Reaction to the heatwave hitting the UK in late July 2019
Comments from Thursday 25 July:
On train tracks:
Dr John Easton, rail expert at the Institution of Engineering and Technology (IET), said:
“The main problem is that as the steel rails heat up, they expand like any other metal. The resulting extra rail length means that the track may begin to curve, a process known as “buckling”. With the track temperature rising to around 20°C higher than the air temperature in strong sunlight, expansion of the metal is to be expected. In most of the network individual pieces of rail are welded together to form longer continuous sections; where this is the case the rails are stretched before welding to reduce the chance of buckling occurring as the track is heated, although the amount of tension is set based on the temperature ranges that we’d normally expect to see in the UK (up to about 30°C).
“More tension could be put into the rails to allow for greater expansion at higher temperatures, however this could mean using slightly different steel grades which would probably cost more and it would almost certainly increase the risk of rail breaks – it’s all a bit of a balancing act. Where temperatures become unusually high, the only solution is to slow the trains down to reduce the impact the tracks. Track temperature is monitored, and forecasting models are used to predict when (and if) the risk of high rail temperatures is significant enough for speed restrictions to be put in place.
“In critical areas, such as the switch and crossings near stations, the insides of the rails are painted white to reflect the sun’s heat. This can reduce the track temperature by 5°C and reduces signalling failures which lead to significant disruption. This technique is also used In countries where high temperatures are more commonplace, such as Italy, where engineers often paint the inside faces of the rails white to reflect the sunlight and lower the risk of buckling.
“Additionally, the phasing in of Connected Driver Advisory (C-DAS) systems and in-cab signalling on the UK rail network over the next 20 years will enable speed restriction information to be delivered to drivers in a much more targeted way than is currently possible. This should allow localised speed restrictions to be applied dynamically, based on live data from rail temperature sensors in that area, and reducing the impact of the speed restriction on the wider network.”
Dr Darren Hughes, Associate Professor in Materials and Manufacturing, University of Warwick, said:
“Fundamentally, this is driven by expansion of material as it changes temperature. The forces involved can be large enough to cause failure, and in this case bending. Think of water in a pipe: as it freezes, it expands inside the pipe which causes splitting of the copper pipe, when it defrosts, the pipe leaks.
“In rails on a hot day, they are exposed to very high temperatures in the sun (if you feel your car roof on a sunny day it will be much hotter than the air temperature). The rail expands, pushing the rails sideways along the length and causing risk of derailment.
“It is impossible to overcome this expansion due to heat. Steel expansion is a fixed value. You could argue that you could leave a gap between sections of rail i.e. an expansion gap. This would help – but imagine on a typical day, you would get the old clickety clack sound and importantly, more wear. To overcome this, we have moved to welded rail, which does expose us to rail bending in very hot conditions.
“Today, engineers optimise the rails and the joining of the rails for a typical hot day. This means you get good performance when cold and when hot. Remember the UK rails could see minus 20 to plus 30 air temperatures usually. Normally this works fine. Sometimes however conditions fall outside this range.
“Whilst we try and engineer out these problems, we are limited by the rules of physics.”
Prof William Powrie, Professor of Geotechnical Engineering, University of Southampton, said:
“The problem is the tendency of rails to expand in heat and contract in the cold. They’re generally laid to be stress free at a particular temperature (typically, 27C in the UK) but as the rail temperature rises above this stress-free temperature the rails go into compression and this makes them more prone to buckling.
“Raising the stress free temperature (by stretching the rails more when they’re laid) would put more tension into the rails when the temperature drops, making them more likely to break in cold weather. But breaks often initiate from flaws in the rails and we are now much better at eliminating these during manufacture and detecting them in service than we were 20 years ago. We can improve the lateral resistance of the track (which helps to prevent buckling) by enhancing the performance of the ballast eg. reducing the shoulder slope or changing the grading, or by sleeper modifications eg. wings or plates, but the latter are used mainly only on tight curves in the UK at present.
“A further potential application of technology would be, for example, to use optical fibres to monitor the actual longitudinal stress / stress free temperature (which, although in theory uniform, in practice varies hugely). That might enable us to manage speed restrictions (the main aim of which is to reduce variable and lateral loads) more selectively.”
