Will the Paris agreement be implemented? Patrick Kovarik/AFP/Getty

Climate change in a “Trump world” in which the Paris agreement isn’t implemented could see the goal to limit warming to 1.5°C breached within a decade.

We could exceed that limit as early as 2026, according to an analysis for the Intergovernmental Panel on Climate Change (IPCC).

“Our paper, by showing the proximity of the 1.5°C level, should be seen as a wake-up call for governments and a catalyst for strong action,” Benjamin Henley at the University of Melbourne, Australia, told New Scientist.


The Paris Climate Agreement, signed in December 2015, commits nations to keeping warming to “well below 2°C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5°C.”

Henley and his colleague Andrew King used climate models to predict what would happen if the “business as usual” scenario – in which the Paris agreement aspirations were not implemented and emissions continued unabated – played out. They found that Earth would experience rapid warming.

Greenhouse gas emissions

The pair found there were two reasons for this. The first is a continued rise in emissions of planet-warming greenhouse gases.

The second is the influence of the Interdecadal Pacific Oscillation (IPO), a cycle of sea-surface temperatures that has a warming or cooling effect on the atmosphere globally.

This oscillation has been in a cooling phase for more than a decade, explaining the apparent stalling of global warming in the early years of the century. “This cool phase may have lulled us into a false sense of security,” says Henley.

But it is now moving into a warm phase. This was behind the record global temperatures in 2015 and 2016, and Henley and King suggest that “a sustained period of rapid temperature rise might be under way… for the next one or two decades”.

If the IPO oscillation remains in a warm phase for the coming decade, then the 1.5°C target would be exceeded between 2024 and 2029, the authors write. If not, then it would probably happen five years later.

Too gloomy?

Some researchers think that, in suggesting the 1.5°C threshold is so close, the latest study is too gloomy.

“The analysis assumes that little or no action is taken to reduce emissions,” says Michiel Schaeffer at the University of Utrecht, the Netherlands. The Paris agreement includes national pledges to cut emissions that should keep temperature 0.2°C cooler than business-as-usual in 2030, and more thereafter, he says.

But will the agreement and those pledges be implemented?

Before his victory in the US presidential election, Donald Trump declared he would withdraw the US from the agreement, and tear up the US promise to reduce emissions by at least 26 per cent between 2005 and 2025. Since the election, his administration has yet to declare its policy, though it has rescinded laws to limit fossil-fuel emissions.

The US is responsible for about 15 per cent of global emissions of greenhouse gases, but the danger is that a US pull-out would bring the Paris agreement crashing down. Meeting in Bonn this week, however, most signatories reaffirmed their commitment to their 2015 promises, and began writing a “rule book” for the agreement’s implementation.

Patchy progress

Progress has bene patchy, though. A recent analysis reveals that, globally, only 14 new laws and 33 new executive policies related to climate change have been introduced since the Paris climate change summit in December 2015.

Even so, the latest study gives renewed urgency to an IPCC review now under way on how to achieve the 1.5°C target, and the consequences for the planet of failing. The review is due to be finished next year.

“We are not discounting the Paris agreement. We can and should stabilise global temperatures at 1.5°C or below,” says Henley. But “most likely there would be a temporary exceedance”.

And the study’s forecast of an imminent overshoot of Paris targets may add to calls for more research into ways of removing greenhouse gases from the atmosphere through geoengineering technologies.

Journal reference: Geophysical Research Letters, DOI: 10.1002/2017GL073480