The science of climate change and the effect of anaesthetic gas emissions: a reply,Anaesthesia

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The science of climate change and the effect of anaesthetic gas emissions: a reply
Anaesthesia ( IF 10.7 ) Pub Date : 2024-03-01 , DOI: 10.1111/anae.16268
J. M. Slingo ₁ , M. E. Slingo ₂

Affiliation

Thank you for the opportunity to reply to Dr Grant's letter [1] regarding our article [2]. Dr Grant includes several serious misstatements and allegations. We will take the most important points in turn.

“The interpretation is that [the volatiles' radiative forcing] is too tiny to matter and, therefore, can be ignored. However, I believe this is more an opinion than a fact and should be challenged.”

This is a fact, founded on appropriately peer-reviewed expert climate science, as we have demonstrated very clearly when we consider the complex energy flows in the climate system. There is no debate regarding the fundamental physics of climate change and radiative forcing. Furthermore, Dame Julia Slingo is a leading international climate scientist, a Fellow of the Royal Society and a Foreign Member of the US National Academy. She has been a chief Science Advisor to the UK Government, the European Commission and the UN World Meteorological Office. To suggest that her views are founded on opinion rather than scientific fact does her, and the expert climate science community, a great disservice.

We would strongly urge all anaesthetists and policy-makers who would seek to undermine the climate science arguments to read and understand the relevant literature. Complex integrated climate science, involving a full understanding of planetary dynamics and physics, is distinct from the specialism of focused atmospheric chemistry and global warming potential (GWP) calculation [3]. There is strong agreement that simplistic metrics such as GWP are inappropriate for short-lived, trace gases – the authoritative voices within the expert speciality of climate science are very clear on this matter.

“Global warming is the result of millions upon millions of small emissions of greenhouse gases, with near universal culpability.”

This is fundamentally incorrect; there is no universal culpability amongst greenhouse gases and this is well-documented. As we have outlined in our article [2] and the references therein, there is a huge difference between how long-lived (> 100 years, e.g. carbon dioxide and nitrous oxide) and short-lived (< 20 years, e.g. methane and many hydrofluorocarbons) gases contribute to global warming. We urge individuals to read the highly insightful and accessible paper by Professor Pierrehumbert on this topic [4]. Global warming is the result of millions upon millions of small emissions of carbon dioxide each with universal culpability.

It is worth noting that although methane is a short-lived gas, it is worthy of attention because its emissions (and thus atmospheric concentrations and radiative forcing) are high and rising steeply, due to both human activities and the response of the Earth's system to warming from climate change that has already occurred [5].

“Therefore, there is no silver bullet solution, but rather we need millions of small solutions working together.”

We agree but in the context of real carbon dioxide emissions. This is why we are all encouraged to reduce our personal carbon dioxide emissions in every way we can and to seek to understand those involved in the full life-cycle of everything we use.

It is a pity that the anaesthetic community did not choose to focus on nitrous oxide emissions from the outset. Nitrous oxide is a long-lived gas and determining its carbon dioxide equivalence via GWP₁₀₀ is scientifically robust. Reducing nitrous oxide emissions from medical practice would be an entirely appropriate action to reduce global warming and NHS greenhouse gas footprints.

“This very issue has been weaponised by those who seek to delay climate action […]. I feel that this is the argument that is being pushed by this article.”

This is a serious allegation, and wholly without basis. We say very clearly that every kilogramme of real carbon dioxide we emit accumulates in the atmosphere through our lifetime and irreversibly changes the climate for generations to come. Our goal has always been to bring the correct science to the anaesthetic community, so that future climate actions will deal appropriately with the crisis that is upon us. We advocate clearly for action – but it must truly make a difference and be based on correct science led by those with appropriate expertise.

“So, the radiative efficiency of volatiles is 0.012% of that caused by carbon dioxide. Let us consider what we are comparing: the impact of a single group of drugs, against all of the carbon dioxide that would have already been present in the atmosphere due to natural processes, plus the combined effect of all fossil fuels ever burned, all forests and peatlands destroyed, and all the cement ever made.”

First, it is radiative forcing and not efficiency. Second, this displays a fundamental misunderstanding of anthropogenic climate change. At least for the period of this interglacial (several 1000 years) natural processes have maintained carbon dioxide levels at near 280 parts per million and the planet has remained in equilibrium with a near-constant radiative forcing – the natural greenhouse effect. But anthropogenic emissions have rapidly driven up carbon dioxide levels to 420 parts per million and beyond. It is this increase that has exerted a radiative forcing today of 2.16 Wm^-2 and unbalanced the Earth's climate; and that unbalance will grow even as we seek to stabilise our carbon dioxide emissions and bring them down to net zero. In fact, Earth's biosphere has buffered us from the warming effects of nearly half of our emissions by taking up carbon dioxide, and without these natural processes, we would be in enormous trouble.

