BMJ 2015;350:h2156 doi: 10.1136/bmj.h2156 (Published 23 April 2015)
Page 1 of 1
News
NEWS Scientists warn that Paris summit is last chance to prevent fatal temperature rise Nigel Hawkes London
The earth can be saved from catastrophic climate change but only if bold action leads to a global agreement at the climate summit in Paris in December, leading climate scientists have said.
In a statement issued for Earth Day, they said that the Paris meeting will be the last chance to prevent global temperatures rising by more than 2°C, which they see as the upper safety limit. Achieving this target would require carbon releases into the atmosphere to peak by 2020 and to decline to near zero by 2050.
This is possible, but only just, Johan Rockström of the Stockholm Resilience Centre told a briefing at the Science Media Centre in London. “The window of opportunity is closing fast,” he said. “We are on a trajectory that will leave our world irrevocably changed, far exceeding the 2°C mark. This gamble risks disaster for humanity with unmanageable sea level rise, heat waves, droughts, and floods. We would never consider this level of risk in any other walk of life, yet we seem prepared to take this risk with our planet.” Rockström was speaking on behalf of the Earth League, a partnership of 17 leading scientists and institutions around the world, which includes two British groups—the Grantham Institute at Imperial College London and the related research institute at London School of Economics. Brian Hoskins, who runs the Imperial College unit, said that there were some encouraging signs. UK carbon emissions from energy use did not rise last year, for the first time in many years, as efficiency gains and policy changes started to work.
The statement set out eight goals, with the 2°C limit heading the list. To achieve that, Hoskins said, the world cannot generate more than another 1000 gigatonnes of carbon dioxide, which
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implies that three quarters of the known fossil fuel reserves will have to stay underground. Countries must commit to deep decarbonisation, with richer countries taking the lead.
Rockström added that so far oceans and forests had absorbed half of all manmade emissions, which was extremely fortunate. “We simply don’t know how long this can continue,” he said. There was a risk that as temperature rose the global system might flip and the environment become a carbon source rather than a sink. Growing emissions of methane from Siberian permafrost might be a warning sign. “We see increasing evidence that nature can buffer emissions and help us, but then abruptly shift,” he said.
The last attempt to set an international agreement on limiting climate change, in Copenhagen in 2009, was a failure. But attitudes had since changed, Rockström said, and he hoped that the Paris meeting might be “a Montreal moment,” recalling the meeting that led to agreement and ultimate success in controlling the chemicals that damaged the ozone layer. Because controlling climate change means leaving many fossil fuel reserves unused, both men were cautious about the merits of fresh exploration. Hoskins said that it could not be ruled out because it might generate cheaper sources of energy in the remaining years of the fossil fuel economy, but was unenthusiastic about fracking in the United Kingdom. Rockström said that the Arctic should be a no go area and that fracking was “not an attractive option,” representing a large investment in a source of energy that would soon be obsolete. Cite this as: BMJ 2015;350:h2156 © BMJ Publishing Group Ltd 2015
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Page 1 of 1
News
NEWS Scientists warn that Paris summit is last chance to prevent fatal temperature rise Nigel Hawkes London
The earth can be saved from catastrophic climate change but only if bold action leads to a global agreement at the climate summit in Paris in December, leading climate scientists have said.
In a statement issued for Earth Day, they said that the Paris meeting will be the last chance to prevent global temperatures rising by more than 2°C, which they see as the upper safety limit. Achieving this target would require carbon releases into the atmosphere to peak by 2020 and to decline to near zero by 2050.
This is possible, but only just, Johan Rockström of the Stockholm Resilience Centre told a briefing at the Science Media Centre in London. “The window of opportunity is closing fast,” he said. “We are on a trajectory that will leave our world irrevocably changed, far exceeding the 2°C mark. This gamble risks disaster for humanity with unmanageable sea level rise, heat waves, droughts, and floods. We would never consider this level of risk in any other walk of life, yet we seem prepared to take this risk with our planet.” Rockström was speaking on behalf of the Earth League, a partnership of 17 leading scientists and institutions around the world, which includes two British groups—the Grantham Institute at Imperial College London and the related research institute at London School of Economics. Brian Hoskins, who runs the Imperial College unit, said that there were some encouraging signs. UK carbon emissions from energy use did not rise last year, for the first time in many years, as efficiency gains and policy changes started to work.
The statement set out eight goals, with the 2°C limit heading the list. To achieve that, Hoskins said, the world cannot generate more than another 1000 gigatonnes of carbon dioxide, which
For personal use only: See rights and reprints http://www.bmj.com/permissions
implies that three quarters of the known fossil fuel reserves will have to stay underground. Countries must commit to deep decarbonisation, with richer countries taking the lead.
Rockström added that so far oceans and forests had absorbed half of all manmade emissions, which was extremely fortunate. “We simply don’t know how long this can continue,” he said. There was a risk that as temperature rose the global system might flip and the environment become a carbon source rather than a sink. Growing emissions of methane from Siberian permafrost might be a warning sign. “We see increasing evidence that nature can buffer emissions and help us, but then abruptly shift,” he said.
The last attempt to set an international agreement on limiting climate change, in Copenhagen in 2009, was a failure. But attitudes had since changed, Rockström said, and he hoped that the Paris meeting might be “a Montreal moment,” recalling the meeting that led to agreement and ultimate success in controlling the chemicals that damaged the ozone layer. Because controlling climate change means leaving many fossil fuel reserves unused, both men were cautious about the merits of fresh exploration. Hoskins said that it could not be ruled out because it might generate cheaper sources of energy in the remaining years of the fossil fuel economy, but was unenthusiastic about fracking in the United Kingdom. Rockström said that the Arctic should be a no go area and that fracking was “not an attractive option,” representing a large investment in a source of energy that would soon be obsolete. Cite this as: BMJ 2015;350:h2156 © BMJ Publishing Group Ltd 2015
Subscribe: http://www.bmj.com/subscribe
