The climate predictions
■ Under a ‘medium’ climate change scenario, by 2080 summer mean daily temperatures will rise by up to 5.4°C in southern Britain and by up to 2.8°C in the North.
Winter rainfall will increase by 33%, but summer rainfall in the South will decrease by 40%. The number of lightning days will increase throughout the year.
■ Cold conditions affecting the railway are projected to decrease by the 2040s (but not cease altogether), with the number of winter days of temperatures below 0°C falling by around 45%. It is estimated that disruption due to ice and snow, including freezing of points and ice formation on the third rail, could fall by more than a third by 2080.
There could be fewer slips, trips and falls due to ice for passengers and workers. Slips, trips and falls currently account for 47% of all safety risk to passengers, according to RSSB.
■ Inundation by the sea is expected to rise in line with the increase in sea level and from increases in storm surge levels.
■ Rainfall will increase by a third in the west (particularly in winter), but by less in the east.
■ River flooding is anticipated as rainfall increases, leading to increased scour of bridge foundations, embankment damage and culvert washout. The number of very wet days will rise by up to 30% by the 2040s.
■ There have been 12 derailments since 2005 as a result of earthworks failure following heavy rain. There were an average of 64 earthworks failures per year during 2006-2012, but better processes have since led to a reducing trend, according to RSSB.
■ More wind gusts above 70mph are predicted. This has implications for track disruption and speed restrictions as a result of tree falls, more intense leaf fall and excessive wind loading on structures.
■ The number of days where speed restrictions are applied because of heat is expected to increase by a factor of between four and seven by the 2040s, in different RSSB estimates. Network Rail estimates a ten-fold increase in rail buckling and misalignment problems by 2080. There have been only two derailments due to track buckling since 2003.
■ The number of days in which overhead line equipment sags to an unacceptable extent is expected to increase by a similar amount.
Increased heat would also lead to an unquantified increase in earthwork failures due to desiccation. An ATOC study found that train reliability starts to decrease above 25°C.
■ Heat stress on both staff and passengers will result from these changes, and there will be strain on air-conditioning systems. There have been four occasions in the past ten years when passengers have forced doors open on overheating stranded trains, leading to RAIB investigations. There is unquantified evidence that higher temperatures lead to increased alcohol use by passengers, resulting in more aggressive behaviour, slips, trips and falls.
■ Network Rail calculated that there were an average of 1.6 million weather-related delay minutes a year between 2006 and 2014. That equated to more than £400m of weather-related delay costs over the same period - £51m a year.
