When I was last writing about this roughly two weeks ago, it was being stated that the impact of the global lockdown was a reduction of about 5% of CO2 emissions.
That 5% is still floating about. To quote Scientific American …
Forecasters expect emissions to fall more than 5% in 2020, the greatest annual reduction on record.
There are a couple of points to draw out from this.
5% feels too low
It is a shockingly low number. Remember that if we wish to truly address climate change then we need to drop emissions by 7.6% each and every year., so how does a global lockdown fall so far short of even that.
It feels wrong. If most people are no longer driving anywhere, or flying, then why is it just 5%.
What is behind that 5% calculation?
When China shutdown earlier Carbon Brief estimated a 25% drop. Rather obviously that was just for a 4 week period. Since then, as they emerge from lockdown emissions start to rise once again.
The US is a similar story, they have roughly about a 25% drop in emissions.
If you are constructing a forecast for the entire year, then you need to make a few assumptions. The rather obvious one is that as we all emerge from lockdown emissions will rebound. So how can you actually calculate 5%, on what basis is that founded?
What is perhaps a key number is that the IMF calculates that global economies will shrink by 3%. Some of the hardest hit nations will see a huge economic hit …
To calculate that 5% you need to consider the entire year, so what do you do?
You work with such economic calculations and also make assumptions regarding rebound, hence you get … not 25%, but rather 5%.
Now we see this number being quoted as if it was rock solid. There is however a problem.
Assumptions are just that
What is becoming clearer is that initial assumptions regarding how long lockdowns are needed may not have been not truly appreciated. It is becoming increasingly clearer that for those nations that were late to lockdown, they may to stay in lockdown for far longer. What is even worse is that there are some US state governors preparing to reopen their economies right in the middle of a pandemic, not because they have been advised that it is safe to do so, nor is it because they have a viable exit strategy, but simply to get their local economy going.
Bottom Line: Take that 5% number with a pinch of salt, there are too many variables and unknowns to cling to it with a high degree of confidence.
One Further twist to all this
With nobody driving and major cities on lockdown people are breathing far clearer air and enjoying far cleaner water. There is a distinct lack of pollution.
This sounds fabulous, except there is a rather unexpected twist to this benefit.
Pollution acts like a barrier and reflects sunlight back out into space to a small degree. Once that shield is gone it leads to even more warming.
So far 2020 is on track to be one of the warmest years ever recorded, and this lack of a pollution shield may potentially lead to an uptick in heat.
CO2 and COVID-19 – Further Reading
- IMF (14th Apr 2020) – The Great Lockdown: Worst Economic Downturn Since the Great Depression
- Scientific American (24th Apr 2020) – Why CO2 Isn’t Falling More During a Global Lockdown