Tag Archives: Extreme heat

More people face greater risk from extreme heat

In a hotter world, periods of extreme heat are on the increase. And that presents a massive threat to life and health.

LONDON, 27 August, 2021 − In 2019, extreme heat claimed almost a thousand lives a day worldwide. And that number will grow. If the world cannot limit planetary temperature increase by just 1.5°C by 2100 − a target agreed by 195 countries − then deaths in heat waves will become substantial.

That’s the verdict of a careful study in one of the world’s oldest and most distinguished medical journals, The Lancet, which warns that almost half the world’s population and more than one billion workers are already exposed to episodes of extreme heat: more than a third of those workers already have what the scientists called “negative health effects.”

Helpfully, the researchers list these effects. They include “an increased risk of hyperthermia and cardiovascular failure or collapse, and increased risk of acute kidney disease.”

The researchers also looked at almost 65 million records of causes of death in nine nations to identify at least 17 conditions linked to heat-related death: ischaemic heart disease, stroke, cardiomyopathy and myocarditis, hypertensive heart disease, diabetes, chronic kidney disease, lower respiratory infection and chronic obstructive pulmonary disease.

Homicide, suicide, drowning and unintentional injury also increased with temperature. Yes, in 2019, more people died from extreme cold − an estimated 1.3 million − and 356,000 from extreme heat. But since 1990, cold-related deaths have increased by 31%. Deaths attributable to extreme heat have gone up by 74%.

“Urgent investment in research and measures to combat the risks of extreme heat is critical if society is not only to survive but thrive”

So besides taking global and concerted action to limit global heating to the 1.5°C target set in Paris in 2015, nations will need to start thinking of sustainable ways to keep populations cool in dangerous temperatures.

“Extremely hot days or heat waves that were experienced approximately every 20 years are now being seen more frequently and could even occur every year by the end of the century if current greenhouse gas emissions continue unabated,” said Kristie Ebi, of the University of Washington in the US, who led the study. “These rising temperatures combined with a larger and older population mean that even more people will be at risk for heat-related health effects.”

Extreme heat is on the way. One recent study in Nature Climate Change calculated that, as humans go on putting more and more carbon dioxide into the atmosphere, the number of week-long record-breaking extremes of heat will become between two and seven times more probable by 2050. By 2080, the probability increases by between three and 21 times.

The Lancet study says that steps to limit global heating and to mitigate the impact of heat extremes could save lives: at the same time global numbers are growing, so ever more people are likely to be at risk, especially in crowded cities.

In 1950, the number of urban dwellers was around 751 million. By 2018, this had grown to 4.2 billion. By 2030, six out of every 10 humans will be living in cities and the number of megacities − metropolitan areas with more than 10 million people − will have grown, from 31 in 2016 to 43.

Olympics ruled out

And air conditioning is unlikely to help. Between 1990 and 2016, the volume of carbon dioxide emitted by air conditioning units actually doubled, to make global heating even more intense. In 2019, space cooling systems added up to one billion tonnes of carbon dioxide to the atmosphere: this is 3% of the entire sum of global emissions that year.

Although more frequent, more prolonged and more intense extremes of heat are likely to hit hardest at the poorest, and at outdoor workers in many countries, such extremes will damage national economies and will diminish life for everybody.

By 2085, the researchers warn, very few of the world’s great cities will be able to host the summer Olympic Games because of the risk to athletes. One study in West Australia calculated that by 2070 the number of days on which it might not be safe to undertake even mild physical activity could increase by a factor of eight, or even 50-fold.

“As a result of human activity, it is inevitable that much of the planet’s population will be at greater risk of exposure to extreme heat than they are today,” said Ollie Jay of the University of Sydney in Australia, another of the authors.

“Amid stark projections about the increasing effects of climate change, urgent investment in research and measures to combat the risks of extreme heat is critical if society is not only to survive, but thrive, in a hotter, future world.” − Climate News Network

In a hotter world, periods of extreme heat are on the increase. And that presents a massive threat to life and health.

LONDON, 27 August, 2021 − In 2019, extreme heat claimed almost a thousand lives a day worldwide. And that number will grow. If the world cannot limit planetary temperature increase by just 1.5°C by 2100 − a target agreed by 195 countries − then deaths in heat waves will become substantial.

That’s the verdict of a careful study in one of the world’s oldest and most distinguished medical journals, The Lancet, which warns that almost half the world’s population and more than one billion workers are already exposed to episodes of extreme heat: more than a third of those workers already have what the scientists called “negative health effects.”

