Global Warming Models and Predictions

The concept of global warming does not imply that the temperature is getting warmer at the same rate all over the surface of the Earth. Although it is on average warmer over time, some regions can experience cooling, whereas other regions can experience warming.

Land surfaces, for example, warm at a faster rate than do oceans because oceans can store more heat and can assimilate it better than land surfaces. Variation will also occur across a continent due to air current patterns, latitude, and distance from large bodies of water, In higher latitudes changes may be more severe in the winter than in the summer or vice versa. Inland ecosystems may experience severe drought, whereas coastal ecosystems may experience flooding more often.

With the discoveries of rapid changes in greenhouse gases and temperatures and the need to better understand how global temperatures and ecosystems would be affected by global warming, in 1988 the Intergovernmental Panel on Climate Change (JPCC) was formed. All countries were invited to participate in the IPCC's efforts with the World Meteorological Organization (WMO) and the U.N. Environment Programme (UNEP).

The IPCC has its secretariat in Geneva, Switzerland, and includes biologists, geologists, glaciologists, health scientists, sociologists, and oceanographers. The mission of the IPCC is to support comprehensive assessment of global warming in order to develop policies, technologies, adaptation and mitigation strategies, and methodologies for emission inventories.

The panel is composed of three groups: WG (Working Group) I (climate science), WG II (impact, adaptation, and mitigation), and WG III (economic and social dimensions). Its third assessment report was published in 2001. This report tends to confirm the previous assessment and strongly recommends actions and policy changes in industrialized countries to reduce gas emissions.

Predicting global warming is not a simple task because many factors have to be considered, from air and ocean movements to land cover and human activities. Since the 1950s scientists have developed models to simulate variation and changes in climate and atmosphere. These models have become very sophisticated in recent years and help determine various scenarios expected across the world. There are still limitations, but improvements of resolution and inclusion of more physical parameters are continuous.

These global climate models (GCMs) examine changes in terrestrial vegetation, land masses, oceans and sea ice movements, and atmospheric components and simulate what the climate could be under different scenarios of greenhouse gas emissions. The main challenge is predicting the levels of gas emissions in the future. These levels can also reflect different conditions in terms of population or economic growth, technological change, energy use, and so forth.

Because experts do not accurately know how policies and other factors are going to vary in the future, all of these human parameters are assumptions. GCMs can be very sensitive to rapid variations in the parameters, but it is not always clear whether the slow changes in oceans will bring slow or rapid climate response. Although GCMs can greatly vary in projections, they predict an increase of global temper at Lire of 1-3.5° C in the next century.