2015 Unambiguously the Hottest Year on Record
For the first time in recorded history, the Earth's temperature is clearly more than 1.0 C (1.8 F) above the 1850-1900 average. 2015 was approximately 0.1 degree C (about 0.2 degrees F) hotter than 2014, which had tied with 2005 and 2010 as the previous hottest years. 2015 set the record with 99.996% confidence.
he analysis covered the entire surface of the Earth, including temperatures from both land and oceans. The warming was not uniform, and for the contiguous United States, it was the 2nd warmest year ever (+1.33 C), surpassed only by 2012.
Including 2015 in the plot of temperature over time also seems to erase the much talked about "pause" in recent warming. Richard Muller, Scientific Director of Berkeley Earth says, "This new high temperature record confirms our previous interpretation that the pause was temporary and that global warming has not slowed." Lead scientist Robert Rohde adds, "The decades-long rise due to greenhouse gas emission is now clearly continuing."
In total, Berkeley Earth estimates that 16.9% of Earth's surface and 16.4% of its land surface set record high annual averages in 2015. There were record highs in much of South America and the Middle East, and parts of the US, Europe, and Asia.
The international community has set a goal of limiting warming to no more than 2 C above pre-industrial levels; the Earth is now approximately half way to that limit. Robert Rohde said "At the recent rate of warming may begin to cross that threshold in about 50 years."