Prof Roger Kemp, Professorial Fellow, Lancaster University, said:
“What can be done to reduce the risk of buckling train tracks? The easy solution would be to divide the rails into sections and install them with gaps between them – as was done in the early 20th century. When the temperature increases, the gaps close up without an increase in rail stresses. This would bring back the annoying clickety-click, clickety-click sound that used to accompany rail travel and would greatly increase wear and maintenance costs.
“Another option might be to find a different steel alloy that expands and contracts less when the temperature changes. But rail steel is already a compromise between strength, wear resistance, impact resistance, corrosion resistance and cost. Adding another requirement would, almost certainly, be to the detriment of the others.
“If we could be sure that global warming meant we would no longer have very cold winters, it would be a good idea to warm rails to a higher temperature when they were being installed and before they are clipped in place. However, just because the global average temperature is increasing, it doesn’t mean that we no longer get any cold winters – in fact, the variability of the jet stream caused by climate change could mean we see more extreme weather – both cold and hot.
“Possibly the easiest option is to clamp the rail better using heavier sleepers, closer together with more ballast to keep the track in place and prevent the small movements that could trigger a buckle.”
Prof Peter Dobson, Principal Fellow, University of Warwick, said:
“Rails buckle in the heat because the steel expands when it gets hot. In the old short lengths of rail this effect was accommodated by having regular expansion/contraction joints. In the modern continuous welded rail track, the rail is stretched when it is laid and welded so that it is under some tension under ordinary average temperatures and in “ordinary” hot weather this tension is reduced, but the rail does not change its length. However, if there are prolonged periods of extreme heat, the expansion may overcome the original induced tension and the rails will bend. The track layers have to judge the tension required according to the maximum and minimum temperatures that the rail will experience. This is a fine balance, because overstretching may cause rails to crack in extreme cold weather.
“I know that people have suggested things such as painting the rails white, but in reality this will have hardly any effect and is impractical.”
On today’s temperatures:
Dr Jon Shonk, Research Scientist, University of Reading, said:
“Today looks likely to be the warmest day on record in the UK, with forecast temperatures in London of 39 °C looking to beat the previous record of 38.5 °C, set in Kent in 2003.
“The reason for the present spell of hot weather is the arrival of hot air from over Europe. France is in the grip an extreme heatwave at the moment, with hot air heading north from Africa. This air has been influencing most of western Europe over the past few days, but today an approaching low pressure system from the west has southerly winds ahead of it, which look set to pull the hot air from France over much of the UK.
“The heatwave looks to be short-lived, though, as the low pressure system passes through on Friday with its cold front sweeping the hot air away and temperatures will return to the July average.
“There is a clear link between climate change and heatwaves. What we are experiencing today is an extreme, record-breaking heatwave event. But as the climate warms, these extreme events will become even hotter. In other words, the sort of heatwaves we are experiencing today could become more frequent in future years as the climate warms.
“While we cannot directly link a single heatwave event to climate change, we can look at trends in heatwaves. We have been experiencing warmer heatwave conditions in the last few years, such as the long, hot spell in June and July 2018.”
Dr Pete Inness, Associate Professor in Meteorology, University of Reading, said:
“The current UK maximum temperature record stands at 38.5C recorded in Kent on the 10th of August 2003. For the temperature to reach 40C this record would have to be beaten by a degree and a half which is a pretty big margin. The normal expectation would be that records would be broken by smaller and smaller margins at longer intervals as the period of the observations that we have increases. However, with the global heating trend we are actually seeing high temperature records for individual months or specific locations being broken more often, and sometimes by quite large margins.
“To beat the existing record will require a set of “perfect” circumstances as well as the ongoing warming trend. Very high temperatures usually only occur after an extended dry spell when there is no moisture on the surface of the ground to use up some of the Sun’s energy through evaporation. The air over the UK will have had to come from somewhere warm, so a southerly flow of air over the previous few days is required. Finally winds on the day itself need to be very light to allow just a thin layer of air directly above the surface to warm up without it being mixed with cooler air from higher up in the atmosphere. High atmospheric pressure will also help to suppress any mixing of the air near the surface with cooler air from higher up. These were certainly the circumstances in August 2003 when the existing record was set although on that day a wind sprung up midway through the afternoon which may have stopped the temperature rising by another few tenths of a degree.
