Here is an update on the global carbon dioxide (CO2) situation. If you need a background on the topic, you may go to my previous posts on this topic. The world needs to restrict the average temperature rise, from the pre-industrial level, to below 1.5 oC to avert catastrophic climate changes. For simplicity, take 1850 as the start of the counting. 1.5 oC corresponds to a median concentration of CO2 of about 507 ppm (parts per million) in the atmosphere (425-785 ppm at 95% confidence range).
From these numbers, one can estimate the quantity of CO2 we could throw into the atmosphere before it crosses the critical concentration. The maximum remaining quantity of CO2 is known as the Carbon Budget.
Now the numbers: Based on the latest estimate at the beginning of 2022,
| Item | Quantity | Unit |
| Carbon Budget | 420 | GtCO2 |
| CO2 Concentration | 414.7 | ppm |
| Global anthropogenic CO2 emissions (2021) | 39.4 | GtCO2 |
| Global fossil CO2 emissions (2021) | 36.4 | GtCO2 |
Spending Wisely
At the current rate, the budget will be over by 2032! There is a resolution from the global fraternity to reduce the net CO2 emission to zero by 2050. If we trust that commitment, one can draw spending scenarios to reach the target. If we spend the remaining 420 Gt in equal chunks, we can do it by spending 15 Gt every year until 2050 and put a hard brake, which is not practical, given the present lifestyle of 36.4 Gt/yr. Another scenario is by reducing 8% every year. Notice that an 8% yearly reduction corresponds to halving every nine years. In other words, the spending in 2030 has to be half of what we did last year.
And How are we doing?
Nothing to cheer about (so far). The emission figures from the last three years have been:
| Year | Total CO2 Emitted (GtCO2) | at 8% reduction (GtCO2) |
| 2019 | 36.7 | 36.7 |
| 2020 | 34.8 | 33.8 |
| 2021 | 36.4 | 31 |
Since we know the real reason for the decline in 2020, the global shutdown due to pandemic, the 8% reduction remains a project without any evidence of progress.
CO2 at 1.5 oC: UK Met office
Carbon Budget Preliminary Data: ESSD
