Analysis: What impact will the coronavirus pandemic have on atmospheric CO2?
Recent weeks have seen a number of estimates of how the coronavirus pandemic has affected CO2 emissions in China , the UK , Europe and the world as a whole in 2020.
But a key question for climate change is what impact this has had on the overall amount of CO2 in the atmosphere – the principal driver of global temperature rise. In our analysis for Carbon Brief, we assess whether the global drop in emissions will have a noticeable impact on atmospheric CO2 concentrations this year.
Our findings show that the annual average CO2 concentrations will still increase through this year, even though emissions are reducing. Across the whole year, we estimate CO2 levels will rise by 2.48 parts per million (ppm). This increase is 0.32ppm smaller than if there had been no lockdown – equivalent to 11% of the expected rise.
This means that, although global emissions are smaller, they are still continuing – just at a slower rate. Additional CO2 is still accumulating in the atmosphere.
An analogy is filling a bath from a tap. If the tap represents CO2 emissions, and the water level in the bath is CO2 concentrations, while we have slightly turned the tap down temporarily, water is still flowing into the bath and so the level is still rising. To slow climate change, the tap needs to be turned right down – and permanently.
Forecasting concentrations
The Met Office routinely forecasts how concentrations of CO2 in the atmosphere will change over the coming year. This is based on human emissions from fossil fuel burning, land use and cement production along with the predicted changes in natural carbon sinks and sources due to recent and predicted climatic conditions.
The predictions are made for CO2 at the Mauna Loa observatory in Hawaii, where monitoring has been carried out since 1958. CO2 has steadily risen every year on record – from an annual average of 316ppm in 1959 to 411ppm in 2019 – at an accelerating rate as human-caused emissions have grown. This CO2 record is the data behind the iconic “ Keelin g Curve ”.
Monthly mean CO2 concentrations measured at Mauna Loa Observatory, Hawaii, from 1958 through to 4 May 2020. Credit: Image courtesy of the Scripps Institution of Oceanography Although human emissions drive the long-term build-up of CO2, the speed of the build-up varies from year to year mainly due to the climate-induced variations, which affect how much CO2 is taken up by land vegetation and the oceans.
For example, the largest annual CO2 rise on record was 3.39ppm between 2015 and 2016, due to the large El Niño event causing drying and warming of the tropics. This caused tropical ecosystems to take up less carbon than in a normal year. While natural land and ocean carbon sinks typically absorb around 50% of fossil-fuel CO2, in 2015-16 it was only about 30%.
Following smaller CO2 increases in subsequent years , we would...