Helpfully, the researchers list these effects. They include “an increased risk of hyperthermia and cardiovascular failure or collapse, and increased risk of acute kidney disease.”

The researchers also looked at almost 65 million records of causes of death in nine nations to identify at least 17 conditions linked to heat-related death: ischaemic heart disease, stroke, cardiomyopathy and myocarditis, hypertensive heart disease, diabetes, chronic kidney disease, lower respiratory infection and chronic obstructive pulmonary disease.

Homicide, suicide, drowning and unintentional injury also increased with temperature. Yes, in 2019, more people died from extreme cold − an estimated 1.3 million − and 356,000 from extreme heat. But since 1990, cold-related deaths have increased by 31%. Deaths attributable to extreme heat have gone up by 74%.

“Urgent investment in research and measures to combat the risks of extreme heat is critical if society is not only to survive but thrive”

So besides taking global and concerted action to limit global heating to the 1.5°C target set in Paris in 2015, nations will need to start thinking of sustainable ways to keep populations cool in dangerous temperatures.

“Extremely hot days or heat waves that were experienced approximately every 20 years are now being seen more frequently and could even occur every year by the end of the century if current greenhouse gas emissions continue unabated,” said Kristie Ebi, of the University of Washington in the US, who led the study. “These rising temperatures combined with a larger and older population mean that even more people will be at risk for heat-related health effects.”

Extreme heat is on the way. One recent study in Nature Climate Change calculated that, as humans go on putting more and more carbon dioxide into the atmosphere, the number of week-long record-breaking extremes of heat will become between two and seven times more probable by 2050. By 2080, the probability increases by between three and 21 times.

The Lancet study says that steps to limit global heating and to mitigate the impact of heat extremes could save lives: at the same time global numbers are growing, so ever more people are likely to be at risk, especially in crowded cities.

In 1950, the number of urban dwellers was around 751 million. By 2018, this had grown to 4.2 billion. By 2030, six out of every 10 humans will be living in cities and the number of megacities − metropolitan areas with more than 10 million people − will have grown, from 31 in 2016 to 43.

Olympics ruled out

And air conditioning is unlikely to help. Between 1990 and 2016, the volume of carbon dioxide emitted by air conditioning units actually doubled, to make global heating even more intense. In 2019, space cooling systems added up to one billion tonnes of carbon dioxide to the atmosphere: this is 3% of the entire sum of global emissions that year.

Although more frequent, more prolonged and more intense extremes of heat are likely to hit hardest at the poorest, and at outdoor workers in many countries, such extremes will damage national economies and will diminish life for everybody.

By 2085, the researchers warn, very few of the world’s great cities will be able to host the summer Olympic Games because of the risk to athletes. One study in West Australia calculated that by 2070 the number of days on which it might not be safe to undertake even mild physical activity could increase by a factor of eight, or even 50-fold.

“As a result of human activity, it is inevitable that much of the planet’s population will be at greater risk of exposure to extreme heat than they are today,” said Ollie Jay of the University of Sydney in Australia, another of the authors.

“Amid stark projections about the increasing effects of climate change, urgent investment in research and measures to combat the risks of extreme heat is critical if society is not only to survive, but thrive, in a hotter, future world.” − Climate News Network

Half a billion people may face heat of 56°C by 2100

Take today’s heat, apply mathematical logic and consider a murderously hot future, 56°C by 2100, for hundreds of millions.

LONDON, 29 March, 2021 − Many millions of people − among them some of the world’s poorest − will be exposed to potentially lethal temperatures on a routine basis. At worst, the mercury could reach 56°C by 2100.

Even if the world keeps its most ambitious promise and contains global heating to no more than 1.5°C above the global average normal for most of human history, the future looks distinctly menacing.

And if the world doesn’t quite get there, and annual average temperatures − already 1°C above the historic norm − rise to 2°C, then vast numbers of people in South Asia will find themselves exposed to deadly conditions at least three times as often.

As the researchers make this sober warning in one journal, researchers on the same day in yet another journal make a simple prediction about the cost of ignoring such warnings altogether, to go on burning ever more fossil fuels and destroying ever more tracts of the natural world.

If this happens, then people in the Middle East and North Africa will be hit by a new category of thermal menace: the arrival of super-extreme and ultra-extreme heatwaves.

