Met Office data for 2015 so far shows that, for the first time, global mean temperature at the Earth's surface is set to reach 1 °C above pre-industrial levels
This represents an important marker as the world continues to warm due to human influence.
Based on data from January to September, the HadCRUT dataset jointly run by the Met Office and the Climate Research Unit at the University of East Anglia shows 2015 global mean temperature at 1.02 °C (±0.11 °C) above pre-industrial levels*.
Stephen Belcher, Director of the Met Office Hadley Centre, said: "We have seen a strong El Nino develop in the Tropical Pacific this year and that will have had some impact on this year's global temperature.
"We've had similar natural events in the past, yet this is the first time we're set to reach the 1 °C marker and it's clear that it is human influence driving our modern climate into uncharted territory."
Early indications suggest 2016 will be similarly warm and while it's more difficult to say exactly what will happen in the years immediately after that, we expect warming to continue in the longer term.
Peter Stott, Head of Climate Monitoring and Attribution, said: "This year marks an important first but that doesn't necessarily mean every year from now on will be a degree or more above pre-industrial levels, as natural variability will still play a role in determining the temperature in any given year.
"As the world continues to warm in the coming decades, however, we will see more and more years passing the 1 degree marker - eventually it will become the norm."