LMU: CO2 emissions in 2021 set to rebound to 2019 levels

Julia Pongratz coordinates the Global Carbon Project’s assessment of emissions from land use change, which stands at around 2.9 billion tons of net CO2 in 2021. Compared to the previous year’s estimate of 3.2 billion tonnes of CO2, the trend is downward but very uncertain. This comparatively small net flux includes substantial gross emissions from deforestation in particular, as well as CO2 removal, for example from afforestation and reforestation after wood harvest. In the decade from 2011 through 2020, annual gross CO2 emissions totaled 14.1 billion tons. “Yet these emissions would drop quickly and sharply if a moratorium on deforestation like the one resolved in Glasgow were implemented,” says LMU geographer Clemens Schwingshackl, who also took part in the study. However, the scientist suspects that the effects of the pandemic probably point in the opposite direction: In several countries, restrictions on the monitoring and legal enforcement of measures to counter tropical deforestation have been observed in the wake of lockdowns and limited budgets.

For the first time, the Global Carbon Project this year linked independent data from global carbon cycle models to the national greenhouse gas inventories reported by countries. While the models distinguish between natural and anthropogenic processes, the data reported by the countries assigns parts of the natural land sinks to the land use sector, when they occur on managed land (counted towards natural processes in the global model’s approach). Across countries, the land-use sector thus constitutes a global CO2 sink. If the different ways of attributing the natural sinks is accounted for, the two approaches are consistent. “Linking the independent estimates of the global carbon cycle models to the national greenhouse gas inventories is an important step in view of the Global Stocktake, with which the implementation of the Paris Agreement and the common progress towards the agreed goals can be evaluated,” Pongratz says.

Oceans and land as natural carbon sinks
According to the preliminary report, the global share of CO2 that remains in the atmosphere is continuing to increase this year, rising by 2.0 parts per million (ppm, the unit used to measure the composition of gases) to what is likely to be 415 ppm. Carbon sinks on land and in the oceans are responding to this gain as expected and absorbing more CO2. Between them, they capture about half of carbon dioxide emissions (a mean of 54 percent over the past ten years).

The forests, which are so important as natural carbon sinks, are under especially severe pressure.