The current rate of greenhouse gas pollution is so high that Earth has about 11 years to rein in emissions if countries want to avoid the worst damage from climate change in the future, a new study concludes.
Despite dipping in 2020 because of the global pandemic, greenhouse gas emissions are on track to return to pre-pandemic levels, according to the annual Global Carbon Budget report.
The findings, currently under review before publication, underscore that the urgency of cutting emissions is even greater than previously thought if the world is to avoid a rise in average global temperatures that is greater than 1.5 degrees Celsius (2.7 degrees Fahrenheit) above preindustrial levels. That was the goal set by the 2015 Paris climate agreement and pursued by countries currently gathered for a major United Nations climate summit in Glasgow, Scotland.
The Global Carbon Budget is compiled with input from dozens of researchers around the world. It monitors the amount of carbon dioxide (CO2) that humans put out and how much room is left for such emissions to stay within the 1.5 C limit.
When the first report was issued in 2015, scientists projected that Earth had a 20-year time horizon before emissions would result in warming above the set limit by the end of the century. But the output of greenhouse gases has risen even faster than expected, with half of that budget expended in just the past six years.
At current levels of emissions, there's a 50% chance that a rise in temperatures of 1.5 C by the end of this century will be locked in by 2033. With no reductions, more dire scenarios are equally likely — with a 1.7 degrees C increase inevitable by 2042 and a 2 degrees C jump unavoidable by 2054.
Global average temperatures over the past 150 years have risen about 1.1 degrees C (or about 2 degrees F), intensifying wildfires, floods and hurricanes worldwide.
"Global fossil CO2 emissions (excluding cement carbonation) in 2021 are returning towards their 2019 levels after decreasing [5.4%] in 2020," the report states.
The authors note that reaching net-zero CO2 emissions by 2050, which is the goal of those pushing climate action at the Glasgow summit, "entails cutting total anthropogenic [human caused] CO2 emissions" by an amount "comparable to the decrease during 2020."
Emissions from China, which in recent years has surpassed the U.S. as the world's largest greenhouse gas emitter, have exceeded pre-pandemic levels, growing by 5.5% according to data in the latest report. India's emissions have increased 4.4%.
However, there are a few encouraging signs in the report, notably that emissions have decreased over the past decade in 23 countries whose economies were growing before the coronavirus pandemic — including the U.S. and the United Kingdom. The list, which accounts for about a quarter of global CO2 emissions, also contains several wealthy nations in Europe as well as Japan.