As expected, the release of a major U.N. climate report yesterday (Working Group I contribution to the IPCC Sixth Assessment Report) has caused a lot of headlines and discussions. The report strengthened worries about the future and caused outrage among vulnerable countries, whose leaders demanded swift actions from the rest of the world to immediately reduce emissions and to help fund preparations for the future.
The key driver of global warming is the amount of CO2 (and other greenhouse gases, GHGs) we keep adding to the atmosphere. Currently it’s about 40 Gt of CO2 per year and the report warned that limiting warming to about 1.5°C would require immediate, drastic cuts in emissions so that we reach carbon neutrality (i.e. net zero emissions) around 2055.
The report also concluded that “it is unequivocal that human influence has warmed the atmosphere, ocean and land. Widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere have occurred”. Earth has already warmed by about 1.1°C compared to pre-industrial levels.
Another data point that keeps popping up in climate science is the global atmospheric CO2 concentration, which currently is around 415 parts per million (ppm). As can be seen from the Keeling Curve below, for thousands of years the level was between 260 and 280 ppm, but quickly shot up to around 400 ppm during the second half of the 20th century.
The Keeling Curve is a daily record of global atmospheric carbon dioxide concentration maintained by Scripps Institution of Oceanography at UC San Diego.
As long as we keep burning fossil fuels and thus adding CO2 to the air, the atmospheric CO2 concentration will go up. For a long time the IPCC has maintained that 450 ppm is a critical number to keep in mind, because emissions scenarios where CO2 concentrations don’t exceed 450 ppm are likely to maintain warming below 2°C over the 21st century relative to pre-industrial levels.
In other words, if the world crosses the 450 ppm threshold, ecosystems worldwide would suffer serious damage. Azeem Azhar from the Exponential View newsletter keeps reminding us that if we don’t do anything, we only have 3,252 days until we reach the threshold. That’s just about nine years!
The IPCC report that was published yesterday didn’t say anything new about the 450 ppm threshold and it remains to be seen if the upcoming deliverables from working groups II and III will have anything to say about it. Whether or not 450 ppm is the correct threshold number is, however, not the main point. The point is that there’s a clear link between global warming and atmospheric CO2 concentration.
We need to stop adding GHGs to the atmosphere and reach carbon neutrality as quickly as possible if we want to ensure that our planet doesn’t continue to warm up, which eventually and inevitably would lead to ecological collapse.