Redefining net zero will not stop global warming - study

Relying on ‘natural carbon sinks’ like forests and oceans to offset ongoing CO2 emissions from fossil fuel use will not actually stop global warming, say an international group of authors who developed the science behind net zero.

The science of net zero, developed over 15 years ago, does not include these natural carbon sinks in the definition of net human-induced CO2 emissions. New research shows that companies are using nature's carbon absorption as an excuse to avoid cutting fossil fuel use, exploiting flawed accounting rules to appear "green" while still warming the planet.

The new study, led by the University of Oxford’s Department of Physics and featuring contributions from partners including the University of Reading, is published today (Monday, 18 November) in Nature. 

Geological Net Zero

Authors of the study are calling on governments and corporations to clarify how much they are counting on natural carbon sinks to meet their climate goals, as well as recognising the need for Geological Net Zero.
 
Geological Net Zero means balancing flows of carbon into and out of the solid Earth, with one tonne of CO2 committed to geological storage for every tonne still generated by any continued fossil fuel use. Given the cost and challenges of permanent geological CO2 storage, achieving Geological Net Zero will require a substantial reduction in fossil fuel use.

Professor Jonathan Gregory, who co-authored the study from the University of Reading, said: “In order to stop climate change, net zero has got to mean geological net zero. This is a really simple and powerful idea. We call it “geological” because we’re taking about what is stored underground, in the Earth. When we mine coal, oil, and gas and burn them, carbon which was underground goes into the atmosphere. In future, if we continue to burn fossil fuels, we must take deliberate action to remove at least as much carbon from the atmosphere and put it underground, where it can’t come back. We can’t rely on Nature to do this for us.”
 
The authors stress the importance of protecting and maintaining natural carbon sinks while accepting that doing so cannot compensate for ongoing fossil fuel use. Total historical CO2 emissions determine how much a country or company has contributed to the global need for ongoing natural carbon sinks. A country like the UK, with large historical emissions and limited natural sinks, has implicitly committed other countries to maintain natural sinks for decades after UK emissions reach net zero. This is not currently addressed in climate talks.

Allen, M. R., Frame, D. J., Friedlingstein, P., Gillett, N. P., Grassi, G., Gregory, J. M., Hare, W., House, J., Huntingford, C., Jenkins, S., Jones, C. D., Knutti, R., Lowe, J. A., Matthews, H. D., Meinshausen, M., Meinshausen, N., Peters, G. P., Plattner, G., Raper, S., . . . Zickfeld, K. (2024). Geological Net Zero and the need for disaggregated accounting for carbon sinks. Nature, 1-3. https://doi.org/10.1038/s41586-024-08326-8