Target far exceeded

Which means that by the end of this century, more than half a billion people could be exposed to temperatures as high as 56°C, not just for days, but for weeks. The hottest temperature so far ever recorded on Earth was 54°C, in Death Valley, California in 2020.

In 2015, almost all of the world’s nations met in Paris and vowed to contain global heating by the century’s end to “well below” a maximum of 2°C. In fact, the less explicit intention was to contain the mercury’s rise to no higher than 1.5°C.

So much for the vow: the latest evidence is that, on the basis of the national declared intentions so far, global temperatures will rise far higher than the 2°C target. And summer − defined as the hottest 25% of the year − could by the century’s end last almost six months.

A new computational study in Geophysical Research Letters warns that the 1.5°C target could be passed by 2040, in just two decades. And with higher average temperatures over longer periods, there will inevitably be higher than average extremes of temperature, more often, for longer periods, and over wider ranges.

“The need for adaptation over South Asia is today, not in the future. It’s not a choice any more.”

The outcome could be devastating for the countries of South Asia − India and Pakistan, Sri Lanka, Bangladesh and Burma among them − as the thermometer rises and the humidity increases. Researchers have warned for years that at a certain level of heat and humidity − meteorologists call it the “wet bulb” temperature − humans cannot labour productively.

That level is 32°C. At a wet bulb temperature of 35°C, humans cannot expect to survive for long. Some parts of the region have already felt such temperatures with a global average rise of just over 1°C: in 2015, at least 3500 people in Pakistan and India died from causes directly related to extreme heat.

At 1.5°C the consequences could be significantly worse, and at 2°C, the scientists say, the hazard will have been amplified by a factor of 2.7: almost threefold. South Asia could later this century be home to more than two billion people: of the working population, 60% are now engaged in agricultural labour out of doors, and many millions live in crowded cities and in severe poverty. The region should prepare itself for a dangerously hot future.

“The future looks bad for South Asia,” said Moetasim Ashfaq, of the US Oak Ridge National Laboratory, one of the authors, “but the worst can be avoided by containing warming to as low as possible. The need for adaptation over South Asia is today, not in the future. It’s not a choice any more.”

That heat extremes are potentially lethal, that the people of South Asia are potentially at risk, and that an enormous proportion of the planet’s population will be exposed to dangerously high temperatures is not in dispute: the questions now are about the degree of danger, and its extent.

Ultra-extreme heat

Once again, the statisticians have been at work, and the answer in the journal Climate and Atmospheric Science is: it will be much worse, over a vaster region and for a very large number of people in the Middle East and North Africa.

Their calculations suggest that temperatures could reach as high as 56°C, and even more than 60° C in sweltering cities. Such heat extremes could endure for weeks.

So within the lifetimes of those alive today, about half the region’s population − that is, about 600 million people − could face extreme temperatures of around 56°C by 2100 every summer.

The researchers put their message with unusual forthrightness in the headline: “Business-as-usual will lead to super- and ultra-extreme heatwaves in the Middle East and North Africa.” − Climate News Network

Take today’s heat, apply mathematical logic and consider a murderously hot future, 56°C by 2100, for hundreds of millions.

LONDON, 29 March, 2021 − Many millions of people − among them some of the world’s poorest − will be exposed to potentially lethal temperatures on a routine basis. At worst, the mercury could reach 56°C by 2100.

Even if the world keeps its most ambitious promise and contains global heating to no more than 1.5°C above the global average normal for most of human history, the future looks distinctly menacing.

And if the world doesn’t quite get there, and annual average temperatures − already 1°C above the historic norm − rise to 2°C, then vast numbers of people in South Asia will find themselves exposed to deadly conditions at least three times as often.

As the researchers make this sober warning in one journal, researchers on the same day in yet another journal make a simple prediction about the cost of ignoring such warnings altogether, to go on burning ever more fossil fuels and destroying ever more tracts of the natural world.

If this happens, then people in the Middle East and North Africa will be hit by a new category of thermal menace: the arrival of super-extreme and ultra-extreme heatwaves.

Target far exceeded

Which means that by the end of this century, more than half a billion people could be exposed to temperatures as high as 56°C, not just for days, but for weeks. The hottest temperature so far ever recorded on Earth was 54°C, in Death Valley, California in 2020.

In 2015, almost all of the world’s nations met in Paris and vowed to contain global heating by the century’s end to “well below” a maximum of 2°C. In fact, the less explicit intention was to contain the mercury’s rise to no higher than 1.5°C.

