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Zero Hour and the CAN Bills: Climate urgency denial

This web page is a critique of the two Climate and Nature (CAN) Bills promoted by the Zero Hour climate campaigning group.

The first CAN Bill (referred to here as the CAN(1) Bill) was published in March 2024. It had several good points, particularly the emphasis on adhering to the UK's per capita share of the global carbon budget for 1.5°C, and highlighting the defects in the UK Government's Net Zero 2050 strategy.

However the CAN(1) Bill had several serious flaws:
  • understating the urgency of climate action
  • controversial carbon accounting
  • lack of transparency in carbon accounting
  • advocating a ludicrous timescale of emission reduction, with little reduction for 2 years and then reduction to zero by 2030.

The CAN(1) Bill understated the urgency of climate action and advocated inadequate action, and so was a part of the spectrum of climate urgency denial of almost all of the UK's climate advocacy groups.


The second CAN Bill (referred to here as the CAN(2) Bill) was published in October 2024, and replaced the CAN(1) Bill.

It is a radical change from the CAN(1) Bill. It has dropped the emphasis on adhering to the UK's per capita share of the global carbon budget for 1.5°C, and merely endorses the UK Government's Net Zero 2050 timescale. This means that the CAN(2) Bill, if replicated globally, would result in global warming of 1.8°C, resulting in an additional 100 million climate deaths. The CAN(2) Bill should therefore not be given support.

The change from the CAN(1) Bill to the CAN(2) Bill has not been well-publicised by Zero Hour - the website and campaigning material refer to "the CAN Bill" as if there is only one, and much of the material on the Zero Hour website applies to the CAN(1) Bill but not to the CAN(2) Bill.

The Zero Hour campaign is part of the shambles of UK climate campaigning. There is a desperate need to improve - for people to work together on the basis of the science - to #BringScienceToActivism.

The two Climate and Nature (CAN) Bills

Zero Hour [1] is a climate campaigning group which has promoted the two Climate and Nature (CAN) Bills. These are Private Members' bills [2] introduced into the UK Parliament via the House of Commons.

Excerpt from the CAN(1) Bill
The first CAN Bill [3], referred to here as the CAN(1) Bill, was published in March 2024 and was presented by Alex Sobel MP.

The emphasis in the CAN(1) Bill was on adhering to the UK's per capita share of the global carbon budget for 1.5°C (see excerpt).

See Appendix 1 for a critique of the CAN(1) Bill.

Excerpt from the CAN(2) Bill
The second CAN Bill [4] (referred to here as the CAN(2) Bill) was published in October 2024 and was presented by Roz Savage MP. It replaced the CAN(1) Bill.

The CAN(2) Bill is a radical change from the CAN(1) Bill. It has
  • dropped the commitment to the 1.5°C Paris target (or any other temperature target),
  • dropped the commitment to the UK staying within its per-capita share of the global carbon budget
and replaced these commitments with merely staying within the UK’s declared Nationally Determined Contributions [5] (see excerpt), i.e. the UK's voluntary commitments (widely regarded as inadequate), i.e. it merely endorses the UK Government's Net Zero 2050 timescale [6].

Furthermore, the Zero Hour briefing document [7] for the Jan 2025 Second Reading of the CAN(2) Bill
  • dropped reference to the need for an emergency strategy, which was a key feature of previous briefing documents e.g. the 2022 Zero Hour Ambition Gap document [8],
  • ignored the "immediate, rapid and large-scale reductions in greenhouse gas emissions" [9] that the IPCC said in 2021 was necessary for the 1.5°C target.

So the CAN(2) Bill is a radical change from the CAN(1) Bill.

The spreadsheet gives calculations for the UK’s CO2 emissions that would result from the CAN(2) Bill timescale of emission cuts.


The total of 7.9 billion tonnes CO2 is much more than the UK’s fair share carbon budget for 1.5°C of 3.4 billion tonnes - it is 2.3 times more.

This calculation is very similar to the Zero Hour calculations in the 2023 Ambition Gap briefing [8] (see image) which seems to have been done to show the inadequacy of the UK Government’s pathway of emission reduction. So it is extraordinary that the CAN(2) Bill abandons the fair-share approach and meekly endorses the UK Government’s approach.

If the UK’s 7.9 billion tonnes CO2 were to be scaled up to the global population, the total emissions would be 970 billion tonnes, which would lead to global warming of 1.8°C according to the IPCC carbon budget calculations (50% confidence) (see image from the AR6 report [10]).

