The International Energy Agency on Monday warned temperatures could jump by as much as 4.3 degrees Celsius by the end of the century and urged countries to improve their pledges on reducing emissions.
In a report ahead of a climate change conference in Paris this year, the IEA said more should be done to reach the goal of keeping the increase in average global temperature below 2C (3.6 degrees Fahrenheit).
Current pledges "will have a positive impact on future energy trends but will fall short of the major course correction required to meet the 2C goal," said the report, which was presented in London.
Instead it estimated there would be an average temperature increase globally of around 2.6C by 2100 and said the rise could be higher at 4.3C for countries in the northern hemisphere.
"The energy sector must play a critical role if efforts to reduce emissions are to succeed. Energy production and use accounts for two thirds of the world greenhouse gas emissions," the IEA's executive director Maria van der Hoeven said.
The agency's chief economist Fatih Birol said extreme weather events would become "much more frequent" as a result, with Africa particularly badly affected despite only minimally contributing to the problem.
Van der Hoeven stressed that "time is of the essence", noting that "the cost and difficulty of mitigating greenhouse-gas emissions increase every year."
While there is "growing consensus among countries that it is time to act", strong vigilance is required to ensure that the pledges are adequate and that commitments are kept, she added.
The IEA suggested five key measures to ensure that global energy-related emissions peak already in 2020.
They call for improved energy efficiency in key industrial sectors, reducing the use of inefficient coal-fired power plants, increased investment in renewable energy technologies, a gradual phasing out of fossil-fuel subsidies and a reduction in methane emissions in oil and gas production.
"This major climate milestone is possible utilising only proven technologies and policies and without changing the economic and development prospects of any region," the IEA said.
Countries are preparing for a crucial UN meeting in Paris—the 21st Conference of Parties, or COP 21—of the UN Framework Convention on Climate Change (UNFCCC), which groups 195 nations.
The European Union earlier this year formally adopted climate change targets for the Paris conference, including a 40 percent cut in greenhouse gas emissions by 2030 compared to 1990 levels.
The United States, which accounts for 12 percent of global emissions, has announced its intention to reduce them by 26-28 percent in 2025 compared with their level in 2005.
China, which is the world's second-largest economy and accounts for 25 percent of global emissions, has set a target date of "about 2030" for its emissions to peak, but has not pledged any reductions.
© 2015 AFP