Global fossil CO2 emissions in 2021 are returning to pre-covid-19 levels according to according to the Global Carbon Project, which has just published the Global Carbon Budget for 2021.

This latest annual update, show 2021 emissions returned towards their 2019 levels after decreasing 5.4 % in 2020. The concentration of CO2 in the atmosphere reached 414.7 ppm, 50 % above pre-industrial levels.

The study, led by Pierre Friedlingstein, and part of the Global Carbon Project (GCP), quantifies the major components of the global carbon budget - and their uncertainties – to determine the remaining net emissions available to avert global warming, covering emissions by sources and removals by land and ocean sinks.

The authors explain that the rebound in emissions reflect the stringency of the COVID-19 confinement levels in 2020 and the pre-covid background trends in emissions in these countries.

The remaining carbon budget for a 50 % likelihood to limit global warming to 1.5, 1.7, and 2 ∘C has respectively reduced to 120 GtC (420 GtCO2), 210 GtC (770 GtCO2) and 350 GtC (1270 GtCO2) from the beginning of 2022, assuming 2021 emissions levels, according to the report.

Highlighting the scale of the action needed the report explains that the remaining carbon budget to keep global temperatures below these climate targets has shrunk by 21 GtC (77 GtCO2) since the release of the IPCC AR6 Working Group 1 assessment. Reaching zero CO2 emissions by 2050, which is needed to limit warming in line with the Paris goals, entails cutting total anthropogenic CO2 emissions by about 0.4 GtC (1.4 GtCO2) on average, each year.

A major advance in this year’s GCP budgeting methods is the ability to link the global carbon budget models' estimates to the official country reporting of national greenhouse gases inventories.

While country reporting is area-based and attributes part of the natural terrestrial sink on managed land to the land-use sector, the global carbon budget makes it possible to distinguish anthropogenic from natural drivers of land carbon fluxes,

This new methodology paves the way for countries and the global community to improve checks and consistency of national inventories so they more accurately reflect global emissions.

A recently published paper by the GCP’s ESA-funded RECCAP-2 project, developed such methods based on atmospheric inversions to assess check consistency of national GHG reports.

This new inversion method harnesses satellite data and in-situ observations to give a full picture of emissions that accumulate in the atmosphere.

“If regularly applied, this inversion method will not only improve transparency in the accounting process but will also improve the effectiveness of mitigation policy and progress by individual countries to meet their pledges as part of the Paris Climate Agreement,” according to Philippe Ciais from the Université Paris-Saclay and contributor to the GCP.