How alive is 1.5?
Part one – a small budget, shrinking fast


Key messages

  1. For a 50:50 chance of staying below 1.5°C, we’re using up the remaining carbon budget at around 1% every month.
  2. Following current national emissions pledges (NDCs) to 2030 puts the temperature commitments within the Paris Agreement beyond reach.
  3. Claims that 1.5°C is now inevitable also assign “well below 2°C” to the scrapheap.
  4. An ‘outside chance’ of not exceeding 1.5°C remains viable, but ongoing fossil fuel use is rapidly undermining it.
  5. The few credible pathways for an outside chance of 1.5°C are not being discussed. This is an active choice by policymakers and experts, who have largely dismissed equity-based social change.

As we await the final text from COP27 in Egypt, we can be confident that the 1.5°C temperature goal of the Paris Agreement will remain a core part of the framing. Yet this year’s greenhouse gas emissions look set to exceed the previous year’s once again, and despite all the fanfare about ‘keep[ing] 1.5 alive’ at the 2021 Glasgow COP26, the intervening year has seen us use up almost 10% of the remaining carbon budget for a 50:50 chance of keeping below 1.5°C. The ongoing and comprehensive failure to tackle climate change is driving us rapidly away from even an outside chance of 1.5°C, prompting a slew of recent commentaries and opinion pieces on the disappearing viability of 1.5°C. The imminent passing of the 1.5°C threshold is now increasingly spoken of as ‘inevitable’.

In this first part of a two-part article on the relevance of 1.5°C, we unpick the policy gulf that exists between the Paris Agreement climate goals and our real-world emissions trajectory. Part two, forthcoming, will ask whether it is still tenable to claim that 1.5°C is in any meaningful sense ‘alive’. Spoiler alert! We disagree with both the techno-optimism that underpins mainstream political narratives on 1.5°C, and with claims that exceeding 1.5°C is now inevitable. These positions ignore, on the one hand, the need and the potential for massive social change, and, on the other, the widely differing emissions budgets for lower, but far from zero, probabilities of not exceeding 1.5°C.

Here in part one we challenge the first, techno-optimistic position (embodied by international leaders and the COP process) as being wilfully ignorant of reality. In part two, we will question recent suggestions that, because a 50% chance has all but slipped beyond reach, 1.5°C is now effectively dead in the water. We explore the dangers of disregarding societal transformations that could yet deliver an outside chance of 1.5°C. We also join-the-dots from budgets with lower probabilities of 1.5°C to respective probabilities of holding warming to below 2°C – a temperature guardrail still widely regarded as sacrosanct, even by those arguing to pull the plug on 1.5.

We’ve written already about the groupthink and mitigation denial that continues to hamstring translation of clear scientific evidence on climate sensitivity and emissions budgets into effective policies to reduce emissions. To recap: the recent history of climate change mitigation research has been dominated by techniques to reconcile the irreconcilable, transferring much of the climate burden from us today on to younger and future generations. Witness the proliferation of offsetting, the clean development mechanism (CDM), negative emission technologies (NETs), nature-based solutions (NBS), carbon dioxide removal (CDR), carbon capture and storage (CCS) and the ubiquitous daddy of them all, net zero bynot-in-my-term-of-office’. While the ideas behind this glossary of techno-jargon may have merit in principle, the prevalence of these concepts should be a serious cause for concern. Far from being wise ‘insurance policies’, they have fundamentally undermined emissions cuts by diverting political attention away from the urgency and sheer scale of reductions needed to meet our high-level climate commitments.

Our aim in this article is to equip the reader with a clear understanding of the scale and scope of the mitigation challenge implied by our commitments under the Paris Agreement and Glasgow Climate Pact. So equipped, it will then be possible to assess the appropriateness or otherwise of establishment narratives of ‘green growth’ and, increasingly, future deployment of still-speculative-at-scale technologies. Part two of this discussion, coming soon, will look more closely at what prospect, if any, remains of keeping an outside chance of 1.5°C in sight. There we illustrate the remaining carbon budgets for various probabilities of 1.5–2°C (and beyond), and explore the literature on rapid social, economic and technical change.

