Tag Archives: Soot

Greenland’s great melt is pinned on climate change

FOR IMMEDIATE RELEASE The forensic search for the mysterious agent that almost melted Greenland goes on. The latest suspect to be rounded up for questioning is the jet stream, according to scientists in Sheffield, in the UK. LONDON, 18, June – First: the story so far. For a few days in July 2012, almost 97% of the surface of Greenland began suddenly to thaw. This was a melt on an unprecedented scale. Greenland carries a burden of three million cubic kilometres of ice and even in the summer, most of it stays frozen, partly because of the island’s high latitude and partly because ice reflects sunlight, and tends normally to serve as its own insulator. The event was so unusual, and so unexpected, and on such a scale that nobody seriously suggested that the dramatic conversion of snow to slush was direct evidence of climate change because of human-induced global warming. Soot, smoke and heat At first, climatologists were inclined to see the thaw as a consequence of the record-breaking heat waves and forest fires that afflicted North America last summer: snow could have been darkened by columns of soot and smoke from forest fires, just enough to start absorbing the sunlight, some reasoned. Then in April a team at the University of Wisconsin-Madison suggested that freak cloud behaviour over Greenland at the time might have caused the melting. Clouds normally block sunlight and keep the terrain below them cool. But these clouds could have been thin enough to let solar radiation through, but thick enough to trap the consequential infra-red radiation from the ground, and raise the local temperature levels. Now Edward Hanna and colleagues at Sheffield report in the International Journal of Climatology that they have another explanation. Unusual atmospheric circulation and changes in the jet stream – the same changes that almost washed away summer in England – sent a blister of warm air sweeping over the ice sheet. Hanna and his team analysed all the weather data collected by the Danish Meteorological Institute and by US researchers, and then employed satellite readings and a computer simulation called SnowModel to reconstruct the strange turn of events. And climate change may after all be a suspect.   High melt years The Greenland Ice Sheet is a highly sensitive indicator of regional and global change, and, says Prof Hanna, been undergoing rapid warming, and losing ice, for at least the last five years and probably the last 20. “Our research found that a ‘heat dome’ of warm southerly winds over the ice sheet led to widespread surface melting.” This was not predicted by the climate models used by the Intergovernmental Panel on Climate Change, and perhaps that indicated a deficiency in those models, he suggested. The event seemed to be linked to changes in a phenomenon known to oceanographers and meteorologists as the summer North Atlantic Oscillation (NAO), another well-observed high pressure system called the Greenland Blocking Index, and the polar jet stream, all of which sent warm southerly winds sweeping over Greenland’s western coast. “The next five to 10 years will reveal whether or not 2012 was a rare event resulting from natural variability of the NAO or part of an emerging pattern of new extreme high melt years.” It was hard to predict future changes in the Greenland climate in the current state of knowledge, but important to keep on trying. There is an awful lot of ice on top of Greenland. Once it starts to melt, it is likely to be, say the Sheffield scientists,  “dominant contributor to global sea level change over the next 100 to 1,000 years.”- Climate News Network

FOR IMMEDIATE RELEASE The forensic search for the mysterious agent that almost melted Greenland goes on. The latest suspect to be rounded up for questioning is the jet stream, according to scientists in Sheffield, in the UK. LONDON, 18, June – First: the story so far. For a few days in July 2012, almost 97% of the surface of Greenland began suddenly to thaw. This was a melt on an unprecedented scale. Greenland carries a burden of three million cubic kilometres of ice and even in the summer, most of it stays frozen, partly because of the island’s high latitude and partly because ice reflects sunlight, and tends normally to serve as its own insulator. The event was so unusual, and so unexpected, and on such a scale that nobody seriously suggested that the dramatic conversion of snow to slush was direct evidence of climate change because of human-induced global warming. Soot, smoke and heat At first, climatologists were inclined to see the thaw as a consequence of the record-breaking heat waves and forest fires that afflicted North America last summer: snow could have been darkened by columns of soot and smoke from forest fires, just enough to start absorbing the sunlight, some reasoned. Then in April a team at the University of Wisconsin-Madison suggested that freak cloud behaviour over Greenland at the time might have caused the melting. Clouds normally block sunlight and keep the terrain below them cool. But these clouds could have been thin enough to let solar radiation through, but thick enough to trap the consequential infra-red radiation from the ground, and raise the local temperature levels. Now Edward Hanna and colleagues at Sheffield report in the International Journal of Climatology that they have another explanation. Unusual atmospheric circulation and changes in the jet stream – the same changes that almost washed away summer in England – sent a blister of warm air sweeping over the ice sheet. Hanna and his team analysed all the weather data collected by the Danish Meteorological Institute and by US researchers, and then employed satellite readings and a computer simulation called SnowModel to reconstruct the strange turn of events. And climate change may after all be a suspect.   High melt years The Greenland Ice Sheet is a highly sensitive indicator of regional and global change, and, says Prof Hanna, been undergoing rapid warming, and losing ice, for at least the last five years and probably the last 20. “Our research found that a ‘heat dome’ of warm southerly winds over the ice sheet led to widespread surface melting.” This was not predicted by the climate models used by the Intergovernmental Panel on Climate Change, and perhaps that indicated a deficiency in those models, he suggested. The event seemed to be linked to changes in a phenomenon known to oceanographers and meteorologists as the summer North Atlantic Oscillation (NAO), another well-observed high pressure system called the Greenland Blocking Index, and the polar jet stream, all of which sent warm southerly winds sweeping over Greenland’s western coast. “The next five to 10 years will reveal whether or not 2012 was a rare event resulting from natural variability of the NAO or part of an emerging pattern of new extreme high melt years.” It was hard to predict future changes in the Greenland climate in the current state of knowledge, but important to keep on trying. There is an awful lot of ice on top of Greenland. Once it starts to melt, it is likely to be, say the Sheffield scientists,  “dominant contributor to global sea level change over the next 100 to 1,000 years.”- Climate News Network

