Tag Archives: Heatwaves

Human activities 'caused record Oz heat'

FOR IMMEDIATE RELEASE
Australia’s 2013 summer was the hottest on record only because of human influences on the climate,  meteorologists say. They report that people’s activities raised the likelihood of a record by about five times.

LONDON, 24 March – Australian researchers are in no doubt about what happened there last year. The country’s Bureau of Meteorology is a model of clarity: “2013 was Australia’s warmest year on record. Persistent and widespread warmth throughout the year led to record-breaking temperatures and several severe bushfires. Nationally-averaged rainfall was slightly below average.”

Now two Australian scientists say it is virtually certain that no records would have been broken had it not been for the influence on the climate of humans. They even put a figure on it: people, they say, raised the stakes about five times.

The World Meteorological Organization devotes a section in its report, WMO statement on the status of the global climate in 2013, to the scientists’ peer-reviewed case study, undertaken by a team at the ARC Centre of Excellence for Climate System Science at the University of Melbourne. It was adapted from an article originally published in the journal Geophysical Research Letters,

The study used nine global climate models to investigate whether changes in the probability of extreme Australian summer temperatures were due to human influences.

More frequent extremes ahead

It concluded: “Comparing climate model simulations with and without human factors shows that the record hot Australian summer of 2012/13 was about five times as likely as a result of human-induced influence on climate, and that the record hot calendar year of 2013 would have been virtually impossible without human contributions of heat-trapping gases, illustrating that some extreme events are becoming much more likely due to climate change.”

The report also strikes a warning note: “These types of extreme Australian summers become even more frequent in simulations of the future under further global warming.”.

It says last year was notable as well because it was marked by what scientists call “neutral to weak La Niña ENSO conditions”, which would normally be expected to produce cooler temperatures across Australia, not hotter. El Niño is characterized by unusually warm temperatures and La Niña by unusually cool ones in the equatorial Pacific.

Before 2013 six of the eight hottest Australian summers occurred during El Niño years. The WMO says natural ENSO variations are very unlikely to explain the record 2013 Australian heat.

“There is no standstill in global warming…The laws of physics are non-negotiable”

Introducng the report the WMO secretary-general, Michel Jarraud, said many of the extreme events of 2013 were consistent with what we would expect as a result of human-induced climate change. And he repeated his insistence that claims of a pause in climate change were mistaken.

There is no standstill in global warming. The warming of our oceans has accelerated, and at lower depths. More than 90% of the excess energy trapped by greenhouse gases is stored in the oceans.

“Levels of these greenhouse gases are at record levels, meaning that our atmosphere and oceans will continue to warm for centuries to come. The laws of physics are non-negotiable.”

The report says 13 of the 14 warmest years on record have all occurred during this century, and each of the last three decades has been warmer than the previous one, culminating with 2001-2010 as the warmest decade on record. It confirms that 2013 tied with 2007 as the sixth warmest year on record, continuing the long-term global warming trend.

Temperatures in many parts of the southern hemisphere were especially warm, and Australia was not the only country to feel the impact: Argentina had its second hottest year on record.- Climate News Network

FOR IMMEDIATE RELEASE
Australia’s 2013 summer was the hottest on record only because of human influences on the climate,  meteorologists say. They report that people’s activities raised the likelihood of a record by about five times.

LONDON, 24 March – Australian researchers are in no doubt about what happened there last year. The country’s Bureau of Meteorology is a model of clarity: “2013 was Australia’s warmest year on record. Persistent and widespread warmth throughout the year led to record-breaking temperatures and several severe bushfires. Nationally-averaged rainfall was slightly below average.”

Now two Australian scientists say it is virtually certain that no records would have been broken had it not been for the influence on the climate of humans. They even put a figure on it: people, they say, raised the stakes about five times.

The World Meteorological Organization devotes a section in its report, WMO statement on the status of the global climate in 2013, to the scientists’ peer-reviewed case study, undertaken by a team at the ARC Centre of Excellence for Climate System Science at the University of Melbourne. It was adapted from an article originally published in the journal Geophysical Research Letters,

The study used nine global climate models to investigate whether changes in the probability of extreme Australian summer temperatures were due to human influences.

More frequent extremes ahead

It concluded: “Comparing climate model simulations with and without human factors shows that the record hot Australian summer of 2012/13 was about five times as likely as a result of human-induced influence on climate, and that the record hot calendar year of 2013 would have been virtually impossible without human contributions of heat-trapping gases, illustrating that some extreme events are becoming much more likely due to climate change.”