From “well below 2°C” to “1.5°C is not negotiable”
In 2015 almost all international leaders signed the Paris Agreement, a commitment to making their fair contribution to cutting emissions in line with staying “well below 2°C” and “pursuing…1.5°C”. The seven years since Paris have seen a major report on climate impacts (SR1.5), a notable tightening of the commitment to 1.5°C in the Glasgow Climate Pact, and a comprehensive update of climate science, impacts and mitigation options by the IPCC. Simultaneously, another quarter of a trillion tonnes of carbon dioxide have been dumped into the atmosphere. Referring specifically to the renewed commitment to 1.5 at the UK-hosted COP26, Patrick Valance, the UK Government’s chief scientist, stated that “1.5°C is really tough, it’s not an easy target”…but it’s “not a negotiable thing. It has to happen”.

Yet here we are, a year on from the Glasgow COP, another forty billion tonnes of carbon dioxide emitted and, Putin’s war notwithstanding, strong signals that global emissions are set to rise again next year. The UK Government (among others) has indicated its intention to open new oil and gas exploration, despite categorical warnings from the United Nations, the International Energy Agency and repeated scientific studies that such moves are incompatible with securing a sub-2°C future. It is against this backdrop of our leaders’ outright mockery of their 1.5–2°C commitments that declarations of ‘climate emergency’ and pledges of ‘net zero’ must be judged.

This ability, on the one hand, to enthusiastically develop new oil, gas and coal resources, while on the other to feign concern over 1.5°C, is facilitated by elaborate models that guide policymakers on ‘least-cost’ options towards 1.5°C. Typically, these models (known as integrated assessment models or IAMs) evoke futures of ever more exotic technologies and so-called ‘nature-based-solutions’. Seldom, if ever, do they question the dominant economic growth paradigm or propose regulatory frameworks to curtail the carbon excesses of the global minority responsible for the lion’s share of emissions.

The mainstream media is also complicit in allowing spurious techno-optimism to go unchallenged in politics. Journalists barely pen a line when BP, Shell, Exxon, Equinor, Chevron, Total, Saudi Aramco, Suncor and PetroChina make grand promises to be net-zero (or near-zero in PetroChina’s case) by 2050. The least investigation would expose such claims for the rhetorical, greenwashing nonsense that they are, applying only to the operational emissions from fuel production and processing (known as Scope 1 and 2 emissions), with no responsibility taken for the colossal quantities of carbon released when their oil, gas or coal is actually transported and burned, the inevitable outcome for extracted fuels (Scope 3 emissions).

Once we see through this ‘drug pusher’s subterfuge’, it quickly becomes clear that governments and oil and gas majors are singing from the same hymn sheet. Quite who is the choirmaster is not immediately clear, the distinction being blurred by revolving doors between ministers and oil and gas executives. The net zero by ‘not-in-my-term-of-office’ dates proposed by governments from the USA to Saudi Arabia, the EU to Russia, and China to Canada, essentially mirror those of the oil and gas companies. Wealthy nations with significant oil and gas production are not looking to phase out existing supply in line with 1.5°C [see endnote 1]. Instead they are licensing new oil and gas developments, including in the Arctic. As the recent minister overseeing the UK’s climate strategy blithely proclaimed, “we will extract every ounce of oil and gas from the North Sea“. Such developments, were they to proceed, would lock in fossil fuel use and high emissions for decades to come. They would also effectively lock out any prospect of 1.5°C and 2°C and bequeath to our children the chaos and suffering of an unstable climate heading towards 3°C and beyond.

