This year is heading to be the hottest or second hottest on record, according to the Met Office. It says the past 12 months are the warmest recorded by Nasa, and are second in the UK data set, HadCRUT3.
The Met Office says it is very confident that man-made global warming is forcing up temperatures.
Until now, the hottest year on record has been 1998, when temperatures were pushed up by a strong El Nino - a warming event in the Pacific.
This year saw a weaker El Nino, and that fizzled out to be replaced by a La Nina cooling event.
So scientists might have expected this year's temperatures to be substantially lower than 1998 - but they are not. Within the bounds of statistical error, the two years are likely to be the same.
"It's a sign that we've got man-made global warming," said Dr Vicky Pope, head of climate science advice at the Met Office.
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