“Given that the heatwave conditions we experienced in Europe in 2003 are set to become pretty much the norm by the middle of this century unless some pretty drastic actions are taken very soon, I’d say that a temperature of 40C may well be recorded somewhere in the UK by 2050 and possibly up to a decade earlier than that. This is a personal assessment and not an official prediction.”
Dr Michael Byrne, Academic Visitor, Imperial & Lecturer, St Andrews & Research Fellow, Oxford University, said:
How significant is it if today becomes the hottest day on record in the UK?
“Hugely significant, yet just the latest in a torrent of temperature records to be broken in the last month. Not only has 2019 brought the world it’s hottest ever June, but in recent days countries from Belgium to the Netherlands to Germany have broken their all-time heat records. It has never been hotter in northern Europe. Such extreme heat poses serious health risks this week as well as uncomfortable questions about how well the UK is preparing for increasingly frequent and severe heatwaves over coming decades.
How much of this heatwave is summer and how much is global warming?
Is this weather clearly man-made global warming?
“It is impossible to say whether individual events – such as this week’s heatwave – are caused by man-made global warming. The kind of weather pattern delivering today’s hot air, a jetstream that is deflected unusually far north and drawing hot air from the south, is not itself caused by global warming. Indeed the famous 1976 heatwave was a result of similar meteorological conditions. What is different now is that the global temperature is about 1 degree Celsius hotter than in 1976, meaning that when these unusual weather patterns occur, the heatwave is guaranteed to be more severe. Met Office scientists found that the 2018 summer heatwave – which delivered the UK’s joint-hottest summer on record – was 30 times more likely because of global warming. Although we cannot say for sure that global warming caused this week’s extreme temperatures, climate change is without doubt “loading the dice” and making heatwaves much more likely and much more severe.”
On the causes of the heatwave:
Prof Grant Allen, Professor of Atmospheric Physics, University of Manchester, said:
“Globally, the past 5 years have been the 5 hottest years on record. While no single weather event can ever be linked directly to climate change, a statistically-significant trend is climate change by definition. This trend is very clearly what we are now seeing and scientific papers published yesterday which were widely reported in the media, confirm this. Climate change is no longer a future problem, it is here and it is accelerating. As climate change progresses, the frequency of previously extreme weather events will increase. There will be a new normal, which will challenge existing UK infrastructure and profoundly impact our ecosystem.”
Prof Richard Allan, Professor of Climate Science, University of Reading, said:
“Summer heatwaves are often caused by weather patterns that block milder ocean winds, moving hot air from continental Europe over the UK with cloud free conditions allowing sunlight to rapidly heat the already dry soil. What is significant is that heatwaves such as this one are becoming more intense due to the warming effect of our emissions of greenhouse gases. Scientists are now able to identify the imprint of these human-caused factors on heatwaves and flooding events using complex computer simulations that compare our present climate with an imaginary one without the warming from carbon dioxide increases.
“Global warming did not cause this heatwave but it certainly made it worse.”
Dr Len Shaffrey, Senior Research Scientist, University of Reading, said:
“The current heatwave is due to a number of factors. First there is an area of high pressure called a blocking anti-cyclone located over Europe. When blocking occurs over Europe in summertime we tend to get clear skies and more sunshine, while hot air is brought from the south. Both of these things lead to hot temperatures in the UK.
“In addition, the global rise in background temperatures due to climate change means the risk that an extreme heatwave will occur has increased. For example, the probability of a heatwave such as that experienced in Europe in June 2019 was estimated to have become at least five time more likely due to climate change”
On the health impacts:
Prof Hugh Montgomery, Director, UCL Institute Human Health and Performance, University College London (UCL), said:
“When the air is cooler than the human body, the body loses heat through conduction (through objects touched), convection (mass air movement), irradiation, and evaporation of sweat. When air temperatures rise, losing heat is harder via these mechanisms and when they are higher than body temperature, the only way to lose heat is through evaporation. This gets harder if the air is humid.
