At least half of climate change man made, report says

Activists gather outside the the United Nation's Intergovernmental Panel on Climate Change on September 27, 2013 in Stockholm.

A United Nations climate change report published Friday concludes that it is "extremely likely" that human activity accounts for at least half of the global warming that has been observed since the 1950s.

The Assessment Report from the Intergovernmental Panel on Climate Change is the benchmark study on global warming published every few years. Nearly 1,000 researchers from around the world work on the document, which then undergoes review by about as many scientists.

This year's report further strengthens the suspicions scientists have already ascertained.

READ: Climate change report: "extremely likely" humans are responsible