“When considering desflurane, Slingo and Slingo argue there is no reason to specifically target this agent. This is despite noting the relevance of atmospheric lifespan to the ability of a gas to exert a warming effect, and that only desflurane ‘persists long enough to be regarded as radiatively effective’.”

This is mixing up completely separate issues. For a gas to be an effective greenhouse gas it has to be well-mixed in the troposphere as we explain in our article, and of the volatiles only desflurane lives long enough for that to be the case. Whether it can be an effective gas in radiatively forcing the planet depends on its atmospheric abundance; and whether it can be an effective gas in changing the climate depends on the magnitude and persistence of that radiative forcing. On all counts desflurane does not fulfil those requirements.

“To add further contradiction, the article ends with the advice that anaesthetists should use low fresh gas flows.”

Emissions of the volatiles are too small to affect the trajectory of climate change. However, they still require manufacture, packaging, transport and carrier gases (which themselves require the same processes). All of this industry will create carbon dioxide emissions, and it is therefore simple common sense, good practice and resource management to avoid any unnecessary waste.

“There is no suggestion that the anaesthetic work on desflurane has substituted for other work on climate: in fact, the opposite is true.”

The work on desflurane has contributed substantially to an ‘echo chamber’ in the anaesthetic community for over a decade, promoting the rhetoric that any volatile agent is causing climate change. This has led to the inappropriate promotion of total intravenous anaesthesia as a more ‘sustainable’ anaesthetic and an entirely unnecessary industry of volatile capture technology that will incur increased carbon dioxide emissions. We do not doubt, and have never said, that other endeavours are taking place to de-carbonise (and de-nitrous) the NHS. But time, energy and money are finite – these projects would be at a much more advanced stage if desflurane had not become the distraction.

“The article by Slingo and Slingo is unhelpful and unwelcome as it undermines and undervalues these achievements and re-animates a debate that seemed in the past.”

We have never sought to undervalue the energy and enthusiasm of the anaesthetic community in tackling climate change and we say that clearly in our article. What we ask is that the community base its actions on robust scientific evidence and focuses its efforts on those that will indeed drive down real carbon dioxide emissions and help to mitigate future climate change. The debate around volatiles should never have occurred in the first place and it is a distraction without scientific basis.

Leadership within both science and medicine requires us to be humble, honest and open to new information. To state that the intervention of expert climate science is unwelcome reveals a concerning inflexibility from those who should be the first to seize new information and strive for climate policies with integrity.

中文翻译：

气候变化科学和麻醉气体排放的影响：答复

感谢您给我们机会回复格兰特博士关于我们的文章 [ 2 ] 的信 [ 1 ] 。格兰特博士包含了一些严重的错误陈述和指控。我们将依次讨论最重要的要点。

“解释是，[挥发物的辐射强迫]太小，不重要，因此可以忽略不计。然而，我认为这更多的是一种观点而不是事实，应该受到质疑。”

这是一个事实，建立在经过适当同行评审的专家气候科学的基础上，正如我们在考虑气候系统中复杂的能量流时已经非常清楚地证明的那样。关于气候变化和辐射强迫的基本物理学没有争议。此外，朱莉娅·斯林戈女爵士是国际领先的气候科学家、英国皇家学会院士和美国国家科学院外籍院士。她曾担任英国政府、欧盟委员会和联合国世界气象办公室的首席科学顾问。如果说她的观点是建立在观点而不是科学事实的基础上，这对她和气候科学专家界来说是一种极大的伤害。

我们强烈敦促所有试图破坏气候科学论点的麻醉师和政策制定者阅读和理解相关文献。复杂的综合气候科学涉及对行星动力学和物理学的充分理解，与专注于大气化学和全球变暖潜势（GWP）计算的专业不同[ 3 ]。人们一致认为，全球升温潜能值等简单化指标不适用于短命的痕量气体——气候科学专家领域的权威声音在这个问题上非常明确。

“全球变暖是数以百万计的温室气体小量排放的结果，几乎是所有人的罪魁祸首。”

这从根本上来说是错误的；温室气体排放不存在普遍的罪责，这一点已有充分记录。正如我们在文章 [ 2 ] 和其中的参考文献中概述的那样，寿命长（> 100 年，例如二氧化碳和一氧化二氮）和寿命短（< 20 年，例如甲烷和许多氢氟碳化物）气体会导致全球变暖。我们强烈建议大家阅读 Pierrehumbert 教授关于该主题的极具洞察力且易于理解的论文 [ 4 ]。全球变暖是数百万小量二氧化碳排放的结果，每一种二氧化碳都有普遍的罪责。

