The world is likely to see a return to rapid warming in the next couple of years, scientists said, in what could signal the end of the "pause" in rising global temperatures.
Experts said big changes were under way in the Earth's climate system, with a natural phenomenon known as El Nino combining with the impact of greenhouse gases to push global temperatures to record highs.
But other changes in the Atlantic Ocean over the coming decades could make relatively cooler and possibly drier summers in the UK and northern Europe more likely.
Globally, the Earth's climate system was at a "turning point", with a number of major changes happening at once, the Met Office's Professor Adam Scaife said.
In the run-up to key United Nations talks in Paris, at which it is hoped a new international agreement to tackle climate change can be agreed, "the signal is very clear" that global warming is happening.
The world has witnessed a slowdown or "pause" in rising temperatures in recent years, which sceptics pointed to as contradicting evidence of ongoing climate change.
The new report from the Met Office, which has been peer-reviewed by the University of Reading's Professor Rowan Sutton, suggests the world is warming again.
Prof Scaife said experts could not be sure it was the end of the slowdown.
However, rates of warming averaged over decades were likely to reach the high levels seen at the end of the 20th century, when the world was warming rapidly, within two years.
The years 2014, 2015 and 2016 are all likely to be at or near record levels, in part due to the influence of the El Nino phenomenon of surface warming in the Pacific Ocean.
Scientists are very confident there is now a major El Nino under way, which is set to peak this winter, on the scale of an El Nino event in 1998 which helped drive global temperatures to record highs.
But Prof Scaife said natural variations such as El Nino were just the "icing on the cake" on top of human activity which is putting greenhouse gases into the atmosphere and driving climate change.
The El Nino could help break records for global temperature as well as having impacts including making the Indian monsoon weaker and raising the possibility of a break in the Californian drought.
He said: "We believe we are at an important point in the time series of the earth's climate and we'll look back on this period as an important turning point.
"That's why we're emphasising it because we're seeing so many big changes at once.
"A lot of those things are natural, we've had El Ninos when we were cavemen, that's been going on a long time, and similarly there is evidence for variations in the Atlantic going back 1,000 years through various proxy measures.
"A lot of these things can occur without the influence of human beings.
"However, they are now occurring on top of the influence coming from man's activity, so when they occur, when an El Nino comes and raises the global temperature, that is the icing on the cake, that is the extra bit that creates a record."
Prof Sutton said natural changes in North Atlantic Ocean temperatures could lead to cooling of the region compared to rising temperatures around the world, and could even see temperatures decrease on current levels.
The fall in temperatures could affect weather patterns in Europe, he said, as "research in the past suggests that when the North Atlantic cools that favours cooler and possibly drier summers in northern Europe".
But he said northern Europe was "absolutely not" heading for the next ice age, adding that he was not predicting cooler, drier summers for the UK, as other factors such as rising global temperatures would also affect our weather.