But still, policymakers and senior oil and gas executives (assuming a distinction can be drawn) are seldom held to account by journalists, academics or NGOs. Certainly, the ‘petro-political’ shared storyline occasionally triggers low-level rumbles of discontent within the expert and media communities, superficially sounding like disagreement. But this almost choreographed dissent is typically constrained to nit-picking refinements, rather than confronting the dire need for deeper societal change or questioning highly asymmetric power and influence.

The rhetorical narrative of ‘keep 1.5°C alive’ is embraced by influential modelling experts, research funders, government leaders and oil and gas CEOs alike, despite their unbridled enthusiasm for ever more oil, gas and even some coal. In contrast, a very different narrative emerges from a direct, honest and pragmatic reading of the IPCC carbon budgets, taking a measured approach to novel technologies and bringing equity into the calculus.

It is this latter framing, guided by the IPCC’s latest carbon budgets [2], that we now turn to.

A small budget, shrinking fast
Here we work from the temperature commitments enshrined in the Paris Agreement, namely,  to cut emissions in line with staying “well below 2°C” and “pursuing…1.5°C”. These are then transposed into the more quantitative language of the IPCC, with the former becoming an 83% chance or better of not exceeding 2°C, and the latter a 50% chance of not exceeding 1.5°C.

With these temperatures and probabilities, we are able to use the carbon budgets provided in the latest IPCC’s scientific assessment (Working Group I of AR6 2021). The budgets they provide are from the start of 2020, so we update these to January 2023 [3].

Table 1 shows the updated remaining budgets (380 and 780 billion tonnes of carbon dioxide, GtCO2, Row 1), also expressed as how many years it would take at current annual global emissions before the budget was all spent (Row 2). Row 3 gives the annual rate of emissions cuts (percentage drop each year) necessary to stop total emissions from exceeding the requisite carbon budget. Row 4 gives the year when emissions would need to be zero if we were to draw a straight line down from today to zero emissions – again with total emissions not exceeding the carbon budget. The numbers in Table 1 are represented diagrammatically in Figure 1.

Row 5 in Table 1 tells just how much of the remaining carbon budget we are emitting each month. Such rapid rates of budget depletion ought to be extremely disturbing for anyone taking climate change seriously. They also illustrate how far removed the distracting nonsense of ‘net zero in decades from now’ is from physical reality.

The numbers in Table 1 are represented diagrammatically in Figure 1 below.

Ominously, the picture described by Table 1 and Figure 1 underplays the seriousness of the situation we are now in. Recent bottom-up assessments of current policies and announced national pledges (nationally determined contributions, NDCs) suggest that global CO2 emissions in 2030 are expected to show virtually no change from the present day. If, as now appears highly likely, emissions are not curtailed in the very near term, then to still deliver on our commitments, the percentage rate of annual reductions must increase significantly, or, if a ‘linear’ path were taken, the zero dates arrive much earlier.

Current NDCs – a calamitous pathway
Following the same format as Table 1, the values in Table 2 are based on global emissions remaining unchanged between now and 2030, as per current NDC pledges.

Two key messages emerge from Table 2. First, that following the NDCs puts the aspiration of holding the rise in temperature to below 1.5°C beyond even theoretical reach [4]. Second, that following the NDCs reduces the remaining (post-2030) carbon budget for “well below 2°C” to the same level as we have today for a 50% of not exceeding 1.5°C. Such a small budget is considered, by virtually all analysts, as offering insufficient opportunity to implement the necessary rates of mitigation, even if there were a global political consensus to do so [5]. In other words, following the NDCs to 2030 puts both the “pursuing…1.5°C” and “well below 2°C” commitments of the Paris Agreement beyond reach [6].

To fully appreciate the challenges and implications of the values in Tables 1 and 2, there are two important issues to understand. First, these values do not include adjustment for additional earth system feedbacks (see Box 1, below). Consequently, and given the tragic implications of failure, what is presented here should be viewed as highly conservative relative to our 1.5 and 2°C commitments.