The report also strikes a warning note: “These types of extreme Australian summers become even more frequent in simulations of the future under further global warming.”.

It says last year was notable as well because it was marked by what scientists call “neutral to weak La Niña ENSO conditions”, which would normally be expected to produce cooler temperatures across Australia, not hotter. El Niño is characterized by unusually warm temperatures and La Niña by unusually cool ones in the equatorial Pacific.

Before 2013 six of the eight hottest Australian summers occurred during El Niño years. The WMO says natural ENSO variations are very unlikely to explain the record 2013 Australian heat.

“There is no standstill in global warming…The laws of physics are non-negotiable”

Introducng the report the WMO secretary-general, Michel Jarraud, said many of the extreme events of 2013 were consistent with what we would expect as a result of human-induced climate change. And he repeated his insistence that claims of a pause in climate change were mistaken.

There is no standstill in global warming. The warming of our oceans has accelerated, and at lower depths. More than 90% of the excess energy trapped by greenhouse gases is stored in the oceans.

“Levels of these greenhouse gases are at record levels, meaning that our atmosphere and oceans will continue to warm for centuries to come. The laws of physics are non-negotiable.”

The report says 13 of the 14 warmest years on record have all occurred during this century, and each of the last three decades has been warmer than the previous one, culminating with 2001-2010 as the warmest decade on record. It confirms that 2013 tied with 2007 as the sixth warmest year on record, continuing the long-term global warming trend.

Temperatures in many parts of the southern hemisphere were especially warm, and Australia was not the only country to feel the impact: Argentina had its second hottest year on record.- Climate News Network

Human activities ’caused record Oz heat’

FOR IMMEDIATE RELEASE Australia’s 2013 summer was the hottest on record only because of human influences on the climate,  meteorologists say. They report that people’s activities raised the likelihood of a record by about five times. LONDON, 24 March – Australian researchers are in no doubt about what happened there last year. The country’s Bureau of Meteorology is a model of clarity: “2013 was Australia’s warmest year on record. Persistent and widespread warmth throughout the year led to record-breaking temperatures and several severe bushfires. Nationally-averaged rainfall was slightly below average.” Now two Australian scientists say it is virtually certain that no records would have been broken had it not been for the influence on the climate of humans. They even put a figure on it: people, they say, raised the stakes about five times. The World Meteorological Organization devotes a section in its report, WMO statement on the status of the global climate in 2013, to the scientists’ peer-reviewed case study, undertaken by a team at the ARC Centre of Excellence for Climate System Science at the University of Melbourne. It was adapted from an article originally published in the journal Geophysical Research Letters, The study used nine global climate models to investigate whether changes in the probability of extreme Australian summer temperatures were due to human influences.

More frequent extremes ahead

It concluded: “Comparing climate model simulations with and without human factors shows that the record hot Australian summer of 2012/13 was about five times as likely as a result of human-induced influence on climate, and that the record hot calendar year of 2013 would have been virtually impossible without human contributions of heat-trapping gases, illustrating that some extreme events are becoming much more likely due to climate change.” The report also strikes a warning note: “These types of extreme Australian summers become even more frequent in simulations of the future under further global warming.”. It says last year was notable as well because it was marked by what scientists call “neutral to weak La Niña ENSO conditions”, which would normally be expected to produce cooler temperatures across Australia, not hotter. El Niño is characterized by unusually warm temperatures and La Niña by unusually cool ones in the equatorial Pacific. Before 2013 six of the eight hottest Australian summers occurred during El Niño years. The WMO says natural ENSO variations are very unlikely to explain the record 2013 Australian heat.

