At the very least, he added, the countries should have 'categorically' committed to cuts by 2020, the date agreed to at the landmark 2007 UN climate change conference in Bali, Indonesia.

Pachauri also pointed out that despite committing to 'deep cuts' in emissions, the leaders of the MEF nations have yet to discuss the substance of the reductions. 'The science is getting clear,' he said.

'The gaps in our knowledge are certainly filling up,' he said, stressing the need for 'the global community to take action' and ensure that this December's climate change conference in Copenhagen, Denmark, ends with countries wrapping up negotiations on a strong successor pact to the Kyoto Protocol, whose first commitment period ends in 2012.

An IPCC meeting in Venice, Italy, last week drew 200 climate change experts from all over the world to discuss the focus of the body's next assessment report - considered to be the most comprehensive study globally on global warming - due to be released in 2014.