Global temperatures are on course to pass the 1°C mark above pre-industrial levels.
Data released by the Met Office and the Climate Research Unit at the University of East Anglia revealed 2015 global mean temperatures at 1.02°C above levels recorded between 1850 and 1900.
They added early indications suggest 2016 will be “similarly warm”.
That means the world is half way to a 2°C temperature rise, which is seen as a gateway to dangerous warming.
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.”
Energy Secretary Amber Rudd added the findings show the need for an ambitious agreement on a global deal to tackle climate change in Paris next month.
She said: “Climate change is one of the most serious threats we face, not just to the environment, but to our economic prosperity, poverty eradication and global security. It’s clear we need to take urgent action to tackle global warming and move to a low carbon future.
“Pledges to reduce emissions made by countries so far represent a significant commitment but that’s just the beginning. We need to ensure that as the costs of clean energy fall, countries can be more ambitious with their climate targets.”