“There is no standstill in global warming…The laws of physics are non-negotiable”

Introducng the report the WMO secretary-general, Michel Jarraud, said many of the extreme events of 2013 were consistent with what we would expect as a result of human-induced climate change. And he repeated his insistence that claims of a pause in climate change were mistaken. “There is no standstill in global warming. The warming of our oceans has accelerated, and at lower depths. More than 90% of the excess energy trapped by greenhouse gases is stored in the oceans. “Levels of these greenhouse gases are at record levels, meaning that our atmosphere and oceans will continue to warm for centuries to come. The laws of physics are non-negotiable.” The report says 13 of the 14 warmest years on record have all occurred during this century, and each of the last three decades has been warmer than the previous one, culminating with 2001-2010 as the warmest decade on record. It confirms that 2013 tied with 2007 as the sixth warmest year on record, continuing the long-term global warming trend. Temperatures in many parts of the southern hemisphere were especially warm, and Australia was not the only country to feel the impact: Argentina had its second hottest year on record.- Climate News Network

FOR IMMEDIATE RELEASE Australia’s 2013 summer was the hottest on record only because of human influences on the climate,  meteorologists say. They report that people’s activities raised the likelihood of a record by about five times. LONDON, 24 March – Australian researchers are in no doubt about what happened there last year. The country’s Bureau of Meteorology is a model of clarity: “2013 was Australia’s warmest year on record. Persistent and widespread warmth throughout the year led to record-breaking temperatures and several severe bushfires. Nationally-averaged rainfall was slightly below average.” Now two Australian scientists say it is virtually certain that no records would have been broken had it not been for the influence on the climate of humans. They even put a figure on it: people, they say, raised the stakes about five times. The World Meteorological Organization devotes a section in its report, WMO statement on the status of the global climate in 2013, to the scientists’ peer-reviewed case study, undertaken by a team at the ARC Centre of Excellence for Climate System Science at the University of Melbourne. It was adapted from an article originally published in the journal Geophysical Research Letters, The study used nine global climate models to investigate whether changes in the probability of extreme Australian summer temperatures were due to human influences.

More frequent extremes ahead

It concluded: “Comparing climate model simulations with and without human factors shows that the record hot Australian summer of 2012/13 was about five times as likely as a result of human-induced influence on climate, and that the record hot calendar year of 2013 would have been virtually impossible without human contributions of heat-trapping gases, illustrating that some extreme events are becoming much more likely due to climate change.” The report also strikes a warning note: “These types of extreme Australian summers become even more frequent in simulations of the future under further global warming.”. It says last year was notable as well because it was marked by what scientists call “neutral to weak La Niña ENSO conditions”, which would normally be expected to produce cooler temperatures across Australia, not hotter. El Niño is characterized by unusually warm temperatures and La Niña by unusually cool ones in the equatorial Pacific. Before 2013 six of the eight hottest Australian summers occurred during El Niño years. The WMO says natural ENSO variations are very unlikely to explain the record 2013 Australian heat.

“There is no standstill in global warming…The laws of physics are non-negotiable”

Introducng the report the WMO secretary-general, Michel Jarraud, said many of the extreme events of 2013 were consistent with what we would expect as a result of human-induced climate change. And he repeated his insistence that claims of a pause in climate change were mistaken. “There is no standstill in global warming. The warming of our oceans has accelerated, and at lower depths. More than 90% of the excess energy trapped by greenhouse gases is stored in the oceans. “Levels of these greenhouse gases are at record levels, meaning that our atmosphere and oceans will continue to warm for centuries to come. The laws of physics are non-negotiable.” The report says 13 of the 14 warmest years on record have all occurred during this century, and each of the last three decades has been warmer than the previous one, culminating with 2001-2010 as the warmest decade on record. It confirms that 2013 tied with 2007 as the sixth warmest year on record, continuing the long-term global warming trend. Temperatures in many parts of the southern hemisphere were especially warm, and Australia was not the only country to feel the impact: Argentina had its second hottest year on record.- Climate News Network

More heatwaves by 2020 'almost certain'

EMBARGOED until 2301 GMT on Wednesday 14 August
European climate scientists say the greenhouse gases already in the atmosphere mean it is virtually inevitable that far more parts of the world will experience more frequent and severe heat waves in the next 30 years.

LONDON, 15 August – Stand by for extreme weather. Prepare for heat waves on a scale that was once unprecedented. For once, there are no “ifs” in the forecast, no caveats about modelling business-as-usual-scenarios rather than dramatic reductions of emissions for near-term warming

Even if governments abandon fossil fuels everywhere, immediately, and invest only in green energy, there will be new record temperatures. The greenhouse gas emissions of the last few decades now mean that regions of the planet subjected to extreme heat will double by 2020 and quadruple by 2040.

Dim Coumou of the Potsdam Institute for Climate Impact Research in Germany and a colleague from Madrid in Spain make this prediction in Environmental Research Letters. In essence, they are only pointing out that the unprecedented heat waves that have already been recorded this century in Australia, the US, Russia, Greece and so on will increase in frequency and extent and in degrees Celsius.

