Yesterday, Kees van der Leun kindly discussed with me on Twitter about the necessary amount of CO2 emission reductions.
Starting point was this Tweet by him, directed at the New York Times:
If we want to *stop* global warming, global CO2 emissions need to fall *to zero*, to be precise. And we’ll probably even need to get some CO2 back from the atmosphere.
I agree completely that it would be desirable to get CO2 emissions to zero. However, it is open to doubt if that is exactly the necessary condition for stopping further rising ppM values.
That’s because there are carbon sinks.
As Glen Peters explained here, for the last ten years’ emission record, only 45% remained in the atmosphere, while the larger part was absorbed in the ocean and land carbon sinks.
That means if we had somehow managed with zero emissions for these ten years, we would have removed those 55% from the atmosphere. It also means that if emissions had been only about half of what they actually were, we would still have come out ahead, reducing the amount of carbon in the atmosphere over those ten years.
There may be room for debate on how those carbon sinks will act in the future. The record for the last 50 years shows that they have increased their uptake, with the ocean sink now about at three times what it was in 1960. Carbon Brief reports that scientists expect at least the ocean sink to increase with rising levels of CO2 in the atmosphere.
That makes sense. With a higher level, there is more to absorb.
Anyway, the record for the past ten years is that more than half of the emissions ended up in the carbon sinks. So it might be a fair rough estimate that only about half of the emissions end up in the atmosphere in the long term.
If so, it is enough to reduce emissions by 50% from present levels to stop further increases in atmospheric CO2 levels. If you assume that carbon sinks will work less in the future, you might use some other estimate.
But there is really no reason to think that carbon sinks will go to zero with rising CO2 levels.
I was not aware of this fact before this discussion. It changes a lot of things.
For one, a goal of reducing by 50% is much more realistic than one of going to zero. With bad news like the 2017 emission record going up again and the German renewable energy policy screwed up completely in the last couple of years, moving the goal posts to a place where people actually still have a faint chance of scoring is welcome news.
More specifically, for Phaseout Profit Theory, this means that not only can oil be still used as raw material in the petrochemical industry (about 10 percent of present oil use) after the phaseout, but some of it may still be burned without increasing atmospheric CO2 levels (as long as that stays below the amount removed by carbon sinks).
It means that there is no need to keep the large majority of oil reserves in the ground, as long as their use is spread over enough time in the future.
That in turn means that the argument for Phaseout Profit can be reduced to “let’s keep a fair share of the treasure for future generations”, which does not rely on accepting the scientific truth on climate change.
Of course, I may be wrong. If so, I would appreciate someone pointing out exactly where.