Second, all values in these tables relate to global mitigation. Once the equity criteria embedded in every international climate agreement since 1992 [7] are taken into account, the rate of reductions for wealthier industrialised nations increases substantially [8]. Based on a peer reviewed analysis with a specific focus on such nations, industrialised countries are squandering their fair carbon budgets for “pursuing…1.5°C” at approximately 2% per month, or twice the global rate [9]. Extrapolating this to “well below 2°C”, the rate also doubles from the global mean to almost 1% per month. Even for the two ‘climate progressive’ nations of Sweden and the UK (case studies within the paper) the official ‘net zero’ pathways give rise to total emissions that are twice their fair contribution to ‘well below 2°C’, and approximately four times their fair share of the smaller “pursuing…1.5°C” carbon budget.

BOX 1: Budgetary adjustments – earth system feedbacks and non-CO2 emissions

While the headline carbon budgets in the IPCC’s AR6 report include a range of ‘earth system feedbacks’, or ESFs (26GtCO2 per degree Celsius), for various reasons there are still many such feedbacks judged to be insufficiently understood to include in the headline values. However, the IPCC does provide a quantitative estimate of these at +/- 97GtCO2 per °C. That is, the IPCC suggests the additional feedbacks could either increase or decrease the size of the remaining budget. Given the devastating scale and scope of climate impacts already observed for just 1.1–1.2°C of warming (as summarised in IPCC WGII), any moderately precautionary approach would lean towards decreasing the remaining carbon budgets, informed by the -97GtCO2/°C estimate. For 1.5°C, this would reduce the budgets by almost 150GtCO2 (i.e. by 40% for a 50:50 chance of not exceeding 1.5°C), rising to a little under 200GtCO2 for 2°C (i.e. by 25% for “well below 2°C”, taken here as the IPCC’s 83% chance, or better, of staying below 2°C).

In addition to possible earth system feedbacks, new scientific evidence (since the publication of AR6) suggests that the influence of non-CO2 emissions (in particular, declining aerosols and below-target reduction of methane) could reduce the remaining CO2 emissions budgets by as much as 120 GtCO2 (i.e. by almost third of the remaining budget for a 50% chance of 1.5°C). Therefore the values given by the IPCC and quoted here should be treated as the absolute maximum budgets for the given probabilities.

An active choice
What is immediately evident from Tables 1 and 2 is just how far removed the current ‘net zero’ framing of climate change is from the arithmetic translation of IPCC carbon budgets. Following the global emissions pathway associated with the summed NDC pledges sees the remaining emissions budget for a 50% chance of 1.5°C disappear within a decade. It is worth pausing to reflect that adherence to such a deeply calamitous pathway has been an active choice by our leaders.

However, a little further probing reveals that the void between our 1.5–2°C commitments and the now ubiquitous net zero rhetoric is even starker than it first appeared. Repeatedly, net zero has been justified by loose and lazy recourse to so-called ‘hard to decarbonise’ sectors. Yet stacked against the dire consequences of escalating climate impacts, ‘hard to decarbonise’ just doesn’t cut it; we simply must try harder.

We should also ask, what actually are the ‘residual emissions’ that lurk behind the cloak of ‘hard to decarbonise’? Here the spreadsheets accompanying the UK Government’s own climate advisory body (the CCC) tell a revealing story [10]. Their ‘Balanced Net Zero 2050’ analysis assumes the UK in 2050 will still emit over 30 million tonnes of CO2 from fossil fuel use. That is to say: more CO2 emitted per UK person in 2050 (factoring in population growth) than is emitted today from a typical Kenyan citizen. But of course the world doesn’t grind to a halt in 2050; if we apply a few fair and simple assumptions going forward, the UK’s post-2050 emissions of CO2 from ongoing fossil fuel use look set to total around half a billion tonnes. In context, that means greater UK fossil fuel CO2 emissions after 2050 than Kenya has emitted in total since 1990 – indeed probably has ever emitted [11].

