Legacy Carbon and the Global Budget: A Race Against Time

In the dynamic weave of our global carbon narrative, numbers, percentages, and projections play pivotal roles. To the uninitiated, the landscape of carbon accounting may appear as cryptic as a relic from an ancient civilization. Yet, buried within this data lies our collective story: a testament to human achievement, folly, resilience, and hope. The global carbon budget paints a clear picture of where we stand, where we might be headed, and most crucially, how much further we must travel to reconcile our past with the promise of a sustainable future.


Understanding the Global Carbon Budget: A Primer

Every year, myriad activities – from burning fossil fuels to deforestation – release vast quantities of carbon dioxide into our atmosphere. Meanwhile, the Earth, like a dutiful accountant, keeps a meticulous record: oceans and terrestrial ecosystems absorb a significant portion of these emissions, but not all. The balance remains in the atmosphere, contributing to the infamous greenhouse effect.

In 2021, a snapshot of this grand ledger presented the following:

  • Fossil CO2 Emissions (EFOS): A surge of 5.1% from the previous year, resulting in a staggering 10.1 ± 0.5 GtC/yr.
  • Land-Use Change Emissions (ELUC): Primarily driven by deforestation, this stood at 1.1 ± 0.7 GtC/yr.
  • The Ocean and Terrestrial Sinks: These natural systems absorbed 2.9 ± 0.4 GtC/yr and 3.5 ± 0.9 GtC/yr respectively, acting as invaluable buffers in our battle against global warming.
  • Atmospheric CO2 Growth Rate (GATM): Despite the natural absorption, the atmospheric CO2 growth rate was a concerning 5.2 ± 0.2 GtC/yr.

The atmosphere’s CO2 concentration, as a result, averaged 414.71 ± 0.1 ppm, a number far removed from pre-industrial levels and one that promises greater challenges ahead.


Where are we heading?

Projections for 2022 are sobering, with preliminary estimates suggesting another 1.0% rise in fossil CO2 emissions. The atmospheric CO2 concentration continues its upward march, estimated to touch 417.2 ppm.

Yet, one of the most alarming revelations lies in the shrinking carbon budget to keep global warming within permissible limits. To stand a 50% chance of capping temperature rise to 1.5°C, our budget from 2023 onwards dwindles to just 105 GtC.


The Legacy We Inherit, and the Legacy We Leave

Deforestation emerges as a double-edged sword: while currently a significant contributor to emissions, it also holds a key to potential mitigation. Sustainable forestry practices, afforestation, and reafforestation can halve emissions from this sector. Yet, this is merely one part of a multi-faceted solution.

Considering the Budget Imbalance of -0.6 GtC/yr, there’s an urgent need for recalibration. The carbon we’ve inherited from centuries of industrial progress – legacy carbon – demands action. It necessitates not just offsetting our current emissions but actively removing what’s already out there.

By a simple mathematical extrapolation, to counterbalance just the emissions of 2021, we would need to sequester approximately 10.9 GtC in a year, a task that becomes dauntingly Herculean when viewed against the cumulative emissions since the onset of industrialization.


In Conclusion

Our Earth, in its timeless wisdom, offers both challenges and solutions. As custodians of this planet, we’re presented with a clear mandate: to leverage nature, technology, policy, and collective will to reverse the tide. The path may be steep, and the journey strenuous, but with every step, we pen a new chapter in our shared legacy. For in the realm of carbon accounting, it’s not just numbers we balance, but the very fate of our blue planet.


Source: Friedlingstein et al., 2022 – “Global Carbon Budget 2022”, Earth System Science Data.