Human activity will push concentrations of planet-warming carbon dioxide (CO2) in the atmosphere to levels 50 per cent higher than before the industrial revolution this year, breaching a symbolic climate change threshold, the United Kingdom’s Meteorological Office said in a forecast. With 2021 seen as a critical year for implementing the 2015 Paris Agreement to avoid catastrophic climate change, scientists said the prediction underscored the need for rapid action to slash emissions of CO2 from burning coal, oil and natural gas.

‘The human-caused build-up of carbon dioxide in the atmosphere is accelerating,” said Met Office climate scientist Richard Betts. ‘It took over 200 years for levels to increase by 25 per cent, but now just over 30 years later we are approaching a 50 per cent increase.’ Emissions from fossil fuels and deforestation will cause carbon dioxide to continue to accumulate in the atmosphere this year, with concentrations expected to exceed 417 parts per million for the first time on record for several weeks from April to June. This is a 50 per cent increase on the 278 parts per million concentration seen at the dawn of the industrial era, in the late 18th century, the Met Office said.

The United Nations says emissions from energy, food production, transport and industry must fall more than 7 per cent every year throughout the next decade to keep the temperature goals of the Paris climate deal in play. The 2015 accord enjoins nations to limiting global warming to “well below” two degrees Celsius (3.6 Fahrenheit) above pre-industrial levels, and to 1.5C if at all possible. With just over 1C of warming so far, Earth is already beset by extreme weather events such as flooding, droughts and tropical storms supercharged by rising sea-levels.