Human-induced climate change has the potential to affect weather systems worldwide. There is increasing evidence that extreme weather events such as heatwaves and flooding are becoming more frequent and severe in the UK. With the country recently surpassing 40C for the first time in history, the effects of global warming are becoming all too clear. We explore the risks of climate change in the UK and what the future holds for the European country according to scientists.
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Extreme weather events – including the destructive winds caused by Storms Arwen and Eunice as well as the most recent, unprecedented heatwave that hit the country in July – have heightened concern about the escalating risk of adverse weather in the UK. It is often intuitive to blame these occurrences on human-induced climate change. While the inherent variability of the weather system along with limitations in weather models have sometimes made it difficult to determine whether specific events can be directly linked to climate change, there is no doubt that this has significantly affected their frequency and intensity.
In the UK, research by the Met Office – the country’s national weather service – has found evidence of the link between global warming and changes in temperatures (both heatwaves and cold fronts) as well as heavy rain. However, there is less evidence to prove that droughts and storms are directly caused by climate change in the UK.
Heatwaves
Unsurprisingly, the increasing intensity of heatwaves and hot spells of weather is one of the extreme weather events most clearly linked to global warming. It is unequivocal that climate change is leading to higher average annual temperatures in the UK, with a 4.2C average rise in temperatures compared to a pre-1990 baseline.
By 2100, scientists predict that heatwaves – once a rare occurrence – will take place every year, especially in the summer months from May to September.
In the UK, the 10 hottest years since 1884 have all occurred after 2002. Troublingly, the chance of exceeding 40C by 2090 is predicted to be 1 in 15 in a medium emissions scenario and up to almost 1 in 5 under a high emissions scenario. In comparison, the risk in 1970 was close to 1 in 1000. Considering the extraordinary heatwave the UK has recently gone through, it seems like this prediction has become a reality much earlier than expected.
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Droughts
Research by the Met Office suggests there has been a decrease in consecutive days of dry weather. Despite this, climate projections indicate an increasing frequency of droughts by 2100. While studies show that drought intensity and frequency will generally increase across the nation, it is likely that these will still be of moderate intensity, rather than extreme ones.
Under the high greenhouse gas emission pathway, the UK Climate Projections (UKCP) – a collection of the main weather prediction models used by the Met Office – suggest a strong drying trend in southern England, especially in summer. Nevertheless, uncertain interactions between rainfall changes, soil moisture, and increasing temperatures make exact predictions difficult. Overall, rainfall estimates range from 57% drier to 9% wetter for England by 2070, illustrating the considerable uncertainty that still exists.
Rainfall, River Flooding, and Flash Flooding
Most river floods occur in autumn and winter, although wide-scale summer floods are not unprecedented. However, the latter are usually less frequent, driven by localised thunderstorms, which typically result in flash flooding when urban drainage systems are overloaded.
Although hotter summer temperatures have been linked to drought risk, there is an increased risk of short-term downpours leading to flash flooding. Recent modelling suggests an intensification of intense summer downpours over southern England by 36% under an (extreme) 4-5C temperature rise. Nevertheless, most models generally struggle with this type of small-scale prediction, so there is a limit to our current knowledge.
In contrast, river flooding is usually caused by large-scale rainfall events in winter and autumn. Six of the 10 wettest years across the UK have occurred since 1998 and 2011-2020 was 9% wetter than 1961-1990. Nevertheless, these changes in rainfall are still defined as being within the bounds of natural variability, despite the increasing trend.
Current evidence suggests overall increases in maximum river flows and flood durations in winter and autumn. This is especially true in northern and western England, where peak river flows usually occur in the autumn months. Nevertheless, river responses in relation to climate change are predicted to vary across the UK. For example, in southern and eastern England, springtime flows are expected to decrease.
Weather Extremes in Urban Areas
Extreme weather can be made more severe due to the characteristics of urban areas. This is especially relevant as almost 83% of Britain’s population lives in cities and towns.
Urban areas are warmer due to the heat-absorbing nature of artificial materials that buildings are made from; this is known as the Urban heat island effect. In Manchester, for example, the urban heat island effect increased by about 0.4C between 1990 and 2010. The intensity of these effects usually varies from city to city but is the most severe in large cities such as London, where temperatures are 1-3C higher than in rural areas. The risk to the elderly and vulnerable is huge in these areas, where heatwave deaths are expected to increase by about 585% by the 2080s.
Flash flooding is common in urban areas due to the non-porous nature of road surfaces and, with trends of increasing winter and intense summer rainfall in some areas, there is a higher risk of this type of flooding. One study suggests that increases in intense summer rainfall mean that by 2050, 1.2 million more people could be at risk of flash flooding in the UK.
Coastal Storms and Erosion
Coastal regions are especially vulnerable to extreme weather, primarily due to coastal erosion and sea level changes. Environmental agency predictions suggest the number of properties vulnerable to erosion will rise from 700 to 2,000 over the next 50 years, but these figures could be as high as 28,000 assuming that local authorities and the government do not invest in protection measures. The risk from erosion is heavily dependent on local geology and glacial legacy effects, with predicted sea level rise being highest in London (0.37m-0.83m by 2100) and lowest in Scotland (0.15m-0.61m by 2100) due to glacial rebound.
Locations with soft rock like boulder clay – such as the coasts of Eastern Norfolk and Holderness – are especially vulnerable. However, some areas may see decreases in erosion. For example, increased erosion along the East Yorkshire coast is actually benefitting locations further south such as Lincolnshire, which is gaining more beach material.
Concluding remarks
This article demonstrates the uncertainties that exist in attributing and predicting weather events and trends in relation to climate change. Nevertheless, there is considerable certainty that many extremes are being and will continue to be, exacerbated by human-induced warming.
Therefore, continuous research into extreme weather is needed to investigate the many uncertainties that still exist and provide early warning systems for extreme weather. Preparation for increased human health costs associated with heatwaves, agricultural disruption due to drought, and improved flood defence are clear priorities.
In years to come, some of the trends associated with global warming are predicted to become clearer, so adaptive government policy is needed. As the July 2022 heatwave illustrates, governments and local communities need to start adapting to extreme events now, as current emission reduction goals will not eliminate the warming that has already occurred, even if CO2 reduction pledges are miraculously met.
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