The underlying data for the UK’s ‘Balanced Net Zero Pathway’ reveal that ‘hard to decarbonise’ is a euphemism for activities that wealthy and influential high-emitters are unprepared to see constrained. For example, residual CO2 emissions after 2030 increasingly come from aviation (dominated by frequent flying, the preserve of a wealthy minority [12]), with the evident assumption that this extends well into the second half of the century. In the nearer term, ‘hard to abate’ also includes ongoing and significant use of private cars, and, from the detailed reports describing the policy landscape accompanying the Balanced Net Zero Pathway, little if any direct change to the deeply inequitable distribution of emissions across income groups. More damning still, the influential high-emitting group includes those of us who formally frame the mitigation agenda, and who are unwilling or unable to imagine futures that would impose immediate and profound changes on our high material and energy consumption.

In essence, the many forms of disproportionate consumption that those of us on high incomes typically enjoy today remains, relatively, unchallenged and unchanged in this supposedly ‘highest possible ambition’ mitigation scenario [13]. As the saying goes, “when you’re accustomed to privilege, equality feels like oppression”. So perhaps it is not too surprising that those highly paid and influential individuals who frame the mitigation agenda favour the allure of carbon markets and future CDR over a near-term and significant reshaping of society. But the rapidly vanishing emissions space (Tables 1 and 2 above) makes it clear that the time for finessing is long gone.

In a single year between Glasgow COP26 and Egypt COP27, we have shrunk the remaining carbon budget for a 50% chance of 1.5°C by around 10%, and run down the budget for an 83% chance of 2°C by 5%. Once again, global leaders have chosen to preside over a rise in total emissions. At COP27, rather than tackle the challenges posed by cutting fossil fuel production in line with 1.5–2°C, negotiations ignored emissions and failed even to acknowledge that oil and gas play any role in climate change. Instead, leaders from authoritarian regimes (e.g. China, Saudi Arabia and Russia) and democracies alike (e.g. UK, Norway and USA) returned home only too eager to expand their development of new oil and gas fields.

Clearly, to many high-emitters, 1.5, or even 2°C, is little more than an abstract academic construct. Worse still, for some it’s an ‘opportunity’ for more accountancy tricks, financial scams and international jamborees on CDR, not to mention more profit and more economic growth. But for those at the sharp end of the impacts caused by our emissions, encroaching on these thresholds means real and deadly harms: another crop failure, a typhoon-devastated landscape, a drowned mother or a destitute child. As the IPCC makes clear, this is how it is already playing out today. Tomorrow it will spread to poorer families within our communities, shortly followed by our own children.

Burning through the remaining carbon budget at around 1% every month is a frankly terrifying rate to be locking-in ever-increasing impacts. The fossil fuel shills and puppets whom we allow to masquerade as our leaders have had decades to get their acts together. It is extremely doubtful whether another year, or even decade, will see them make any progress. Set against such catastrophic failure of top-down leadership, if the 1.5–2°C Paris goal is still to have any meaningful currency, then others must take the wheel, and soon.

Part two of this article, coming soon, will further unpack the importance of recognising the range of emissions budgets associated with varying probabilities of each increment of temperature rise, and look at the implications for both the rates and the forms of mitigation applicable.


Click on reference numbers to return to place in main article.

[1] For a detailed account of what phasing out fossil fuels in line with the IPCC headline carbon budget for a 50% chance of not exceeding 1.5°C, see the recent Tyndall Centre Report on fossil fuel phaseout pathways.

[2] See Table SPM.2 on page 29 of AR6 WGI Summary for Policymakers. For a very recent update to these budgetary values, see Lamboll et al (2022). NB: this paper is still in peer review. Nevertheless, given the urgency of responding to the 1.5°C commitment and that AR6 was unavoidably based on papers that are now several years old, this update still adds understanding and value, but must be read with recognition that it is still subject to change depending on the judgements of the reviewers.

