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We’ve had a lot of questions from journalists about the ongoing heatwaves in Europe and the US, so here are some comments from scientists in case useful.
Dr Malcolm Mistry, Assistant Professor in Climate and Geo-spatial Modelling, London School of Hygiene & Tropical Medicine, said:
What is going on right now in the northern hemisphere?
“The large-scale wave-like wind pattern in the upper atmosphere known as the Jet stream is a fast-moving wind that flows from west to east at a global scale.
“Currently, the Jet stream from North America to Europe is stuck in a position that is roughly south of the English Channel in a U-shape flow, with both the trough and the crest of this wave lying south of the UK.
“To the north of the jet stream, we have cooler Arctic air and areas of low pressure, which in turn bringing rain spells to the UK.
“To the south of the jet stream, we have an opposite weather pattern with a high-pressure system stalled drawing hot air from north Africa and maintaining the hot dry conditions.
“A similar pattern currently exists over the U.S. with the Jet stream positioned approximately in southern US with a stalled high-pressure weather pattern over large parts of California, Texas and Florida for instance, thus giving rise to abnormally high temperatures, but with the northern states having below average temperatures in some instances.
“Since this Jet Stream is a large-scale wave pattern, parts of Asia too are experiencing similar blocking patterns with hot air being drawn to specific mainland regions (such as China), thereby increasing the temperatures to above normal conditions that would be expected this time of the year.”
When was the last time we saw simultaneous heat records on 3 continents like this?
“This is a difficult question to answer as accurate record-keeping differs by regions. By and large the U.S. and a number of countries in Europe (including the UK) have longer historical records of observed temperature dating back to 1800s. In the absence of ground-station network, we would need to rely on climate reanalysis data, which are basically a blend of ground-station, satellite and climate model simulated data. However, simultaneous occurrences of heat records in 3 different continents even in boreal summer appears to be rare.”
Are we seeing an increase in duration of heatwaves?
“A few peer-reviewed studies have demonstrated that heatwaves in recent years have increased both in frequency and magnitude. Similarly, studies based both on climate model simulations as well as statistical approaches also indicate a similar trend in a warming climate in the future.”
Has El Nino really kicked in yet or will its effect increase over the coming year?
“The El Nino gathered momentum since May this year and its effects have already kicked in with significant anomalies in upper-surface sea temperatures in the Pacific. This in turn is known to disturb wider weather patterns not only in the Pacific, but also globally such as over Eastern US and parts of Europe, Africa and Asia. As per current seasonal forecasts, the El Nino is expected to strengthen and its effects to remain persistent till the rest of the year.”
What’s driving it?
“The El Nino Southern Oscillation (ENSO) is a natural variability in our climate system in the Pacific on timescales of 3-7 years. It has two phases, namely the cooler (La Nina) and warm (El Nino). There is no scientific consensus on what causes it or why it becomes stronger in some years.”
Why is the jet stream still blocked and keeping high pressure over the continent and low pressure over UK?
“Our weather system is a complex non-linear dynamic (fluid) system driven largely by the temperature gradient (difference) between the equator and poles (north and south), as well as the difference in temperature between the land and ocean bodies. Small changes in temperature whether due to natural climate variability or human-induced climate forcing can have wider effects in different parts of the world. The current blocking pattern is not uncommon in historical climate, but the strength and the duration can show variability on a year-to-year basis.”
How long will it last?
“The current extended weather forecasts from the ECMWF for example suggest this blocking pattern to dissipate in about a week’s time. We have to keep in mind that the accuracy of a weather forecast decreases as the lead time of the forecast increases, and generally a forecast for up to a week ahead shows moderate to high accuracy in the current generation of weather forecasts, beyond which the accuracy begins to deteriorate. This again goes back to the non-linear dynamic nature of our weather system.”
Are such ‘blocking events’ becoming more frequent or longer, and is climate change playing any role in that?
“As mentioned above, the current blocking pattern is not uncommon in historical climate, but the strength and the duration can show variability on a year-to-year basis. Recent years (e.g., the summer of 2023, the spring heatwave over Spring in April 2023) tend to suggest that such blocking events are becoming more persistent in nature, but more studies would be required to confirm this hypothesis. Whether climate change can make such blocking patterns more frequent, erratic, and longer is something that the researchers have been examining using climate model simulations, and again, we need to find a strong scientific consensus to say so.”
