As the world prepares for the COP21 climate negotiations in Paris this year, the new book Energy Efficiency Market Report 2015 reveals that energy efficiency improvements since 1990 in IEA member countries avoided 870 million tonnes of CO2 emissions in 2014 – and a cumulative 10 billion tonnes over the last 25 years, roughly equivalent to current annual emissions by all IEA member countries. Energy Efficiency Market Report 2015 adds to IEA analysis that has shown energy efficiency to be the most effective tool to reduce energy sector carbon emissions, accounting for more than 40% of the required reductions to limit global warming to 2 degrees centigrade. The new findings make clear that energy efficiency improvements have effectively been rolling back the clock on carbon emissions.