winter – Cabot Institute for the Environment blog

Four ways winter heatwaves affect humans and nature

Posted on January 11, 2023April 14, 2023 by janet.crompton

Temperature anomaly in Europe, Jan 1. Much of the continent was 10°C or more (dark red and grey) above the long-term average.
WX Charts, CC BY-NC

An extreme winter heatwave meant countries across Europe experienced a record-breaking New Year’s Day. New daily temperature records for the month of January were set in at least eight countries: Belarus, Czechia, Denmark, Latvia, Liechtenstein, Lithuania, Netherlands and Poland.

In many cases the temperatures were not just breaking the old highs, but smashing them by massive margins. On a typical January day in Warsaw, Poland, temperatures would barely go above freezing, yet the city recently experienced 19℃, breaking the previous January high by 5.1℃.

New January records were set at thousands of individual stations in many other countries such as 25.1℃ at Bilbao airport in Spain, 0.7℃ hotter than the previous record set only last year. Large areas of central and Eastern Europe experienced temperatures 10℃ to 15℃ warmer than average for this time of year – and that has persisted through the week.

When Europe experienced extreme heat in July of last year, more than 20,000 died. Fortunately winter heatwaves are much less deadly, but they can still affect both human society and natural ecosystems in many ways.

1. Less energy is needed

In Europe deaths due to cold weather vastly outweigh those caused by extreme high temperatures – in the UK there are ten times more. Warmer winters will reduce this excess mortality and, with the current cost-of-living crisis, many will have been relieved that a heatwave meant less energy was needed to heat their homes.

Electricity demand is influenced by things like the time of day, the day of the week and socio-economic factors like the COVID pandemic or the war in Ukraine. The weather also makes a difference. For example, in Poland and the Netherlands demand was noticeably lower than average, especially since January 1 was a Sunday. The extent of the heatwave also meant countries could refill some of their winter gas reserves, or large batteries.

Energy consumption in Poland December 28 to January 5. The red line shows the 2022-2023 heatwave period, and the grey lines show available data from 2015-2022.
Hannah Bloomfield / data: transparency.entsoe.eu, Author provided

2. Reduced yields for some crops

Winter warm spells don’t always have such a positive impact though. For instance a lack of snow in the mountains affects agriculture and can reduce crop yield, since snow creates an insulating blanket that prevents frost from penetrating into the soil. This means snow can actually increase soil moisture more than rainfall, thus improving growing conditions later in the season.

The big snow melt in spring time replenishes reservoirs and allows hydroelectricity generation, but unexpected snow melt can lead to flooding. Changes to the timings of these events will require preparation and adaptation to enable a steady supply of water to where we need it.

Warmer temperatures will create longer growing seasons in many regions. This is not always the case though. A recent study showed that for alpine grasslands an earlier growing season (the point when snow has melted entirely) leads to ageing and browning of the grasses in the later part of the summer.

3. The snow economy is in trouble

The heatwave caused ski resorts across the Alps to close in what should be their busiest time of year. In January the slopes would be expected to have a good covering of snow – but instead we saw green grassy fields.

This hits the local economy where many people rely on winter sports tourism. Events such as the Adelboden alpine ski World Cup are relying on artificial snow, which comes with a further environmental cost increasing the carbon footprint of ski resorts and requiring a large water supply. Indeed, the Beijing winter Olympics used the equivalent of daily drinking water for 900 million people to generate the artificial snow it required.

4. Animals out of sync with the climate

We humans are perhaps fortunate, as we are able to adapt. Some ski resorts have already opened mountain bike trails in winter to offer alternative tourism, but wildlife and ecosystems cannot adjust so rapidly.

In the mountains many species, such as ptarmigan and mountain hares, change their colouring for winter to camouflage in the white snow. The timing of this change is determined by length of day – not the temperature or amount of snow. These creatures are at greater risk of being preyed on when it is warmer.

White rabbit, brown background — Mountain hares are dressed for a climate that has changed.
Mark Medcalf / shutterstock

Over the past century heat extremes in Europe have increased in intensity and frequency. Both the general warming and heatwave events have been firmly attributed to humans.

Future projections suggest these trends will continue and heatwaves in both summer and winter will get hotter, last longer, and occur more often. We need to learn to adapt for these changes in all seasons and think about the impacts on everyone – and everything – on our planet.

