What climate change may happen in the future?
It is impossible to predict with certainty what climate change might happen in the future. But it is possible to make projections of what might happen under different scenarios, on the basis of the best evidence available.
How can projections be made?
We can assess how greenhouse gas emissions will change in different scenarios and what this will mean in terms of changes to the climate. These assessments are made using mathematical models of our climate system. The more sophisticated of these produce a range of projections for each scenario, reflecting uncertainty in different parameters.
A lot of scenario development and climate change modelling has been undertaken around the world and as part of the IPCC (Intergovernmental Panel on Climate Change) process. The projections made by the models used by the IPCC in 1990 are consistent with current climatic conditions.
Global projections
Globally, the IPCC scenarios in 2007 suggest that:
Greenhouse gas emissions are likely to rise by between 25 and 90 per cent up to 2030, although emissions are currently rising at levels that are higher than the most extreme scenario.
By the end of the 21st century, global temperatures are projected to rise by between 1.8 and 4ºC.
There will be a loss of summer sea-ice by the end of the century, although this could happen a lot sooner.
It is very likely there will be an increase in heat waves and heavy rainfall events.
Projections for the UK
The UK Climate Change Impacts Programme in 2009 gave projections for a number of climate scenarios (based around levels of global greenhouse gas emissions- low, medium and high) over seven overlapping 30 year time periods for different sub-national areas and river catchments.
The projects are much more detailed than previous scenarios and offer a range of possible outcomes of based around probability, of which 50% is the most likely outcome (figures in brackets, for 10% and 90% probability show the ranges which are unlikely to be exceeded. The medium scenario projections are broadly in the same range as the earlier scenarios (UKCIP02), indicating that the UK will experience hotter, drier summers and warmer, wetter winters. Projections for 2080, on a medium scenario are:
All areas of the UK be warmer, more so in summer than in winter, with changes in summer mean temperatures greatest southern England, up 4.2˚C (2.2˚C to 6.8˚C) compared to North East England up 3.7˚C (2˚C to5.8˚C).
Mean daily temperatures will increase everywhere. Increase in summer averages are up to 5.4˚C (2.2˚C to 9.5˚C) in parts of southern England and up 2.8˚C (1˚C to 5˚C) in parts of the north. Increases in winter temperatures are 1.5˚C (0.7˚C to 2.7˚C) to 2.5˚C (1.3˚C to 4.4˚C) across the country.
There will be an increase in the number of hot days with changes in the warmest summer day ranging from 2.x˚C (-2.4 to +6.8˚C to 4.8˚C (+0.2 to+12.3˚C) depending on location with no geographical pattern.
Estimates of annual precipitation show very little change everywhere at a 50% probability level.
The biggest change in winter precipitation is predicted to be along the western side of the UK, up 33% (9% to 70%) compared to south east England, up 22% (4% to 50%) compared to 1990 levels.
Summer precipitation levels are projected to be down by -40% (-65% to-6%) in parts of southern England compared to more northern regions; Yorkshire & Humber is likely to see a reduction of precipitation by -22% (-43% to 1%) compared to 1990 levels.
There will be an increase in the number of extreme weather events such as storm surges, intense rainfall and heat waves.
Sea level is projected to increase by 36.3 cm (43.3cm -30.5 cm) near London, compared to 24.4 cm (31.4-18.8cm) near Edinburgh, compared to 1990 levels.
It should be noted that current trajectory of global greenhouse gas emissions are closest to that of the high emissions scenario.
