14 June 2012, 10:10 BST
Getting ever louder in its calls for the world to get serious about climate change, the International Energy Agency (IEA) is also increasingly concrete about what needs to be done.
Global investments in renewable energy must double by 2020 to $23.9 trillion to keep global temperatures from rising beyond 2°C, says IEA in its new book, Energy Technology Perspectives 2012. And they must grow to $140 trillion by 2050.
That's $36 trillion more than currently projected where controlling emissions is not a priority - the equivalent of $130 per person each year.
It sounds like an enormous amount of money, but the plan more than pays for itself. By 2025, reduced spending for fossil fuels would outweigh the investment, and for every $1 invested, $3 would be saved by 2050, adding up to at least $100 trillion in savings.
"The window of opportunity is closing rapidly on achieving the 2°C target. The investments made today will determine the energy system that is in place in 2050; therefore, the lack of progress in clean energy is alarming," says IEA.
"Continued heavy reliance on a narrow set of technologies and fossil fuels is a significant threat to energy security, stable economic growth and global welfare, as well as to the environment."
"Renewable energy resources and significant potential for energy efficiency exist virtually everywhere, in contrast to other energy sources, which are concentrated in a limited number of countries. Reduced energy intensity, as well as geographical and technological diversification of energy sources, would result in far-reaching energy security and economic benefits."
In April, IEA released the Tracking Clean Energy Progress report, warning that despite recent progress in deploying renewable energy, it must be sped up.
IEA's 2°C Scenario prioritizes the clean energy technologies that can ensure an 80% chance of limiting long-term global temperature increase to 2°C.
It starts with energy efficiency to cut energy consumption in the world economy by two-thirds before 2050. Annual improvements in energy intensity must double, from 1.2% over the last 40 years to 2.4 % in the coming four decades. Economic incentives and more stringent standards are necessary, particularly in buildings and transportation.
While more mature technologies - hydro, biomass, onshore wind and solar PV - are making sufficient progress, others lag. "Particularly worrisome is the slow uptake of energy efficiency technologies, the lack of progress in carbon capture and storage and, to a lesser extent, of offshore wind and concentrating solar," says IEA.
Reducing coal use and improving efficiency of coal-fired generation are important first steps. Cutting carbon emissions 50% by 2050, requires coal demand to fall by 45% compared to 2009 levels.
"Against that background, the current increase in the use of coal for electricity generation is the single most problematic trend," says IEA.
Fossil fuels would not disappear, but its role would change. Higher steam temperatures in coal plants, for example, would cut emissions 30% as natural gas increasingly complements so-called variable renewable sources (primarily wind and solar), providing the flexibility that energy systems need to balance generation and demand fluctuations.
Over the past year, the typically conservative International Energy Agency has urged governments to stop subsidizing fossil fuels and to instead subsidize renewable energy to stabilize the earth's climate.
Read the Executive Summary: