Immediate phase out of fossil fuels could keep warming below 1.5°C

Despite some positive climate action, new fossil fuel infrastructure is still being built and deployed. Dozens of new coal power plants are currently planned or under construction, for instance, while petrol car sales will nearly hit 100m in 2019.

But what if all that ceased tomorrow? It turns out that if we built no more fossil fuel infrastructure and instead replaced existing infrastructure at the end of its productive life with a zero carbon alternative we could limit peak temperature rise to 1.5°C – as long as we start now.

Colleagues and I recently analysed what would happen to global emissions if fossil fuel power plants, cars, ships, aircraft and industrial infrastructure were all phased out. Our results are published in Nature Communications. This may be a hypothetical scenario, given a full phase out is unlikely to happen any time soon, but calculating what would happen in such a scenario gives us a better idea of the challenge ahead.

In our optimistic scenario, the process of replacing all the fossil fuel infrastructure with zero carbon alternatives (or not replacing it at all) began from the end of 2018. Doing this we found that the chance of keeping global temperature rise to below 1.5°C was 64%.

Delaying a fossil phase out until 2030 would make this a lot less likely, even if the phase out rate was sped up.

Four decades of committed warming

A coal power plant is typically operated and emits carbon dioxide (CO₂) for about 40 years. So, every new coal plant built in the recent past or today carries a climate change commitment. For instance, Drax, the UK’s largest power plant, used to burn coal exclusively and has probably warmed the planet by a few ten-thousandths of a degree over its lifetime. That isn’t much by itself, but such warming all adds up. We call this the “committed warming” from fossil fuel infrastructure. Drax now predominately burns wood pellets, and is one example of how fossil fuel infrastructure could be replaced.

Our analysis produces a scenario that reduces CO₂ emissions to nearly zero over 40 years. This compares with the recent IPCC special report on 1.5°C, which concluded that reducing emissions to net zero over 35 years was required to get even a 50% chance of limiting global warming to 1.5°C.

The additional, narrow window of five years to get to net zero can be explained by different approaches. Some of this difference is accounted for by the timing of emissions phase out. As every year of procrastination brings the date by which we’ll have to reach net zero emissions forward by two years, even delaying until after 2020 rather than 2018 means that a 40 year phase out would have to happen in 36 years to achieve the same outcome. We also used historical temperature observations to guide the future climate response to emissions. Our projection of additional warming for each additional tonne of CO₂ is a little lower than the IPCC’s best estimate, although well within the “likely” range.

Alongside power stations, cars, ships and planes, we also applied the “asset lifetime” assumption to meat cattle. Cows produce a lot of methane, so if we ate them all over the next three years without breeding any more, we could certainly reduce our greenhouse gas emissions considerably while having a gluttonous time doing so. Non-livestock emissions are more tricky and harder to mitigate – we still need to eat, and grow crops using fertilisers – but we assumed that we get more savvy at doing so, eventually reaching zero emissions by 2100.

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