They have followed the mathematical logic of climate models and simple thermodynamics. Extra greenhouse gas already in the atmosphere has pushed up global average temperatures. But an average is only the sum of all the extremes divided by the days in the year.

And as average temperatures rise in response to carbon dioxide levels, so will the extremes. And their forecast says the second half of the century will be even worse – unless global greenhouse emissions are reduced substantially.

“In many regions, the coldest summer months by the end of the century will be hotter than the hottest experienced today –  that’s what our calculations show for a scenario of unabated climate change. We would enter a new climatic regime”, said Dr Coumou.

A done deal

Such warnings are not new: the World Meteorological Organisation made similar predictions in July, and the first years of this century have been marked by dramatic spells of record-breaking heat. In Russia in 2010, for instance, the temperature in July went up by 7°C to a daily peak of 40°C in Moscow.

Right now, 5% of the land area of the planet has experienced heat extremes, that is, temperatures far beyond the normal for summer at that latitude: temperatures that spell out deaths from heat stroke or heat exhaustion, harvest loss, devastating drought and forest fires.

By 2020 the area at risk will reach 10%, and by 2040, one fifth of the land area of the planet will be experiencing extreme temperatures at some point in the summer, just because of the extra energy already in the planetary system. “There’s already so much greenhouse gas in the atmosphere today that the near-term increase of heat extremes seems to be almost inevitable”, says Coumou.

The researchers combined the results from a comprehensive set of climate models, and used them to predict not only the next 30 years but the past as well.

“We show that these simulations capture the observed rise in heat extremes over the past 50 years very well”, said Alex Robinson of the University Complutense in Madrid. “This makes us confident that they are able to robustly indicate what is to be expected in future.”

But, on the same day, another study of climate extremes suggests that heat waves could actually make things even worse. A team of 18 European scientists led by Markus Reichstein of the Max-Planck Institute for Biogeochemistry in Jena in Germany reports in Nature that extreme weather events could actually lead to more carbon dioxide in the atmosphere, starting a vicious cycle of feedback.

In normal climatic conditions, plants absorb carbon dioxide and lock much of it away. In abnormal conditions, the response could be the reverse: forest fires, for instance, would release huge volumes of carbon dioxide. Drought, too, would constrain any plant growth.

Increasing frequency

The researchers calculate that because of extreme events that already occur, terrestrial ecosystems – forests, marshes, mangrove swamps, grasslands and so on – absorb around 11 billion tons of carbon dioxide less than they would if there were no extremes.

This time, they weren’t working just with simulations. They pored over satellite images from 1982 to 2011 to work out how much biomass a particular ecosystem accumulated during or after an extreme weather event.

They also used data from a global network of recording stations that samples the air above forest canopies to check their figures, and came to the total of 11 billion tons. “That is roughly equivalent to the amount of carbon dioxide sequestered in terrestrial environments every year”, said Dr Reichstein.  “It is therefore by no means negligible.”

Such a finding is tentative, because extremes of some kind must occur, no matter how stable the climate, and so the “normal” pattern of events is difficult to determine. In the stilted language of science, the researchers point out that the effect of fires, drought and baking heat on carbon stores and the flow of greenhouse gases is “non-linear.” That means that a small change in average temperatures can have dramatic effects.

The next step is to investigate the ways that ecosystems respond to events. Experiments so far have measured responses only to so-called “once a century” events.

“We should also take account of events which so far have happened once in 1,000 years or even 10,000 years”, said Michael Bahn from the University of Innsbruck, “because they are likely to become much more frequent by the end of this century.” – Climate News Network

EMBARGOED until 2301 GMT on Wednesday 14 August
European climate scientists say the greenhouse gases already in the atmosphere mean it is virtually inevitable that far more parts of the world will experience more frequent and severe heat waves in the next 30 years.

LONDON, 15 August – Stand by for extreme weather. Prepare for heat waves on a scale that was once unprecedented. For once, there are no “ifs” in the forecast, no caveats about modelling business-as-usual-scenarios rather than dramatic reductions of emissions for near-term warming

Even if governments abandon fossil fuels everywhere, immediately, and invest only in green energy, there will be new record temperatures. The greenhouse gas emissions of the last few decades now mean that regions of the planet subjected to extreme heat will double by 2020 and quadruple by 2040.