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This blog is written by Cabot Institute for the Environment members Dr Vikki Thompson, Senior Research Associate in Geographical Sciences, University of Bristol and Dr Hannah Bloomfield, Postdoctoral Researcher in Climate Risk Analytics, University of Bristol. This article is republished from The Conversation under a Creative Commons license. Read the original article.

Cost of living crisis: the health risks of not turning the heating on in winter

Posted on September 20, 2022March 29, 2023 by janet.crompton

People in the UK might be tempted to keep their heating turned off to offset the large increases in energy bills this winter. A recent YouGov poll, revealed that 21% of respondents would not turn their heating on until at least November. Could the health of these people be endangered?

Before COVID, an average of 25,000 extra deaths occurred between December and March compared with any other four-month period of the year. Even if COVID did not exist, the cost of living crisis could result in the toll from the coming winter being worse than usual.

The Marmot review (a report investigating the effects of cold homes and fuel poverty) estimated that 21.5% of all excess winter deaths could be attributed to the coldest 25% of homes in the UK population.

This would suggest that 5,000 extra deaths occur in winter because people live in cold homes. But this does not mean the cold homes cause the deaths. People who live in cold homes may have other disadvantages, making them less able to survive winter.

Would it make any difference whether they leave their heating on or off? Studies suggest temperatures should be kept to at least 18℃ to minimise the risk to health, but how easy is it to maintain this if homes are poorly insulated?

Research into what is best for people’s health ideally relies on randomised controlled trials to tell us about cause and effect. But it would be unethical to conduct a trial where some people were told to leave their heating off and others were told to keep it on to see if it had any effect on mortality. Instead, we have to rely on what are known as “longitudinal studies” where people are followed over many years and respond regularly to questionnaires.

In one such study in the 1970s, the British Regional Heart Study recruited thousands of men, then in middle age, from across Great Britain. In 2014, around 1,400 of these men, then aged 74-96 years, answered a questionnaire that included questions on home heating.

One question asked whether, during the previous winter, the respondent had: “Turned off the heating, even when you were cold because you were worried about the cost?” One hundred and thirty men (9.4%) said yes. These men seemed no more likely to die in the following two years than men who had replied no.

A larger study would have given a more robust answer. And in the absence of other direct evidence, we have to draw conclusions from indirect evidence, such as this.

The most vulnerable

Recently, researchers in Sweden tried to assess a range of questions about the effects of energy use, fuel poverty and energy efficiency improvements on people’s health. They systematically reviewed all the relevant studies on the topic. One of their findings showed consistently across four studies the link between fuel poverty and premature death.

The British Regional Heart Study showed that fuel poverty was more likely to be found among people who were single, poor and working class. This suggests that people who are the most financially vulnerable will be those most likely to leave the heating off. As with climate change, the poorest are hit hardest.

So far I have only discussed effects on health in terms of death, which in the UK concerns mainly older people. The winter deaths that occur are usually the result of heart disease, stroke and respiratory disease. Yet increasing attention has also been paid to the strong effects of the cold on mental health.

The Marmot review quoted studies that drew attention to the depressive effect of living in a cold home. Children in adolescent years may seek respite and privacy away from home, with consequent exposure to mental health risks. The misery caused by financial pressures only add to this burden.

Because the most financially vulnerable people are also the most vulnerable in their health, it should follow that interventions at government level are urgently needed to offset the likely health crisis looming from increased energy costs.

The most vulnerable will need the most help. Yet a common paradox seen in public health is that interventions applying to the whole population will lead to more lives saved than those targeted only to those at greatest risk.

This is because there are far more people in the population at moderate risk than at high risk. Only a modest proportion of people at moderate risk will benefit. Yet because this group is so much larger than the high-risk group, more lives may be saved among those at moderate risk.

Buildings in the UK clearly need to be better insulated, but these sorts of interventions will come too late for this winter. Mitigating the rising costs of energy must be the only way forward to allow homes to be heated to a comfortable level and prevent a tidal wave of excess winter deaths.

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This blog is written by Cabot Institute for the Environment member Richard Morris, Honorary Professor in Medical Statistics, University of Bristol

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Richard Morris

Watch Richard speak more about this issue in our Cabot Conversations video on Heatwaves and Health.