Do we know why these European heatwaves are happening?
“The current state of the oceans both in the Atlantic and Pacific basins show a by-and-large above normal sea surface temperatures. This in turn can have a larger effect on global-scale weather patterns, one of them being slow-moving high-pressure weather patterns in some parts, and conversely low-pressure systems bringing unseasonal or heavy rainfall elsewhere. The current positioning of the stalled high-pressure system over Southern Europe with the Jet stream bringing in dry hot air largely from sub-Saharan and northern Africa makes this a recipe of what we are currently experiencing in Italy, Spain and Greece for instance.”
Are the three large heatwaves we’re seeing in US, Europe, Asia all due to “heat domes”?
“The ones over the US and China can be classed as ‘heat domes’. The one over Europe is more of a sub-Saharan heat blast. Irrespective of the underlying dynamics and what we call them, the resulting effect is largely similar.”
Is there any potential mechanism (behind an increase in global average temperature) behind the fact we have three, concurrent heat extremes on three continents?
“It is too early to attribute single events such as the concurrent occurrence of these heatwaves in the three continents to a rise in global average temperature. This research question will be investigated, but the correct question would be to examine ‘how likely or what is the return period of such a concurrent event of similar magnitude and persistence in a warming climate?’.”
How can we determine whether or not a specific extreme weather event can be attributed to climate change?
“We cannot attribute a single specific extreme weather event to climate change. What we can attribute is the likelihood of such an event occurring with shorter return periods (i.e., higher probability) in a warming climate.”
Are these heatwaves unusual / alarming? How do the length and/or intensity of the heatwaves compare in the grand scheme of things?
“The present heatwave is alarming in terms of the intensity and duration. The temperatures in some locations have either touched their historical high records or forecasted to be surpassed. While there is no reason to say that such heatwaves are unusual in a natural climate system such as in a strong El-Nino year, it is reasonable to expect that the additional heat from our warming climate can add the extra energy in our weather system. With regards to the length and intensity of the heatwaves in the grand scheme of things, historical ground-station observation records are not consistently long enough in all parts of the world, and thus a bit difficult to address this question. Historical observations in the UK (as well as some countries in Europe) and in the US though do date back to over a century and the current heatwave is at par with (if not already broken) the earlier records.”
How could the heatwave impact agriculture?
“Heat stress has a detrimental effect on crop productivity. Most crops require an optimum range of temperatures between 10-30 deg C (along with moisture or water either as natural rainfall or irrigation) to reach nutritious (calorie) levels. Heatwaves can have a damaging effect on the crops irrespective of the timing of the crop growing season. Similarly, it can also exacerbate soil moisture and droughts, thus affecting the wider flora and fauna.”
How could the heatwave impact energy?
“Usage of air conditioning to maintain thermal comfort levels indoors has risen energy demand especially during peak daytime hours when the temperatures are highest, which in turn can result in potential blackouts if the energy infrastructure is incapable of coping with the demand load”.
How could the heatwave impact health?
“Added pressure on ambulance callouts, hospitalisations and public health infrastructure. Excess deaths from heatwaves have been well documented in recent years.”
What health conditions are you most worried about during the heatwaves?
“Heat strokes, cardiovascular disease, renal disorders are common causes of deaths during heatwaves. In addition, for those regions with elevated pollution levels, the heatwaves can have a compounded effect on health and put people at added risk.”
Are there any groups that shouldn’t travel abroad to impacted regions at all?
“Yes, people with heart conditions, pregnant women, and generally the aged (above 65 years) should avoid travel at such times, or take added precautions.”
Could there be long-term health impacts of this weather?
“Yes. For instance, exposure to heat especially for outdoor workers can be detrimental. For instance, chronic kidney disease have been documented with construction and farm workers among others.”
How prepared are countries for extreme heat and its effects on humans?
“The countries in Southern Europe are adapting to extreme heat by way of air conditioning. The adoption for air conditioning for residential space cooling for instance has been steadily rising in recent years. Another shift has been to build or transform cities with additional green spaces (e.g., Barcelona).”
How can healthy landscapes help us mitigate the impacts of heatwaves?
“The heat effect can be more severe in urban areas due to the urban heat island effect. Green spaces for instance can offset the heat to some extent providing a natural shield from the direct sunlight. Similarly, white roof tops and using a lighter colour shade for outdoor paints are also known to increase the reflectivity of the building space, thus helping to reduce the indoor temperatures albeit marginally.”
