Washington: There is only a 5pc chance that the Earth will avoid warming by at least 2C come the end of the century, according to new research that paints a sobering picture of the international effort to stem dangerous climate change.
Global trends in the economy, emissions and population growth make it extremely unlikely that the planet will remain below the 2C threshold set out in the Paris climate agreement in 2015, the study states.
The Paris accord, signed by 195 countries, commits to holding the average global temperature to “well below 2C” above pre-industrial levels and sets a more aspirational goal to limit warming to 1.5C. This latter target is barely plausible, the new research finds, with just a 1pc chance that temperatures will rise by less than 1.5C.
Governments settled on the 2C threshold partly through political expediency but also because scientists have warned of severe consequences from sea level rise, drought, heatwaves and social unrest should the temperature rise beyond this.
Such risks have been underscored by a separate study, also released on Monday, that shows unabated climate change will cause around 60,000 deaths globally in 2030 and 260,000 deaths by 2100.
The study, by the University of North Carolina, found that rising temperatures will exacerbate air pollutants that will particularly threaten those with existing conditions.
According to the University of Washington study, there is a 90pc likelihood that temperatures will rise between 2C and 4.9C by 2100. This would put the world in the mid-range warming scenarios mapped out by the UN’s Intergovernmental Panel on Climate Change.
It negates the most optimistic outcome as well as the worst case, which would see temperatures climb nearly 6C beyond the pre-industrial era.
Rather than look at how greenhouse gases will influence temperature, the new research analyzed the past 50 years of trends in world population, per capita gross domestic product (GDP) and carbon intensity, which is the amount of carbon dioxide emitted for each dollar of economic activity.
After building a statistical model covering a range of emissions scenarios, the researchers found that carbon intensity will be a crucial factor in future warming.
Technological advances are expected to cut global carbon intensity by 90pc over the course of the century, with sharp declines in China and India – two newly voracious consumers of energy.
However, this decline still will not be steep enough to avoid breaching the 2C limit.
The world’s population is expected to grow to about 11 billion people by 2100, but the research found that this will have a relatively small impact upon temperatures as much of this growth will take place in sub-Saharan Africa, which is a minor contributor of greenhouse gas emissions.
It has long been acknowledged that emissions cuts promised under the Paris agreement would not be sufficient to avoid 2C warming. However, it is hoped that periodic reviews of commitments will result in more severe reductions.
Donald Trump’s pledge to remove the US, the world’s second-largest emitter, from the accord has cast a large shadow over these ambitions.