In a first of its kind study to identify human and natural emissions of carbon dioxide, scientists found fluctuations in atmospheric CO2 across the globe due to emissions from human activities.
Scientists used a combination of satellites observing the planet to conduct atmospheric modelling and measure drops in CO2 emissions during the Covid-19 pandemic from space. Using the Orbiting Carbon Observatory-2 (OCO-2), scientists found that global CO2 levels dropped slightly in 2020.
“Early in 2020, we saw fires in Australia that released CO2, we saw more uptake from plants over India, and we saw all these different influences mixed up. The challenge is to try to disentangle that and understand what all the different components were,” Lesley Ott, a research meteorologist said.
Carbon dioxide (CO2) is a greenhouse gas present in the atmosphere and its concentration changes due to natural processes like respiration from plants, exchange with the world’s oceans, and human activities like fossil fuel combustion and deforestation. Its concentration has jumped nearly 49 per cent in the atmosphere, and can last in the atmosphere for up to a century after it is released, which is why short-term changes could get lost in the overall global carbon cycle.
The OCO-2 tracked how human emissions shifted in response to climate policies, which are expected to produce small, gradual changes in CO2. The satellite has high-precision spectrometers designed to pick up even smaller fluctuations in CO2, and combined with the comprehensive GEOS Earth system model, were a perfect fit to spot the pandemic-related changes. The team’s results showed that growth in CO2 concentrations dropped in the Northern Hemisphere from February through May 2020 (corresponding to global emissions decrease of 3% and 13%).
The team compared the measured changes in atmospheric CO2 with independent estimates of emissions changes due to lockdowns. In addition to confirming those other estimates, the agreement between emissions models and atmospheric CO2 measurements provides strong evidence that the reductions were due to human activities.
The results represent a leap forward for researchers studying regional effects of climate change and tracking results of mitigation strategies, the team said. The method allows detection of changes in atmospheric CO2 just a month or two after they happen, providing fast, actionable information about how human and natural emissions are evolving.