In February 1884, the English art critic and polymath John Ruskin took the lectern at the London Institution for a pair of lectures on the weather. ‘The Storm-Cloud of the Nineteenth Century’ was his invective against a particular ‘wind of darkness’ and ‘plague-cloud’ that, in his estimate, had begun to envelope Victorian cities only in recent years. He had been taking careful meteorological measurements, he told a sceptical audience. He railed against the ‘bitterness and malice’ of the new weather in question; and, perhaps more importantly, about how it mirrored a certain societal ‘moral gloom’. You could read in us what you could read in the weather, he suggested.
July Thundercloud in the Val d’Aosta (1858) by John Ruskin. Courtesy Wikipedia
It was easy that February, and perhaps easy today, to disregard any alleged winds of darkness as the ravings of a madman. Clouds are clouds: even if Ruskin’s existed – which was a question of some contemporaneous debate – it would be untoward to imagine they bore any relationship with the human psyche. As Brian Dillon observed of the cloud lectures in The Paris Review in 2019, it can be hard to tell where Ruskin’s ‘bad weather ends and his own ragged, doleful mood begins.’ In 1886, Ruskin suffered a mental breakdown while giving a talk in Oxford. By the end of his life at the turn of the century, he was widely considered insane. His ramblings on meteorology and the human spirit aren’t exactly treated with the same gravitas as his books on J M W Turner.
And yet, for Ruskin, the clouds weren’t just clouds: they were juiced up by a ‘dense manufacturing mist’, as he’d noted in a diary entry. The plague-clouds embodied the miasma of the Industrial Revolution; the moral gloom was specifically that which arose from the rapid societal and environmental changes that were afoot. Ruskin’s era had seen relentless transformation of pastoral landscapes into industrial hubs. Everything smelled like sulphur and suffering. Soot-filled air, chemical and human waste, the clamour of machinery – these were more than just physical nuisances. They were assaults on the senses, shaping moods and behaviour in ways that were not yet fully understood.
Mining Area (1852-1905) by Constantin Meunier. Courtesy Wikipedia
Ruskin believed that the relentless pace of industrialisation, with its cacophony of tools and sprawling factories and environmental destruction, undermined psychological wellbeing: that the mind, much like the body, required a healthy social and physical environment to thrive. This was actually a somewhat new idea. (Isaac Ray, a founder of the American Psychiatric Association, wouldn’t define the idea of ‘mental hygiene’, the precursor to mental health, until 1893.) Instability in the environment, for Ruskin, begot instability in the mind. One reflected the other.
More than a century later, as we grapple with a new suite of breakneck environmental changes, the plague-clouds are again darkly literal. Global average surface temperatures have risen by about 1.1°C (2°F) since the pre-industrial era, with most of this warming occurring in the past 40 years. Ice is melting; seas are steadily rising; storms are – well, you know this story. And yet, most frequently, it is still a story of the world out there: the world outside of us. The narrative of climate change is one of meteorological extremes, economic upheaval and biodiversity losses. But perhaps it is worth taking a maybe-mad Ruskin seriously. What of our internal clouds? As the climate crisis warps weather and acidifies oceans and shatters temperature records with frightening regularity, one is tempted to ask if our minds are changing in kind.
Here are some of the most concerning answers in the affirmative. Immigration judges are less likely to rule in favour of asylum seekers on hotter days. On such days, students behave as if they’ve lost a quarter-year of education, relative to temperate days. Warmer school years correspond to lower rates of learning. Temperature predicts the incidence of online hate speech. Domestic violence spikes with warmer weather. Suicide, too.
In baseball, pitchers are more likely to hit batters with their pitches on hot days
But you already know what this feels like. Perhaps you’re more ornery in the heat. Maybe you feel a little slow in the head. It’s harder to focus and easier to act impulsively. Tomes of cognitive neuroscience and behavioural economics research back you up, and it’s not all as dire as domestic violence. Drivers honk their horns more frequently (and lean on them longer) at higher temperatures. Heat predicts more aggressive penalties in sport. In baseball, pitchers are more likely to hit batters with their pitches on hot days – and the outdoor temperature is an even stronger predictor of their tendency to retaliate in this manner if they’ve witnessed an opposing pitcher do the same thing.