So much for the vow: the latest evidence is that, on the basis of the national declared intentions so far, global temperatures will rise far higher than the 2°C target. And summer − defined as the hottest 25% of the year − could by the century’s end last almost six months.

A new computational study in Geophysical Research Letters warns that the 1.5°C target could be passed by 2040, in just two decades. And with higher average temperatures over longer periods, there will inevitably be higher than average extremes of temperature, more often, for longer periods, and over wider ranges.

“The need for adaptation over South Asia is today, not in the future. It’s not a choice any more.”

The outcome could be devastating for the countries of South Asia − India and Pakistan, Sri Lanka, Bangladesh and Burma among them − as the thermometer rises and the humidity increases. Researchers have warned for years that at a certain level of heat and humidity − meteorologists call it the “wet bulb” temperature − humans cannot labour productively.

That level is 32°C. At a wet bulb temperature of 35°C, humans cannot expect to survive for long. Some parts of the region have already felt such temperatures with a global average rise of just over 1°C: in 2015, at least 3500 people in Pakistan and India died from causes directly related to extreme heat.

At 1.5°C the consequences could be significantly worse, and at 2°C, the scientists say, the hazard will have been amplified by a factor of 2.7: almost threefold. South Asia could later this century be home to more than two billion people: of the working population, 60% are now engaged in agricultural labour out of doors, and many millions live in crowded cities and in severe poverty. The region should prepare itself for a dangerously hot future.

“The future looks bad for South Asia,” said Moetasim Ashfaq, of the US Oak Ridge National Laboratory, one of the authors, “but the worst can be avoided by containing warming to as low as possible. The need for adaptation over South Asia is today, not in the future. It’s not a choice any more.”

That heat extremes are potentially lethal, that the people of South Asia are potentially at risk, and that an enormous proportion of the planet’s population will be exposed to dangerously high temperatures is not in dispute: the questions now are about the degree of danger, and its extent.

Ultra-extreme heat

Once again, the statisticians have been at work, and the answer in the journal Climate and Atmospheric Science is: it will be much worse, over a vaster region and for a very large number of people in the Middle East and North Africa.

Their calculations suggest that temperatures could reach as high as 56°C, and even more than 60° C in sweltering cities. Such heat extremes could endure for weeks.

So within the lifetimes of those alive today, about half the region’s population − that is, about 600 million people − could face extreme temperatures of around 56°C by 2100 every summer.

The researchers put their message with unusual forthrightness in the headline: “Business-as-usual will lead to super- and ultra-extreme heatwaves in the Middle East and North Africa.” − Climate News Network

Stockholm heat toll 'doubled in 30 years'

FOR IMMEDIATE RELEASE
Swedish researchers think the changing climate was responsible for doubling the number of heat-related deaths in the capital, Stockholm, in the 30 years from 1980.

LONDON, 23 October – It’s a small sample – just one city, during one 30-year interval – but it could have significance everywhere: deaths from extreme heat doubled in Stockholm, Sweden, between 1980 and 2009 and the agent behind this grim reckoning looks very much like global warming.

Daniel Oudin Åström of Umeå University, Sweden, and colleagues, report in Nature Climate Change that they looked at recent mortality in Stockholm, and then compared the records of deaths with those from 1900-1929.  The period 1980-2009 was marked by northern hemisphere summers with unprecedented extremes of heat – in 2003, 2007, 2010 and 2012 – and in 2010, temperatures in Europe exceeded all 20th and 21st century records.

Stockholm is a city more adapted to cold than heat, more associated with long bleak winters than stifling summers. Sweden is a society with a long history of good record-keeping, but Stockholm in particular is also a city of demographic change and immigration. So the population at risk from extremes of heat in this century cannot be matched very easily with that of a century ago, but Åström and his fellow researchers decided it was worth a try.

They calculated the weeks in which people would have been most at risk – from cold in winter as well as heat in summer – and considered the age groups most likely to suffer and collapse from heat exhaustion and heat stroke or from hypothermia and other winter hazards. They counted 220 extremes of cold at the beginning of the 20th century, and 251 such extremes in the last 30 years. Then they compared the pattern of mortality over the two timespans, and concluded that the extra 31 cold spells accounted for 75 premature deaths.

