Redefining net zero will not stop global warming University of Oxford

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.

Natural sinks play a vital role to moderate the impact of current emissions and draw down atmospheric CO2 concentrations after the date of net zero, stabilizing global temperatures. Yet governments and corporations are increasingly turning to them to offset emissions, rather than reducing fossil fuel use or developing more permanent CO2 disposal options. Emissions accounting rules encourage this by creating an apparent equivalence between fossil fuel emissions and drawdown of CO2 by some natural carbon sinks, meaning a country could appear to have ‘achieved net zero’ whilst still contributing to ongoing warming.

The researchers call 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.

"We need to stop dumping carbon dioxide into the atmosphere and scale up our ability to get rid of it permanently. We can’t take credit for the absorption of carbon which would happen naturally – the carbon we remove must be in addition to that.

Professor Myles Allen, Department of Physics.

The study was led by Professor Myles Allen, of the University of Oxford’s Department of Physics, known as ‘the physicist behind net zero.’ In 2005, Professor Allen introduced the notion of a finite carbon budget, implying net zero emissions of carbon dioxide are necessary to halt global warming.

He summarised: ‘We are already counting on forests and oceans to mop up our past emissions, most of which came from burning stuff we dug out of the ground. We can’t expect them to compensate for future emissions as well. By mid-century, any carbon that still comes out of the ground will have to go back down, to permanent storage. That’s Geological Net Zero.’

Professor Allen, who founded the Oxford Net Zero initiative, added: ‘This is not a new target: it is a recognition of what we actually meant by net zero emissions back in the late 2000s. As the climate challenge starts to bite, there is naturally pressure to soften it. Universities like Oxford are uniquely placed to make sure that doesn’t happen.’

"In the end, this is a global waste disposal problem. Companies selling fossil fuels should be required to dispose responsibly of the carbon dioxide those fuels generate. If they did, this could solve global warming completely within a generation.

Professor Myles Allen, Department of Physics.