“So, the key is:
“Check on the old. Don’t leave animals or children in cars untended. It can get very hot very fast.
“The issue with overdrinking is that excess water can lower sodium (‘salt’) concentrations in the blood (‘hyponatraemia’), and that can be very dangerous (or fatal). Thus, hot marathons have seen more injury and death from over-consumption of water than from too little in recent years.
“So, drink when thirsty, keep an eye on losses (very heavy sweating means there’s likely a need for more fluid), and urine output (infrequent small volumes of urine may suggest a need for more fluid). Note that urine colour is not a good guide to dehydration overall.
“Thirst may be less good a driver in the elderly, who may also have mobility problems, etc which make it harder to maintain water intake….”
Prof Andy Jones, Professor in Public Health, University of East Anglia (UEA), said:
Might people adapt biologically over-time to warmer temperatures?
“Whilst evolution means that humans can adapt to changing environmental conditions as a species, the problem we face now is that the pace of climate change is far outstripping our ability to evolve.
“We therefore need to look at adapting as a society rather than biologically. We need to think about things like the design of buildings, and the way we incorporate shade and greenspace into our urban landscape, as well as considering how we plan our days so as not to be exposed to the midday heat. We can learn much from countries like Greece where walls are painted white to reflect the sun, shade and vegetation are treasured, and a longer lunchbreak means the heat of the midday sun can be more easily avoided.”
Prof Glenn Gibson, Professor of Food Microbiology, University of Reading, said:
“As Europe basks in exceptional temperatures and many people might be thinking about getting away – traveller’s sickness is a major challenge affecting around 10 million people a year – and can be the difference between a holiday of a lifetime and a break to forget.
“Part of the biggest challenge is avoiding the bugs which cause food poisoning. However, you can help to boost your own defences, including immunity. Our research has shown that prebiotics help prime your gut in anticipation for international travel and were shown to significantly reduce the incidence and duration of gastroenteritis when holiday makers travelled to high risk destinations.”
Professor Hannah Cloke, Natural Hazards Researcher, University of Reading, said:
“Here we go again. Hard on the heels of June’s record temperatures, today looks as if it will be what we scientists like to call another stinking hot one.
“Britain’s heatwave will mercifully be relatively short-lived, with some respite over the weekend. But these uncomfortably hot few days and nights should serve as a reminder of what we, as a country, need to do to prepare ourselves for more heatwaves in the future.
“First of all, we must take the entirely achievable steps to stop making this problem worse. Unless we follow up on our commitments to tackle climate change, lethal heatwaves could become the norm in Britain by the middle of the century. And of course, that’s just one tiny part of the impacts of climate change, in the UK and globally, that will have a major impact on all our lives.
“Just to cope with the warmer climate that we are already experiencing, we have to make changes to the way we live our lives. We need to adapt our homes and buildings to stay cool, change our activities to stay out of harm’s way, and take action to protect the most vulnerable people.
“We have good forecasts of heatwaves, but need to be smarter about how we act on early warnings. Key authorities such as councils, hospitals, fire brigades and anyone looking after core infrastructure must act quickly to make sure that they keep vital services going, and don’t make problems such as air pollution any worse.”
Dr Stefan Smith, Lecturer in Energy Systems in the Built Environment, University of Reading, said:
“Being able to adapt our work environment is a crucial aspect of coping with excessive heat – from when we work, when we take breaks, and what we wear.
“Working from home is one measure that could be available as part of this. On one hand, there may be advantages for some to going to work, especially those with active (air conditioning) and passive (building design) cooling measures to helping people stay cool. Staying at home is one example that speaks more to the idea of being flexible in our expectations (i.e. working hours, dress codes, etc.)
“More broadly, heatwaves and associated issues such as overheating are projected to become a growing problem for the UK and Europe more widely and we need to incorporate it more fully in thinking around policy, planning, and infrastructure development.”
Prof Richard Tiffin, Director of Science at the Centre for Agrimetrics, University of Reading, said:
“The extreme weather that we are currently experiencing undoubtedly makes life difficult for agriculture. Heavy rain last week caused a lot of crops to fall to the ground and this week’s high temperatures will stress crops, livestock and workers alike, all of which may reduce productivity. The real risk with extreme events however is that they precipitate an irreversible change on either a local, or worse, a global scale.
