2015 Paris Agreement: Temperatures must not rise above 2ºC

Based on scientific reports, the international community signed the Paris Agreement in 2015 to curb emissions in order to keep the temperature increase below 2ºC and to make efforts to try to keep it below 1.5ºC. 

Why is it very important to keep this increase as low as possible? 

The CO₂ we emit is partly absorbed by vegetation and the Earth's oceans. If the temperature has not increased further so far, it is because nature has absorbed a large part of our impact. But this natural system does not work so well at high temperatures, so the situation would become much worse if we exceed a temperature increase that spoils our "absorption focus." For example, there is big amount of CO₂ dissolved in the oceans water. If the temperature of the ocean water increases, this CO₂ will be released into the atmosphere, feeding back into the problem.

The maximum amount of CO₂ that the world can emit to keep warming below a given temperature (we can calculate it for 1.5°C, 2°C, etc.) is called the Global Carbon Budget (GCB). Imagine counting all the CO₂ that could be released into the atmosphere since industrial activity began to keep temperatures from exceeding those limits. If we put that amount of CO₂ in a container and see what percentage of the total we have been using over the years and how the temperature has increased as a result, how much would we have left to use? This video shows you:

How much CO₂ are we emitting?

The graph on the left shows the total amount of CO₂ released into the atmosphere each year since 1850. Of the 41 trillion tons released by the world in 2023, 11.6 trillion tons were released by China, 5 trillion by the US, and 2.4 trillion by Europe. The total amounts released by Europe and the US have stabilized in recent years, but not by China and India, whose populations are larger and continue to grow.

The second graph shows the amount of CO₂ emitted per person. In this case, you can see that although the amount emitted by an average American has decreased in recent years, their emissions are considerably higher than those of any other inhabitant of the planet (more than double that of a European, for example). Although in the previous graph it was observed that, in total, China emits more than the USA, that is because it has more inhabitants, since in this graph we see that an average inhabitant of China emits less than an average American.

CO₂ emissions, Global Carbon Budget (2024), data mainly processed by Our World in Data, Our World in Data , CC-BY-4.0 

How much more CO₂ can we emit? Carbon budget

There is some uncertainty about how the climate responds to our emissions. That means there is no single “budget,” but rather a range of probabilities. The lower our emissions, the more likely we are to keep temperature rise below our targets. The chart below shows the remaining carbon budget for 1.5°C and 2°C based on those probabilities. 

To have a chance a 50% chance of limiting temperatures to 1.5°C, we should emit less than 250 billion tonnes of CO₂ from now. And there would still be a 50% chance that temperatures would exceed that limit.

The world emitted 41 billion tonnes of CO₂ in 2022. If we continue to emit at the current rate we will exhaust our budget in 6 years: 

250,000 tonnes/41,000 tonnes/year = 6 years. 

From there, continuing to emit more CO₂ means that the temperature will probably rise by more than 1.5°C.