This additional warming would cause an additional 100 million climate deaths, with the UK being responsible for an additional one million deaths (in round numbers), using the estimate of one death per 4000 tonnes CO2 [11].


The CAN(2) Bill should therefore not be given support.

The change to the CAN(2) Bill

The change from the CAN(1) Bill to the CAN(2) Bill has not been well-publicised by Zero Hour - the website [1] refers to "the CAN Bill" as if there is only one, and much of the material on the Zero Hour website is relevant to the CAN(1) Bill but not to the CAN(2) Bill.

The Zero Hour website home page [1] still says "The Climate and Nature Bill makes sure the UK does its bit to keep global warming down to 1.5°C".

But the change to the CAN(2) Bill and merely supporting the UK Government's timescale of emission cuts means 1.8°C of global warming, not 1.5°C.

The website is seriously misleading, and needs to be changed.

The Climate Emergency requires emergency action, and Zero Hour should be saying so.

Comment

The Zero Hour campaign is part of the shambles and denial of climate urgency of UK climate campaigning.

There is a desperate need to improve - for people to work together on the basis of the science - to #BringScienceToActivism.


References

[1]https://www.zerohour.uk
[2]https://www.parliament.uk/about/how/laws/bills/private-members/
[3]First Climate and Nature Bill (March 2024) https://publications.parliament.uk/pa/bills/cbill/58-04/0192/230192.pdf
[4]Second Climate and Nature Bill (October 2024) https://publications.parliament.uk/pa/bills/cbill/59-01/0014/240014.pdf
[5]UK Nationally Determined Contributions https://www.gov.uk/government/publications/uks-2035-nationally-determined-contribution-ndc-emissions-reduction-target-under-the-paris-agreement
[6]Net Zero Strategy: Build Back Greener (2021) https://assets.publishing.service.gov.uk/media/6194dfa4d3bf7f0555071b1b/net-zero-strategy-beis.pdf
[7]Zero Hour briefing (Jan 2025) https://www.zerohour.uk/downloads/climate-and-nature-bill-briefing.pdf
[8]Net Zero: The Ambition Gap (2022) Zero Hour https://zerohour.uk/downloads/ambition-gap.pdf
[9]IPCC Press Release (2021) https://un-spbf.org/event/ipcc-press-release-climate-action-cannot-wait/
[10]IPCC (Aug 2021) AR6 Climate Change 2021: The Physical Science Basis (Table TS.3 on page 115) https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_FullReport.pdf
[11]Mortality and other harms from climate change https://www.carbonindependent.org/144.html
[12]Carbon budget calculations for the UK https://www.carbonindependent.org/170.html
[13]https://cusp.ac.uk/wp-content/uploads/WP-29-Zero-Carbon-Sooner-update.pdf
[14]https://www.un.org/en/development/desa/population/migration/generalassembly/docs/globalcompact/A_CONF.151_26_Vol.I_Declaration.pdf
[15]Wullenkord & Reese (2021) https://www.sciencedirect.com/science/article/abs/pii/S0272494421001365

Appendix 1: Critique of the CAN(1) Bill

Good points in the CAN(1) Bill

The Zero Hour briefing documents
  • make a good case for climate change being an overriding priority
  • clearly state a target limit for global warming (1.5°C)
  • emphasize the importance of adhering to the UK's per capita share of the global carbon budget for 1.5°C
  • emphasize accounting for all the CO2 emissions that the UK is responsible for, including those from imports and aviation
  • expose serious flaws in the UK Government's Net Zero 2050 strategy [6], namely the failure to reduce emissions faster than the global average (as
    specified in the Paris Agreement
    ), and the failure to properly account for emissions embedded in imports.

Serious flaws in the CAN(1) Bill

Understating the urgency of climate action
In 2021, the IPCC said [9]:
"unless there are immediate, rapid and large-scale reductions in greenhouse gas emissions, limiting warming to close to 1.5°C or even 2°C will be beyond reach"
Numerically, the urgency of climate action is given by
  • the short time before the UK's per capita carbon budget is exhausted at current emission rates:
    • including imports, the UK's carbon budget for 1.5°C runs out in 2026 [12]
    • excluding imports, the UK's carbon budget for 1.5°C runs out in 2028 [12]
  • the size of the emission cuts needed to stay within the carbon budget, i.e. of the order of 20% per year [13].

