Nations have so dragged their feet in battling climate change that the situation has grown critical and the risk of severe economic disruption is rising, according to a draft United Nations report. Another 15 years of failure to limit carbon emissions could make the problem virtually impossible to solve with current technologies, experts found.

A delay would most likely force future generations to develop the ability to suck greenhouse gases out of the atmosphere and store them underground to preserve the livability of the planet, the report found. But it is not clear whether such technologies will ever exist at the necessary scale, and even if they do, the approach would probably be wildly expensive compared with taking steps now to slow emissions.

The report said that governments of the world were still spending far more money to subsidize fossil fuels than to accelerate the shift to cleaner energy, thus encouraging continued investment in projects like coal-burning power plants that pose a long-term climate risk.

While the spread of technologies like solar power and wind farms might give the impression of progress, the report said, such developments are being overtaken by rising emissions from fossil fuels over the past decade, especially in fast-growing countries like China. And one of the most important sources of low-carbon energy, nuclear power, is actually declining over time as a percentage of the global energy mix, the report said.