Critics fear the climate deal may have been undermined by compromises
European Union leaders have reached a deal on a package of measures to fight global warming.
The plan, agreed at a Brussels summit, sets out how 27 member-countries will cut carbon emissions by 20% by 2020, compared with 1990 levels.
French President Nicolas Sarkozy, the summit chairman, said something "quite historic" had happened in Brussels.
But critics said concessions made to some nations and sectors would lessen the package's long-term impact.
Scientists say carbon dioxide emissions need to be cut by 25-40% by 2020 for there to be a reasonable chance of avoiding dangerous climate change.
In other developments:
• EU leaders agreed an economic recovery package worth 200bn euros (£180bn) to ease the economic downturn
• A deal was reached on concessions enabling the Irish Republic to hold a second referendum on the Lisbon Treaty, which aims to streamline EU decision-making
EU leaders have been discussing the so-called "20/20/20" package to tackle climate change and concessions to limit its impact on struggling industries.
The measures, which also require approval by the European Parliament to become law, commit the EU to cutting carbon dioxide (CO2) emissions by 20% by 2020.
It must also raise renewable sources to 20% of total energy use and achieve a 20% cut in energy use.
EU Commission President Jose Manuel Barroso called the plans "the most ambitious proposals anywhere in the world".
"Europe has today passed its credibility test. We mean business when we talk about climate," he said, appealing to US President-elect Barack Obama to follow Europe's lead.
But critics said the package - which includes concessions to heavy industry and Eastern European countries worried that pollution cuts will harm their economic growth - did not go far enough.
"This is a flagship EU policy with no captain, a mutinous crew and several gaping holes in it," said Sanjeev Kumar of WWF.
'Act of leadership'
Delegates at a UN conference in the Polish city of Poznan have meanwhile been trying to find a way forward in their attempts to reach a global climate change deal by the end of next year in Copenhagen.
Al Gore won the biggest applause of the gathering with a speech predicting a far more active US climate change policy under President-elect Barack Obama.
The former US vice-president also said he was optimistic that a climate change accord could be agreed despite the financial crisis.
"To those who say it's too difficult to conclude a deal by Copenhagen, I say it can be done, it will be done, let's finish this process," he said.
One of the reasons Mr Gore gave for his optimism was that a number of developing countries have come forward with firm pledges on restraining the rise in greenhouse gas emissions, including China, Brazil and Mexico.
But he said the science mandated moving from a target of keeping atmospheric greenhouse gas levels below 450 parts per million (ppm) - a level that is regarded by many countries as a threshold above which climate impacts are likely to become severe - to 350ppm, which would be much harder to achieve.
Capacity for reducing emissions and for adapting to climate impacts needed to be improved in developing countries - but the "sclerotic" politics of today also had to change, he added.
UN officials at the conference said the EU's climate deal was a success and would contribute towards an agreement in Copenhagen, although environmental groups said they were dismayed about a number of concessions it offered to industry.