World’s remaining carbon budget ‘significantly smaller’ than previous estimates

Experts at the University of Washington have released new data taking into account all human-generated pollutants, suggesting we have a far shorter timeline to reach temperature targets.

When the Paris Agreement was signed in 2016 it committed participating countries to the target of limiting global warming to 1.5C above pre-industrial levels, or 2C at the very most. Countless studies have been undertaken to better understand the speed at which greenhouse gas emissions need to be reduced to meet those goals, but according to a new assessment many have failed to paint an accurate picture of the situation. 

The work of researchers at the University of Washington, this latest investigation takes into account not just carbon dioxide, but also the release of nitrogen oxides, aerosols, particulate matter, and other human-made pollutants. When all these aspects are factored in, the world’s remaining carbon budget becomes ‘significantly smaller’ than previous estimates suggested.

This is due to the varying impacts of pollutants, with carbon dioxide directly linked to warming, while particulate matter working to block out sunlight and rays, leading to a mild cooling effect. Previous investigations pointed to a ‘no warming in the pipeline’ outcome after emissions cease, however this new attempt to understand the challenge ahead shows that if emissions stop completely there could still be a 0.2C rise in temperatures lasting between ten and 20 years because those elements responsible for artificially reducing warming would no longer have that impact.

Using this approach to modelling, under a moderate future emissions scenario, by 2029 the planet still has a two-thirds chance of at least temporarily exceeding the 1.5C warming target, even if all emissions stop at that time. Continuing on a moderate emissions path to 2057 means there is a two-thirds chance of exceeding the 2C warming goal. Simply put, the new data points to an urgent need for governments globally to set stricter and faster emissions targets to avoid the worst case scenario impacts of climate change. 

‘This paper looks at the temporary warming that can’t be avoided, and that’s important if you think about components of the climate system that respond quickly to global temperature changes, including Arctic sea ice, extreme events such as heat waves or floods, and many ecosystems,’ said co-author Kyle Armour, a University of Washington associate professor of atmospheric sciences and oceanography. ‘Our study found that in all cases, we are committed by past emissions to reaching peak temperatures about five to 10 years before we experience them.’

Image credit: Etienne Girardet