The year 2015 was set to be the warmest on record and 2016 could be hotter, the United Nations' weather agency said on 25 November, warning that inaction on climate change could see temperatures rise by 6C or more.
"Unfortunately, the news [is] not good," said Michel Jarraud, secretary-general of the World Meteorological Organisation (WMO). "2015 will make history for a number of reasons. One of them, I'm repeating what we said just a few weeks ago, is that we have broken new records for the concentration of greenhouse gases as you know. CO2, methane, nitrous oxide and a few others, we have broken, once again, absolute records of that. The other reason is that 2015 will be the warmest year on record."
Global average surface temperatures in 2015 were likely to reach what the agency called the symbolic and significant milestone of 1C above the pre-industrial era.
"Next year is likely to be warm again because, when you have an El Nino, statistically, the impact of the El Nino is not only on this side of the El Nino, but it has also an impact over the next four, five, six months, which itself will influence the temperatures next year," Jarraud told a Geneva news conference.
He said that El Nino might be responsible for between 16% and 20% of the rise and longer-term averages showed temperatures were rising regardless of El Nino or its cooling counterpart, La Nina. El Nino, a naturally occurring weather pattern marked by warming sea-surface temperatures in the Pacific Ocean, causes extremes such as scorching weather, droughts and flooding around the world. Meteorologists expect El Nino to peak between October and January and to be one of the strongest on record.
A preliminary estimate based on data from January to October showed the global average surface temperature for 2015 was around 0.73C above the 1961-1990 average of 14C and around 1C above the pre-industrial 1880-1899 period, the WMO said.
But decisions made at a summit of world leaders in Paris starting on 29 November could keep global temperature rises within 2C over pre-industrial times, a target set down in 2010 to try to prevent dangerous climate change.
"You have scenarios assuming very strong decisions, very quick and sharp reduction in emission of greenhouse gases; you have other scenarios with business as usual, where you end up with predictions of additional warming of five or six degrees, maybe even more. So that will very much depend on the decisions [made at the climate conference in Paris]," Jarraud said.
2011-2015 has been the hottest five-year period on record, with temperatures about 0.57C above the 1961-1990 reference period.