Pledges made so far by Europe, the United States and China to cut greenhouse gas emissions aren't enough to keep global warming within safe limits, according to a new report by the International Energy Agency.
But the agency also said that if nations increase their efforts, there is just enough time to change direction with existing technology and without economic penalty.
In this year's climate talks, the analysis says, the overall test of success is whether the world's governments demonstrate their resolve to meet their longstanding goal of keeping warming below 2 degrees Celsius.
If there's a will, the IEA said, there's a way.
The agency, which advises leading industrialized nations on energy policy, was the first to review the effects of pledges made in the past year by the nations that emit the most greenhouse gases. Those pledges are part of the negotiations toward a global treaty meant to be signed in Paris at the end of this year.
If the leading nations keep their promises, the world's emissions will use up the planet's so-called carbon budget by 2040. That is the amount of carbon dioxide that can be released into the atmosphere without risking more than 2 degrees Celsius of warming. Beyond that, warming becomes increasingly dangerous and costly.
According to the IEA, the pledges received so far have delayed the budget-busting moment by just eight months––a calculation that underscores the urgency of acting more swiftly to control emissions.
As things stand, the agency saw "no peak by 2030" in worldwide emissions; to meet the safe climate target, emissions should peak by 2020.
Without stronger action, the report said, the world might warm 2.6 degrees by 2100 and 3.5 degrees after 2200, compared to its average surface temperatures at the start of the industrial era.
The study presented what the agency called a "bridging strategy" in which a peak in energy-related emissions in 2020 would lead to a world with zero carbon dioxide emissions from energy in the decades that follow.
"The peak can be achieved relying solely on proven technologies and policies, without changing the economic and development prospects of any region," it said.
This would "help keep the door to the 2 degree Celsius goal open."
The use of coal would peak by 2020 in this scenario, and then would decline. Oil demand would go up until 2020, then would flatten out. The amount of energy used for each unit of economic growth and for each unit of electric power would both drop 40 percent by 2030, in a fundamental transformation of energy systems.
It called for five broad measures: increasing energy efficiency in industry, buildings and transportation; limiting the use of the least efficient coal fired power plants and banning their construction; increasing investment in renewable electricity by about 50 percent in the next 15 years, to $400 billion a year; phasing out fossil fuel subsidies to end users, and reducing the emissions of methane, another potent greenhouse gas, from oil and gas production.
After crossing the bridge, the world would need to keep pushing new technologies forward, including energy storage in support of renewables, carbon capture and sequestration, and the like.