Past the ‘point of no return’ on climate change: Ending greenhouse gas emissions tomorrow would still see global temperatures continuing to rise for several centuries, study claims
If humans ended greenhouse gas emissions tomorrow we would still see global temperatures continuing to rise for several centuries, a new study claims.
Scientists used a computer model called ESCIMO to simulate the effect of different greenhouse gas emission reductions on changes in the global climate to 2500, spanning all the way back from 1850.
Even if all human-made greenhouse-gas emissions were reduced to zero this year, global temperatures will still be around 5.4°F (3°C) warmer than 1850, they found.
Sea levels, meanwhile will rise by around eight feet (2.5 metres) by 2500, compared to 1850, submerging glaciers and flooding land.
Even if human-induced greenhouse gas emissions can be reduced to zero, global temperatures may continue to rise for centuries afterwards, according to a simulation of the global climate between 1850 and 2500
‘Recently, there have been warnings that some of these tipping points are coming closer and are too dangerous to be disregarded,’ say the scientists, from BI Norwegian Business School in Oslo.
‘In this paper we report that in the ESCIMO climate model the world is already past a point-of-no-return for global warming.’
Under conditions where all human-made greenhouse-gas emissions are reduced to zero this year, the authors estimate that, after an initial decline, global temperatures will still be around 5.4°F (3°C) warmer and sea levels will rise by around eight feet (2.5 metres) by 2500, compared to 1850.
Under another scenario, under conditions where human-made greenhouse gas emissions peak during the 2030s and decline to zero by 2100, global temperatures will be 5.4°F (3°C) warmer and sea levels 10 feet (three metres) higher by 2500 than they were in 1850.
The authors suggest that global temperatures could continue to increase after human-made greenhouse gas emissions have reduced.
Continued melting of Arctic ice and carbon-containing permafrost may increase the greenhouse gases’ water vapour, methane and carbon dioxide in the atmosphere.
Melting of Arctic ice and permafrost would also reduce the area of ice reflecting heat and light from the sun.
To prevent the projected temperature and sea level rises, the authors suggest that all human-made greenhouse gas emissions would have had to be reduced to zero between 1960 and 1970.
To prevent global temperature and sea level rises after greenhouse gas emissions have ceased, and to limit the potentially catastrophic impacts of this on Earth’s ecosystems and human society, at least 33 gigatonnes of carbon dioxide would need to be removed from the atmosphere each year from 2020 onwards through carbon capture and storage methods, according to the authors.
Prof Phillip Williamson, an environmental scientist at the University of East Anglia who was not involved in the project, said: ‘This study provides evidence for what we don’t want to hear – that global heating may have already become self-reinforcing, and that we have therefore passed the point of no-return.
‘But the findings should not be misinterpreted as saying that we are doomed, with nothing that can be done to make any difference.
‘On the contrary, the differences between their scenarios – net-zero by the end of the century and net-zero now – are dramatic, giving the choice of climate catastrophe within our children’s lifetimes or keeping future temperature increases below 1.5°C for at least a century.’
The study has been published in Scientific Reports.
SEA LEVELS COULD RISE BY UP TO 4 FEET BY THE YEAR 2300
Global sea levels could rise as much as 1.2 metres (4 feet) by 2300 even if we meet the 2015 Paris climate goals, scientists have warned.
The long-term change will be driven by a thaw of ice from Greenland to Antarctica that is set to re-draw global coastlines.
Sea level rise threatens cities from Shanghai to London, to low-lying swathes of Florida or Bangladesh, and to entire nations such as the Maldives.
It is vital that we curb emissions as soon as possible to avoid an even greater rise, a German-led team of researchers said in a new report.
By 2300, the report projected that sea levels would gain by 0.7-1.2 metres, even if almost 200 nations fully meet goals under the 2015 Paris Agreement.
Targets set by the accords include cutting greenhouse gas emissions to net zero in the second half of this century.
Ocean levels will rise inexorably because heat-trapping industrial gases already emitted will linger in the atmosphere, melting more ice, it said.
In addition, water naturally expands as it warms above four degrees Celsius (39.2°F).
Every five years of delay beyond 2020 in peaking global emissions would mean an extra 20 centimetres (8 inches) of sea level rise by 2300.
‘Sea level is often communicated as a really slow process that you can’t do much about … but the next 30 years really matter,’ lead author Dr Matthias Mengel, of the Potsdam Institute for Climate Impact Research, in Potsdam, Germany, told Reuters.
None of the nearly 200 governments to sign the Paris Accords are on track to meet its pledges.