The two top scientific agencies in the United States have released separate reports on last year’s climate, and both confirm the global warming trend is continuing.
The American space agency, NASA, releases a climate report each year, alongside a separate report from its sister agency, the National Oceanic and Atmospheric Administration (NOAA).
The French newsagency AFP reports the two agencies collect their data separately and their reports show slightly different results, although the trend is clear.
At least nine of the warmest years on record have happened since 2000.
According to NOAA, 2013 was the fourth warmest year for the planet since records began in 1880.
Ocean temperatures were half a degree Celsius above the 20th century average.
NASA said carbon dioxide (CO2) was at its highest level in the atmosphere in 800,000 years, having risen from 285 parts per million (ppm) in 1880 to almost 400ppm last year.
Unless current trends change, the world should expect each of the coming decades to be warmer than the last, NASA climatologist Dr Gavin Schmidt said.
AFP reports he describes the warming of the past few decades as “unusual,” and urged people not to judge whether climate change is happening or not based on random weather events such as cold snaps.
“The long-term trends in climate are extremely robust,” he said.
“People have a very short memory when it comes to their own experience of weather and climate, and the only way that we can have a long-term assessment of what is going on is by looking at the data.”
Last year also marked the 37th year in a row with higher than average global temperatures.
A key difference between last year and other top years of the past decade is that 2013 had no El Nino effect to warm the equatorial region, a weather phenomenon that would have been expected to cause an increase in global temperatures.
However, forecasters say El Nino could return this year, with the potential to make 2014 even hotter than last.
Another concerning effect of global warming is the melting of sea ice in the Arctic, which is expected to cause sea level rises over time that will endanger coastal communities around the world.
“Arctic sea ice is down considerably, especially over the past 10 to 11 years,” the director of NOAA’s Climatic Data Centre, Tom Karl, said.
Last year marked the sixth smallest sea ice extent in the Arctic on record, while the Antarctic saw the opposite trend, and sea ice was above average.
While most of the world experienced above-average annual temperatures, a few small regions in the central United States, eastern Pacific and South America were cooler than average, according to NOAA.
