EU leaders have reached a landmark deal to cut greenhouse gas emissions by 40% by 2030, compared with 1990 levels.
The binding decision came after heated discussions at a summit in Brussels, as some members had argued that their varied interests should be protected.
Correspondents say the final deal is a compromise between countries that rely heavily on coal, and those willing to instill greater emissions cuts.
Environmental groups welcomed the deal, but said it did not go far enough.
The bloc also agreed to boost the use of renewable energy to 27% in the total energy mix and increase energy efficiency to at least 27%.
There were deep divisions within the EU on emissions cuts.
Poland, which is heavily reliant on coal, fears that the costs of decarbonising its economy will slow business growth. Its concerns at the summit were echoed by other central and east European members.
The President of the European Council, Herman Van Rompuy, said afterwards that some poorer EU members would get help – including additional funds – in reaching the agreed targets.
The UK also had opposed nationally binding targets for renewables – mainly wind, solar and hydroelectric power. It is embracing shale gas and nuclear as alternatives to the current over-reliance on oil and gas imports.