Last year tied with 2010 as the warmest year globally since record began in 1850, according to the Met Office.
Data complied by the UK forecaster and the University of East Anglia, showed 2014 was 0.56C above the long-term average (1961-1990) of 14C.
This means that all of the 10 warmest years on record have occurred in this century, with the exception of 1998.
Colin Morice, a Met Office climate change monitoring scientist, said: “We can say with confidence that 2014 is one of the 10 warmest years in the series and that it adds to the set of near-record temperatures we have seen over the last two decades.”
Phil Jones, a professor in the University of East Anglia’s school of environmental sciences, added: “2014 was an exceptionally warm year which saw warm tropical pacific temperatures, despite not being officially regarded as an El Niño.”
In the UK, the most notable weather events affecting farmers in 2014 were the winter storms of January and February, which left farmland on Somerset and parts of the Thames region under water for eight weeks.
The NFU said the “near perfect” summer for growing conditions contrasted the wettest winter on record. However, although crop yields were up for many, growers were hit hard as prices dropped.
The NFU said the volatility of global commodity markets contributed to wheat prices falling from £177/t in the summer to just over £100/t ex-farm in the autumn.
Guy Gagen, NFU chief arable adviser, said: “The persistent rain meant farmers were unable to apply fungicides, while disease in wheat reached critical levels, where the uppermost leaves and grain-heads were about to become infected.
“However, from June the rain stopped and conditions become ideal for capturing sunlight and turning it into yield, leading to bumper, high-quality wheat crops for many.
“Barley and rapeseed crops matured earlier, while light levels were stubbornly low, so did not benefit from the brilliant summer conditions as much as wheat.”
NFU Sugar said the weather in 2014 was ideal for growing sugar beet crops.
Ruth Digby, NFU chief sugar adviser, said: “Rain came when needed during the growing season (March to November), keeping the crop growing well and the warm sunny weather has meant the crop has put on good root weight and sugars have been at a good level,” said a union spokesman.
“The mild winter has also meant we have currently good harvest conditions and no frost losses experienced so far. Still at least two months of harvest left but currently expecting a record crop yield.”
Scientists believe Britain’s extreme weather over the past decade could be partly due to man-made climate change.
Dr Peter Stott, of the Met Office, said: “It’s important to look over long timescales to see how human influence has affected global climate.
“Looking at three decades or more, we can observe a clear warming trend which is reflected in the near-record temperatures we have seen in recent years.”
According to the Met Office, the global mean temperature for 2015 is expected to be higher than 2014. It is estimated to be between 0.52C and 0.76C higher than the long-term average.