The Ocean Carbon Response to COVID‐Related Emissions Reductions

Abstract

The socioeconomic disruptions associated with the COVID-19 pandemic have caused an unprecedented drop in global emissions of carbon dioxide (CO 2) and other atmospheric pollutants. The year 2020 was characterized by a 6.4% decrease in global CO 2 emissions relative to the previous year (Carbon Monitor Project, 2021; Liu et al., 2020), with average daily emissions declines peaking at −26% in individual countries (Le Quéré et al., 2020). The duration and severity of the emissions decline in the future is as yet unknown, but anomalously low CO 2 emissions are also expected in 2021 (Liu et al., 2020). The important role of CO 2 emissions in the global carbon cycle and climate system motivates further research on this topic. Several research groups are actively studying the impact of the COVID-related emissions reductions on the atmosphere and climate system. The latest World Meteorological Organization bulletin reports slight reductions in 2020 atmospheric CO 2 levels (−0.08 to −0.23 ppm) as a result of the COVID pandemic, though they emphasize that this reduction is difficult to detect given typical year-to-year variations in atmospheric CO 2 (± 1 ppm; World Meteorological Organization, 2020). A recent modeling study concurs that COVID-related reductions in atmospheric CO 2 levels are likely undetectable, but also demonstrates that these short-term

Societal shifts due to COVID-19 reveal large-scale complexities and feedbacks between atmospheric chemistry and climate change

“…However, it does match the bottom-up emissions shown in Fig. 4A (13) reasonably well through November 2020 (26).…”

Societal shifts due to COVID-19 reveal large-scale complexities and feedbacks between atmospheric chemistry and climate change

“…This uncertainty is due both to the forced response of the ocean and to interannual variability. Lovenduski et al (26) found that, for a change in ocean carbon uptake to be observable with our current network of ocean buoy measurements, it would need to be four times larger than the COVID-19 emissions reductions. This will be a challenge as we work to quantify the effect of future permanent CO2 emissions reductions on atmospheric CO2 mixing ratios.…”

On the detection of COVID-driven changes in atmospheric carbon dioxide

“…[2021] and mimics the approach for the detection of a climate change signal in real-world observations [Bindoff and Stott, 2013]. The resulting correlation coefficients are shown in the subplots of Figure 1, where small circles show the set of 30 Pearson's correlation coefficients (r) with the ensemble mean fingerprint across the 30 ensemble members, and large circles show the mean correlation coefficients [calculated using a Fisher's z transform; see Lovenduski et al, 2021] for each COVID-like emissions scenario. For the model sampled at Mauna Loa, the mean correlation coefficient for the COVID-like ensemble is 0.4 with a wide range; stronger emissions reductions increase the mean correlation coefficient and narrow the range (subplot in Figure 1a), suggesting a higher probability of detecting the fingerprint from a single ensemble member or hypothetical observational record under higher emissions reductions.…”

“…The remaining 3 ensembles span 2019-2040 and consist of 30 members each that are forced with COVID-like CO2 emissions reductions beginning in December 2019 and resolving in December 2021; peak emissions reductions of 25% (COVID-like), 50% (2 × COVID-like), and 100% (4 × COVID-like) occur in May 2020 (Figure S1b). Hereafter, we refer to these later three ensembles collectively as the CanESM5-COVID ensemble, as described in Fyfe et al [2021] and Lovenduski et al [2021]. The CO2 emissions in the historical and control ensembles have spatial and seasonal variability; emissions are highest near urban centers in the Northern Hemisphere (Figure S2a) and peak in boreal winter when energy consumption in the Northern Hemisphere is at a maximum (Figure S2b).…”

“…For both the 2 × COVID-like and 4 × COVID-like scenarios, the atmosphere reservoir anomaly falls outside of the ensemble spread due to internal variability (gray shading) for several years. Meanwhile, the ocean and land carbon reservoirs also respond to the COVID-like emissions reductions -the ocean carbon sink immediately slows with decreasing χCO2 under all COVID-like scenarios [Figure 3b; Lovenduski et al, 2021], and the land carbon sink also weakens, most noticeably under the 2 × COVID-like and 4× COVID-like scenarios (Figure 3c). The ocean reservoir anomaly falls outside of the spread due to internal variability only in the 2 × COVID-like and 4 × COVID-like scenarios [Figure 3b; Lovenduski et al, 2021].…”