Climate projections

Because we can’t know the future for certain, our climate change scientists use computer-based climate models to project plausible scenarios, or projections, for coming centuries.

It is important to be aware that projections from climate models are always subject to uncertainty because of limitations on our knowledge of how the climate system works and on the computing resources available. Different climate models can give different projections. More on using computer models (external page)

The projections are also based on emissions scenarios, such as the level of CO₂ emissions increasing or decreasing. Many different scenarios are used, based on estimates of economic and social growth, and this is one of the major sources of uncertainty in climate prediction. But even if greenhouse gas emissions are substantially reduced, the long lifespan of CO₂ in the atmosphere means that we cannot avoid further climate change due to CO₂ already in the atmosphere.

Despite the uncertainties, all models show that the Earth will warm in the next century, with a consistent geographical pattern.

Climate change projections

The globes below show latest results from the Met Office’s climate change research. The data are based on a mid-range IPCC emissions scenario A1B.

Some of the diagrams below are maps of differences between the current climate, conventionally defined as 1960–1990, and the climate of the end of the 21st century, taken to be 2070–2100. For most quantities, changes are shown both for the annual average and for each of the four seasons December–February (Winter), March–May (Spring), June–August (Summer) and September–November (Autumn). The other diagrams are time-series, showing changes which occur as time passes.

Time series and maps generated from the HadCM3 climate model
Surface air temperature
Change in the average temperature of air 1.5 metres above the ground (a typical height for standard meteorological measurements), in degrees Celsius.
Time series	Annual	Winter	Spring	Summer	Autumn
Precipitation
Change in the total of rainfall and snowfall, in millimetres per day (liquid water equivalent for snowfall).
	Annual	Winter	Spring	Summer	Autumn
Soil moisture content
Change in the amount of water in the soil which is available to plants, in millimetres.
	Annual	Winter	Spring	Summer	Autumn
Sea-level change
Change in mean sea level from ocean thermal expansion and melting of glaciers, in metres.
Time series	Annual
Sea-ice area
Percentage change.
Time series
Sea-ice volume
Percentage change.
Time series

Computer models used by the Met Office

The computer climate models used for the majority of the work at the Met Office Hadley Centre are detailed three-dimensional representations of major components of the climate system. They are mostly run on the Met Office's supercomputers. As part of the Met Office's Unified Model, the atmosphere component of the climate model represents the same physical processes as that used for operational weather forecasts. However, due to the longer timescales involved in climate prediction, other components of the climate system are added including:

• Three-dimensional representation of the ocean and sea ice
• An interactive carbon cycle model
• Interactive atmospheric chemistry models
• The coupled atmosphere - ocean - carbon-cycle - chemistry model is known as an earth system model.

For both weather and climate prediction, the Met Office also runs its models at higher resolution over particular regions. Currently regional climate models are typically run at 25 km resolution.