A carbon budget can be spent only once too

The immense challenge countries are facing in Glasgow is the consequence of postponing climate policy for years. We cannot continue to put problems ahead of us, Oreane Edelenbosch and Detlef van Vuuren argue.

The amount of greenhouse-gas emissions the world has produced in the past century can be compared to a jar of money: if you spend little, you have more left. But if you have spent big in the past, you can still be in debt even if you are living very economically. That also applies to the so-called carbon budget.

Just like every other budget, the carbon budget will also run out eventually. The global emissions will therefore have to drop to ‘net zero’ in order to stabilise the rise in temperature.

In the Paris Accord, the agreement was made to limit global warming to far below 2 degrees and preferably 1.5 degrees Celsius, compared to pre-industrial values. Like how we express money in euros, the emission of CO₂ is expressed in gigatonnes (Gton, or GtCO₂), meaning billion tonnes. The world has only 400 Gton CO₂ left to spend in order to limit the temperature increase to 1.5 degrees and approximately 1000 Gton CO₂ for far below 2 degrees Celcius. There currently is a global annual emission of roughly 42 Gton of CO₂ by means of burning fossil fuels and changing land use such as deforestation. If emissions stay the same in the upcoming years, we will run out of the 1.5 degrees budget in 8 years and out of the 2 degrees budget in 25 years.

Just like every other budget, the carbon budget will also run out eventually. The global emissions will therefore have to drop to ‘net zero’ in order to stabilise the rise in temperature. That would approximately have to happen in 2035 for 1.5 degrees and in 2065 for 2 degrees (if the trend continues). They speak of ‘net zero’ because emissions can be compensated by uptakes of CO₂ by means of measures such as reforestation. These ‘negative emissions’ are important and can give the world some more time, but are definitely not unlimited and without consequences. We therefore have to prevent getting deeper and deeper into the red figures.

The Earth Summit

Already in the first IPCC report from 1990, the climate problem was called a big threat. That report formed a reason for the Earth Summit in 1992 in Rio de Janeiro, where the countries of the United Nations made a treaty in which the first careful steps to address climate change were taken. The carbon budget was almost four times its current size at the time, and the annual emissions of greenhouse gases were much lower. If the world had acted back then, we would have been granted much more time to address the climate problem. We did not do that, resulting in us currently being almost in the red. The graph shows it: if we had immediately started back then with a modest reduction of emissions, we could have taken the entire 21st century to solve the problem.

Since the Paris Accord, many countries have flipped the switch and active climate policy is being carried out. 148 countries have drafted national contributions (NDCs) that together, according to calculations of the PBL, would make for an emission reduction of a few percent in 2030, which is far from enough for the end goal. The attempt to submit additional plans for the 2021 climate summit in Glasgow has resulted in an expected additional reduction of 4 to 5 GtCO₂ in 2030 (also see the Emissions Gap Report by UNEP), instead of the 15 to 30 GtCO₂ that are needed to achieve an optimal line. Long story short, we are postponing the problem once again.

Seven-league boots

In Paris, the agreement was made to evaluate the progression of all national climate plans once every five years (2018, 2023 etc.). In the years in between (2020 – 2021 due to Covid, 2025 etc) there is room for new, adjusted plans. So the upcoming period consists of five very expensive years. Because as long as the emissions remain high, we are exhausting our budget with seven-league boots.

That is why it is crucial that in the very short run, preferably still in Glasgow, we figure out how to reduce that extremely high annual ‘spending’ of 42 Gton – in order to make the problem somewhat manageable again. That will not be easy: A CO₂-neutral society means that a close to full transition has to take place in all sectors that contribute to the current emission: traffic, constructed environment, industry, the energy sector and agriculture. The speed in which these changes have to take place puts pressure on society as a consequence of years of postponing. But as we have seen from the past: dawdling will not help.

The climate problem has been known for years, but although the emissions were increasing, the direct consequences were not tangible yet. They are now. Here as well, the comparison to a financial budget applies. As long as there is still money, you will not notice the consequences immediately, rent is paid and you have a roof over your head. You will only feel the blow once the wallet is empty. The transition is inevitable, so we should start quickly to stay ahead of that moment.