The Direct Link Between CO₂ and Temperature

The graph reveals a clear relationship: the higher the CO₂ concentration, the higher the global temperature. To stop global warming, the world needs to stop CO₂ emissions.

The points in the graph show individual years in the period of 1884–2024. The location of each point corresponds to the CO₂ concentration values in Mauna Loa in that year (on the horizontal axis)¹ and the global temperature anomaly values for that year (on the vertical axis).²

The graph indicates that within the range of concentrations shown, the relationship is approximately linear – each 10 ppm increase in CO₂ concentration leads to a temperature increase of about 0.1 °C – though over larger ranges this proportionality becomes less precise.

The dots in the graph are colour-coded and grouped (each period of 20 years has its own colour). It is clear that the increase in CO₂ concentrations has been accelerating in recent years, corresponding to increasing annual CO₂ emissions.

The right part of the graph shows the expected global warming for higher CO₂ concentrations in the future, provided CO₂ emissions continue.

How are other greenhouse gases and aerosols affecting the warming beyond CO₂?

Carbon dioxide is responsible for over half of observed global warming. The remaining part is due to other greenhouse gases, mainly methane, nitrous oxide, and F-gases: their concentrations in the atmosphere are also increasing.³ (See also: all main greenhouse gases.)

Along with greenhouse gases, humankind also emits aerosols, which have a cooling effect on the planet – they reflect solar radiation and participate in the formation of clouds.

The global warming shown in the graph on the vertical axis includes all of these phenomena, but only CO₂ concentrations are plotted on the horizontal axis. Thus, the claim of proportionality between increasing concentration of CO₂ and warming is somewhat simplified. While CO₂ concentration is the dominant factor, it is not the only one.

What happens if emissions stop?

As simple as this question seems, the answer is complex and depends entirely on which emissions are stopped.

If only CO₂ emissions were to stop – the dominant warming factor – global temperatures would stabilise within a few years.⁴

However, in the real world, CO₂ emissions are closely tied to aerosols. Most cooling aerosols are formed from substances such as sulphur dioxide, which are direct byproducts of burning the same fossil fuels that produce CO₂.

So if the world stopped both CO₂ and related aerosol emissions simultaneously, temperatures would actually rise – first rapidly, then more gradually – by about 0.5 °C. This is because the cooling “mask” of aerosols washes out of the atmosphere, while the CO₂ remains.⁵

Finally, if all greenhouse gas and aerosol emissions stopped, we would see an initial rapid temperature spike as aerosols disappeared, followed by a gradual cooling trend as methane and other short-lived greenhouse gases broke down. This would eventually lead to a slight overall decrease in global temperature.⁶

Footnotes

1. Mean annual CO2 concentration data in Mauna Loa come from NOAA, Global Monitoring Library, Trends in CO2, CH4, N2O, SF6. Dataset accessed 2026-01-22. ↩

2. Temperature data come from NASA Goddard Institute for Space Studies, The GISS Surface Temperature Analysis version 4 (GISTEMP v4). Dataset accessed 2026-01-22. ↩

3. For detailed decomposition of different contributions to warming see Figure SMP.2 in IPCC AR6 WGI Summary for Policymakers. Intergovernmental Panel on Climate Change. (2021). Summary for Policymakers. In: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to AR6. DOI: 10.1017/9781009157896.001. ↩

4. Hausfather, Z. (2021, 29 April). Explainer: Will global warming ‘stop’ as soon as net-zero emissions are reached? CarbonBrief. ↩

5. Hausfather, Z. (2025, 10 June). Explainer: How human-caused aerosols are ‘masking’ global warming. CarbonBrief. ↩

6. For details see Figure 1.5 in IPCC SR15. Intergovernmental Panel on Climate Change (2018). Global Warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty. DOI: 10.1017/9781009157940. ↩