Tag Archives: Climate sensitivity

Warming bad for life in freshwater lakes and rivers

For immediate release On both sides of the Atlantic scientists studying lakes have discovered they are warming – and this is bad news both for water quality and the fish. London, 14 June – The Alpine lakes of Austria are warming up. By 2050, their surface waters could be up to 3°C warmer, according to new research in the journal Hydrobiologia. Martin Dokulil of the Institute for Limnology at the University of Innsbruck studied data from nine lakes larger than 10km2. The largest, Bodensee or Lake Constance, touches Austria’s border with Germany and Switzerland to the west; 800 kms to the east, Neusiedler See borders Germany and Hungary. The nine lakes range from 254 to 1.8 metres maximum depth and they are vital to Austria’s tourist industry: they play powerful roles in the Alpine ecosystem and they are of course reservoirs of water. But the Alpine valleys are warming: between 1980 and 1999 the region warmed at three times the global average and by 2050 the median temperatures for the region could have risen by 3.5°C. The challenge has been to anticipate the impact of global warming on the lakes. “The predicted changes in surface water temperatures will affect the thermal characteristics of the lakes,” says Dr Dokulil. “Warmer water temperatures could lead to enhanced nutrient loads and affect water quality by promoting algal blooms and impairing the biological functions of aquatic organisms. “Significant increases in summer temperatures will affect the carbon cycling in the lakes, with potential consequences on atmospheric carbon dioxide levels and the Earth’s climate.”  Next, the fish The Austrian research so far is concerned only with freshwater temperatures. Peter Moyle, a biologist at the University of California Davis, has been more concerned with the freshwater fish that make their homes in, or migrate to, California’s rivers and lakes. He and colleagues report in the journal PLOS One – the Public Library of Science – that if current climate trends continue, then 82 per cent of California’s native fish could be extinct, and their native homes colonized by invasive species. The scientists looked at 121 native species and found that four fifths of them were likely to be driven to extinction or at least to very low numbers. These include prized sporting fish such as the Klamath River summer steelhead and other trout, the Central Valley Chinook salmon, the Central Coast coho salmon and many others that depend on cold water. “These fish are part of the endemic flora and fauna that makes California such a special place,” said Prof Moyle. “As we lose these fishes, we lose their environments and are much poorer for it.” – Climate News Network        

For immediate release On both sides of the Atlantic scientists studying lakes have discovered they are warming – and this is bad news both for water quality and the fish. London, 14 June – The Alpine lakes of Austria are warming up. By 2050, their surface waters could be up to 3°C warmer, according to new research in the journal Hydrobiologia. Martin Dokulil of the Institute for Limnology at the University of Innsbruck studied data from nine lakes larger than 10km2. The largest, Bodensee or Lake Constance, touches Austria’s border with Germany and Switzerland to the west; 800 kms to the east, Neusiedler See borders Germany and Hungary. The nine lakes range from 254 to 1.8 metres maximum depth and they are vital to Austria’s tourist industry: they play powerful roles in the Alpine ecosystem and they are of course reservoirs of water. But the Alpine valleys are warming: between 1980 and 1999 the region warmed at three times the global average and by 2050 the median temperatures for the region could have risen by 3.5°C. The challenge has been to anticipate the impact of global warming on the lakes. “The predicted changes in surface water temperatures will affect the thermal characteristics of the lakes,” says Dr Dokulil. “Warmer water temperatures could lead to enhanced nutrient loads and affect water quality by promoting algal blooms and impairing the biological functions of aquatic organisms. “Significant increases in summer temperatures will affect the carbon cycling in the lakes, with potential consequences on atmospheric carbon dioxide levels and the Earth’s climate.”  Next, the fish The Austrian research so far is concerned only with freshwater temperatures. Peter Moyle, a biologist at the University of California Davis, has been more concerned with the freshwater fish that make their homes in, or migrate to, California’s rivers and lakes. He and colleagues report in the journal PLOS One – the Public Library of Science – that if current climate trends continue, then 82 per cent of California’s native fish could be extinct, and their native homes colonized by invasive species. The scientists looked at 121 native species and found that four fifths of them were likely to be driven to extinction or at least to very low numbers. These include prized sporting fish such as the Klamath River summer steelhead and other trout, the Central Valley Chinook salmon, the Central Coast coho salmon and many others that depend on cold water. “These fish are part of the endemic flora and fauna that makes California such a special place,” said Prof Moyle. “As we lose these fishes, we lose their environments and are much poorer for it.” – Climate News Network        

