The climate of the future

 

There is now convincing evidence that the climate is changing at an unprecedented rate for modern times. This change is occurring both a global and national scale. The enhancement of the greenhouse effect by human activities is viewed as being largely responsible.

Global Climate Models (GCM) predict that this change will continue, causing parts of the UK to be subject to climatic conditions beyond those experienced since before the last ice age.

Observed changes in global climate

• Average global temperature has risen by about 0.6°C since the beginning of the 20th century, with about 0.4^oC of this warming occuring since the 1970s
• 1998 was the warmest year record since records began in 1860
• The 1990s were the warmest decade in the last 100 years
• Rainfall events have become more intense over many Northern Hemisphere mid-to-high latitude land areas
• There has been a near worldwide decrease in the extent of mountain glaciers and ice mass
• The Northern Hemisphere has experienced a decrease in sea-ice amounts
• There has been a substantial thinning of Arctic sea-ice in late summer.

Observed change in the UK climate

• The 1990s was the warmest decade in since records began in the 1660s (Central England Temperature Record)
• The thermal growing season for plants in central England has lengthened by about one month since 1900
• Heatwaves have become more frequent in summer, while there are now fewer frosts and winter cold spells
• In August 2003 record breaking temperatures seen during summer heat wave
• Winters over the last 200 years have become much wetter relative to summers throughout the UK
• A larger proportion of winter precipitation in all regions now falls on heavy rainfall days than was the case 50 years ago.

How will the climate change in the future?

The best estimate that we have of how the climate is likely to change in the future is the UKCIP02 scenarios. This set of predictions is based on the output of HADCM3, a GCM developed by the UK Meteorogical Office. Different emission scenarios, ranging from an environmentally sustainable future to an economy based on an increased reliance on fossil fuels are used as inputs to the model. These scenarios give a spatial representation of the UK based on a series of 96 50 x 50 km grid squares. The scenarios provide predictions of future climate, together with an indication of inter- and intra-annual variability in some parameters.

The predictions are based on thirty year time slices centred on the 2020s, 2050s and 2080s. For each time-slice, data are presented for the four emissions scenarios given in IPCC. These emission scenarios cover a range of global economic futures, from a complete uptake of renewable energy through to one based on an increased reliance on fossil fuels.

Key UKCIP02 predictions

Temperature:

• Overall the UK climate will become warmer. The average annual temperature in the UK may rise by between 2°C-3.5°C (Low and High emission scenarios respectively)
• There will be greater warming in the south and east rather than in the north and west
• There may be greater warming in summer and autumn than in winter and spring
• High summer temperatures will become more frequent, whilst very cold winters will become increasingly rare
• The temperature of UK coastal waters will also increase, although not as rapidly as over land.

Precipitation (rain and snow):

• Winters will become wetter
• Summers may become drier throughout the UK, the relative changes will be largest for the High emissions scenario and in the south and east of the UK
• Summer soil moisture by the 2080s may be reduced by 40% or more over large parts of England for the High emissions scenario
• Snowfall amounts will decrease throughout the UK
• Heavy winter precipitation will become more frequent.