Fourteen of 15 Hottest Years Have Been in 21st Century

A press release from the World Meteorological Organization: The World Meteorological Organization (WMO) has ranked 2014 as the hottest year on record, as part of a continuing trend. After consolidating leading international datasets, WMO noted that the difference in temperature between the warmest years is only a few hundredths of a degree – less than the margin of uncertainty.

Average global air temperatures over land and sea surface in 2014 were 0.57 °C (1.03°F) above the long-term average of 14.00°C (57.2 °F) for the 1961-1990 reference period. By comparison, temperatures were 0.55 °C (1.00°F) above average in 2010 and 0.54°C (0.98°F) above average in 2005,  according to WMO calculations. The estimated margin of uncertainty was 0.10°C (0.18°F).

“The overall warming trend is more important than the ranking of an individual year,” said WMO Secretary-General Michel Jarraud. “Analysis of the datasets indicates that 2014 was nominally the warmest on record, although there is very little difference between the three hottest years,” said Mr Jarraud.

“Fourteen of the fifteen hottest years have all been this century. We expect global warming to continue, given that rising levels of greenhouse gases in the atmosphere and the increasing heat content of the oceans are committing us to a warmer future,” he said. Around 93% of the excess energy trapped in the atmosphere by greenhouse gases from fossil fuels and other human activities ends up in the oceans. Therefore, the heat content of the oceans is key to understanding the climate system. Global sea-surface temperatures reached record levels in 2014.[1]

It is notable that the high 2014 temperatures occurred in the absence of a fully developed El Niño. El Niño occurs when warmer than average sea-surface temperatures in the eastern tropical Pacific combine, in a self-reinforcing loop, with atmospheric pressure systems. This has an overall warming impact on the climate. High temperatures in 1998 – the hottest year before the 21st century – occurred during a strong El-Niño year....

Graph from the WMO website