Are we going to have to treat the annual summer holiday to Europe differently in the future as heatwaves increase in frequency and intensity?
“It is too soon to say so without a thorough analysis. But clearly, people need to be better prepared as such short-term weather blocking events that are difficult to forecast more than a fortnight in advance can result in similar heat (or cold) wave conditions in the coming year with greater intensity and/or persistence.”
Should tourists be considering going at different times as temperatures make some places unbearable? Or will other areas in Northern Europe become the new holiday hotspots?
“Countries that are dependent on tourism and at the same time of higher risk from heatwaves (such as in Southern Europe) will need to find a right balance to maintain public health facilities and resources for their local population, yet at the same time not having a negative impact on their tourism industry. One way could be to provide tourists some incentives to avoid visiting popular attractions during peak daytime hours when the ambient conditions are less demanding, particularly in crowded places. Yet another could be to arrange for some make-shift zones where the tourists could take regular breaks and keep themselves hydrated. A far more radical approach could involve encouraging tourists to visit in off-tourist season months, though this would naturally depend on individuals able to take time off from work.”
How could the heatwave impact infrastructure, including cooling systems, buildings, etc.?
“A closer synergy between building architects, town planners, engineers and climate scientists would be required to address this problem. Cities and urban infrastructures in general will need to be designed to cope up with the extreme weather events (be it heatwaves or flooding), and modern designs and materials will need to be explored to withstand these forces of nature.”
Dr Modi Mwatsama, Head of Capacity and Field Development at Wellcome, said:
“The above-average Pacific Ocean temperatures are driving the current El Niño, but it is still early days. We’ll only see the full effects in another few months.
“El Niño will likely continue to gain in strength as the year continues. And as it does, we will see more people’s health affected due to the increase in the extreme weather events that we’ll see.
“It is more important than ever that we put in place measures to limit the harm on our health. These can be simple solutions like providing shade and painting buildings white to reduce heat, to investing in early-warning systems for climate-sensitive infectious disease outbreaks such as cholera.”
Dr Karsten Haustein, Climate Service Center Germany, said:
What is going on right now in the northern hemisphere?
“The North Atlantic region is particularly warm (in fact record warm by a large margin). Part of it is down to a weak Azores high and associated weak trade winds that reduced the mineral dust production in North Africa. As a feedback, the ocean waters can warm more than usual. Whether or not El Niño is to blame for the weak Azores high is not clear, but it might have played a role (due to so-called global teleconnection patterns in the atmosphere). Another factor that is discussed is the impact of reduced ship emissions due to changed regulation in 2020. Less cooling aerosols from ships might have helped to accelerate warming temporarily. This is also true over the North Pacific, whereas El Niño is warming the central Pacific. Of course the main driver for the record warmth is human-induced climate change, with land temperatures seeing record values at various places as an inevitable consequence.”
Are we seeing an increase in duration of heatwaves?
“The warmer the global average temperature, the more intense – and thus longer – heatwaves become.”
Has El Nino really kicked in yet or will its effect increase over the coming year?
“El Niño has already been officially declared. The full effect is usually only seen in the coming winter and early next year. Having said that, whether or not next year is going to be warmer than this year depends on the strength of El Niño during the coming winter. There’s still no guarantee that it will be a strong El Niño. It might fade a bit and become ‘only’ moderate, in which case 2024 sets less of a new record than previous El Niño years.”
What’s driving it?
“El Niño is a natural phenomenon driven by changes in the Pacific trade winds. Ironically, during the last two decades or so, there is a tendency towards more La Niña years. It is still under debate whether this is a response of the climate system due to anthropogenic warming or just a temporary fluke associated with natural variability. That said, there is an increasing amount of evidence that we should expect more La Niña years, interrupted from fewer, but potentially stronger El Niño events.”
Why is the jet stream still blocked and keeping high pressure over the continent and low pressure over UK?
“So far, there is not enough evidence to claim that the jet stream has slowed on average. It’s not unusual to get stationary high pressure systems (and associated areas of lower pressure with unsettled weather) in summer, but there certainly have been a couple years lately which did feature persistent weather patterns with long dry spells and frequent extreme heat episodes. Yet, it’s too early to say that this is caused by climate change.”
Are the three large heatwaves we’re seeing in US, Europe, Asia all due to “heat domes”?
