The +1.5°C threshold had a simple political virtue: a memorable figure around which to mobilize. In 2026, the WMO gives 91% for at least one year above 1.5°C between 2026 and 2030, and 75% for the 2026-2030 average. This partial failure is real, and acknowledging this fact can redirect action toward a redefined objective rather than lead to disengagement.
The essentials
- Ritchie argues that the likely overshoot of +1.5°C does not render climate action obsolete, but allows redirecting effort toward +2°C, a threshold still attainable provided emissions reductions accelerate.
- In 2026, the WMO estimates at 91% the probability of at least one year 2026-2030 above 1.5°C; every tenth of a degree avoided matters: the difference between +1.8°C and +2.4°C is substantial.
- Climate catastrophism and denial produce the same political effect, inaction, through opposite paths.
- The central wager of the book is institutional: maintaining a political coalition around a redefined objective, without letting the admission of an initial failure serve as an alibi for disengagement.
Hannah Ritchie, data researcher against discouragement
Hannah Ritchie directs research at Our World in Data, the platform founded by Max Roser at Oxford that documents global trends from primary data. She grew up in Scotland and trained in environmental geosciences at Edinburgh. For about a decade, she has championed methodological optimism: looking at data honestly is, in her view, the condition for progress.
Her first book, Not the End of the World (2024), already translated and discussed in several countries, laid the foundations for her positioning: against catastrophism that paralyzes, against denial that lulls. Clearing the Air extends this work by narrowing focus on the path to carbon neutrality. Published in the United Kingdom on September 18, 2025, by Chatto & Windus, it appears at the precise moment when the international climate agenda wavers between pressure from the results of the first cycle of the Paris Agreement and the rise of skeptical governments.
The thesis: a lost threshold is not a lost war
The heart of the book rests on an idea that Ritchie defends with almost clinical precision. The +1.5°C threshold established in the Paris Agreement was not a physical limit beyond which everything collapses. It is a negotiated political objective, justified by the reduction of climate risks and impacts, and its value lies in the mobilization it enabled. Now that it is becoming improbable to meet, its usefulness changes: it can continue to serve as a reference, provided it is not treated as a final verdict.
Ritchie writes that the worst reaction to foreseeable overshoot would be to decree the failure of the climate project itself. Every tenth of a degree avoided matters. The difference in damage between a world at +1.8°C and a world at +2.4°C affects a growing number of people exposed to heat waves, coastal flooding, agricultural instability. Presenting these scenarios as equivalent—“we failed, it’s all ruined anyway”—is an error of measurement as much as a moral error.
The +2°C threshold remains attainable. But the conditions are strict. Ritchie cites projections: the 2024 UNEP estimates are 4% annually for 2°C and 7.5% annually for 1.5°C through 2035 with immediate action. The recent global level does not correspond to an annual decline of 2%: GHG emissions rose 1.3% in 2023 according to UNEP. The gap between the two trajectories is not a technical detail: it is the political space that remains open.
The argument on mitigation and adaptation: a false opposition to untangle
One of the most solid sections of Clearing the Air addresses the relationship between mitigation—reducing emissions—and adaptation—living with the consequences of those already occurred. The debate is often presented as a funding choice: $800 billion annually for global mitigation, $300 to $500 billion for adaptation. Ritchie refuses this framing.
Treating both items as competitive amounts to assuming that action on emissions and protection of exposed populations are mutually exclusive. In fact, underinvestment in adaptation is observed mainly in low-income countries, where resources for mitigation are in any case marginal. Underfunded adaptation is not the price of climate ambition: it is one of the most visible forms of injustice in the crisis—emissions historically come from wealthy economies, effects fall on the most vulnerable.
This section converges with analyses that can be compared to work on energy transitions in Gulf countries, where installed renewable capacity is useful only if regional markets exist to absorb it, a reminder that technique alone is insufficient without appropriate institutional and financial structures.
Ritchie’s auditable optimism
The great contribution of Clearing the Air is not to be reassuring. It is to render optimism verifiable. Ritchie does not say “it will work out.” She says: here are the trajectories, here are the conditions, here is what changes if we accelerate by one percentage point.
This stance distinguishes her from the ambient techno-optimism, which treats decarbonization as a settled matter once renewable energy costs fall. The decline in solar and wind costs is real, and carefully documented in the book. But Ritchie insists on what price curves do not show: the inertia of infrastructure systems, political resistance, delays between investment decisions and service deployment. On small modular reactors, whose proponents regularly announce decisive acceleration, fuel supply chain obstacles remain intact, a sign that technical progress and industrial implementation follow very different rhythms.
