Climate change has potential risks for the British Isles. Most critical of these risks is an increase in frequency and intensity of extreme weather such as hot spells, drought and storms. Accompanying a projected rise in average surface temperature of between 0.9 and 2.4°C by 2050 will be the increased occurrence of hot, dry summers, particularly in the southeast. Mild wet winters are expected to occur more often by the middle of the 21st century, especially in the northwest, but the chance of extreme winter freezing should diminish.
Higher temperatures may reduce the water-holding capacity of soils and increase the likelihood of soil moisture deficits, particularly if precipitation does not increase as well. These changes would have a major effect on the types of crops, trees or other vegetation that the soils can support. The stability of building foundations and other structures, especially in central, eastern and southern England, where clay soils with a large shrink-swell potential are abundant, would be affected if summers became drier and winters wetter.
Any sustained rise in mean surface temperature exceeding 1°C, with the associated extreme weather events and soil water deficits, would have marked effects on the UK flora and fauna. There may be significant movements of species northwards and to higher elevations. Predicted rates of climate change may be too great for many species, particularly trees, to adapt genetically. Many native species and communities would be adversely affected and may be lost to the UK, especially endangered species which occur in isolated damp, coastal or cool habitats. It is likely that there would be an increased invasion and spread of alien weeds, pests, diseases and viruses, some of which may be potentially harmful. Increased numbers of foreign species of invertebrates, birds and mammals may out-compete native species.
Climate changes are likely to have a substantial effect on agriculture in the UK. In general, higher temperatures would decrease the yields of cereal crops (such as wheat) although the yield of crops such as potatoes and sugar beet would tend to increase. However, pests such as the Colorado beetle on potatoes and rhizomania on sugar beet, currently thought to be limited by temperature, could become more prevalent in the future. The length of the growing season for grasses and trees would increase by about 15 days per degree Celsius rise in average surface temperature, an increase that could improve the viability of crops such as maize and sunflower, which are currently grown more in warmer climates.
Increases in sea level, and the frequency and magnitude of storms, storm surges and waves would lead to an enhanced frequency of coastal flooding. A number of low-lying areas are particularly vulnerable to sea level rise, including the coasts of East Anglia, Lancashire, Lincolnshire and Essex, the Thames estuary, parts of the North Wales coast, the Clyde/Forth estuaries and the Belfast Lough. Flooding would result in short-term disruption to transport, manufacturing and housing, and long-term damage to engineering structures such as coastal power stations, rail and road systems. In addition, long-term damage to agricultural land and groundwater supplies, which provide about 30% of the water supply in the UK, would occur in some areas due to salt water infiltration.
Water resources would generally benefit from wetter winters, but warmer summers with longer growing seasons and increased evaporation would lead to greater pressures on water resources, especially in the southeast of the UK. Increased rainfall variability, even in a wetter climate, could lead to more droughts in any region in the UK. Higher temperatures would lead to increased demand for water and higher peak demands, requiring increased investment in water resources and infrastructure. An increase in temperature would increase demand for irrigation, and abstraction from agriculture would compete with abstractions for piped water supply by other users.
Higher temperatures would have a pronounced effect on energy demand. Space heating needs would decrease substantially but increased demand for air conditioning may entail greater electricity use. Repeated annual droughts could adversely affect certain manufacturing industries requiring large amounts of process water, such as paper-making, brewing and food industries, as well as power generation and the chemical industry.
Sensitivity to weather and climate change is high for all forms of transport. Snow and ice present a very difficult weather related problem for the transport sector. A reduction in the frequency, severity and duration of winter freeze in the British Isles would be likely under conditions associated with global warming and could be beneficial. However, any increase in the frequency of severe gale episodes could increase disruption to all transport sectors.
The insurance industry would be immediately affected by a shift in the risk of damaging weather events arising from climate change in the British Isles. If the risk of flooding increases due to sea level rise, this would expose the financial sector to the greatest potential losses.
UK tourism has an international dimension which is sensitive to any change in climate which alters the competitive balance of holiday destinations worldwide. If any changes to warmer, drier summer conditions occur, this could stimulate an overall increase in tourism in the UK. However, any significant increase in rainfall, wind speed or cloud cover could offset some of the general advantages expected from higher temperatures.