“Most longer lasting heat wave are down to excessive high pressure where large air masses are forced to sink downwards and thereby warming up. Short heat episodes are often down to advection of hot air masses from places further south. Most extreme heat events are a combination of the two, which is why I consider the term ‘heat dome’ slightly misleading.”
Is there any potential mechanism (behind an increase in global average temperature) behind the fact we have three, concurrent heat extremes on three continents?
“Generally, on a warming planet, concurrent heat waves should be expected as the general threshold above which a warm episode turns into a heatwaves increases everywhere. Alteration in the jet stream is a potent mechanism to increase the number of compound climate extremes, but as mentioned above, there isn’t enough evidence yet that it has happened yet.”
How can we determine whether or not a specific extreme weather event can be attributed to climate change?
“First, no event is solely attributable to human-induced climate chance. Any event is made more or less likely to occur because of it. In that sense the change in risk is what we attribute. That said, each event requires a dedicated attribution study the way World Weather Attribution is carrying them out on a frequent basis now (https://www.worldweatherattribution.org/). There are too many extremes for them all to be attributed separately, so some of them won’t have a readily quantifiable result. For heatwaves and extreme hot temperatures, it is safe to say that almost all such events are made (much) more likely due to climate change. Some hot extremes – such as the UK temperature record last summer – are so extreme that it’s virtually certain that they wouldn’t have happened without climate change. But that’s still the exception.”
Why are these heatwaves are so unusual / alarming. How do the length and/or intensity of the heatwaves compare in the grand scheme of things?
“Both length and intensity of heatwaves increases as long as we keep warming the planet by virtue of emitting greenhouse gases into the atmosphere. It’s simple physics and nothing will change that. El Niño and particularly rare atmospheric circulation anomalies (aka unusual large scale weather pattern) have the potential to exacerbate the problem. Should some of the changing weather patterns turn out to be driven by the warming itself, some regions may be seeing more drastic warming and/or drying than other places. The UK, for example, is not necessarily at high risk in this regard, but a really relentless summer heat wave can cause massive damage in terms of heat related fatalities and water shortage due to drought.”
Prof Liz Stephens, researcher in climate risk and resilience, University of Reading, said:
“Seven countries in Southern Europe currently have the most severe ‘red’ warning for heat, and in many of these locations the above average temperatures are expected to last well into August.
“The jet stream is currently in a stationary position, which means that weather systems are kept in a holding pattern that makes heat build up in some regions of the world such as southern Europe, southern North America and Eastern China, while other parts of the world such as New York state and Japan suffer from persistent heavy rainfall.
“Current extreme sea surface temperatures in the Mediterranean Sea are fuelling the heat wave by keeping night-time temperatures at uncomfortable levels. This worsens the impacts on human health.
“Extreme fire danger is accompanying the heat wave as a result of dry vegetation and the high temperatures. As well as the direct risk to life, the resultant air pollution can exacerbate health impacts.
“There is strong evidence that climate change is increasing the frequency and intensity of heat waves, though there is still a lot of debate around how climate change is affecting the stationary jet stream pattern. This kind of pattern was also linked to the European floods in 2021.
“Heat waves are a silent and invisible killer. We don’t often see the impact that they have had on human health until the mortality statistics are published many months later.”
Dr Chris Huntingford of the UK Centre for Ecology and Hydrology said:
“Climate research suggests that global warming will not simply occur as the extremes we have seen in the past, but with the same amount of extra warming everywhere. Instead, complex patterns may emerge where some locations become prone to a much more rapid ramp-up of temperature extremes, others less so. Hopefully, in parallel with supercomputer time, new generation climate computer models will more tightly identify the places in the world of particular concern and allow better-targeted heatwave adaptation planning.”
Prof John Marsham, School of Earth and Environment at the University of Leeds, said:
“I think a lot of people in the UK are really questioning what’s going on with the weather now. 40 degrees last summer, this year our warmest June on record, but now it’s July and it feels like it’s raining every day. Meanwhile news headlines are showing the ongoing heatwave in Southern Europe, which may break records. I like to think I’m fairly on top of weather news’ but it’s actually getting very hard to keep up with the sheer number of extremes affecting people globally now, with extreme heat and floods affecting USA, Canada, Japan, South Korea, China, Europe and others. There at least 80 million people under extreme heat warnings on Sunday in the USA alone. That’s about 1 in 4 Americans. And of course other parts of the USA have had floods.