Ritchie distinguishes with precision reasons for hope from pretexts for inaction. This work of sorting gives the book its operational value. Reading Clearing the Air produces less a feeling of consolation than a sense of being better equipped.
Blind spots: the politics of collective grief
Clearing the Air is rigorous on the figures. It develops less the question that data alone cannot settle: how a society absorbs a missed objective and redeploys toward the next one, without political grief becoming a rout.
Ritchie poses the question. She does not answer it completely, and it is honest of her—it is more a matter of political psychology and political economy than climate modeling. But it is also the question that determines whether her reasoning will have any practical effect.
The stakes can be put in tension with Acemoglu’s analyses on institutional capture by existing interests. If coalitions benefiting from the fossil status quo are capable of transforming the admission of a +1.5°C overshoot into an argument for abandoning any target, then the rigor of Ritchie’s analysis, however well-founded, can serve to legitimize what she fights. This risk of reversal, Ritchie names as a crucial political issue. But the book offers no institutional mechanism to avoid it, beyond the wager that data transparency is ultimately more useful than obscuring it.
This is a defensible hypothesis. It is also a hypothesis that would deserve a full section on the political conditions of climate recommunication. This work remains to be done, it exceeds the scope Ritchie set for herself, but the reader emerges with awareness of this gap.
The coming decade: mitigation, adaptation, or abandonment
The final third of Clearing the Air is the most ambitious and most uncertain. Ritchie explores there what it concretely means to pursue a double commitment strategy: maintaining pressure on emissions while funding adaptation, in a context of politically sustainable budgetary constraints.
The 2026-2030 window is presented as determining for trajectories in the second half of the century. Rapid and deep reductions, consistent with ambitious climate trajectories before and after 2030, can keep open a limitation close to +2°C or lower. According to UNEP 2024, continuation of current policies leads to a median maximum warming of approximately +3.1°C over the century, with increasing climate risks.
Ritchie treats these scenarios as conditional ranges, which is correct. She avoids claiming the good scenario will occur. She stresses that political choices and investment decisions in the coming years will shape climate trajectories. AR6 concludes that limiting warming to 2°C requires profound, rapid, and generally immediate reductions, beyond policies then in place.
Ritchie leaves the reader with an open question: can a democratic political system sustain a strategy combining mitigation and adaptation simultaneously over short electoral cycles, when the benefits of mitigation measure in decades and costs in years? The book does not answer it. Political science literature does not either with certainty.
Ritchie nonetheless exits the rhetoric of absolute urgency to enter the logic of a strategy sustained over time. This shift in frame constitutes in itself a contribution to the debate.
Reading this book
Clearing the Air is addressed to those who have followed the climate debate long enough to have mourned easy optimism, but who refuse to yield to the inverse reading, the idea that the scale of the problem justifies fatalism. Ritchie writes for them with analytical density rare in mainstream climate literature.
There is no political program. There is something more useful: a framework for evaluating policies as they are proposed, a vocabulary to distinguish real progress from hollow announcements, and a method to maintain pressure without losing oneself in rhetoric that has exhausted part of its audience.
It is a book for decision-makers who must justify difficult budgetary trade-offs, for journalists covering COP with growing fatigue, and for citizens who want to understand why Paris commitments were insufficient without concluding that no commitment serves any purpose. It usefully complements other readings on the governance of technological progress, particularly on the institutional conditions in which energy investments do or do not translate into effective decarbonization.
Bibliographic information
Title: Clearing the Air: Climate Change and the Path to Net Zero Author: Hannah Ritchie Publisher: Chatto & Windus (British edition); The MIT Press (North American edition) Publication date: September 18, 2025 (United Kingdom); February 17, 2026 (North America)
Sources
- Hannah Ritchie, Clearing the Air: Climate Change and the Path to Net Zero, Bloomsbury Publishing, 2025, https://www.bloomsbury.com/uk/clearing-the-air-9781399414104/
- Hannah Ritchie, Our World in Data, atmospheric data and emissions, https://our-world-in-data.org/atmospheric-co2
- IPCC, Sixth Assessment Report (AR6), Synthesis Report, 2023, IPCC, Geneva