The Zero Hour documents do not mention the 2026 date. There is a mention of the 2028 date for exhaustion of the UK's carbon budget excluding imports, but this is only in the Appendix of the Ambition Gap document [8], and is not in other documents, e.g. in the approaches to MPs. The imminent exhaustion of the UK's carbon budget is such a crucial point that it should be highlighted everywhere.

The size of the emission cuts needed (of the order of 20% per year) is not stated in the Zero Hour documents in numerical terms, just in text such as "a pace unprecedented in peacetime" [8], which is open to wide interpretation. This is a serious omission.

Controversial carbon accounting: omitting emissions from imports in calculating the UK's cumulative CO2 emissions
The Zero Hour briefing documents emphasize the the importance of counting all CO2 emissions including those generated in the production of imported goods (termed "consumption emissions" rather than "territorial emissions"), but the wording of the CAN(1) Bill specifies that only territorial and aviation emissions would be included in totting up the UK's cumulative emissions in order to keep within a fair carbon budget. This would mean that, including imports, the UK would take about 40% more than its fair share of the global carbon budget for 1.5°C. If other countries followed suit, the total additional global emissions would be an extra 40%. This would lead to global warming of 1.6°C, not 1.5°C.

There are several arguments in favour of including emissions from imports in carbon accounting. A principal one is that this is in line with the UK's international commitments since Principle 2 of the Rio Declaration is "States should ... discourage or prevent the relocation and transfer to other States of any activities and substances that cause severe environmental degradation ..." [14]. So the transfer of much manufacturing from the UK to abroad that has taken place for several decades goes against the Rio Declaration, and should not be ignored.

Lack of transparency over carbon accounting
There is inconsistency in terminology in the Zero Hour initiative e.g. "total carbon footprint" is used in the Ambition Gap report [8] to mean including emissions embedded in imports, but in the CAN(1) Bill, "total emissions" is used to mean excluding imports. It seems likely that many readers will be unaware that this is what the Bill intends. Whether or not imports are included is such a crucial point that this exclusion from Zero Hour's calculation of the UK's cumulative emissions should be prominently and explicitly stated.

Advocating inadequate action
Zero Hour documents fail to highlight the scale and speed of changes needed throughout society to achieve the emission cuts effectively promised in the Paris Agreement, e.g. an immediate end to leisure flights. It is not good enough to say that changes will be decided in consultation with a citizens' assembly without giving any indication of the radical transformation that is needed.

There is a common misconception that a gradual decarbonisation is all that is needed - even The Guardian is still promoting flights to Japan, India and South America for holidays. Zero Hour is adding to this misconception, leaving an information vacuum where the Government can continue to freeze fuel duty, and invest in unproven technological "solutions".

UK carbon budget chart for Zero Hour proposalThe proposed Zero Hour procedure was that the CAN(1) Bill would progress through Parliament during 2025 as a Private Members' Bill, and that once passed the Government would have 12 months to present a plan, i.e. potentially in 2026. This would mean that of the 2 years to when the UK's fair carbon budget including imports runs out in 2026, all of the time would be spent in drawing up a plan. And of the 4 years from now to when the UK's carbon budget excluding imports runs out in 2028, half the time would be spent passing the Bill and drawing up a plan, after which emissions would have to reduce to zero by 2030, as in the chart. This timescale is nonsensical; the planet needs radical action now, not in 2 years time. Everyone who cares about the climate should be saying this.

CAN(1) Bill: Conclusion

The CAN(1) Bill understated the urgency of climate change, and advocated an inadequate timescale of action. This made it a part of the spectrum of climate denial of climate advocacy groups (implicatory climate denial [15]).

Appendix 2: History of the CE and CAN Bills

There have been five related Private Members' Bills.

PublishedPresented byTitleTemperature target statedIncluding international equityIncluding imports/exportsEffective temperature target
1Sep 2020Caroline LucasClimate and Ecology Bill1.5°CYes
2Jun 2021Caroline LucasClimate and Ecology Bill1.5°C-Yes
3May 2023Olivia BlakeClimate and Ecology (No. 2) Bill1.5°CYes-
4Mar 2024Alex SobelClimate and Nature Bill1.5°CYes-1.6°C
5Oct 2024Roz SavageClimate and Nature Bill---1.8°C


First published: 1 Nov 2024
Last updated: 20 Aug 2025     Page No: 174