“I think people are really waking up now to the fact that the man-made climate crisis is very much to blame, and that we have to act. Pollution from fossil fuels has heated our planet, and this makes not only heatwaves more likely and more intense, but also increases extreme rainfall and floods. The extreme weather is already leading to crop losses, high food prices and loss of life. This will continue to get worse, and wipe out entire ecosystems, unless we rapidly make the switch from fossil fuels to renewables and clean power. The good news is that people want the government to act, and that doing this will create jobs, reduce energy costs and by producing clean UK energy we can reduce our dependence on foreign energy sources. But we need to make sure that the government does act. If we don’t act soon, future news headlines won’t so much be about holidays, but about food prices, and food and water supplies.”
Prof Daniela Schmidt, Professor of Earth Sciences, University of Bristol, said:
“The current extreme heat highlights what will happen more and more frequent in the future. The combination of humans warming up the planet with natural climate variability will continue to breach records.
“Heat, and the combination of heat and drought, was identified as a key risk for people and ecosystems in the last IPCC report. The heatwave last summer in Europe ended the life of over 60000 people prematurely, there was not enough water in the Rhine for shipping and energy production was limited as the water was too warm to cool power stations.
“This year, for the first time, we also see extreme heat in the ocean around the northern parts of Europe. The rapid recurrence of extreme heat does not allow ecosystems to recover. How many more warnings, reports of impacts, losses of life do we need to take action?”
Dr Akshay Deoras, meteorologist at the University of Reading, said:
What is going on right now in the northern hemisphere?
“Parts of Asia, Europe and the US are witnessing a simultaneous occurrence of record-breaking temperatures and dangerous heatwaves that are fuelling wildfires and risking the lives of millions of people. The air temperature in China exceeded 50 degrees Celsius, whereas the land temperature in Spain exceeded 60 degrees Celsius. The human body is not built to handle such high temperatures without any adequate protection.”
Has El Nino really kicked in yet or will its effect increase over the coming year?
“El Niño is still weak and in its early stages of development. Its effect on the global weather patterns will become more robust in the coming months.”
Why are these heatwaves are so unusual / alarming. How do the length and/or intensity of the heatwaves compare in the grand scheme of things?
“Heatwaves are common in the northern hemisphere at this time of year. However, the temperatures we are expecting in parts of southern Europe in the coming days are what we normally get in the tropical deserts or tropical countries such as India, Pakistan or the Middle East during summer. The simultaneous occurrence of heatwaves in different regions of the world as well as their forecasted intensity fits well with the anticipated impact of climate change on global temperatures.”
Dr Melissa Lazenby, Senior Lecturer in Climate Change at the University of Sussex, said:
What is going on right now in the northern hemisphere?
“Exactly what climate scientists have been predicting, warmer and more extreme conditions due to anthropogenic warming of the planet. The northern hemisphere is experiencing a combined effect of both natural and anthropogenic climate change resulting in extreme heat over 3 NH continents. There is a developing El Nino event as well as the additional warming from human emissions therefore resulting in abnormally warmer temperatures than without human emissions. Current conditions of the atmosphere over Europe, the US and Asia have high pressure systems dominating those regions that are as a result experiencing heatwave conditions. There are also anomalously warm sea surface temperatures (SST’s) in the northern hemisphere this summer which are additionally contributing to heatwave conditions experienced over land.
When was the last time we saw simultaneous heat records on 3 continents like this?
“Last year (2022) in summer there were record breaking heatwaves experienced in Europe, including the UK, China and parts of the US. https://www.carbonbrief.org/state-of-the-climate-2022-on-track-for-a-summer-of-extreme-heat/
Are we seeing an increase in duration of heatwaves?
“Yes, globally and regionally (source: Perkins-Kirkpatrick & Lewis, 2020) https://www.nature.com/articles/s41467-020-16970-7#citeas
Has El Nino really kicked in yet or will its effect increase over the coming year?
“El Nino is still in its developing stages and typically peaks in December-January-February and therefore there is likely more extreme events and heat to come globally. This current El Nino looks to peak earlier than usual around September and October, see figures below from the IRI. https://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/
What’s driving it?
“El Nino is driven by natural climate variability and human emissions are affecting the natural patterns by making them more extreme through adding more heat and energy into the earth’s system.
Is there any potential mechanism (behind an increase in global average temperature) behind the fact we have three, concurrent heat extremes on three continents?
