The main cause of the plummeting CO
2
emissions was the declining economic output due to globally imposed measures such as lockdowns to curb the spread of the virus. This is unsurprising, as the growth of the economic output has been the strongest driver of changes in global fossil CO
2
emissions for more than 30 years. One bright spot, however, is that the trend toward improved energy efficiency and reduced CO
2
intensity of energy production has continued in the pandemic year of 2020. This means that less CO
2
is being emitted to achieve the same economic output.
This confirms a development that has been ongoing for more than a decade. Thanks to higher energy efficiency and reduced CO
2
intensity, economic output and emissions are becoming increasingly decoupled. This is very encouraging, because this decoupling forms the backbone for the decarbonization of the global economy. It is particularly noteworthy that there are already 27 countries where fossil CO
2
emissions have actually fallen over the last decade while the economy has grown. Among them is Switzerland, although it should be noted here that this only applies to the so-called territorial emissions. If the import of "grey" CO
2
is taken into account, Switzerland loses its pioneering role.
No help for climate change
How does the temporary dip in emissions affect the global carbon budget and climate? The short answer is: practically not at all.
This is mainly because it is the total amount of CO
2
in the atmosphere that is relevant for climate change. Cumulative emissions are much more important than the emissions of a single year. And in terms of the accumulation of CO
2
in the atmosphere, we increased it substantially during 2020 as well - despite the Corona-induced decline in emissions. CO
2
concentrations rose by a hefty 2.4 parts per million (ppm) to a new record high of 412 ppm, an increase of more than 18 billion metric tons of CO
2
. That's a lot, but only about half of the total man-made emissions of about 37 billion metric tons of CO
2
in 2020, the other half being removed from the atmosphere by sinks on land and in the ocean.
The sinks continue to work amazingly well
These strong sinks are another bright spot for me. For more than 60 years, the land and oceans have almost consistently absorbed about half of the total man-made emissions, even though they have more than tripled. This means that the sinks have grown in sync, and now also absorb more than three times as much CO
2
. This is astonishing given how complex and potentially prone to change the underlying processes are, especially with respect to climate change. This threat is supported by latest report from the Intergovernmental Panel on Climate Change (IPCC). We must assume that the sinks will generally decrease in the future with climate change.
5
Fortunately, we do not yet see this in the sink estimates to which my group has contributed with model calculations and data analyses.
The residual budget is shrinking fast
Even though the pandemic year 2020 brought the biggest drop in emissions in the last 60 years - more than five percent - the decline is not particularly impressive in relation to the reduction required by the Paris climate targets. To meet the two-degree target, we would need to reduce emissions by at least five percent every year from now on.
Meanwhile, the carbon budgets for the Paris climate goals are shrinking rapidly. As of 2022, the remaining allowed emissions to meet the 1.5-degree target with 67 percent probability is about 325 billion metric tons of CO
2
. For the two-degree target, the budget is around 1075 billion metric tons. With emissions remaining constant, this would leave less than 10 years for a 1.5-degree warmer world, and less than 30 years for a maximum two degree warmer world.
6
Given the long renewal cycles of energy systems, the window for the 1.5-degree target is probably closed by now. Nevertheless, we should make every effort to keep warming as low as possible, because every additional tenth of a degree harms us and our environment more.
The direction is right
Certainly, the resurgent emissions in 2021 are a concern because we missed a real opportunity to accelerate the sustainable transformation of the economy through the Corona bailout. Nevertheless, I am optimistic. The decarbonization of the economy is underway. Renewables have a steep growth curve. Their costs have fallen sharply and they are competitive with fossil fuels in many areas. A great many countries have set themselves longer-term climate targets since Paris.
These are major steps, and their impact should not be underestimated. Clearly, we are moving far too slowly; clearly, we need to massively accelerate decarbonization across all countries and sectors. But the direction is right. That makes me confident that we can still achieve the Paris climate targets.