A cooler century? Wait and see

EMBARGOED until 2301 GMT on Wednesday 22 May New research suggesting that the Earth may be warming a little more slowly than expected certainly does not  mean climate change is a false alarm, experts say. LONDON, 23 May – Several leading authorities on climate change have given a guarded welcome to research suggesting the Earth may warm more slowly than scientists had expected. An international research team led by Dr Alexander Otto of the Environmental Change Institute (ECI) at the University of Oxford, UK, has reported its conclusions in the journal Nature Geoscience. The Earth is now warming faster than at any time in the last 11,000 years, but scientists do not understand clearly why the atmosphere has warmed less than they expected over the last decade or so, and more slowly than in the 1990s. The researchers looked at how the last decade would affect the long-term sensitivity of the climate to a doubling of atmospheric concentrations of carbon dioxide, and suggest the Earth will warm more slowly than expected this century. But even though the heating may be slower, giving politicians more time to act, the scientists still believe temperatures will eventually climb to 4°C above pre-industrial levels, well above danger levels. Clive Hamilton is professor of public ethics at Charles Sturt University,  Australia, and author of Requiem for a Species: Why we resist the truth about climate change. Published in 2010, it says climate change will bring about large-scale, harmful consequences for life on Earth which it is too late to prevent. Professor Hamilton told Climate News Network: “The study should certainly be taken very seriously, although we will need to see over the next year or two how well it stands up to scrutiny. Let’s hope they are right; it’s the first bit of good news we have had a for a long time.”

Too soon to say

  Dr Geoff Jenkins is the former head of climate change prediction at the UK Met Office’s Hadley Centre for Climate Prediction and Research. He told the Network: “Until we actually understand why the global temperature rise has paused over the last decade – and we don’t yet – it’s still guesswork what the implications are for climate sensitivity and hence the future projections. “If the pause is a ‘correction’ to a naturally-boosted rise over previous decades, then maybe the climate sensitivity is indeed lower than the Intergovernmental Panel on Climate Change’s central estimate and future rises will be towards the lower end of the range. “But if the pause is a temporary natural offset to the man-made rise, then this offset would disappear at some stage and put us back on the central estimate track. I don’t see how we can say which it is until we understand the reason for it.” Many governments have promised to try to limit atmospheric warming to no more than 2 °C above pre-industrial levels, believing that threshold will prevent dangerous climate change. Previous estimates showed that would require global greenhouse gas emissions to peak by 2020 and then fall, a prospect that seemed out of reach while emissions continue to rise fast. Another member of the research team is Professor Myles Allen, also of ECI Oxford. “Prior to this, a lot of us were feeling quite gloomy that whatever we did, we’ll go over 2 °C”,  he said. “It’s not a foregone conclusion any more.” That means the protracted UN climate negotiations could still produce a workable agreement. If a deal enters force in 2020 and leads to rapid emissions cuts, “there remains a good chance we could hit the 2°C target”,  Professor Allen says.

Models ‘pretty accurate’

  Explanations for the current pause are the masking effects on greenhouse gases of pollution, the seasonal weather-disrupting El Niño phenomenon, and slight variations in the Sun’s output. It also appears that much of the heat has been going, not into the atmosphere, but into the oceans. What Dr Otto and his colleagues have done is to estimate how much warming, with rising emissions, the world is likely to experience by the time carbon dioxide levels have doubled since pre-industrial times. Their most likely estimate is 1.3°C, not the rise of up to 1.6 °C suggested by previous studies. “In the short term, there is maybe a bit less warming than expected,” said Dr Otto. But he told the London Guardian that the findings of his team’s research did not constitute evidence that climate change had stopped. He said: “Given the noise in the climate and temperature system, you would need to see a much longer period of any pause in order to draw the conclusion that global warming was not occurring.” Such a period could be as long as 40 years. The team’s study had found that most of the climate change models used by scientists were “pretty accurate”. On such a contentious subject some scientists would argue for caution in evaluating the research. A rise of 4°C in global average temperatures could mean far higher regional rises. The oceans are likely one day to give up much of the heat they are now absorbing, which will return to the atmosphere. So warming could accelerate fast and unpredictably. And on present trends, fossil fuel use is likely to go on increasing for several decades at least. There are qualifications and conditions in the research, “ifs” and “buts” which suggest there may be unknown unknowns ahead. Its conclusion is that the world is still warming – much too fast for comfort. – Climate News Network