Then they looked at the high end of the thermometer, and saw a much more dramatic change. In the early 20th century, there were 220 very hot spells. In the most recent period, there were 381 extremes of heat. On this basis, an additional 288 people who died in Stockholm from the effects of heat did so with a 95% probability that climate change was implicated.

Determining the cause

Comparisons like these are very difficult to make. Human life expectancy has increased, and so has overall health care, sanitation and education.  Cities have expanded dramatically in the last 100 years. Motor traffic, street lighting, central heating and air conditioning have all helped make air temperatures in cities so much higher than in the surrounding countryside, where comparative meteorological measurements are normally made.

The Swedish scientists took such changes into account: without such adjustments, their extra death toll would have been 447.  They concluded that heat-related deaths in the last 30 years were twice those to be expected in the period before global warming.

Despite overall warming, and higher than average winter temperatures overall, the frequency of extremes of cold had increased during the same period, with a smaller excess of deaths. And the researchers confirm that they found no evidence that humans had physiologically adapted to a warmer world in the years since global temperatures began to rise.

Scientists make such calculations and then publish them, inviting other researchers to pour cold water on them. In fact, the cold water is coming anyway, according to Andrea Toreti of Justus Liebig University Giessen in Germany and colleagues.

They report in Geophysical Research Letters that as the atmosphere warms, so the air will be able to hold more water vapour, with all the more to fall on rainy days. The researchers took eight high resolution global general circulation models and tried to calculate rainfall extremes for the remainder of the century.

To do that, they took reliable data from the past, and projected the pattern of extremes to 2099. They also divided their projections into three time periods: from 1966 to 2005; from 2020 to 2059; and from 2060 to 2099.

The not very surprising conclusion is that with increasing temperatures, and with more moisture in the air, there will be more rain. But the scientists were looking for extreme events, and conclude that as the century wears on, extreme torrential downpours of the kind that once happened only every 50 years will start to happen every 20 years or so.

In the high latitude northern hemisphere (and that includes Stockholm) the strongest change will be in autumn and spring, where the daily extreme precipitation is expected to increase by 45% and 39% respectively. – Climate News Network

FOR IMMEDIATE RELEASE
Swedish researchers think the changing climate was responsible for doubling the number of heat-related deaths in the capital, Stockholm, in the 30 years from 1980.

LONDON, 23 October – It’s a small sample – just one city, during one 30-year interval – but it could have significance everywhere: deaths from extreme heat doubled in Stockholm, Sweden, between 1980 and 2009 and the agent behind this grim reckoning looks very much like global warming.

Daniel Oudin Åström of Umeå University, Sweden, and colleagues, report in Nature Climate Change that they looked at recent mortality in Stockholm, and then compared the records of deaths with those from 1900-1929.  The period 1980-2009 was marked by northern hemisphere summers with unprecedented extremes of heat – in 2003, 2007, 2010 and 2012 – and in 2010, temperatures in Europe exceeded all 20th and 21st century records.

Stockholm is a city more adapted to cold than heat, more associated with long bleak winters than stifling summers. Sweden is a society with a long history of good record-keeping, but Stockholm in particular is also a city of demographic change and immigration. So the population at risk from extremes of heat in this century cannot be matched very easily with that of a century ago, but Åström and his fellow researchers decided it was worth a try.

They calculated the weeks in which people would have been most at risk – from cold in winter as well as heat in summer – and considered the age groups most likely to suffer and collapse from heat exhaustion and heat stroke or from hypothermia and other winter hazards. They counted 220 extremes of cold at the beginning of the 20th century, and 251 such extremes in the last 30 years. Then they compared the pattern of mortality over the two timespans, and concluded that the extra 31 cold spells accounted for 75 premature deaths.

Then they looked at the high end of the thermometer, and saw a much more dramatic change. In the early 20th century, there were 220 very hot spells. In the most recent period, there were 381 extremes of heat. On this basis, an additional 288 people who died in Stockholm from the effects of heat did so with a 95% probability that climate change was implicated.

Determining the cause

Comparisons like these are very difficult to make. Human life expectancy has increased, and so has overall health care, sanitation and education.  Cities have expanded dramatically in the last 100 years. Motor traffic, street lighting, central heating and air conditioning have all helped make air temperatures in cities so much higher than in the surrounding countryside, where comparative meteorological measurements are normally made.

The Swedish scientists took such changes into account: without such adjustments, their extra death toll would have been 447.  They concluded that heat-related deaths in the last 30 years were twice those to be expected in the period before global warming.