Dim Coumou of the Potsdam Institute for Climate Impact Research in Germany and a colleague from Madrid in Spain make this prediction in Environmental Research Letters. In essence, they are only pointing out that the unprecedented heat waves that have already been recorded this century in Australia, the US, Russia, Greece and so on will increase in frequency and extent and in degrees Celsius.

They have followed the mathematical logic of climate models and simple thermodynamics. Extra greenhouse gas already in the atmosphere has pushed up global average temperatures. But an average is only the sum of all the extremes divided by the days in the year.

And as average temperatures rise in response to carbon dioxide levels, so will the extremes. And their forecast says the second half of the century will be even worse – unless global greenhouse emissions are reduced substantially.

“In many regions, the coldest summer months by the end of the century will be hotter than the hottest experienced today –  that’s what our calculations show for a scenario of unabated climate change. We would enter a new climatic regime”, said Dr Coumou.

A done deal

Such warnings are not new: the World Meteorological Organisation made similar predictions in July, and the first years of this century have been marked by dramatic spells of record-breaking heat. In Russia in 2010, for instance, the temperature in July went up by 7°C to a daily peak of 40°C in Moscow.

Right now, 5% of the land area of the planet has experienced heat extremes, that is, temperatures far beyond the normal for summer at that latitude: temperatures that spell out deaths from heat stroke or heat exhaustion, harvest loss, devastating drought and forest fires.

By 2020 the area at risk will reach 10%, and by 2040, one fifth of the land area of the planet will be experiencing extreme temperatures at some point in the summer, just because of the extra energy already in the planetary system. “There’s already so much greenhouse gas in the atmosphere today that the near-term increase of heat extremes seems to be almost inevitable”, says Coumou.

The researchers combined the results from a comprehensive set of climate models, and used them to predict not only the next 30 years but the past as well.

“We show that these simulations capture the observed rise in heat extremes over the past 50 years very well”, said Alex Robinson of the University Complutense in Madrid. “This makes us confident that they are able to robustly indicate what is to be expected in future.”

But, on the same day, another study of climate extremes suggests that heat waves could actually make things even worse. A team of 18 European scientists led by Markus Reichstein of the Max-Planck Institute for Biogeochemistry in Jena in Germany reports in Nature that extreme weather events could actually lead to more carbon dioxide in the atmosphere, starting a vicious cycle of feedback.

In normal climatic conditions, plants absorb carbon dioxide and lock much of it away. In abnormal conditions, the response could be the reverse: forest fires, for instance, would release huge volumes of carbon dioxide. Drought, too, would constrain any plant growth.

Increasing frequency

The researchers calculate that because of extreme events that already occur, terrestrial ecosystems – forests, marshes, mangrove swamps, grasslands and so on – absorb around 11 billion tons of carbon dioxide less than they would if there were no extremes.

This time, they weren’t working just with simulations. They pored over satellite images from 1982 to 2011 to work out how much biomass a particular ecosystem accumulated during or after an extreme weather event.

They also used data from a global network of recording stations that samples the air above forest canopies to check their figures, and came to the total of 11 billion tons. “That is roughly equivalent to the amount of carbon dioxide sequestered in terrestrial environments every year”, said Dr Reichstein.  “It is therefore by no means negligible.”

Such a finding is tentative, because extremes of some kind must occur, no matter how stable the climate, and so the “normal” pattern of events is difficult to determine. In the stilted language of science, the researchers point out that the effect of fires, drought and baking heat on carbon stores and the flow of greenhouse gases is “non-linear.” That means that a small change in average temperatures can have dramatic effects.

The next step is to investigate the ways that ecosystems respond to events. Experiments so far have measured responses only to so-called “once a century” events.

