G8 leaders have agreed at a summit to limit the global average temperature to just two degrees Celsius above pre-industrialisation levels by 2050. The summit, held in the central Italian town of L'Aquila, also agreed to cut carbon emissions in an effort to reduce global warming.

The United States, which, under president George W. Bush, was against the 2-degree norm last year, voted in favour of the package in L'Aquila. The deal says developed nations should reduce carbon emissions by 80 percent by 2050, while less wealthier nations should aim for a 50 percent reduction by the same date. An economic aide for Russian President Dmitry Medvedev has already dismissed the 80 percent as unrealistic for his country.

Italian Prime Minister Silvio Berlusconi moved the three-day conference to L'Aquila to show solidarity with the victims of the major earthquake in April. High security measures were in place at the summit. Police arrested 36 people after masked protesters blocked roads, threw objects and set fire to tyres. Greenpeace activists occupied four coal power plants in different regions of Italy, demanding tougher measures from G8 leaders on climate change.

G8 venue by Downing Street (Flickr)