Why snow days are becoming increasingly rare in the UK

Posted on December 17, 2020April 4, 2023 by janet.crompton

A snowy start to the day at Watlington station, King’s Lynn. December 18 2009.
Lewis Collard/Wikipedia

Winter frost fairs were common on the frozen River Thames between the 17th and 19th centuries, but they’ve become unimaginable in our lifetime. Over decades and centuries, natural variability in the climate has plunged the UK into sub-zero temperatures from time to time. But global warming is tipping the odds away from the weather we once knew.

These days, people in the UK have become accustomed to much warmer, wetter winters. In fact, winter is warming faster than any other season. This is bad news for those holding out for a white Christmas – the Met Office reports that only four Christmases in over five decades recorded snow at more than 40% of UK weather stations.

Painting of people, tents and horse-drawn carriages on the frozen river.

A frost fair on the River Thames, painted by Thomas Wyke (1683-1684).
Thomas Wyke/Wikipedia

Christmas is a magical day for many, but meteorologically, it’s no different from other winter periods, when snow and ice are also becoming less common. The Met Office definition of a snow day at a given location in the UK is when snow lies on at least 50% of the ground at 9am. Currently, the Cairngorms around Aviemore receive over 70 snow-lying days per year – the most in the UK.

This amount is smaller than in previous decades though. Met Office data shows that, since 1979, the number of snow-lying days has generally decreased by up to five days per decade, and up to ten days per decade in the North Pennines, near Penrith. Around a fifth of the total area of the UK has experienced a significant drop in the prevalence of days with snow lying on the ground.

Two maps of the UK depicting the change in prevalence of snow days throughout the UK from 1971-2019.

Snow days are a rarer occasion in the UK today than they were five decades ago.
Met Office, Author provided

What causes snow days?

Snow days are often the result of a meandering jet stream, the fast-flowing current of air that’s between 9km and 16km above the Earth’s surface. The jet stream normally transports temperate weather from the Atlantic across the UK, but if it’s displaced southwards, it allows persistent high pressure systems of colder air from the north and east, originating in the Arctic or over the Eurasian continent, known as blocking high pressures, to settle over the UK for extended periods.

A number of atmospheric processes can cause the jet stream to meander, but perhaps the most dramatic is when the stratospheric polar vortex, a huge rotating air mass in the middle atmosphere, breaks down. This disruption causes the jet stream to weaken, leading to events such as the infamous 2018 Beast from the East, which brought widespread snowfall to the UK.

The winter of 2018 was not unique in this sense – 2009-2010 and 2013 both brought snowfall because of these dynamic “beasts”. So why is there still a decline in winter snow days in the UK?

The snows of yesteryear

There’s no strong evidence for a long-term trend in polar vortex disruptions, or other atmospheric processes that influence the jet stream. So the fact that people in the UK have fewer snow days to enjoy each year than they did in the past can’t be blamed on the invisible twists and turns above their heads.

But as the concentration of CO₂ in the atmosphere climbs, disruptions that do occur sit on top of increasing background temperatures, reducing the likelihood of the cold spells that bring widespread snowfall. Just as natural climate trends have lowered the severity of winters since the days of the frost fairs, man-made climate change will increasingly keep the UK’s average temperature above zero.

A heavy covering of snow can transform the country and our perception of it. Snow days, with the closures of schools and workplaces that they bring, evoke fond memories and bring out the child in many as hillslopes and parks become sledging highways. More tangibly, in Scotland, the snowsports industry is estimated to be worth over £30 million a year.

But wintry weather can be dangerous too. The cold affects our health, exacerbating heart and lung conditions and the spread of infectious diseases. In extreme cases, heavy snowfall can cause widespread livestock deaths, which happened in Northern Ireland in 2013. The inevitable disruption to travel and businesses can cause economic damage running into billions of pounds, with sectors like the construction industry halted entirely.

While the falling chances of a white Christmas might disappoint many, the current trajectory of less and less snow will at least come as a relief to some.

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This blog is written by Cabot Institute members Dr Alan Thomas Kennedy-Asser, Research Associate in Climate Science, University of Bristol; Dr Dann Mitchell, Met Office Co-Chair in Climate Hazards, University of Bristol, and Dr Eunice Lo, Research Associate in Climate Science, University of Bristol.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Dann Mitchell

Alan Kennedy-Asser

Eunice Lo