“We should also take account of events which so far have happened once in 1,000 years or even 10,000 years”, said Michael Bahn from the University of Innsbruck, “because they are likely to become much more frequent by the end of this century.” – Climate News Network

More heatwaves by 2020 ‘almost certain’

EMBARGOED until 2301 GMT on Wednesday 14 August European climate scientists say the greenhouse gases already in the atmosphere mean it is virtually inevitable that far more parts of the world will experience more frequent and severe heat waves in the next 30 years. LONDON, 15 August – Stand by for extreme weather. Prepare for heat waves on a scale that was once unprecedented. For once, there are no “ifs” in the forecast, no caveats about modelling business-as-usual-scenarios rather than dramatic reductions of emissions for near-term warming Even if governments abandon fossil fuels everywhere, immediately, and invest only in green energy, there will be new record temperatures. The greenhouse gas emissions of the last few decades now mean that regions of the planet subjected to extreme heat will double by 2020 and quadruple by 2040. Dim Coumou of the Potsdam Institute for Climate Impact Research in Germany and a colleague from Madrid in Spain make this prediction in Environmental Research Letters. In essence, they are only pointing out that the unprecedented heat waves that have already been recorded this century in Australia, the US, Russia, Greece and so on will increase in frequency and extent and in degrees Celsius. They have followed the mathematical logic of climate models and simple thermodynamics. Extra greenhouse gas already in the atmosphere has pushed up global average temperatures. But an average is only the sum of all the extremes divided by the days in the year. And as average temperatures rise in response to carbon dioxide levels, so will the extremes. And their forecast says the second half of the century will be even worse – unless global greenhouse emissions are reduced substantially. “In many regions, the coldest summer months by the end of the century will be hotter than the hottest experienced today –  that’s what our calculations show for a scenario of unabated climate change. We would enter a new climatic regime”, said Dr Coumou.

A done deal

Such warnings are not new: the World Meteorological Organisation made similar predictions in July, and the first years of this century have been marked by dramatic spells of record-breaking heat. In Russia in 2010, for instance, the temperature in July went up by 7°C to a daily peak of 40°C in Moscow. Right now, 5% of the land area of the planet has experienced heat extremes, that is, temperatures far beyond the normal for summer at that latitude: temperatures that spell out deaths from heat stroke or heat exhaustion, harvest loss, devastating drought and forest fires. By 2020 the area at risk will reach 10%, and by 2040, one fifth of the land area of the planet will be experiencing extreme temperatures at some point in the summer, just because of the extra energy already in the planetary system. “There’s already so much greenhouse gas in the atmosphere today that the near-term increase of heat extremes seems to be almost inevitable”, says Coumou. The researchers combined the results from a comprehensive set of climate models, and used them to predict not only the next 30 years but the past as well. “We show that these simulations capture the observed rise in heat extremes over the past 50 years very well”, said Alex Robinson of the University Complutense in Madrid. “This makes us confident that they are able to robustly indicate what is to be expected in future.” But, on the same day, another study of climate extremes suggests that heat waves could actually make things even worse. A team of 18 European scientists led by Markus Reichstein of the Max-Planck Institute for Biogeochemistry in Jena in Germany reports in Nature that extreme weather events could actually lead to more carbon dioxide in the atmosphere, starting a vicious cycle of feedback. In normal climatic conditions, plants absorb carbon dioxide and lock much of it away. In abnormal conditions, the response could be the reverse: forest fires, for instance, would release huge volumes of carbon dioxide. Drought, too, would constrain any plant growth.

Increasing frequency

The researchers calculate that because of extreme events that already occur, terrestrial ecosystems – forests, marshes, mangrove swamps, grasslands and so on – absorb around 11 billion tons of carbon dioxide less than they would if there were no extremes. This time, they weren’t working just with simulations. They pored over satellite images from 1982 to 2011 to work out how much biomass a particular ecosystem accumulated during or after an extreme weather event. They also used data from a global network of recording stations that samples the air above forest canopies to check their figures, and came to the total of 11 billion tons. “That is roughly equivalent to the amount of carbon dioxide sequestered in terrestrial environments every year”, said Dr Reichstein.  “It is therefore by no means negligible.” Such a finding is tentative, because extremes of some kind must occur, no matter how stable the climate, and so the “normal” pattern of events is difficult to determine. In the stilted language of science, the researchers point out that the effect of fires, drought and baking heat on carbon stores and the flow of greenhouse gases is “non-linear.” That means that a small change in average temperatures can have dramatic effects. The next step is to investigate the ways that ecosystems respond to events. Experiments so far have measured responses only to so-called “once a century” events. “We should also take account of events which so far have happened once in 1,000 years or even 10,000 years”, said Michael Bahn from the University of Innsbruck, “because they are likely to become much more frequent by the end of this century.” – Climate News Network