In other words: it would appear the plague-clouds are within us, too. They illustrate the interconnectedness of our inner and outer worlds. They betray a certain flimsiness of human agency, painting our decision-making in strokes of environmental influence far bolder than our intuition suggests. And they throw the climate crisis into fresh, stark relief: because, yes, as the climate changes, so do we.
The London Institution closed in 1912. These days, when you want to inveigh against adverse environmental-mind interactions, you publish a paper in The Lancet. And so that is what 24 mostly British, mostly clinical neurologists did in May 2024, arguing that the ‘incidence, prevalence, and severity of many nervous system conditions’ can be affected by global warming. For these researchers, led by Sanjay Sisodiya, professor of neurology at University College London in the UK, the climate story is indeed one of internal clouds.
In their survey of 332 scientific studies, Sisodiya and his colleagues show that climatic influence extends far beyond behaviour and deep into cortical fissures. Aspects of migraine, stroke, seizure and multiple sclerosis all appear to be temperature dependent. In Taiwan, report the authors, the risk of schizophrenia hospitalisation increases with widening daytime temperature ranges. In California, too, ‘hospital visits for any mental health disorder, self-harm, intentional injury of another person, or homicide’ rise with broader daily temperature swings. In Switzerland, hospitalisations for psychiatric disorders increase with temperature, with the risk particularly pronounced for those with developmental disorders and schizophrenia.
Outside the hospital, climate change is extending the habitable range of disease vectors like ticks, mosquitoes and bats, causing scientists to forecast an increased incidence of vector-borne and zoonotic brain maladies like yellow fever, Zika and cerebral malaria. Outside the healthcare system writ large, a changing environment bears on sensory systems and perception, degrading both sensory information and the biological tools we use to process it. Outside the realm of the even remotely reasonable, warming freshwater brings with it an increased frequency of cyanobacterial blooms, the likes of which release neurotoxins that increase the risk of neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS, also known as Lou Gehrig’s disease).
Experiencing natural disasters in utero greatly increases children’s risk of anxiety, depression and ADHD
Indeed, recent studies suggest that climate change may be exacerbating the already substantial burden of neurodegenerative diseases like Parkinson’s and Alzheimer’s. In countries with warmer-than-average climates, more intense warming has been linked to a greater increase in Parkinson’s cases and, as Sisodiya et al note, the highest forecasted rates of increase in dementia prevalence are ‘expected to be in countries experiencing the largest effects of climate change’. Similarly, short-term exposure to high temperatures appears to drive up emergency department visits for Alzheimer’s patients. The air we breathe likely plays a complementary role: in Mexico City, for example, where residents are exposed to high levels of fine particulate matter and ozone from a young age, autopsies have revealed progressive Alzheimer’s pathology in 99 per cent of those under the age of 30.
The risks aren’t limited to those alive today. In 2022, for example, an epidemiological study revealed that heat exposure during early pregnancy is associated with a significantly increased risk of children developing schizophrenia, anorexia and other neuropsychiatric conditions. High temperatures during gestation have long been known to delay neurodevelopment in rats. Other scientists have shown that experiencing natural disasters in utero greatly increases children’s risk of anxiety, depression, attention-deficit/hyperactivity disorder and conduct disorders later in life. Such effects cast the intergenerational responsibilities of the Anthropocene in harsh new light – not least because, as Sisodiya and colleagues write, there is a tremendous ‘global disparity between regions most affected by climate change (both now and in the future) and regions in which the majority of studies are undertaken.’ We don’t know what we don’t know.
What we do know is that the brain is emerging, in study after study, as one of climate change’s most vulnerable landscapes.
