London, Jan 25 : Scientists have issued a statement warning that the world's climate is "clearly out of balance and is warming", and that changes to Earth's climate system were not natural.
According to a report in BBC news, the word of warning was made by The American Geophysical Union (AGU), which is the world's largest society of Earth and space scientists.
This is the first time that AGU has updated its policy position on climate change since 2003, when it called for a concerted worldwide study to understand how the Earth would change as a result of climate change.
Now, the revised statement has gone further, stating that the changes to the planet's climate system were "best explained by the increased atmospheric abundances of greenhouse gases and aerosols generated by human activities in the 20th Century".
The statement warned that the world faced a tough challenge over the coming 50 years in regards to global warming.
"Even the lower limit of impending climate change - an additional global mean warming of 1.0C (1.8F) above the last decade - is far beyond the range of climate variability experienced during the past 1,000 years," it said.
According to the statement, "Warming greater than 2.0C (3.6F) above 19th Century levels is projected to be disruptive, reducing global agricultural productivity, causing widespread loss of biodiversity, and - if sustained over centuries - melting of much of the Greenland ice sheet."
If the 2C rise was to be avoided, the AGU said, net annual emissions of carbon dioxide had to be cut by at least 50% by the end of the century.
"This is a fast-moving field of science and the AGU felt it was time to update the statement," AGU president, Tim Killeen, told BBC News.
"We took seven months to do it; we brought together a panel of experts, who created drafts which underwent extensive critical review, and it was formally approved by the elected Council in December," he added.
Although the new statement is consistent with previous positions adopted by the AGU, according to Professor Killeen, it differed in a number of ways.
"It is more of a declarative statement that the climate is changing and those changes are best explained by human effects due to greenhouse gases and aerosols," said Killeen.
"Secondly, rather than the AGU saying that this is important and should be looked at, I think this is a call that we need to do something about it," he added.