Cumulative Net Zero — Incorporating climate justice into climate goals.

What should be humanity’s goal in the fight against climate change? UN’s current target is to limit the warming below 1.5 deg C below by the end of the century. To achieve this target, the world needs to reach net-zero by 2050. However, the path the net-zero can be quite different. It is essential to look at the total carbon dioxide emitted from now till 2050 rather than a particular target for the year 2050.

With this insight that the total carbon emitted is more critical than a carbon emission of a particular year, I wanted to extend the line of thought. So instead of having a target of 1.5 deg C heating over pre-industrial levels, we should look at having the same amount of Carbon dioxide in the air and oceans as when the industrial revolution started. We should look from the perspective that humanity was living in a time where there was 300 ppm CO2 in the atmosphere and a particular amount of ocean acidity. Our aim should be to reach back to that number. This thought process is a more comprehensive task than achieving net-zero by a specific year. Post net-zero is achieved, we need to ensure that the additional carbon dioxide is sequestered. We cannot wait for 100 years for carbon dioxide to disintegrate naturally.

The significant advantage of thinking from this perspective is that historical emissions start becoming a part of the discussion. Historical emissions are intricately linked with Climate Justice. The developed world has had the biggest share of emissions; however, the developing world will face the largest consequences. Our World in Data has good information for a deep dive into historical emissions. How do we devise a fair system which incorporates the historical emissions with relevant climate targets?

Proposal

The cumulative carbon budget of a country is how much carbon dioxide the country can emit post the industrial revolution. In this thought process, the cumulative carbon budget is zero. So it is not essential to achieve net zero in a particular year, say 2050. The country must become cumulatively net-zero by a specific target date, say 2075. Developed countries are in a better position to achieve net-zero quickly because they have taken advantage of fossil fuels; however, this would mean that they have to work more to become cumulatively net zero. Similarly, a developing country like India cannot think it has a carbon budget because it will eventually have to be cumulatively net zero. Smaller countries that have used less carbon in the past would have it more manageable to get to cumulative net zero.

How do you become cumulatively net-zero once you have become net-zero? Carbon sequestration, both from natural and artificial solutions, is the most obvious pathway. However, as the carbon credits trading market evolves, it should enable developed countries to get credits for projects in the developing world.

The principle of the Cumulative net-zero is simple; no country has a carbon budget. Since it is the same for all countries, it is fair.

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Challenges and potential solutions

Challenge: The industrial era started a long time ago. The carbon dioxide emitted then would have disintegrated by now. If we remove that carbon now, it may reduce the atmospheric concentration below 300 ppm.

Proposed solution: In reality, nature is quite complex, with many carbon sinks and sources. So it is right that a simple budgeting canceling exercise would be too simplistic. Since we aim to reach an atmosphere with the same carbon dioxide and ocean acidity as the pre-industrial level, we must adjust our removal targets accordingly. For example, the total carbon dioxide sent to the atmosphere is 900 Gtonnes. However, to get back to similar atmospheric concentrations and ocean acidity, we may need to remove 500 Gtonnes. This difference would be because there may be some feedback loops that sequester carbon dioxide as we stop releasing greenhouse gases. The principle of Cumulative net-zero is that the removal responsibility would be based on the proportion of the emissions.

Challenge: Why is only carbon dioxide concentration in the atmosphere and ocean acidity considered? Should we get all parameters back to before the industrial revolution numbers?

Explanation: Human society and the standard of living have grown quite a lot during pre-industrial times. The growth of any species has an impact on its surrounding. To expect that we can perfectly go back to pre-industrial level parameters across the board would be naive. We need to focus on the significant and impactful parameters. The concentration of CO2 in the air is the most obvious, but since oceans actually have taken up a significant part of our emissions, it becomes essential to look at them. The atmosphere and oceans are the most important from all species’ perspectives.

Challenge: What about other Greenhouse gases apart from CO2?

Proposed solution: The cumulative net-zero thought process can be extended across different greenhouse gases. However, we would need a nuanced approach to figure out how much needs to be sequestered for each of them. In cases where sequestration isn’t possible, we may use its equivalency to CO2 to determine the quantity of carbon dioxide that is required to sequester

Challenge: If I can emit now and remove it later, isn’t this kicking things down the road in terms of progress?

Proposed solution: The question isn’t relevant to historical emissions since the choice has been made in the past, and now we need to remove it. With regards to current emissions, this is a genuine concern. One potential solution would be the price of carbon which is slowly getting adopted worldwide. There would be a difference between the price of carbon and the cost of carbon sequestration; however, a common trend would increase. Since it would increase over time, it would incentivize immediate reduction strategies.