The scientific assessment concerning the climatic reheating
In 2001, the Intergovernmental Group of experts on the evolution of climate (GIEC) made public his last report/ratio which comprises three aspects.
The scientific assessment drawn up by the experts of the GIEC shows the existence from a quantity increasing from indices testifying to a reheating of planet and other modifications of the climatic system.
• The average temperature of surface (average temperature of the air above the grounds and the temperature on the surface of the sea) increased by 0.6 °C (with a margin of error of ± 0.2 °C) during the 20th century.
• The reheating in particular occurred during two periods, of 1910 to 1945 and since 1976. Since 1861, decade 90 was most probably hottest and the year 1998, the hottest year. New analyses indicate that the reheating which has occurred in the northern hemisphere at the 20th century was probably most important of every century of the last millenium.
• The snow-covered cover and the extension of the glaciers decreased. Satellite data show a probable reduction in 10% of the snow-covered cover since the end of the Sixties
• The mean level of the sea progressed Between 10 and 20 centimetres during the 20th century
• Climatic Changes
Increase in precipitations in the zones of averages and high latitudes of the northern hemisphere and increase in the frequency of the episodes of strong precipitations in the same zones.
Hot episodes of the El Nino phenomenon were more frequent, more durable and more intense since the middle of the years 1970.
In certain areas, in particular in certain zones of Asia and Africa, increase in the frequency and the intensity of the drynesses during these last decades.
The gas emissions for purpose of greenhouse and aerosols due to the human activities continue to deteriorate the atmosphere in a manner which affects the climate.
• Because of the human activities, the concentration of the GES in the atmosphere continued to increase.
The carbon dioxide concentration in the atmosphere increased by 31% since 1750. The current rate of increase has been without precedent for at least 20.000 years.
Approximately ¾ of the human CO2 emissions during twenty last years is due to the combustion of fossil energies. The remainder is primarily due to the change in the use of the grounds, in particular with deforestation.
Confidence in the capacities of the models to envisage the future climate increased.
One has evidence larger today than the reheating noted during fifty last years is ascribable to the human activities. The GIEC announces that it has today analyses of a very great reliability that it enables him to affirm that the reheating observed during fifty last years is quite due to the human activities.
The human influences will continue to change the atmospheric composition throughout XXIe century. · GES : CO2 emissions due to fossil combustions of energies will be still prevalent in XXIe century. All the results of the models of the GIEC result in envisaging an increase in the total temperature and a rise in the sea level.
Temperatures : · the average temperature of surface should further increase between 1, 4 and 5,8 °C between 1990 and 2100 · it has been expected that the rate of reheating is much more important than the changes observed during the XXe century, phenomenon without precedent for at least 10.000 years. · the reheating should intensify in particular during the winter in the areas of high latitudes of the northern hemisphere.
One can quote the notable cases of the septentrional areas of America and Asia and the Central Asia where the reheating could exceed of 40% the average reheating of the whole of planet.
Precipitations : · The average concentration of steam in the atmosphere and precipitations should increase during XXIe century. · The climatic reheating should increase the extreme phenomena (drynesses/strong precipitation-floods) which accompany the demonstrations by El Nino. · The climatic reheating should involve a disordered state of the monsoon of summer in Asia. · The extent of the snow-covered cover and the ice-barrier of the northern hemisphere should continue to decrease. Idem for the glaciers.
Sea level · the rise in the mean level of the oceans is estimated between 9 and 88 cm, according to the models
The climatic changes due to the human activities will persist during many centuries. · emissions of certain gases for purpose of greenhouse, of which CO2, have very durable effects hard the composition of the atmosphere. “
Source : IPCC WGI Third Assessment Carryforward. The Scientific Basis. Summary for Policymakers. With Carryforward of Working group I of the Intergouvernmental Panel one climate Exchange.