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This editorial does not defend any particular anaesthetic agent. Rather, it asks how clinicians should reason when symbolic gestures risk displacing interventions with greater capacity to decarbonise care. We argue that medicine's response to the climate crisis must rest on a synthesis of physics and ethics, anchored in a disciplined sense of proportionality in judgement and action. Using desflurane as a case in point, we argue that sustainability succeeds when it transforms systems, not merely symbols. Climate discourse in medicine often conflates physical magnitude with moral urgency. Anaesthetic gases, and desflurane in particular, illustrate this tension. Physically, the contribution of inhaled anaesthetic agents to global warming is quantifiable yet imperceptible; ethically, their symbolism is powerful. The contrast between negligible climatic impact and high institutional visibility exposes a fundamental problem in professional reasoning: when the measurable and the meaningful diverge, which should guide professional conduct? In the UK, desflurane has already been removed from routine practice following national sustainability guidance and professional endorsement rather than clinical necessity [1, 2]. Nitrous oxide, by contrast, remains widely used globally, though successful reduction has been achieved in the UK through the Nitrous Oxide Project [3]. Nitrous oxide causes considerable environmental harm through distinct mechanisms via ozone depletion and its long atmospheric lifetime [4]. Desflurane serves as a model case precisely because it is climatologically trivial, operationally replaceable and politically achievable – an easy problem that foreshadows harder questions ahead. This editorial does not argue for the reinstatement of desflurane. Instead, we examine the proportionality of the policy reasoning used to justify its withdrawal and the conceptual frameworks guiding environmental decision-making in anaesthesia. Climate impact is governe by two parameters: radiative efficiency and atmospheric lifetime. Desflurane persists for approximately 14 years and absorbs infrared radiation approximately 35,000 times more efficiently than carbon dioxide on a per-molecule basis. Yet the global annual desflurane emissions of < 1000 tonnes are negligible with respect to the planet's 40 gigatonnes of carbon dioxide, a 40-million-fold difference representing 0.0025% of global carbon dioxide emissions by mass [5-7]. Under current usage patterns, the associated increase in global mean surface temperature is estimated to be on the order of 0.00015°C; even under maximal theoretical assumptions, such as universal global use for all surgical procedures over many decades, the projected temperature increase remains approximately 0.001–0.002°C [5-8]. In a world approaching the 1.5°C warming threshold recognised in international climate policy, additional warming cannot be dismissed simply because it is numerically small. However, ethical evaluation also requires proportional reasoning: does eliminating sources responsible for 0.00015–0.0020°C of warming represent a proportionate response, particularly when clinically equivalent alternatives exist and larger system-level drivers remain unaddressed? The signal is physically real but operationally negligible, mathematically indistinguishable from natural variability at global temperature scales. Desflurane is a short-lived climate pollutant whose continuous use generates a finite temperature increase that plateaus once atmospheric degradation balances emissions. This contrasts with carbon dioxide, which accumulates over centuries and produces indefinitely increasing warming [5-8]. This misapplication of radiative forcing metrics has been discussed extensively in the climate science literature [9-11], but against this backdrop, the pertinent ethical question changes shape. If a century of universal use produces a temperature change indistinguishable from noise, what are we preventing: atmospheric warming or institutional alignment with environmental values? The honest answer is both, but this distinction matters. Eliminating desflurane does not alter the climate trajectory but signals institutional values – an ethical, not climatic, achievement. After explicit scaling, justification for restriction must be grounded in ethics, belonging within clinical governance frameworks rather than administrative prohibition based on climate impact alone. Climate science detects the signal, but ethics decides whether constraint is warranted and proportionate. Life-cycle analysis shows that desflurane has higher cradle-to-grave greenhouse gas emissions per MAC hour than sevoflurane, even when manufacturing and transport are included [7]. Desflurane is also more expensive than sevoflurane on a MAC-hour basis due to its lower potency [12]. These upstream emissions strengthen the case for minimising routine desflurane use on environmental and economic grounds. Beyond climate forcing, inhaled anaesthetic agents contribute to environmental harm through biosphere pollution and mass-based emissions. Fluorinated volatiles such as desflurane, sevoflurane and isoflurane generate persistent per- and polyfluoroalkyl substances (PFAS) that resist degradation and accumulate in rainwater and surface water as trifluoroacetic acid [13, 14]. Sevoflurane is also metabolised to hexafluoroisopropanol, a fluorinated compound excreted in urine that is poorly removed by conventional wastewater treatment and contributes to local PFAS contamination. Ecotoxicity analyses show that inhaled anaesthetic agents differ in persistence and biological impact per MAC hour [12, 15]. Desflurane generates the greatest mass-based emissions per MAC-equivalent hour in some analyses, emphasising that environmental stewardship must address multiple dimensions of harm beyond warming potential. Comparative framing also requires symmetry. Nitrous oxide has a far longer atmospheric lifetime and contributes meaningfully to ozone depletion [4]. Total intravenous anaesthesia avoids direct atmospheric release but introduces upstream and downstream environmental impacts including pharmaceutical manufacture, plastic waste and propofol metabolite contamination in wastewater [16, 17]. In contrast with the persistent PFAS products from inhaled anaesthetic agents, propofol metabolites degrade relatively rapidly in aerobic wastewater systems and reach environmental concentrations well below ecotoxicity thresholds. Comprehensive sustainability must address the full life-cycle impacts of all