“At a local scale the loss in productivity may lead to a farm going out of business whilst at a global scale a rise in food prices might precipitate civil unrest that destabilises established social arrangements. The increasing frequency of extreme events means that the risk of a catastrophic, irreversible change in the food system is real. The need for increased resilience in the food system is now pressing.”
Comments from Tuesday 23 July:
Dr Declan Finney, Research Fellow, University of Leeds, said:
“We have already seen the probability of hot summers like 2018 become more likely because of climate change, and they are expected to become even more likely in future. 2018 was the joint hottest on record with highest temperature measured at around 35degC, similar to temperatures expected this week. The probability of 2018-like summers has increased from less than 10% in the 80s and 90s to around 10-25% today. With further climate change there could be a 50% chance of having hot summer in future. That’s similar to saying that a normal summer in future will be as hot as our hottest summers to date.”
Dr Kate Sambrook, Research Assistant, School of Earth and Environment, University of Leeds, said:
“Heatwave conditions in the U.S Midwest and the East coast have strengthened the jet stream and the resulting thunderstorms occurring on the continent have helped the jet stream to meander and move to the north of the U.K. As a result of this shift, hot air has been drawn up from Europe causing the high temperatures we are experiencing this week.
“Record temperatures have been witnessed across the globe over the last few weeks. If conditions continue, it is likely that we could experience the hottest July on record. However, the outcome is uncertain as conditions are expected to change early next week.”
Dr Karsten Haustein, Environmental Change Institute, University of Oxford, said:
Is it going to be the hottest July on record globally?
“There is a 40-50% chance that this will be the warmest July on record. The final estimate will depend on which observational dataset is used.
Are the heatwaves we are seeing in line with climate predictions?
“This heatwave is exactly in line with climate change predictions. This is also true of current drought conditions, for example in many parts of Germany.
Why are different weather forecasts predicting different things?
“Weather forecasts are inherently uncertain the longer the lead time. However, the current heatwave was predicted almost 10 days in advance.”
Dr Peter Inness, Senior Research Fellow (NCAS – Climate), University of Reading, said:
“It is hot across the UK, and particularly England, because we currently have a flow of air across the country which is coming from the south. At this time of year southerly winds will always lead to above average temperatures as air from continental Europe, the Mediterranean and even North Africa is brought over the UK.
“It’s still too early to say whether July 2019 will be the warmest July on record globally as there’s still over a week to go. However, June 2019 was the warmest June since global records began in 1880. In fact, 9 of the 10 warmest Junes in the global record have happened since 2000. In Europe, June 2019 was also the warmest on record, almost a whole degree Celsius above the previous record which was set in 2003. Weather records are not normally broken by such large margins – a few tenths of a degree would be more likely.
“The fact that so many recent years have had very high summer temperatures both globally and across Europe is very much in line with what we expect from man-made global warming. A study published in Nature by Stott, Stone and Allen in 2004, looking at the 2003 European heatwave, showed that human influence had more than doubled the risk of this type of event occurring, and that by the middle of the 21st century heatwaves of this nature could be the norm. It has been estimated that about 35,000 people died as a result of the European heatwave in 2003, so this is not a trivial issue.
“Different weather forecasts may be predicting slightly different details for the weather across the UK over the next few days in terms of maximum temperatures and the location and timing of any possible thunderstorm activity. However, the broad message of all the forecasts is the same – it will be hot, with high temperatures persisting through the night time periods, and there is the risk of some thunderstorms over the UK through Tuesday and Wednesday.”
Dr Len Shaffrey, Senior Research Scientist, University of Reading, said:
“The forecasted heatwave is associated with high pressure that has been building up over Europe over the past few days. This leads to warmer air moving northwards from Europe, clear skies and more sunshine over the UK. Forecasts suggest maximum temperatures might get into the mid-30s over central and eastern England on Thursday.
“The eastward passage of weather fronts and low pressures from the North Atlantic are currently being blocked by the high pressure over Europe. Although there is some uncertainty in the forecast, it looks like it will become cooler on Friday as the high pressure over Europe moves slowly towards the east. This will allow weather fronts to move over the UK, bringing cooler air and possibly some rain.”
