Climate Scenarios
A climate scenario is a description of a possible future development of the climate. Climate scenarios are several possible climate developments that require a long chain of assumptions and calculations. The description of the scenario can be in the form of, for example, a map, a diagram or a table. The values can be absolute numbers, differences, or related to a value like for example time.
To describe the current climate, the last completed 30-year reference period, which is year 1991 to 2020, is used. If older climate conditions are to be described, an earlier reference period can be used and if climate change is to be studied, different reference periods can be compared. When studying climate change, the period year 1961 to 1990 is primarily used as a reference, according to WMO guidelines. However, in some cases it can be motivated to use other time periods for various reasons. For example, many climate simulations, greenhouse gas emission scenarios begin in the year 2006, which means that the future begins as early as 2006 and that the years from then on do not represent actual levels of greenhouse gases.