anaesthetic modalities, not merely visible atmospheric emissions. Globally, volatile anaesthetics contribute < 0.001°C to anthropogenic warming and < 0.1% of total radiative forcing. In hospitals, desflurane can represent 70–80% of inhaled anaesthetic agent impact, highlighting planetary irrelevance vs. local prominence [18, 19]. In operating theatres, inhaled anaesthetic agents are given prominence but are actually minor in carbon footprint compared with factors such as energy-intensive air-handling, sterilisation and supply-chain plastics [19, 20]. The institutional resources consumed by desflurane elimination – policy development, vaporiser modification, compliance monitoring – represent finite capacity that could be directed to interventions with substantially greater impact, such as operating theatre heating; ventilation; air conditioning system optimisation; and supply-chain consolidation [19, 20]. Symbolic measures targeting clinician-visible sources risk exhausting political capital for material decarbonisation, reducing sustainability to communication rather than technical change. There is a principled argument that healthcare must model prescribed behaviour: hospitals cannot maintain high-emission practices without ethical incoherence. However, symbolic integrity succeeds as a catalyst only when it prompts deeper scrutiny of energy systems and supply chains, not when it serves as an alibi for leaving systemic emissions unaddressed. Implementation matters. Reduction achieved through transparent clinical reasoning supports professional development; administrative mandates imposed without evidence discussion erode the judgement essential for navigating complex future decisions [21]. Environmental stewardship requires clinician engagement and trust, not passive compliance. Opaque policies erode confidence, whereas transparent, co-design and proportionate frameworks enhance adoption and maintain commitment. The ethical case for eliminating desflurane rests on proportionality, not on harm magnitude alone. Restriction is justified when it preserves patient welfare, has low opportunity cost, produces system benefit and avoids moral distress or clinician disempowerment. The life-cycle environmental burden and cost disadvantage of desflurane support its minimisation from routine practice. At the same time, desflurane offers faster emergence compared with other inhaled anaesthetic agents; these pharmacological differences are real but generally modest and rarely outcome-defining in clinical practice. Clinically equivalent alternatives exist for most contexts and some argue there is no situation where desflurane offers meaningful advantages even accounting for offset kinetics. The distinction between pharmacological difference (which is measurable) and clinical benefit (which is context-dependent) is important: the more rapid offset of desflurane translates to minutes of difference in emergence and early recovery, but this advantage rarely affects meaningful patient outcomes or throughput in contemporary practice [22, 23]. This clinical replaceability distinguishes desflurane from other environmental debates in anaesthesia. Unlike nitrous oxide removal from labour analgesia, where alternatives may be less acceptable to patients, less effective for pain control or practically unavailable [24, 25], desflurane restriction imposes minimal clinical cost. Because desflurane can be replaced without meaningful clinical harm, restricting it is ethically straightforward but risks becoming disproportionate if framed as a primary climate solution. If desflurane disappears, stewardship should preserve judgement over simple abstinence, teaching why it is generally unnecessary and when, in rare circumstances, it might offer distinct advantage. Teaching desflurane as ‘forbidden for the environment’ instils compliance rather than calibration, failing to equip residents for the trade-offs, metric nuances and value-based reasoning that climate policy demands. Transparent, proportionate frameworks that explain the reasoning behind restrictions enhance professional uptake and trust, whereas opaque mandates erode the capacity for clinical judgement essential for harder decisions ahead [21, 26, 27]. Leadership occupies the space between exaggeration and dismissal: not banning inhaled anaesthetic agents as a reflex but showing reasoning through complexity without abandoning moral conviction. The desflurane debate offers actionable principles. Speak accurately: distinguish relative from absolute impacts, short-lived from cumulative gases and symbolic from systemic reforms. Precision in language underpins credibility. Act proportionally: recognise that operating theatre emissions arise predominantly from energy, nitrous oxide and supply chains rather than inhaled anaesthetic agent alone; compare total life-cycle impacts instead of isolated metrics. Protect judgement: use transparent, teachable reasoning that bridges ethics and accountability; preserve clinician autonomy and decision-making capacity. Lead by example: model rational environmentalism, critical of hype, yet committed to evidence, that extends influence beyond operating theatres. Desflurane is the simplest test case for whether medicine can think proportionally about climate change. Because desflurane is climatologically trivial, operationally replaceable and politically achievable, it poses an easy problem, yet it foreshadows more difficult tests ahead that cannot be solved through restriction alone (e.g. operating theatre ventilation, the proliferation of single-use devices, supply-chain carbon intensity, waste sterilisation and building energy systems). Solving these challenges will require redesigns not bans; innovations not prohibitions; and creativity not compliance. The challenge for medicine is to sustain both the planet and the moral ecology of professional judgement. If desflurane is eliminated through administrative fiat rather than proportional reasoning, and if this elimination is celebrated as a climate victory rather than incremental stewardship, the wrong lesson will have been learned: that sustainability means restricting what is visible rather than transforming what matters. The profession that succeeds here will preserve proportional judgement amid moral absolutism, choosing truth over theatrics, proportion over panic and stewardship over symbolism. This, ultimately, is the question at stake, not merely the continued use of desflurane, but the kind of reasoning that will govern professional conscience in an age of climate urgency. No competing interests declared.