[3] We conservatively assumed the emissions for 2022 would be the same as 2021 at 40.5 GtCO2; this includes energy, industrial and land use sources of CO2

[4] We acknowledge that the simple arithmetic does leave 56 GtCO2, but for all practical purpose this equates to zero carbon budget remaining.

[5] We are unaware of any analytical work that suggests global political, social, economic and technical inertia could be reconciled with a carbon budget of around 400GtCO2.

[6] The political wording of the Paris Agreement does not map easily onto the scientific language of temperature probabilities and their associated emissions budgets. Arguably, ‘well below 2°C’ indicates an increase in warming substantially below 2°C, while the Paris term ‘holding’ conveys that this sub-2°C increase should carry a high probability (and, one might logically infer, that the increase should, under no circumstance, exceed 2°C). Such an interpretation requires that a very high probability (at least 83%) of not exceeding 2°C is secured, because the associated emissions budget would also carry diminishing probabilities of not exceeding all temperature thresholds ‘well below 2°C’ (e.g. 1.9°C, 1.8°C, 1.7°C and so on). Conversely, if one allowed a lower probability of not exceeding 2°C (say 67%) to represent the Paris Agreement, then the corresponding probabilities of incremental temperature increases ‘well below 2°C’ drop to around 50% for 1.9°C, closer to 33% for 1.8°C and less than 33% for 1.7°C (IPCC AR6 WG1, Table 5.8). As this weaker characterisation would entail a 50:50 chance of not exceeding 1.9°C (the highest increment of warming one could reasonably claim was ‘well below 2°C’) it clearly would not be commensurate with the Paris imperative of ‘holding’ to that threshold.

[7] United Nations Framework Convention on Climate Change (UNFCCC), where the concept of Common but Differentiated Responsibilities and Respective Capabilities (CBDR-RC) was first introduced. The UNFCCC came into force in March 1994.

[8] Referred to as ‘developed country parties’ in the Paris Agreement. While there is a long history of wealthier nations endeavouring to weaken the differentiation between ‘developed’ and ‘developing’ nations in relation to both mitigation and adaptation, the Paris Agreement still maintains a consistent and clear distinction between the two. Despite this, in deriving national determined contributions (NDCs and the earlier INDCs) and in the development of more general climate policies, there is little to suggest that wealthier “developed” nations give any weight to issues of equity (i.e. CBDR-RC). However, in this piece and specifically in making the statement that the inclusion of CBDR-RC sees “the rate of reductions for wealthier industrialised nations increases substantially”, we are taking national leaders’ signatory to the Paris and other international climate agreements at face value. For an account of the central importance of CBDR-RC, the differentiation between ‘developed’ and ‘developing’ country parties, and the subsequent requirement of ‘developed’ nations to deliver higher rates of mitigation. See supplementary information – Equity in the Paris Agreement.

[9] The focus on ‘developed country parties’ was subsequently refined to two case study nations, the UK and Sweden.

[10] The datasets underpinning the UK Climate Change Committee’s Balanced Net Zero (BNZ) Pathway are published as downloadable spreadsheets alongside the Sixth Carbon Budget Report (2019). In this article, we refer particularly to the BNZ CO2 pathway detailed on the ‘Different Methodologies’ tab of the dataset.  

[11] Based on the data from the Global Carbon Atlas, Kenya emitted around 330 MtCO2 between 1990 and 2020 inclusive, and 450 MtCO2 since 1960.

[12] Based on UK Department for Transport data, in any one year a little over half of the population do not fly, 2% are responsible for 90% of all domestic flights, 1% take 20% of all overseas flights, with 15% taking around 70% of such flights.

[13] For context, in 2021 UK mean ‘household’ income was £38,000 (mean), £31,000 (median) and £23,000 (mode). (See also the BBC radio broadcast, ‘Typical’). Compare this with the mean annual salary for a UK professor being £85,000 – over three times the typical household income (the mode) and over twice the mean.