EMBARGOED until 2301 GMT on Wednesday 14 August European climate scientists say the greenhouse gases already in the atmosphere mean it is virtually inevitable that far more parts of the world will experience more frequent and severe heat waves in the next 30 years. LONDON, 15 August – Stand by for extreme weather. Prepare for heat waves on a scale that was once unprecedented. For once, there are no “ifs” in the forecast, no caveats about modelling business-as-usual-scenarios rather than dramatic reductions of emissions for near-term warming Even if governments abandon fossil fuels everywhere, immediately, and invest only in green energy, there will be new record temperatures. The greenhouse gas emissions of the last few decades now mean that regions of the planet subjected to extreme heat will double by 2020 and quadruple by 2040. Dim Coumou of the Potsdam Institute for Climate Impact Research in Germany and a colleague from Madrid in Spain make this prediction in Environmental Research Letters. In essence, they are only pointing out that the unprecedented heat waves that have already been recorded this century in Australia, the US, Russia, Greece and so on will increase in frequency and extent and in degrees Celsius. They have followed the mathematical logic of climate models and simple thermodynamics. Extra greenhouse gas already in the atmosphere has pushed up global average temperatures. But an average is only the sum of all the extremes divided by the days in the year. And as average temperatures rise in response to carbon dioxide levels, so will the extremes. And their forecast says the second half of the century will be even worse – unless global greenhouse emissions are reduced substantially. “In many regions, the coldest summer months by the end of the century will be hotter than the hottest experienced today –  that’s what our calculations show for a scenario of unabated climate change. We would enter a new climatic regime”, said Dr Coumou.

A done deal

Such warnings are not new: the World Meteorological Organisation made similar predictions in July, and the first years of this century have been marked by dramatic spells of record-breaking heat. In Russia in 2010, for instance, the temperature in July went up by 7°C to a daily peak of 40°C in Moscow. Right now, 5% of the land area of the planet has experienced heat extremes, that is, temperatures far beyond the normal for summer at that latitude: temperatures that spell out deaths from heat stroke or heat exhaustion, harvest loss, devastating drought and forest fires. By 2020 the area at risk will reach 10%, and by 2040, one fifth of the land area of the planet will be experiencing extreme temperatures at some point in the summer, just because of the extra energy already in the planetary system. “There’s already so much greenhouse gas in the atmosphere today that the near-term increase of heat extremes seems to be almost inevitable”, says Coumou. The researchers combined the results from a comprehensive set of climate models, and used them to predict not only the next 30 years but the past as well. “We show that these simulations capture the observed rise in heat extremes over the past 50 years very well”, said Alex Robinson of the University Complutense in Madrid. “This makes us confident that they are able to robustly indicate what is to be expected in future.” But, on the same day, another study of climate extremes suggests that heat waves could actually make things even worse. A team of 18 European scientists led by Markus Reichstein of the Max-Planck Institute for Biogeochemistry in Jena in Germany reports in Nature that extreme weather events could actually lead to more carbon dioxide in the atmosphere, starting a vicious cycle of feedback. In normal climatic conditions, plants absorb carbon dioxide and lock much of it away. In abnormal conditions, the response could be the reverse: forest fires, for instance, would release huge volumes of carbon dioxide. Drought, too, would constrain any plant growth.

Increasing frequency

The researchers calculate that because of extreme events that already occur, terrestrial ecosystems – forests, marshes, mangrove swamps, grasslands and so on – absorb around 11 billion tons of carbon dioxide less than they would if there were no extremes. This time, they weren’t working just with simulations. They pored over satellite images from 1982 to 2011 to work out how much biomass a particular ecosystem accumulated during or after an extreme weather event. They also used data from a global network of recording stations that samples the air above forest canopies to check their figures, and came to the total of 11 billion tons. “That is roughly equivalent to the amount of carbon dioxide sequestered in terrestrial environments every year”, said Dr Reichstein.  “It is therefore by no means negligible.” Such a finding is tentative, because extremes of some kind must occur, no matter how stable the climate, and so the “normal” pattern of events is difficult to determine. In the stilted language of science, the researchers point out that the effect of fires, drought and baking heat on carbon stores and the flow of greenhouse gases is “non-linear.” That means that a small change in average temperatures can have dramatic effects. The next step is to investigate the ways that ecosystems respond to events. Experiments so far have measured responses only to so-called “once a century” events. “We should also take account of events which so far have happened once in 1,000 years or even 10,000 years”, said Michael Bahn from the University of Innsbruck, “because they are likely to become much more frequent by the end of this century.” – Climate News Network