Climate Models and Warming
Climate models use various methods to simulate the interactions of the atmosphere, oceans, land surface, and ice. All climate models take account of incoming energy as short wave electromagnetic radiation, chiefly visible and short wave infrared, as well as outgoing energy as long wave infrared electromagnetic radiation from the earth. Any imbalance results in a change in temperature. The most talked about models of recent years have been those relating temperature to emissions of carbon dioxide. These models project an upward trend in the surface temperature record, as well as a more rapid increase in temperature at higher altitudes. Researchers at the Max Planck Institute for Meteorology in Hamburg have developed a new model that specifies the maximum volumes of carbon dioxide that humans may emit to remain below the increased climate warming of two degrees Celsius. To do this, the scientists incorporated into their calculations data relating to the carbon cycle, namely the volume of carbon dioxide absorbed and released by the oceans and forests.
The concentration of carbon dioxide in the atmosphere caused by the combustion of fossil fuels (gas, oil) has increased significantly since the beginning of the Industrial Revolution. If carbon dioxide emissions and, as a result, atmospheric carbon dioxide concentrations continue to increase unchecked, a further increase in the global temperature can be expected before the end of this century.
In the newest model, European scientists have now calculated for the first time the extent to which the global carbon dioxide emissions must be reduced to halt global warming.
"What's new about this research is that we have integrated the carbon cycle into our model to obtain the emissions data," says Erich Roeckner. According to the model, admissible carbon dioxide emissions will increase from approximately seven billion tons of carbon in the year 2000 to a maximum value of around ten billion tons in 2015. In order to achieve the long term stabilization of the atmospheric carbon dioxide concentration, the emissions will then have to be reduced by 56% by the year 2050 and be reduced even further thereafter. This model then predicts that global warming would remain under the two degree Celsius (about 4 degrees Fahrenheit) threshold until 2100.
The model used for this study is based on a low resolution spatial grid with a grid spacing of around 400 kilometers, which takes the atmosphere, plus the land surface, the ocean, including sea ice, and the marine and terrestrial carbon cycle into account.
The study intent is to predict future changes in the climate and relate them to carbon dioxide emissions and then to see the results if carbon dioxide concentrations in the atmosphere are stabilized in the long term at 450 parts per million (ppm). Holding at 450 ppm may stop further global warming at 2 degrees Celsius.
Other climate model projections summarized in the latest United Nations Intergovernmental Panel on Climate Change report indicate that the global surface temperature may rise a further 1.1 to 6.4 °C (2.0 to 11.5 °F) during the 21st century. The uncertainty in this estimate arises from the use of models with differing sensitivity to greenhouse gas concentrations and the use of differing estimates of future greenhouse gas emissions. In other words models predict but sometimes are not complete enough to predict accurately.
For further information: http://www.eurekalert.org/pub_releases/2010-08/m-ncd080210.php