2015 was the warmest year in history, NASA and NOAA have confirmed, calling for a more urgent action to mitigate the effects of greenhouse gas emission.
According to data released on Wednesday, global average temperatures in 2015 had been 0.9 °C higher than the 20th century average and 0.16 °C above 2014 values, which had set the previous record. This difference between the old and the new record is the biggest ever, Nasa said.
The UK’s Met Office confirmed the conclusions with its own set of data also published on Wednesday.
The temperature rise in 2015, the scientists believe, was partly driven by the El Niño effect that warms the surface of the Pacific Ocean every two to seven years. However, the researchers said that the main driver are growing concentrations of greenhouse gases in the atmosphere - a result of burning fossil fuels.
“2015 was remarkable even in the context of the ongoing El Niño,” said Gavin Schmidt, Director of NASA’s Goddard Institute for Space Studies (GISS). “Last year’s temperatures had an assist from El Niño, but it is the cumulative effect of the long-term trend that has resulted in the record warming that we are seeing.”
With the global mean surface temperature in 2015 more than 1 °C above late-19th century levels, the world is now halfway to the 2 °C limit set by scientists as a threshold to prevent dangerous consequences to the ecosystem. A temperature increase beyond this limit could lead to widespread damage due to extreme weather events and severe societal and economic impacts. In November, at the UN climate change conference in Paris, global leaders agreed to aim to keep the warming well below the 2 °C target.
The continuing warming trend underscores the importance of stricter measures to be put in place to wean the world off damaging fossil fuels.
"This announcement should put pressure on governments to urgently implement their commitments to act against climate change, and to increase the strength of their planned cuts in annual emissions of greenhouse gases," said Bob Ward, policy director of the Grantham Research Institute on Climate Change and the Environment in London.
Reliable global temperature records date back to the end of the 19th century. In the last 35 years scientists have observed a consistent warming trend. 15 of the 16 warmest years on record occurred since 2001, signalling the worsening nature of the problem.
Thomas Karl, director of NOAA's National Centers for Environmental Information said that 2016 will most probably set a new temperature record.
"There is no sign of a pause and slowing," he said.