Holding up a new global climate deal will add $500 billion for each year of delay to the total cost of measures needed to keep global warming to a 2 degrees Celsius minimum, the International Energy Agency (IEA) has warned.

An energy revolution is needed if the required cuts to carbon emissions in coming decades are to be achieved, the agency said in its annual World Energy Outlook. It says the world’s use of fossil fuels must peak by the early 2020s and be wound back thereafter.

The IEA forecasts global energy demand rising 2.5 percent a year over the next give years, translating into increased use of fossil fuels and rising emissions, if current policy settings are maintained. Oil demand, for example, was set to rise from 85 million barrels per day currently to 105 million by 2030 in the absence of measures to switch to clean energy.

“We need a deal in Copenhagen. We need a signal for the energy industry. Without that, nothing will move,” the Financial Times quoted IEA Chief Economist Faith Birol as saying.