Black carbon flows from soil to seas

FOR IMMEDIATE RELEASE Charcoal and other forms of black carbon do not, as previously thought, stay where they are buried: they migrate to the oceans and recirculate the carbon they contain. LONDON, 25 April – Climate scientists may have to rethink some of their old assumptions about carbon. US and European researchers have just established that black carbon, soot and biochar – the burnt remains from countless forest fires –  doesn’t stay in the soil indefinitely. Around 27 million tons of the stuff gets dissolved in water and washed down the rivers into the oceans each year. Black carbon or biochar has been hailed as one possible way of limiting greenhouse gas emissions, by taking carbon out of circulation. But this study, according to a report in the journal Science, “closes a major gap in the global charcoal budget and provides critical information in the context of geo-engineering”. Forest, bush, scrub and peat fires produce somewhere between 40 and 250 million tons of black carbon every year. Had this burning been complete, this would have ended up as carbon dioxide, back in the atmosphere. So researchers have counted the biochar locked in the soil – where it enhances fertility – as carbon out of circulation for millions of years. But analysis of water from the world’s 10 largest rivers – the Amazon, the Yangtse, the Congo and so on – told a different story. “Each sample included a significant amount of black carbon”, said Anssi Vähätalo, now of the University of Jyväskylä in Finland. “On average, the amount of black carbon was 10% of the amount of dissolved organic carbon. “The results prove that the proportion of water-soluble carbon may be as much as 40% of black carbon created annually.” The sampled rivers carry one third of the water running to the oceans, from a catchment area that embraces 28% of the planet’s land area.

More CO2 released

  The research is yet another step in the long and tricky international effort to understand just how the world works: how life’s raw materials are consumed, exploited and recycled, and why greenhouse gas emissions are stubbornly on the increase. Fossil fuel burning puts back into the atmosphere the carbon dioxide – and the warmth – locked away in the Carboniferous period and buried for 300 million years. Log fires simply restore carbon dioxide to the atmosphere that was locked up a few decades earlier, in the growing tree: log fires in that sense are carbon neutral, or even carbon negative, since a lot of the carbon lingers and is buried as ash, soot or charcoal. Some environmentalists have argued that greater use of biochar could slow and perhaps ultimately reduce global warming by taking carbon out of circulation. The accounting may not be so simple. “Most scientists thought charcoal was resistant. They thought, once it is incorporated in the soils, it would stay there,” said Rudolf Jaffé from Florida University. “When charcoal forms it is typically deposited in the soil. From a chemical perspective, no one really thought it dissolves, but it does. “It doesn’t accumulate, like we had for a long time believed. Rather, it is transported into wetlands and rivers, eventually making its way into the oceans.” – Climate News Network

FOR IMMEDIATE RELEASE Charcoal and other forms of black carbon do not, as previously thought, stay where they are buried: they migrate to the oceans and recirculate the carbon they contain. LONDON, 25 April – Climate scientists may have to rethink some of their old assumptions about carbon. US and European researchers have just established that black carbon, soot and biochar – the burnt remains from countless forest fires –  doesn’t stay in the soil indefinitely. Around 27 million tons of the stuff gets dissolved in water and washed down the rivers into the oceans each year. Black carbon or biochar has been hailed as one possible way of limiting greenhouse gas emissions, by taking carbon out of circulation. But this study, according to a report in the journal Science, “closes a major gap in the global charcoal budget and provides critical information in the context of geo-engineering”. Forest, bush, scrub and peat fires produce somewhere between 40 and 250 million tons of black carbon every year. Had this burning been complete, this would have ended up as carbon dioxide, back in the atmosphere. So researchers have counted the biochar locked in the soil – where it enhances fertility – as carbon out of circulation for millions of years. But analysis of water from the world’s 10 largest rivers – the Amazon, the Yangtse, the Congo and so on – told a different story. “Each sample included a significant amount of black carbon”, said Anssi Vähätalo, now of the University of Jyväskylä in Finland. “On average, the amount of black carbon was 10% of the amount of dissolved organic carbon. “The results prove that the proportion of water-soluble carbon may be as much as 40% of black carbon created annually.” The sampled rivers carry one third of the water running to the oceans, from a catchment area that embraces 28% of the planet’s land area.

More CO2 released

  The research is yet another step in the long and tricky international effort to understand just how the world works: how life’s raw materials are consumed, exploited and recycled, and why greenhouse gas emissions are stubbornly on the increase. Fossil fuel burning puts back into the atmosphere the carbon dioxide – and the warmth – locked away in the Carboniferous period and buried for 300 million years. Log fires simply restore carbon dioxide to the atmosphere that was locked up a few decades earlier, in the growing tree: log fires in that sense are carbon neutral, or even carbon negative, since a lot of the carbon lingers and is buried as ash, soot or charcoal. Some environmentalists have argued that greater use of biochar could slow and perhaps ultimately reduce global warming by taking carbon out of circulation. The accounting may not be so simple. “Most scientists thought charcoal was resistant. They thought, once it is incorporated in the soils, it would stay there,” said Rudolf Jaffé from Florida University. “When charcoal forms it is typically deposited in the soil. From a chemical perspective, no one really thought it dissolves, but it does. “It doesn’t accumulate, like we had for a long time believed. Rather, it is transported into wetlands and rivers, eventually making its way into the oceans.” – Climate News Network