The 2013 Intergovernmental Panel on Climate Change Fifth Assessment Report noted that it is "extremely likely" that climate change is being driven by humans:
It is extremely likely [defined as 95-100 percent certainty] that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic [human-caused] increase in greenhouse gas concentrations and other anthropogenic forcings together. [IPCC]
But a new paper by Philip Kokic, Steven Crimp, and Mark Howden published in the journal Climate Risk Management and focusing in depth on historical climate records puts the certainty even higher.
Investigating the large rise in temperatures in recent years — July 2014 was the 353rd consecutive month in which global land and ocean average surface temperature exceeded the 20th-century monthly average — the authors of the paper used a statistical model to deduce that there is "less than one chance in 100,000 that global average temperature over the past 60 years would have been as high without human-caused greenhouse gas emissions" warming the climate.