“Human Induced climate change is likely the common mechanism for all 3 alongside other natural climate variability.
How can we determine whether or not a specific extreme weather event can be attributed to climate change?
“We run an attribution study after the event has occurred and separate out the various natural and anthropogenic forcings that affect the climate and weather and see which combination of what factors lead to the exact observed event that was experienced. It is only after this analysis that climate scientists can determine the proportions of the various natural and anthropogenic factors that resulted in the extreme event. However, based on the current understanding of heatwaves and their drivers, there is a high chance it will be driven largely by anthropogenic climate change and to a lesser degree natural factors.
Why are these heatwaves so unusual / alarming. How do the length and/or intensity of the heatwaves compare in the grand scheme of things?
“Heatwaves are extreme events and have an adverse impact on humans and the environment. They are occurring more frequently and are becoming more intense and are resulting in infrastructure breakdown, human health issues and fatalities, drought and water shortages and we are not currently prepared for these types of events. We are moving out the usual and well-known natural oscillations of the climate to unchartered and more extreme territory. However, we have the ability to reduce our human influence on the climate and weather and to not create more extreme and long-lasting heatwaves and therefore we should really be focusing on that!”
Dr Nicole Miranda, Senior Researcher on the Oxford Martin Future of Cooling, said:
How can healthy landscapes help us mitigate the impacts of heatwaves?
“The presence of vegetation and water in our landscape can serve as ways to passively cool our surroundings. Trees and plants provide shading and also have the mechanism of evapo-transpiration. Large-scale green corridors in the city of Medellin have been reported to reduce urban uncomfortable heat by 2°C. Bodies of water, such as ponds and fountains, capture the heat around them by evaporating water.”
On infrastructure impacts:
“Buildings in places traditionally prepared for harsh winters and not summers, are not necessarily designed with cooling in mind. Lack of ventilation, the orientation towards/away from the sun and shading need to be considered more to increase gains in the winter, while reducing them in the summer. They are compatible, if smart design is used – e.g. knowing about the angle of the sun which in winter is lower than in summer, and using that concept for shading.”
“The electrical network infrastructure is at a big risk of being further stressed if we all install the go-to solution of air conditioning. These are energy- (and carbon-) intensive technologies.”
How prepared are countries for extreme heat and its effects on humans?
“It depends where we look. Those countries that have traditionally been exposed to heat are already developing with the right architecture and know-how. Even their behaviours has adjusted for heat. However, if unbearable heat is reached even those will suffer.
“For countries that ‘aren’t used’ to heat, their historical/traditional infrastructure have been designed with only cold winter temperatures in mind. That ‘know-how’ on how to make, for example, passive houses that will resist different temperatures throughout the year is not as well established. So knowing what materials to use and how to incorporate smart shading still needs to be further developed in those places.”
Prof Nigel Arnell, Professor of Climate System Science at the University of Reading, said:
“The sorts of extreme heatwave that we’re seeing at the moment clearly affect people directly, and it’s not just those with underlying health conditions who are at risk from the extreme temperatures in Europe, China and the USA.
“But heatwaves also reduce our capacity for labour – particularly outdoors – so reduce productivity. They damage infrastructure, and they lead to increased demand for electricity and water – which leads to power and water shortages. And they increase dramatically the risk of wildfire. We’ve got record temperatures this year, and we had them last year too. What more of a wake-up call do we need to seriously reduce our emissions and to improve our resilience to extreme events? These events are damaging lives, our economy and the environment.”
Prof Richard Allan, Professor of Climate Science, University of Reading, said:
“The fickle nature of weather patterns determines where and when extreme weather events take place but the giant waves propagating around the hemispheres can often connect areas of extreme heat, drought and deluge. The heatwaves affecting parts of north America, southern Europe and areas of Asia are linked through these giant planetary waves that have become lodged in place, causing extreme heat in these regions but also intense rainfall and flooding in others. Where stagnant high pressure areas persist over continents, the air sinks and warms, melting away clouds, causing intense summer sunshine to parch the soils, heating the ground and air above rather than being used up evaporating moisture.
