The earth has become warmer since the 1970s as a result of which there may be an increase of overall rainfall as well as heavy rainfall events in future, says the leaked version of a new report from the world's top scientific body on climate change.

Days before the Intergovernmental Panel on Climate Change – headed by Indian engineer and environmentalist R K Pachauri – is to release the first part of its fifth assessment report at Stockholm next week, a leaked version of the report is doing the rounds.

Going by the leaked report, the upcoming IPCC report would conclude that it is now “extremely likely”  that human activities have caused more than half of the observed temperature increase from 1951 to 2010. The level of scientific confidence on the data has increased from IPCC's fourth assessment report in 2007, which fetched a Nobel Prize for the UN climate change body.

Warming has been particularly marked since the 1970s and each of the last three decades has been significantly warmer than all preceding decades since 1850.

While the global sea level is expected to rise more by 2100 than previously projected, the new report would point at increased global average rainfall as well as rise in heavy rainfall events like the one that took place in Uttarakhand.  There is no change to earlier conclusions about trends in flooding.
The IPCC has not denied the contents of the leaked report after it appeared in the circle of climate sceptics and a section of British press. The official report from IPCC Working Group-I on physical sciences behind climate change will be unveiled at a conference in Stockholm.

Reports from two more working groups will come out in the first half of 2014 before a synthesis report is published in October 2014. The IPCC report would be the basis of arriving at a post-2020 climate deal in Paris in 2015, says Sunita Narain, director of Centre for Science and Environment in Delhi.