The world must invest $2.4-trillion in clean energy every year to 2035 and cut the use of coal-fired power to almost nothing by 2050 to avoid catastrophic damage from climate change, according to scientists convened by the United Nations.

Their report, published on October 8, adds pressure on policymakers and businesses to step up their response to global warming, which is boosting sea levels, resulting in storms becoming more violent and exacerbating poverty. The atmosphere is already almost 1 ºC hotter than it was at the start of the industrial revolution and on track to rise 3 ºC by 2100, according to the report. That is double the pace targeted under the 2015 Paris climate agreements endorsed by almost 200 nations.

“We are already seeing the consequences of 1 ºC of global warming through more extreme weather, rising sea levels and diminishing Arctic sea ice,” said Panmao Zhai, one of the cochairs of the UN’s Intergovernmental Panel on Climate Change (IPCC), which brought together the work of hundreds of researchers and thousands of scientific papers.

Even a rise of 1.5 ºC would have massive consequences, including a “multimetre rise in sea levels” over hundreds to thousands of years and a mass extinction of plants and animals. With a temperature increase of that scale, of the 105 000 species studied, 6% of insects, 8% of pants and 4% of vertebrates lose half their habitat. Those proportions double with a 2 ºC gain.

Envoys at the 2015 Paris talks asked the IPCC to study what it would take to limit warming to 1.5 ºC, a more ambitious goal than the previous 2 ºC target. The scientists concluded that carbon dioxide emissions should be cut 45% by 2030 from 2010 levels then reduced to zero by 2050. That would require “unprecedented changes in all aspects of society”, most especially within the energy industry. The report acknowledges those changes would be difficult and costly, but not impossible.

“These systems transitions are unprecedented in terms of scale, but not necessarily in terms of speed, and imply deep emissions reductions in all sectors,” the IPCC said in the report. “These options are technically proven at various scales, but their large-scale deployment may be limited by economic, financial, human capacity and institutional constraints.’’

To limit warming to 1.5 ºC would require a roughly fivefold increase in average annual investment in low-carbon energy technologies by 2050, compared with 2015, according to the report. The $2.4-trillion needed annually to 2035 is also an almost sevenfold increase from the $333.5-billion Bloomberg NEF estimated had been invested in renewable energy last year.

The IPCC report also recommended that, by 2050, coal’s share of electricity supply should be cut to 2% or less. Renewables should supply 70% to 85% of power generation. Carbon capture and storage (CCS) technology should be deployed to absorb remaining fossil-fuel emissions. Natural gas could maintain an 8% share of electricity generation if CCS reduced total global net emissions to zero by 2050.

Those ambitions would mark a massive upheaval to the energy system, with coal currently accounting for about 37% of power and gas 24%, according to the International Energy Agency (IEA).

The IPCC’s proposals are bolder than the most ambitious scenario set out by the IEA. The Paris-based institution envisioned coal maintaining a 6% share of the power generation market and gas 16% by 2040 under one pathway that is compatible with 2 ºC of warming.

“We assess the scientific information and then provide policy-relevant messages to our member governments as well as the relevant stakeholders,” Hoesung Lee, chairperson of the IPCC, said in an interview. “We provide a manual of solutions. It’s up to them to use this manual, considering the constraints or opportunities existing in different countries. It’s their decision, but we provide the scientific information.”

Organisations and investors that back green energy say the report makes it clear that the world should accelerate the shift away from coal, the most polluting fossil fuel.

“The coal industry has no role in a climate- stable world,” said Jan Erik Saugestad, CEO of Norway’s Storebrand Asset Management, which oversees $88-billion. “It’s our pressing duty to call on other investors to end meaningless engagement with coal-exposed companies.”

The report also highlights the risk to further investments in natural-gas-fired power plants and suggests that more of them be replaced by renewables, said Han Chen, who follows energy finance for the Natural Resources Defense Council.

“Large quantities of current gas plants will need to be retired early, while those under construction or in planning stages must be reconsidered immediately as they are not compatible with the 1.5 ºC future,” Chen said.

The World Coal Association (WCA) noted the IEA and other forecasters expect the fuel to remain an important part of the energy system for the foreseeable future. That would make it crucial to expand carbon capture projects, which siphon off the gas from smokestacks and store it permanently underground.

“Any credible pathway to meeting the 1.5 ºC scenario must focus on emissions rather than fuel,” Katie Warrick, interim CEO of the WCA, said after reviewing a draft of the report.