“The developing natural El Nino phenomena is taking hold in the eastern Pacific, which is steadily warming this year, but an unusually warm north Pacific ocean and eastern Atlantic are also capable of nudging weather patterns out of kilter and it would be surprising if the unprecedented pattern of warming being unleashed on the oceans did not disrupt our weather patterns. The warming of climate due to emissions of greenhouse gases by human activity is further magnifying the severity of extreme heat where it occurs, promoting moderately hot spells to premier league extremes. A warmer climate is making heatwaves hotter and longer lasting and a warmer, thirstier atmosphere is capable of sapping moisture more effectively from one region and subsuming this excess water into monsoons and storm systems elsewhere, intensifying rainfall and associated flooding. It’s only with massive and rapid cuts in greenhouse gas emissions that we can avoid further worsening of weather extremes due to the heating of the planet.”
Dr Chloe Brimicombe, Climate Scientist and Extreme Heat Researcher, University of Graz, said:
“The extreme heat occurring in the northern hemisphere is more likely to be the result of climate change, the last time we saw heat in different regions at the same time was last summer.
“There is some evidence to show that heat is affecting a larger proportion of the population year on year.
“This is in addition to heat occurring for longer durations, more frequently and more intense.
“The heatwave in Southern Europe in the ECMWF extended range forecast is forecasted to not end really until maybe as late as the end of July.
“Heat does not just cause excess death amongst the elderly. I’m most worried about the impact of heat on pregnant women, young babies and children. We see a rise in preterm birth as an outcome of pregnancy with exposure to extreme heat. And a rise in hospital admissions amongst all of these groups.
“This heat is a symptom of climate change. We need urgent action on climate mitigation to net zero and beyond – this is 1.2C above baseline temperature warming, 3C is unimaginable.
“Action like urban greening, investment on retrofitting buildings, supporting breaks for outdoor workers and providing cooling centres to the most vulnerable are some essential ways to help reduce the impact of heat.”
Prof Simon Lewis, Chair of Global Change Science, University College London, said:
“This is just the beginning. This is what the climate system can do at just 1.2 degrees C warming. Current policies globally have us hitting 2.7 degrees C warming by 2100. That’s truly terrifying. As scientists agreed last year: There is a rapidly closing window of opportunity to secure a liveable and sustainable future for all. Deep, rapid and sustained cuts in carbon emissions to net zero can halt the warming, but humanity will have to adapt to even more severe heatwaves in the future.”
Prof Elizabeth Robinson, Director of the Grantham Research Institute on Climate Change and the Environment, London School of Economics and Political Science (LSE), said:
“It is clear that in many parts of the world, workers in high exposure sectors such as agriculture and construction are at increasing risk from heat stress, yet there are still insufficient health and safety protections.”
“There is still insufficient understanding of how worker health is being harmed, the extent to which workers are able to adapt to the reality of increasing frequency and intensity of extreme heat, and the extent to which employers are taking action to protect workers’ health.”
Dr Shouro Dasgupta, Visiting Senior Fellow, Grantham Research Institute on Climate Change and the Environment, London School of Economics and Political Science (LSE), said:
“Heatwaves result in increased risk of discomfort, of limitations in physical functions and capabilities, and ultimately also of injuries and heat-related illnesses such as heat cramps, and heat exhaustion, to potentially fatal heat stroke. Workers might think about changing what they wear, taking additional breaks, and increasing rehydration.”
Prof Hannah Cloke, University of Reading, said:
“The bubble of hot air that has inflated over southern Europe has turned Italy and surrounding countries into a giant pizza oven.
“The hot air which pushed in from Africa is now staying put, with settled high pressure conditions meaning that heat in warm sea, land and air continues to build.
“It is not surprising that different parts of the northern hemisphere have heatwaves during our summer months, but the combined picture is starting to look like climate change impacts all happening at the same time, as scientists have forecast for decades. We are now living through these impacts, rather than predicting them in a computer simulation of the future climate.
“Sea level rise, melting ice, extreme heatwaves, intense rainfall, wildfires, drought and floods are cropping up in many parts of the world at the same time. In previous heatwaves, such as Britain’s hot summer of 1976, other parts of the globe had a relatively cool year. Today’s extremes of weather are increasingly throwing everything everywhere all at once.”