EMBARGOED until 2301 GMT on Wednesday 22 May New research suggesting that the Earth may be warming a little more slowly than expected certainly does not  mean climate change is a false alarm, experts say. LONDON, 23 May – Several leading authorities on climate change have given a guarded welcome to research suggesting the Earth may warm more slowly than scientists had expected. An international research team led by Dr Alexander Otto of the Environmental Change Institute (ECI) at the University of Oxford, UK, has reported its conclusions in the journal Nature Geoscience. The Earth is now warming faster than at any time in the last 11,000 years, but scientists do not understand clearly why the atmosphere has warmed less than they expected over the last decade or so, and more slowly than in the 1990s. The researchers looked at how the last decade would affect the long-term sensitivity of the climate to a doubling of atmospheric concentrations of carbon dioxide, and suggest the Earth will warm more slowly than expected this century. But even though the heating may be slower, giving politicians more time to act, the scientists still believe temperatures will eventually climb to 4°C above pre-industrial levels, well above danger levels. Clive Hamilton is professor of public ethics at Charles Sturt University,  Australia, and author of Requiem for a Species: Why we resist the truth about climate change. Published in 2010, it says climate change will bring about large-scale, harmful consequences for life on Earth which it is too late to prevent. Professor Hamilton told Climate News Network: “The study should certainly be taken very seriously, although we will need to see over the next year or two how well it stands up to scrutiny. Let’s hope they are right; it’s the first bit of good news we have had a for a long time.”

Too soon to say

  Dr Geoff Jenkins is the former head of climate change prediction at the UK Met Office’s Hadley Centre for Climate Prediction and Research. He told the Network: “Until we actually understand why the global temperature rise has paused over the last decade – and we don’t yet – it’s still guesswork what the implications are for climate sensitivity and hence the future projections. “If the pause is a ‘correction’ to a naturally-boosted rise over previous decades, then maybe the climate sensitivity is indeed lower than the Intergovernmental Panel on Climate Change’s central estimate and future rises will be towards the lower end of the range. “But if the pause is a temporary natural offset to the man-made rise, then this offset would disappear at some stage and put us back on the central estimate track. I don’t see how we can say which it is until we understand the reason for it.” Many governments have promised to try to limit atmospheric warming to no more than 2 °C above pre-industrial levels, believing that threshold will prevent dangerous climate change. Previous estimates showed that would require global greenhouse gas emissions to peak by 2020 and then fall, a prospect that seemed out of reach while emissions continue to rise fast. Another member of the research team is Professor Myles Allen, also of ECI Oxford. “Prior to this, a lot of us were feeling quite gloomy that whatever we did, we’ll go over 2 °C”,  he said. “It’s not a foregone conclusion any more.” That means the protracted UN climate negotiations could still produce a workable agreement. If a deal enters force in 2020 and leads to rapid emissions cuts, “there remains a good chance we could hit the 2°C target”,  Professor Allen says.

Models ‘pretty accurate’

  Explanations for the current pause are the masking effects on greenhouse gases of pollution, the seasonal weather-disrupting El Niño phenomenon, and slight variations in the Sun’s output. It also appears that much of the heat has been going, not into the atmosphere, but into the oceans. What Dr Otto and his colleagues have done is to estimate how much warming, with rising emissions, the world is likely to experience by the time carbon dioxide levels have doubled since pre-industrial times. Their most likely estimate is 1.3°C, not the rise of up to 1.6 °C suggested by previous studies. “In the short term, there is maybe a bit less warming than expected,” said Dr Otto. But he told the London Guardian that the findings of his team’s research did not constitute evidence that climate change had stopped. He said: “Given the noise in the climate and temperature system, you would need to see a much longer period of any pause in order to draw the conclusion that global warming was not occurring.” Such a period could be as long as 40 years. The team’s study had found that most of the climate change models used by scientists were “pretty accurate”. On such a contentious subject some scientists would argue for caution in evaluating the research. A rise of 4°C in global average temperatures could mean far higher regional rises. The oceans are likely one day to give up much of the heat they are now absorbing, which will return to the atmosphere. So warming could accelerate fast and unpredictably. And on present trends, fossil fuel use is likely to go on increasing for several decades at least. There are qualifications and conditions in the research, “ifs” and “buts” which suggest there may be unknown unknowns ahead. Its conclusion is that the world is still warming – much too fast for comfort. – Climate News Network