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Rapid response to:


Call for emergency action to limit global temperature increases, restore biodiversity, and protect health

BMJ 2021; 374 doi: (Published 06 September 2021) Cite this as: BMJ 2021;374:n1734

Linked News

Climate crisis: Over 200 health journals urge world leaders to tackle “catastrophic harm”

Rapid Response:

The UK's share of the Paris-compliant global carbon budget will be used up in 3.3 years

Dear Editor,

How urgent is an "emergency"? The word usually implies that immediate action is needed, but in the two years since the declarations of a climate emergency by many national and local administrations following the 2019 street protests, there has been little effective action. In some countries, e.g. the UK, fossil fuel use has even been encouraged by measures such as further road building. It is all a long way from the "rapid and far-reaching transitions", taking just a few years, that was envisaged by the IPCC SR15 report of 2018 [1], which sparked the street protests.

We can quantify the urgency of the climate emergency in terms of the residual carbon budget - i.e. how much more CO2 can be dumped into the atmosphere without a major risk of exceeding 1.5°C global warming - and how soon this budget will be used up at current emission rates. It turns out that the UK's fair share of the global carbon budget will be used up in 3.3 years. The maths are simple, but this timescale of 3.3 years is so far from what is being discussed, even in your editorial, that it is worth explaining the calculations in detail, as follows, so that readers can check for themselves.

The 2021 IPCC AR6 report [2] (Table SPM.2 p38) gives 400 billion tonnes CO2 as the global carbon budget to keep global warming to less than 1.5°C with 67% confidence. This is from the start of 2020. With a world population close to 8 billion, and using an assumption of global equity, this is 50 tonnes per person on the planet as a lifetime limit. The UK's current CO2 emissions are around 10 tonnes per person per year, according to a WWF report [3] (Figure 21, p46). So the UK's 50 tonnes per person will be used up in 5 years from January 2020, i.e. in December 2024, which is 3.3 years from now.

This should not come as a surprise to people in the UK since similar calculations were done by the Tyndall Centre after the 2018 SR15 report, and are readily available for each UK local authority [4]. These typically give a fair share of the global carbon budget as running out in 7 years from 2020 at current emission rates - the period is 7 rather than 5 years since the local authority data provided by BEIS is incomplete in not including emissions that are embedded in imports. Despite being so readily available, these reports have been almost completely ignored.

Why is the need for radical change (emission cuts of double digit percentages per year) not common knowledge? Firstly, the UK Government promotes its Net Zero 2050 plan [5] as a satisfactory solution, but the Government is not being sufficiently transparent that emissions from aviation, shipping and imports are excluded, or about the implications of the commitment to global equity, or about the feasibility of the implied technological solutions. Many commentators repeat the Government's claims without challenge, but youth climate activists see through them and are speaking up about the deceits [6][7]. Secondly, for various reasons, many climate scientists and many NGOs are self-censoring about the size and urgency of the changes needed [8] - it is easier to campaign against the expansion of a particular airport than to explain the blunt truth that any leisure flying using fossil fuels is incompatible with a lifetime personal carbon budget of 50 tonnes CO2, since a reliable food supply and keeping warm are much higher priorities.

Yet another COP may help, but what is really needed is for everyone to tell the truth about the climate emergency so that it is treated as an emergency, and to call out misinformation and deceits whoever makes them (however uncomfortable that is), as is advocated by Scientists for Global Responsibility in their Science Oath [9]. It is clear that we cannot rely on governments to take the right decisions by themselves, however much they are urged to. It is up to citizens to be much more involved in policy making, and health professionals with their independence and their experience in making and explaining tough choices are well placed to make a major contribution to this.


Competing interests: No competing interests

17 September 2021
Ian R Campbell
Medical statistician
Merseyside, UK