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Levels of accumulated CO2 hit record high during pandemic

Greenhouse gas emissions may have fallen when COVID-19 lockdowns were in place around the world – but new research shows that atmospheric carbon dioxide concentrations hit a new high this May.

According to figures from California’s Scripps Institution of Oceanography and the US National Oceanic and Atmospheric Administration (NOAA), the amount of CO2 in the air in May hit an average of slightly greater than 417 parts per million (ppm). This is the highest total ever recorded and represents a significant increase from 414.8 ppm recorded in May 2019.

Monthly CO2 values at the Mauna Loa Observatory – which is located atop the Mauna Loa volcano on the island of Hawaii – first crossed the 400 ppm threshold in 2014. These levels have not been so high for approximately 3mn years. The reason that the temporary drop in emissions brought about by the coronavirus has not impacted the CO2 concentration is that the reduction is too small to stand out from natural variability.

Such natural fluctuations – which are caused by the response of plants and soils to variable temperature and moisture factors – are large enough that COVID lockdowns have only a minimal impact.According to Scripps scientists, the rate of CO2 increase measured at Mauna Loa would only slow if emissions reductions of 20 to 30% were sustained for six to 12 months.

‘Progress in emissions reductions is not visible in the CO2 record,’ explained Pieter Tans, Senior Scientist with NOAA’s Global Monitoring Laboratory. ‘We continue to commit our planet – for centuries or longer – to more global heating, sea-level rise, and extreme weather events every year. If humans were to suddenly stop emitting CO2, it would take thousands of years for our CO2 emissions so far to be absorbed into the deep ocean and atmospheric CO2 to return to preindustrial levels.’

The average annual growth in atmospheric CO2 concentrations was 0.8 ppm in the 1960s. This figure doubled to 1.6 ppm per year in the 1980s and remained constant at 1.5 ppm in the 1990s. It surged to 2.0 ppm per year in the 2000s and then to 2.4 ppm per year in the last 10 years.

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