值得注意的是，虽然甲烷是一种短命气体，但由于人类活动和地球系统对甲烷的响应，其排放量（以及大气浓度和辐射强迫）很高且急剧上升，因此值得关注。已经发生的气候变化导致的变暖[ 5 ]。

“因此，不存在灵丹妙药的解决方案，而是我们需要数百万个小解决方案一起工作。”

我们同意，但要考虑到实际二氧化碳排放量。这就是为什么我们都被鼓励尽一切努力减少个人二氧化碳排放，并寻求了解那些参与我们使用的一切的整个生命周期的人。

遗憾的是，麻醉界并没有从一开始就选择关注一氧化二氮的排放。一氧化二氮是一种长寿命气体，通过 GWP ₁₀₀确定其二氧化碳当量具有科学依据。减少医疗实践中的一氧化二氮排放量将是减少全球变暖和 NHS 温室气体足迹的完全适当的行动。

“这个问题已被那些寻求推迟气候行动的人武器化了[……]。我觉得这就是这篇文章所要推动的论点。”

这是一项严重的指控，而且完全没有根据。我们非常明确地说，我们排放的每一公斤真实二氧化碳都会在我们的一生中积累在大气中，并不可逆转地改变子孙后代的气候。我们的目标始终是为麻醉界带来正确的科学，以便未来的气候行动能够妥善应对我们面临的危机。我们明确提倡采取行动——但它必须真正产生影响，并基于由具有适当专业知识的人领导的正确科学。

“所以，挥发物的辐射效率是二氧化碳辐射效率的0.012%。让我们考虑一下我们正在比较的内容：一组药物对自然过程中已经存在于大气中的所有二氧化碳的影响，加上所有燃烧过的化石燃料、所有森林的综合影响泥炭地被毁，所有水泥都被毁了。”

首先，它是辐射强迫而不是效率。其次，这显示出对人为气候变化的根本误解。至少在这次间冰期（几千年）的自然过程中，二氧化碳浓度维持在接近百万分之280，并且地球在近乎恒定的辐射强迫（自然温室效应）下保持着平衡。但人为排放已迅速将二氧化碳浓度提高至百万分之 420 甚至更高。正是这种增加造成了今天2.16 Wm ^-2的辐射强迫，并使地球气候失衡；即使我们寻求稳定二氧化碳排放并将其降至净零，这种不平衡也会加剧。事实上，地球生物圈通过吸收二氧化碳，缓冲了我们近一半排放物造成的变暖影响，如果没有这些自然过程，我们将陷入巨大的麻烦。

“在考虑地氟烷时，Slingo 和 Slingo 认为没有理由专门针对这种药物。尽管注意到大气寿命与气体发挥变暖效应的能力之间的相关性，并且只有地氟烷“持续时间足够长才能被视为具有辐射效果”。

这是混淆了完全不同的问题。正如我们在文章中所解释的那样，一种气体要成为有效的温室气体，它必须在对流层中充分混合，而在挥发物中，只有地氟醚的寿命足够长，才能达到这种情况。它是否能成为对地球产生辐射作用力的有效气体，取决于它的大气丰度；它是否能成为改变气候的有效气体取决于辐射强迫的大小和持久性。从所有方面来看，地氟醚都不能满足这些要求。

“为了增加进一步的矛盾，文章最后建议麻醉师应该使用低新鲜气体流量。”

挥发物的排放量太小，不足以影响气候变化的轨迹。然而，它们仍然需要制造、包装、运输和载气（它们本身需要相同的工艺）。所有这个行业都会产生二氧化碳排放，因此简单的常识、良好的做法和资源管理可以避免任何不必要的浪费。

“没有任何迹象表明地氟烷的麻醉研究已经取代了其他气候研究：事实上，事实恰恰相反。”

十多年来，地氟烷的研究对麻醉界的“回音室”做出了重大贡献，宣扬了任何挥发性物质都会导致气候变化的论调。这导致了全静脉麻醉作为一种更“可持续”的麻醉剂的不当推广，并且是一个完全不必要的挥发性捕获技术行业，会导致二氧化碳排放量增加。我们并不怀疑，也从未说过，正在采取其他努力来使 NHS 脱碳（和脱氮）。但时间、精力和金钱都是有限的——如果地氟烷没有成为干扰因素，这些项目将会处于更高级的阶段。