Prof Chris Hilson, Director of the University of Reading’s Centre for Climate and Justice, said:
“The current heatwave being experienced in southern Europe has undoubtedly brought the climate crisis closer to home for many people. But news reports from tourist hotspots like the Acropolis and Rome have tended to make this extreme weather event seem merely like a summer holiday inconvenience. However, the reality is that these heatwaves often lead to many premature deaths, especially among the elderly. This is a matter of climate justice or fairness because climate harms such as extreme heat are being unequally felt. We must ensure that we continue to cut polluting emissions of carbon dioxide to prevent these events from becoming even more frequent; but the authorities also need to put adaptation measures in place with an eye on these unequally felt harms. That includes cool zones or drop-in centres with transport to get there, more trees in relevant residential neighbourhoods, and appropriate (and preferably renewable-powered) aircon in care homes.”
Dr Alan Kennedy-Asser, Research Associate at the University of Bristol Cabot Institute for the Environment, said:
“Certain factors will make certain areas and certain demographics of people more at risk during extreme heat events. For example, generally areas with high air pollution and older people are more at risk. However, that does not mean that all older people are equally vulnerable or that no one in their 20s is vulnerable. As a society we need a better understanding of heat risk, and indeed what our vulnerabilities are, regardless of what age we are or where we live.”
Prof Ilan Kelman, Professor of Disasters and Health at University College London, said:
“These heat waves are exactly in line with expectations under human-caused climate change. As the rising temperatures drive worsening heatwaves, including terrible humidity, we expect to see substantial increases in related deaths. Many people cannot afford indoor cooling and some people must be outside for work. Heat-humidity then becomes the ‘silent killer’, since we often do not realise how many people are in lethal difficulty, especially when it does not cool down at night.
“When we get too hot, our organs have trouble functioning, so we die. Dehydration is a big killer. Without enough fluids, again our organs cannot work properly. Although we are warm-blooded so that we burn calories to regulate our body temperature, we reach limits and summer UK temperatures are exceeding those limits.
“Humidity adds to the equation. With higher humidity, the temperature feels higher (called ‘humidex’) and our sweat evaporates less, not cooling our bodies as much. Then, deaths occur at lower temperatures.
“Plus, if it does not cool down at night, our bodies do not recover from the day’s heat and so death rates rise. Fans might add to our woes if they simply blow hot, humid air onto us, dehydrating us faster.
“We see other heat-related deaths. Sunburn can be severe, but is only lethal occasionally. The smoke from vegetation fires harms people with breathing difficulties, such as asthma. They might be struggling already as heat waves exacerbate air pollution. Many of us respond with a day by the seaside or a quick dip in the lake, sadly leading to many drownings.
“Drink plenty of fluids, preferably water and neither alcohol nor coffee. Stay in cool rooms indoors during the hottest part of the day. Parked vehicles heat up quickly and kill kids and pets left inside. Do not rely on air conditioning, since widespread use could lead to power outages. Watch children and babies for signs of overheating, notably those at the age where they cannot communicate how they are feeling. Check on people living alone, especially the elderly, since their bodies do not regulate temperature well.
“Not everyone has these options. Agricultural and construction workers might lose a day’s income or be fired if they decline to exert themselves as the day broils. Not all public transport is air conditioned and the frontline staff serve us all.”
Dr Vikki Thompson, Climate Scientist, Royal Netherlands Meteorological Institute, said:
“China, North America, and Europe are all seeing record-breaking heatwaves right now. Scientists have shown that such heatwaves are occurring more often with climate change, and with El Nino conditions this year we are likely to see many more temperatures records broken in the coming months. Heatwaves will continue to increase in intensity, frequency, and duration unless we reduce greenhouse gas emissions drastically.
“It is hard for countries to prepare for heatwaves beyond what they have recently experienced – especially when we are regularly seeing record smashing events that are unimaginable until they occur. Our recent study2 showed that such heatwaves could occur anywhere globally.
“Heatwaves are one of the most deadly natural hazards; recent research1 found that over 60,000 heat related deaths occurred in Europe last summer. The health issues related to heat include direct effects, such as heat stroke and cardiovascular failure, and indirect effects including poorer mental health and an increase in accidents such as car crashes and drownings. To keep safe make sure you stay cool, drink plenty of water, and wear suncream. Look out for the more vulnerable such as young children and older people.
“In Europe, reduced snowfall in the Alps severely impacted winter tourism earlier this year, and now we are seeing extreme temperatures affecting summer holiday plans for many. Climate change will impact many aspects of our lives, forcing adaptation on both a personal scale and from our governments.”
1 https://www.nature.com/articles/s41591-023-02419-z
2 https://www.nature.com/articles/s41467-023-37554-1
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