Despite overall warming, and higher than average winter temperatures overall, the frequency of extremes of cold had increased during the same period, with a smaller excess of deaths. And the researchers confirm that they found no evidence that humans had physiologically adapted to a warmer world in the years since global temperatures began to rise.

Scientists make such calculations and then publish them, inviting other researchers to pour cold water on them. In fact, the cold water is coming anyway, according to Andrea Toreti of Justus Liebig University Giessen in Germany and colleagues.

They report in Geophysical Research Letters that as the atmosphere warms, so the air will be able to hold more water vapour, with all the more to fall on rainy days. The researchers took eight high resolution global general circulation models and tried to calculate rainfall extremes for the remainder of the century.

To do that, they took reliable data from the past, and projected the pattern of extremes to 2099. They also divided their projections into three time periods: from 1966 to 2005; from 2020 to 2059; and from 2060 to 2099.

The not very surprising conclusion is that with increasing temperatures, and with more moisture in the air, there will be more rain. But the scientists were looking for extreme events, and conclude that as the century wears on, extreme torrential downpours of the kind that once happened only every 50 years will start to happen every 20 years or so.

In the high latitude northern hemisphere (and that includes Stockholm) the strongest change will be in autumn and spring, where the daily extreme precipitation is expected to increase by 45% and 39% respectively. – Climate News Network

Stockholm heat toll ‘doubled in 30 years’

FOR IMMEDIATE RELEASE Swedish researchers think the changing climate was responsible for doubling the number of heat-related deaths in the capital, Stockholm, in the 30 years from 1980. LONDON, 23 October – It’s a small sample – just one city, during one 30-year interval – but it could have significance everywhere: deaths from extreme heat doubled in Stockholm, Sweden, between 1980 and 2009 and the agent behind this grim reckoning looks very much like global warming. Daniel Oudin Åström of Umeå University, Sweden, and colleagues, report in Nature Climate Change that they looked at recent mortality in Stockholm, and then compared the records of deaths with those from 1900-1929.  The period 1980-2009 was marked by northern hemisphere summers with unprecedented extremes of heat – in 2003, 2007, 2010 and 2012 – and in 2010, temperatures in Europe exceeded all 20th and 21st century records. Stockholm is a city more adapted to cold than heat, more associated with long bleak winters than stifling summers. Sweden is a society with a long history of good record-keeping, but Stockholm in particular is also a city of demographic change and immigration. So the population at risk from extremes of heat in this century cannot be matched very easily with that of a century ago, but Åström and his fellow researchers decided it was worth a try. They calculated the weeks in which people would have been most at risk – from cold in winter as well as heat in summer – and considered the age groups most likely to suffer and collapse from heat exhaustion and heat stroke or from hypothermia and other winter hazards. They counted 220 extremes of cold at the beginning of the 20th century, and 251 such extremes in the last 30 years. Then they compared the pattern of mortality over the two timespans, and concluded that the extra 31 cold spells accounted for 75 premature deaths. Then they looked at the high end of the thermometer, and saw a much more dramatic change. In the early 20th century, there were 220 very hot spells. In the most recent period, there were 381 extremes of heat. On this basis, an additional 288 people who died in Stockholm from the effects of heat did so with a 95% probability that climate change was implicated.

Determining the cause

Comparisons like these are very difficult to make. Human life expectancy has increased, and so has overall health care, sanitation and education.  Cities have expanded dramatically in the last 100 years. Motor traffic, street lighting, central heating and air conditioning have all helped make air temperatures in cities so much higher than in the surrounding countryside, where comparative meteorological measurements are normally made. The Swedish scientists took such changes into account: without such adjustments, their extra death toll would have been 447.  They concluded that heat-related deaths in the last 30 years were twice those to be expected in the period before global warming. Despite overall warming, and higher than average winter temperatures overall, the frequency of extremes of cold had increased during the same period, with a smaller excess of deaths. And the researchers confirm that they found no evidence that humans had physiologically adapted to a warmer world in the years since global temperatures began to rise. Scientists make such calculations and then publish them, inviting other researchers to pour cold water on them. In fact, the cold water is coming anyway, according to Andrea Toreti of Justus Liebig University Giessen in Germany and colleagues. They report in Geophysical Research Letters that as the atmosphere warms, so the air will be able to hold more water vapour, with all the more to fall on rainy days. The researchers took eight high resolution global general circulation models and tried to calculate rainfall extremes for the remainder of the century. To do that, they took reliable data from the past, and projected the pattern of extremes to 2099. They also divided their projections into three time periods: from 1966 to 2005; from 2020 to 2059; and from 2060 to 2099. The not very surprising conclusion is that with increasing temperatures, and with more moisture in the air, there will be more rain. But the scientists were looking for extreme events, and conclude that as the century wears on, extreme torrential downpours of the kind that once happened only every 50 years will start to happen every 20 years or so. In the high latitude northern hemisphere (and that includes Stockholm) the strongest change will be in autumn and spring, where the daily extreme precipitation is expected to increase by 45% and 39% respectively. – Climate News Network

