2014 was the warmest year on record, with global temperatures 0.68C (1.24F) above the long-term average, US government scientists have said.

The results mean that 14 of the 15 warmest years on record have occurred since the turn of the century.

The analysis was published on Friday by Nasa and Noaa researchers.

Last month, the World Meteorological Organization released provisional figures that predicted the past 12 months were set to be record breakers.

The long-term global average temperature is calculated from data collected between 1951 and 1980.

"This is the latest in a series of warm years, in a series of warm decades," said Gavin Schmidt, director of Nasa's Goddard Institute for Space Studies.

"While the ranking of individual years can be affected by chaotic weather patterns, the long-term trends are attributable to drivers of climate change that right now are dominated by human emissions of greenhouse gases," he added.

Nasa and the US National Oceanic and Atmospheric Administration (Noaa) maintain two of the three global datasets of global temperatures. The UK's Met Office maintains the third.

Data from all three are used by the World Meteorological Organization (WMO) and formed the basis of its provisional figures in December.

Talking to journalists, Dr Schmidt said the results from the two sets of data showed "a lot of warmth in the oceans".

"It shows very clearly that it has been the warmest year on record in the oceans but it wasn't quite the warmest year in the land records but combined it did give us the warmest year," he explained.

Hot water

During a presentation of the two agencies' reports, Thomas Karl, director of Noaa's National Climatic Data Center, said there was a "considerable amount of area where we saw the record highest temperature observed, such as many portions of Europe and every ocean had parts that were [the warmest on record]".

Australia was another nation to set record-breaking average temperatures.

But Dr Karl added that not all parts of the globe recorded temperatures above the long-term average.

"There were actually some areas that were cooler than average, particularly across some parts of the US that were much cooler than average," he observed.

"But that was overwhelmed by the far greater proportion of land and ocean areas that was much warmer than average or record temperatures.

"If you put it all together then it comes out as the warmest year on record."

Records stretch back to the late 19th Century when scientists began using scientific instruments to collect temperature data.

Today, as well as in-situ instruments recording information on the Earth's surface, satellites closely monitor temperatures across the planet.

During its review of extreme weather during 2014, the WMO highlighted a number of record-breaking events:

• In September, parts of the Balkans received more than double the average monthly rainfall and parts of Turkey were hit by four times the average.
• The town of Guelmin in Morocco was swamped by more than a year's rain in just four days.
• Western Japan saw the heaviest August rain since records began.
• Parts of the western US endured persistent drought, as did parts of China and Central and South America.
• Tropical storms, on the other hand, totalled 72 which is less than the average of 89 judged by 1981-2010 figures. The North Atlantic, western North Pacific and northern Indian Ocean were among regions seeing slightly below-average cyclone activity.

Responding to the reports' findings, Bob Ward, policy and communications director at the Grantham Research Institute on Climate Change at the London School of Economics, said:

"The new global temperature record announced today completely exposes the myth that global warming has stopped.

"There is mounting evidence all around the world that the Earth is warming and the climate is changing in response to rising levels of greenhouse gases in the atmosphere."

A small but vocal number of people maintain that the observed temperature anomalies are not the result of greenhouse gas emissions from human activities warming the planet.

It is also a view that is held by a number of politicians, making them reluctant to introduce regulations or legislation aimed at cutting emissions.

He added: "No politician can afford to ignore this overwhelming scientific evidence or claim that global warming is a hoax.

"Climate change is happening, and as the Intergovernmental Panel on Climate Change, national scientific academies and scientific organisations across the world have all concluded [that] human activities, particularly burning of fossil fuels and deforestation, are primarily responsible."

Emma Pinchbeck, head of climate and energy policy at WWF-UK, said there were reasons to be optimistic that the international community would act to curb emissions.

"There is still time to cut emissions and keep the rise in global temperature under 2C (3.6F)," she said.

"This is the year for politicians in the UK and abroad to show leadership and to deliver the global agreements and national policy we need needed to avoid the worst impacts of climate change."

The UN climate summit in Paris at the end of the year has become the focus for campaigners and policymakers alike.

It is being billed as the time when nations will come together to agree on a global roadmap to reduce emissions from human activities and prevent dangerous climate change.

However, many commentators refer to the 2009 talks in Copenhagen that promised so much but, in the end, delivered so little.

BBC