Climate model output: period-averages
Welcome to the Climate Scenario section of the Data Distribution Centre (DDC) of the Intergovernmental Panel on Climate Change (IPCC). The DDC distributes a number of datasets, derived from various climate modelling experiments using general circulation models (GCMs), that are commonly used in the construction and application of climate change scenarios for climate change impacts assessments. The intention is to provide a common set of scenario data for use in climate impacts research that may get reported in the Fourth Assessment Report of the IPCC and beyond. These datasets are described within this site and pointers to outside sites are made where more detailed, or complementary, data may be found.
Explanations and illustrations of how these various datasets can be combined to construct a climate change scenario and how such scenarios can be applied in an impacts study can be found in the Guidance Materials. It is also possible to view some of these datasets (e.g. observed climate and GCM scenarios) using the DDC Data Visualisation pages. You can download many of these data from the DDC web site. 30 year climatologies are available here:
If users wish to access the full GCM monthly datasets from which the scenarios described here are derived they are directed to the DDC GCM Data Archive.
The choice of climate scenarios and related non-climatic scenarios is important because it can determine the outcome of a climate impact assessment. Extreme scenarios can produce extreme impacts; moderate scenarios may produce more modest effects. It follows that the selection of scenarios can also be controversial, unless the fundamental uncertainties inherent in future projections are properly addressed in the impact analysis.
Although there is increasing confidence among atmospheric scientists that increased atmospheric greenhouse gas concentrations will increase global temperatures, there is much less confidence in estimates of how the climate will change at a regional scale. However, it is precisely at this regional or local level (e.g. at the scale of a farm, a river catchment or even an individual organism) that climate change will be felt. Since no method yet exists of providing confident predictions of climate change at these scales, an alternative approach is to specify a number of plausible future climates. These are termed "climate scenarios".
Climate scenarios are plausible representations of the future that are consistent with assumptions about future emissions of greenhouse gases and other pollutants and with our understanding of the effect of increased atmospheric concentrations of these gases on global climate. A range of scenarios can be used to identify the sensitivity of an exposure unit to climate change and to help policy makers decide on appropriate policy responses. It is important to emphasise that climate scenarios are not predictions, like weather forecasts are. Weather forecasts make use of enormous quantities of information on the observed state of the atmosphere and calculate, using the laws of physics, how this state will evolve during the next few days, producing a prediction of the future - a forecast. In contrast, a climate scenario is a plausible indication of what the future could be like over decades or centuries, given a specific set of assumptions. These assumptions include future trends in energy demand, emissions of greenhouse gases, land use change as well as assumptions about the behaviour of the climate system over long time scales. It is largely the uncertainty surrounding these assumptions which determines the range of possible scenarios.
Page last modified: 28 November 2011*Most models outputs are referred to in the report, but a few (comparable) outputs were included later.