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Global warming is the phenomenon of increasing average temperatures on the surface of our planet (air and oceans), which began several decades ago and is still continuing.
The average air temperature at the surface of the Earth has increased between 0,6 and 1 °C over the last 100 years (see picture 2). According to the Intergovernmental Panel on Climate Change (IPCC), « the essential part of the increase in the average global temperature during the second half of the XXth century is very probably due to the increase observed in the concentrations of greenhouse gases of anthropogenic origin ».
More about the greenhouse effect
These conclusions of the IPCC are the same as those reached by 30 major scientific associations, including those in the largest industrialised countries. Only a small number of scientists have expressed disagreement with the findings. The climate models cited by the 2001 report of the IPCC forecast an increase in temperature of between 1 and 6 °C in the period from 1990 to 2100, given the scenarios retained and the models used. Whilst most studies stop at the horizon of 2100, the warming effect and the rise in sea levels should continue for more than a thousand years, even if the levels of greenhouse gases were to be stabilised at current levels. This is a reflection of the slowness of the oceans to warm up, given their enormous mass and thermal capacity.
Global warming is expected to have many consequences, including an increase in the level of the oceans, a greater frequency of extreme climate events (hurricanes, coastal flooding, etc.) (see picure 1) and changes in rainfall patterns. Other forecast effects are changes in agricultural yields, retreating glaciers, the disappearance of numerous species and an increase in the range and impact of certain mechanisms responsible for the spread of disease.
Many scientific uncertainties remain as to the average level of warming and its regional distribution (see picure 3). A major debate is currently underway, concerning the actions to be implemented to limit and to reverse the trend to global warming in the future and to find ways of adapting to its consequences, which are themselves still ill-defined. Most governments, with the important exception of the United States, have signed and ratified the Kyoto protocol which aims to reduce greenhouse gas emissions to 1990 levels.
New technological solutions could radically modify the economies of human society. |