By now, hopefully, most people understand the huge problems caused by global warming – but most people probably don’t understand just how bad things are. Even if all emissions would somehow magically stop right now, the Earth would continue to warm for hundreds of years, according to a study published in the journal Nature Climate Change by researchers from Princeton.
The researchers conducted a computer simulation of Earth in which after 1,800 billion tons of carbon entered the atmosphere (the estimated value of all human emissions), all emissions suddenly stopped. They found that while 40 percent of the carbon was absorbed by oceans and landmasses in just 20 years, it took the rest about 1.000 years to be absorbed.
After a century of cooling, the planet warmed by 0.37 degrees Celsius (0.66 Fahrenheit) during the next 400 years as the ocean absorbed less and less heat. It may not seem like much, but keep in mind that since pre-industrial times, the temperature has risen with “only” 0.85 degrees Celsius (1.5 degrees Fahrenheit) – and this would happen if all emissions stopped now, which, of course, doesn’t seem possible.
Currently, the IPCC (International Panel on Climate Change) that if temperatures rise by 2 degrees in total, then the results will dramatically affect the world’s climate, and they believe that if we want to avoid this situation, we must keep cummulated emissions from now on under 1.000 billion tons – about half of which has already been put into the atmosphere. But Thomas Frölicher, who conducted the work as a postdoctoral researcher in Princeton’s Program in Atmospheric and Oceanic Sciences under co-author Jorge Sarmiento, the George J. Magee Professor of Geoscience and Geological Engineering think that that’s a little bit too optimistic.
“If our results are correct, the total carbon emissions required to stay below 2 degrees of warming would have to be three-quarters of previous estimates, only 750 billion tons instead of 1,000 billion tons of carbon,” said Frölicher, now a researcher at the Swiss Federal Institute of Technology in Zurich. “Thus, limiting the warming to 2 degrees would require keeping future cumulative carbon emissions below 250 billion tons, only half of the already emitted amount of 500 billion tons.”
Their work contradicts currently accepted ideas that global temperature would remain constant or decline if emissions were suddenly cut to zero. But they believe that until now, scientists didn’t take into consideration the gradual reduction in the oceans’ ability to absorb heat from the atmosphere, particularly the polar oceans.
“The regional uptake of heat plays a central role. Previous models have not really represented that very well,” Frölicher said. “Scientists have thought that the temperature stays constant or declines once emissions stop, but now we show that the possibility of a temperature increase can not be excluded,” Frölicher said. “This is illustrative of how difficult it may be to reverse climate change — we stop the emissions, but still get an increase in the global mean temperature.”
Thomas Lukas Frölicher, Michael Winton, Jorge Louis Sarmiento. Continued global warming after CO2 emissions stoppage. Nature Climate Change, 2013; DOI:10.1038/nclimate2060