Nov. 12 (UPI) -- Even if global greenhouse gas emissions are reduced to zero by the end of the year, new research out of Norway suggests Earth's climate will, after a brief decline in global temperatures, continue to warm through at least 2500.
By 2500, simulations suggest Earth's climate will be 3 degrees Celsius warmer, on average, than it was in 1850 -- even with rapid elimination of human greenhouse gas emissions. Sea levels will be at least eight feet higher, according to the model.
Using data from various IPCC reports, researchers at the BI Norwegian Business School analyzed the relationship between greenhouse gas emission reductions and changes in the global climate between 1850 and the present.
"We then used the resulting set of estimated causal relations -- the causal structure of the model -- to calculate future developments," lead author Jorgen Randers told UPI in an email.
"Each run, or each future scenario, is driven by an exogenously determined rate of man-made greenhouse gas emissions," said Randers, a professor of climate strategy at BI.
Unlike many of the leading climate models, which are exceedingly complex, requiring lots of time and computing power, the model developed by Randers and his research partners is rather lean.
"Ours is a relatively simple model compared to the big general circulation models that are commonly used," Randers said. "It runs in seconds on a laptop computer."
The model showed that if greenhouse gas emissions peak during the 2030s and are reduced to zero by the end of the century, global temperatures will be 3 degrees Celsius warmer by 2500 than they were in 1850. Sea levels will rise nearly 10 feet.
The findings, published Thursday in the journal Scientific Reports, echo those of previous studies, which have shown some insignificant level of warming and sea level rise has already been baked into Earth's climate systems.
The authors of the new paper suspect Earth will continue to warm, even after human-caused greenhouse gas emissions are eliminated, because Earth's permafrost will continue to melt in the coming centuries, releasing water vapor, methane and CO2 -- all planet-warming gases -- into Earth's atmosphere.
Additionally, the new simulations suggest the loss of polar ice will result in less of the sun's energy being reflected back into space.
The authors say their findings aren't permission to give up.
"We keep stressing that humanity can improve the situation dramatically by phasing out the use of fossil fuels as soon as possible -- to limit the temperature rise before self-sustained melting accelerates -- and by preparing for the large scale removal of CO2 from the atmosphere," Randers said.
Randers acknowledged that there are plenty of uncertainties in their climate model, as there are in most climate models. That's one of the reasons he and his colleagues tried to keep their model as simple as possible, so that other scientists could easily use it for their own research.
"We published in order to get the big model builders to check whether the phenomenon of self-sustained melting of the permafrost also can be observed in their models when they run them far enough into the future," Randers said.