Dr Radhika Khosla, Senior Researcher at the Smith School of Enterprise and the Environment, University of Oxford.
“If you are going to invest in an air conditioner, make sure it is energy efficient. The energy needed for cooling is projected to triple by 2050, with 10 new ACs sold every second for the next 30 years. We need to avoid a feedback loop where this energy demand causes more greenhouse gas emissions and contributes to further climate change and dangerous heatwaves.”
Dr Sam Hampton, Post-doctoral Research Associate, Environmental Change Institute, University of Oxford, said:
“Some comments with regards to energy consumption during the hot weather:
“Choose lighter, loose fitting clothing before cranking up the air conditioner. If necessary, air-conditioners should only be run when all the windows are closed.
“Employers can support these measures by promoting alternative ideas of ‘smartness’. There is a great example called Coolbiz from Japan, where the government teamed up with Uniqlo to offer a range of smart summer clothing, allowing them to reduce their dependence on air-conditioning.
“Direct sunlight through windows can increase internal temperatures by 50%. Use blinds.
“Maybe Thursday is a good day to work from home? It’s going to be quite windy and very sunny, so the UK will be generating a lot of renewable energy. It’s a good day to do the weekly laundry.”
Dr Lucelia Rodrigues, Associate Professor in Architecture, University of Nottingham, said:
“Contrary to what most people do, you should close your windows during a heat wave, at least during the day when outdoor temperatures are above comfortable temperatures. This way you will stop some of the heat from coming in. If the temperature drop at night then it is time to ventilate as much as you can and try to cool the fabric of your home so you can have a ‘fresh start’ the next day.”
Dr. Ana Raquel Nunes, Senior Research Fellow, University of Warwick, said:
“Most advice given during heatwaves very much focuses on medical advice in relation to health which most people may feel is quite obvious and common sense. Such advice focuses on telling the general public what they already know such as: drink more water, stay out of the sun, wear light, loose and cool clothes, apply sunscreen, avoid strenuous physical activity, among others.
“But what is lacking in most cases is advice that focuses on high-risk or the most vulnerable people in society, usually people with pre-existing illnesses such as cardiovascular and respiratory diseases, the very young or very old, those working outdoors, those who are socially isolated and the homeless. What needs adopting is a social model of health addressing the wider determinants of health such as income, housing quality, social networks and healthy workplaces. This could include providing other types of advice that people may not be aware of such as identifying and going to cool public places within the community such as libraries and community centres, as well as promoting checks on vulnerable family members, friends and neighbours either in person or via the telephone, and providing information via heat-health telephone helplines.”
Prof Mike Tipton, Professor of Human & Applied Physiology, University of Portsmouth, said:
“The elderly (75+) are at most risk due to inclination to become dehydrated, poorer cardiovascular stability and poorer endothelial function. Check on elderly relatives.
Prof Hugh Montgomery, Director, UCL Institute Human Health and Performance, University College London (UCL), said:
“We should not encourage ‘quirky tips’. All advice should be evidence-based. Lives are at stake.
“Tea and coffee at conventional levels do not cause significant dehydration.”
Dr Friederike Otto, Acting Director of the Environmental Change Institute (ECI), University of Oxford:
“Changes in the intensity and likelihood of extreme weather is how climate change manifests. That doesn’t mean every extreme event is more intense because of it, but a lot are. For example, every heatwave occurring in Europe today is made more likely and more intense by human-induced climate change. But extreme events occur locally, so many things play a role: location, season, intensity and duration. The influence of each of these factors depends strongly on the specific event. With our international initiative World Weather Attribution, we did in a rapid analysis of the heatwave that struck large parts of Europe during the last week of June 2019. We found that it was made at least five times more likely due to human induced climate change.”
“To stay cool during the heatwave: drink water, a lot of it, stay indoors during peak heat, look after your elderly relatives and friends and those who sleep rough. Take heatwaves seriously, they can be killers for all those who are already vulnerable. And talk about climate change all the time to everyone – that is by far the most important individual action you can do to tackle climate change.”