Record-breaking global temperatures seen last year are continuing, the World Meteorological Organisation says.
The UN agency said in its State of the Climate: Record Heat and Weather Extremes report that monthly temperature records were smashed in January and February.
It warned climate change was moving at an unprecedented rate.
It cited intense heat waves in Asia, South America, western and central Europe, the northwest US and western Canada.
World Climate Research Programme director David Carlson said he didn't expect temperatures to stabilise.
"We're on a slope - sometimes the slope goes very steep, sometimes it's a bit more shallow - but we're going upwards.
"So the normal is going to be increases. It's going to be increased temperature, increased ocean heat content, loss of ice. We know all the things."
The high temperatures so far in 2016 had sent "shockwaves" around the climate science community, Mr Carlson said.
The organisation said last year that sea level rise was the highest recorded, and the volumes of Arctic Sea ice were the lowest on record.
The organisation's chief Petteri Taalas said "the future is happening now" - with the Earth 1°C warmer than at the start of the 20th century.
"The alarming rate of change we are now witnessing in our climate as a result of greenhouse gas emissions is unprecedented in modern records," Mr Taalas said.
Data from NASA and the National Oceanic and Atmospheric Administration showed that, in 2015, the average temperature across global land and ocean surfaces was 0.9°C above the 20th century average, surpassing 2014's previous record by 0.16°C.