FOR IMMEDIATE RELEASE Swedish researchers think the changing climate was responsible for doubling the number of heat-related deaths in the capital, Stockholm, in the 30 years from 1980. LONDON, 23 October – It’s a small sample – just one city, during one 30-year interval – but it could have significance everywhere: deaths from extreme heat doubled in Stockholm, Sweden, between 1980 and 2009 and the agent behind this grim reckoning looks very much like global warming. Daniel Oudin Åström of Umeå University, Sweden, and colleagues, report in Nature Climate Change that they looked at recent mortality in Stockholm, and then compared the records of deaths with those from 1900-1929.  The period 1980-2009 was marked by northern hemisphere summers with unprecedented extremes of heat – in 2003, 2007, 2010 and 2012 – and in 2010, temperatures in Europe exceeded all 20th and 21st century records. Stockholm is a city more adapted to cold than heat, more associated with long bleak winters than stifling summers. Sweden is a society with a long history of good record-keeping, but Stockholm in particular is also a city of demographic change and immigration. So the population at risk from extremes of heat in this century cannot be matched very easily with that of a century ago, but Åström and his fellow researchers decided it was worth a try. They calculated the weeks in which people would have been most at risk – from cold in winter as well as heat in summer – and considered the age groups most likely to suffer and collapse from heat exhaustion and heat stroke or from hypothermia and other winter hazards. They counted 220 extremes of cold at the beginning of the 20th century, and 251 such extremes in the last 30 years. Then they compared the pattern of mortality over the two timespans, and concluded that the extra 31 cold spells accounted for 75 premature deaths. Then they looked at the high end of the thermometer, and saw a much more dramatic change. In the early 20th century, there were 220 very hot spells. In the most recent period, there were 381 extremes of heat. On this basis, an additional 288 people who died in Stockholm from the effects of heat did so with a 95% probability that climate change was implicated.

Determining the cause

Comparisons like these are very difficult to make. Human life expectancy has increased, and so has overall health care, sanitation and education.  Cities have expanded dramatically in the last 100 years. Motor traffic, street lighting, central heating and air conditioning have all helped make air temperatures in cities so much higher than in the surrounding countryside, where comparative meteorological measurements are normally made. The Swedish scientists took such changes into account: without such adjustments, their extra death toll would have been 447.  They concluded that heat-related deaths in the last 30 years were twice those to be expected in the period before global warming. Despite overall warming, and higher than average winter temperatures overall, the frequency of extremes of cold had increased during the same period, with a smaller excess of deaths. And the researchers confirm that they found no evidence that humans had physiologically adapted to a warmer world in the years since global temperatures began to rise. Scientists make such calculations and then publish them, inviting other researchers to pour cold water on them. In fact, the cold water is coming anyway, according to Andrea Toreti of Justus Liebig University Giessen in Germany and colleagues. They report in Geophysical Research Letters that as the atmosphere warms, so the air will be able to hold more water vapour, with all the more to fall on rainy days. The researchers took eight high resolution global general circulation models and tried to calculate rainfall extremes for the remainder of the century. To do that, they took reliable data from the past, and projected the pattern of extremes to 2099. They also divided their projections into three time periods: from 1966 to 2005; from 2020 to 2059; and from 2060 to 2099. The not very surprising conclusion is that with increasing temperatures, and with more moisture in the air, there will be more rain. But the scientists were looking for extreme events, and conclude that as the century wears on, extreme torrential downpours of the kind that once happened only every 50 years will start to happen every 20 years or so. In the high latitude northern hemisphere (and that includes Stockholm) the strongest change will be in autumn and spring, where the daily extreme precipitation is expected to increase by 45% and 39% respectively. – Climate News Network