The build-up of the key greenhouse gas could be larger than last year as changing weather patterns in the Pacific looks set to reduce the ability of natural "sinks" such as forests or grasslands to absorb excess carbon in 2019.

This reduction combined with rising emissions from human activity such as burning fossil fuels mean experts expect to see one of the largest rises in the concentration of atmospheric carbon dioxide in 62 years of measurements.

Weather patterns linked to year-by-year swings in Pacific Ocean temperatures are known to affect the uptake of carbon by plants.

In years with a warmer tropical Pacific, many regions become warmer and drier which limits plants growing and absorbing carbon dioxide, and the opposite occurs when the Pacific is cooler, as it was a year ago.

Professor Richard Betts of the Met Office Hadley Centre said: "Since 1958, monitoring at the Mauna Loa observatory in Hawaii has registered around a 30 per cent increase in the concentration of carbon dioxide in the atmosphere.

"This is caused by emissions from fossil fuels, deforestation and cement production, and the increase would have been even larger if it were not for natural carbon sinks which soak up some of the excess carbon dioxide.

"This year we expect these carbon sinks to be relatively weak, so the impact of record high human-caused emissions will be larger than last year."

Average concentrations of carbon dioxide are forecast to be 411 parts per million (ppm) in 2019, reaching a peak of 414 ppm in May before dropping back to 408 ppm in September and rising again at the end of the year.

This compares to around 315 ppm when measurements began at Mauna Loa in 1958, and around 280 ppm before the Industrial Revolution based on ice core samples.

Prof Betts said: "Looking at the monthly figures, it's as if you can see the planet 'breathing' as the levels of carbon dioxide fall and rise with seasonal cycle of plant growth and decay in the northern hemisphere.

"But each year's carbon dioxide is higher than the last, and this will keep happening until humans stop adding carbon dioxide to the atmosphere."

Australian Associated Press