According to new Berkeley Earth analysis, 2015 was 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. The 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.
Elizabeth Muller, Executive Director of Berkeley Earth, notes, “Berkeley Earth has taken a cautious approach to announcing hottest years. A year ago, we announced that 2014 was not a clear record, but only in a statistical tie with 2005 and 2010. Now, however, it is clear that 2015 is the hottest year on record by a significant margin.”
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.”
Elizabeth Muller stressed, “The most important things we can do to mitigate global warming include energy efficiency and the increased use of renewables, natural gas, and nuclear power. It is time for us to stop being picky about which is the very best solution to global warming – we need all solutions that are available to us today.”
According to Mashable, the NOAA, NASA, Hadley Center and Japan Meteorological Agency (JMA) are all expected to make their annual temperature announcements by Jan. 21. The JMA has published a preliminary determination on its website, stating that 2015 was, by far, the warmest year on record according to its database.