There is just a 5% chance of keeping global temperature rises at or below 2°C by the end of this century, according to new research by the University of Washington.
This temperature is the upper limit set out in the Paris agreement, while the more aspirational goal of capping increases at 1.5°C is only given a 1% chance of succeeding.
“Our analysis shows that the goal of 2°C is very much a best-case scenario,” research lead author, Adrian Raftery, said. “It is achievable, but only with major, sustained effort on all fronts over the next 80 years.”
Instead, the statistically based projections, published on Monday in Nature Climate Change, show a 90% chance of global warming between 2 and 4.9°C over this century.
If this were to materalise, it is thought that countries will experience severe damages from heat extremes, droughts, sea-level rises, and other forms of extreme weather.
“Overall, the goals expressed in the Paris Agreement are ambitious but realistic,” Raftery said. “The bad news is they are unlikely to be enough to achieve the target of keeping warming at or below 1.5 °C.”
The forecasts consider world populations, gross domestic product per person, and the amount of carbon emitted for each dollar of economic activity – the three factors most expected to impact CO2 emissions.
It was found that population rises are likely to have a limited impact on global warming, as most of the projected increase is expected in Africa, which uses few fossil fuels.
It is instead carbon emissions in relation to economic activity, which was found to be likely to matter more, the amount of which has fallen in recent decades as countries boost efficiency.
The research argues that how much this continues to drop will be crucial for determining future warming, and will depend on technological progress and countries’ commitment to change.
However, Raftery adds: “Our analysis is compatible with previous estimates, and it finds that the most optimistic projections are unlikely to happen. We’re closer to the margin than we think.”
