atmospheric concentration of carbon dioxide from preindustrial levels of 280 ppm (parts per million) to 380 ppm. Whilst this concentration is still low, studies from ice cores show that the concentration of carbon dioxide in the atmosphere is a steering factor in climate and temperature. It is therefore vital that we move away from the use of fossil fuels and take measures to prevent continued deforestation. Read more about this on the UN's Climate Panel IPCC website. |
