Average 2015 surface temperatures beat the hottest year record held by 2014 by 0.13 degree Celsius (C), according to studies by National Aeronautical and Space Administration (Nasa) and National Oceanic and Atmospheric Administration (NOAA). Scientists noted that the 2015 temperatures continue a long-term warming trend.

The World Meteorological Organization (WMO), the United Nations weather agency, had warned in November last year that 2015 was on its way to becoming the hottest on record since 1880. In fact, WMO noted that the years 2011-2015 have been the warmest five-year period on record, with many extreme weather events influenced by climate change.

“Today’s announcement not only underscores how critical Nasa’s Earth observation programme is, it is a key data point that should make policymakers stand up and take notice—now is the time to act on climate,” Nasa administrator Charles Bolden said in an NOAA press release on Wednesday.

Bolden added that the planet’s average surface temperature has risen about 1 degree C since the late 19th century, mostly attributable to increased carbon dioxide and other human-made emissions into the atmosphere.

Last year also recorded the El Nino phenomenon, which was one of the strongest on record, sending global weather conditions into a tizzy. But El Nino was only one of several contributors to the hottest year.

“2015 was remarkable even in the context of the ongoing El Niño,” said Goddard Institute of Space Studies director Gavin Schmidt. “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,” Schmidt explained.

Nasa’s analyses are based on surface temperature measurements from 6,300 weather stations, ship- and buoy-based observations of sea surface temperatures, and temperature measurements from Antarctic research stations. Then these measurements are analysed using an algorithm that considers the varied spacing of temperature stations around the globe and urban heating effects.

WMO data showed that significant warmer temperatures were recorded over most of the observed land areas, especially western North America, large areas of South America, Africa and southern and eastern Eurasia. China and Russia had their warmest January-October period on record, with average temperatures some 2.1 degrees C above the long-term average.

Berkeley Earth, a California-based non-profit organisation that works on climate science, released a report last week on 2015 being unambiguously the hottest year on record. The scientists who prepared the report noted that the new high temperature record confirms previous interpretations that the pause in global warming was temporary and that global warming has not slowed.

“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,” said Elizabeth Muller, executive director, Berkeley Earth.