It is a useful reorientation. Return to the horn-honking and the baseball pitchers for a moment. A focus on the brain sheds some potential mechanistic light on the case studies and allows us to avoid phrases like ‘wind of darkness’. Higher temperatures, for example, appear to shift functional brain networks – the coordinated behaviour of various regions – toward randomised activity. In extreme heat, scientists have taken note of an overworked dorsolateral prefrontal cortex (dlPFC), the evolutionarily new brain region that the neuroendocrinologist Robert M Sapolsky at Stanford University in the US calls ‘the definitive rational decider in the frontal cortex’. The dlPFC limits the degree to which people make impulsive decisions; disrupted dlPFC activity tends to imply a relatively heightened influence of limbic structures (like the emotionally attuned amygdala) on behaviour. More heat, less rational decision-making.
When extreme heat reaches into your mind and tips your scales toward violence, it is constraining your choices
The physicality of environmental influence on the brain is more widespread than the dlPFC – and spans multiple spatial scales. Heat stress in zebrafish, for example, down-regulates the expression of proteins relevant to synapse construction and neurotransmitter release. In mice, heat also triggers inflammation in the hippocampus, a brain region necessary for memory formation and storage. While neuroinflammation often plays an initially protective role, chronic activation of immune cells – like microglia and astrocytes – can turn poisonous, since pro-inflammatory molecules can damage brain cells in the long run. In people, hyperthermia is associated with decreased blood flow to this region. Psychologists’ observations of waning cognition and waxing aggression at higher temperatures makes a world of sense in the context of such findings.
The nascent field of environmental neuroscience seeks to ‘understand the qualitative and quantitative relationships between the external environment, neurobiology, psychology and behaviour’. Searching for a more specific neologism – since that particular phrase also encompasses environmental exposures like noise, urban development, lighting and crime – we might refer to our budding, integrative field as climatological neuroepidemiology. Or, I don’t know, maybe we need something snappier for TikTok. Neuroclimatology? Ecological neurodynamics?
I tend to prefer: the weight of nature.
The weight forces our hands, as in the case of the behavioural effects highlighted above. When extreme heat reaches into your mind and tips your scales toward violence, it is constraining your choices. By definition, impulsive decisions are rooted in comparatively less reflection than considered decisions: to the extent that a changing climate influences our reactions and decision-making, we should understand it as compromising our perceived free will. The weight of nature is heavy. It displaces us.
It is also a heavy psychological burden to carry. You are likely familiar with the notion of climate anxiety. The phrase, which tends to refer to a near-pathological state of worry and fear of impending environmental destruction, has never sat particularly well with me. Anxiety, as defined by the Diagnostic and Statistical Manual, is usually couched in terms of ‘excessive’ worry. I’m not convinced there’s anything excessive about seeing the climatic writing on the wall and feeling a sense of doom. Perhaps we ought to consider the climate-anxious as having more developed brains than the rest of the litter – that the Cassandras are the only sane ones left.
I’m not exactly joking. Neuroscience has begun to study the brains in question, and not for nothing. The midcingulate cortex, a central hub in the brain’s threat-detection circuitry, may hold some clues to the condition’s biological basis: in one 2024 study, for example, researchers at Northern Michigan University in the US found that people who reported higher levels of anxiety about climate change showed distinct patterns of brain structure and function in this region, relative to those with lower levels of climate anxiety – and irrespective of base levels of anxiety writ large. In particular, the climate-anxious brain appears to play host to a smaller midcingulate (in terms of grey matter), but one that’s functionally more connected to other key hubs in the brain’s salience network, a system understood to constantly scan the environment for emotionally relevant information. In the salience network, the midcingulate cortex works hand in hand with limbic structures like the amygdala and insula to prepare the body to respond appropriately to this type of information. In people with climate anxiety, this network may be especially attuned to signals of climate-related threats.
Rather than indicating a deficiency, then, a diminutive midcingulate might reflect a more efficient, finely honed threat-detection system. The brain is well known to prune redundant connections over time, preserving only the most useful neural pathways. Selective sculpting, suggest the Michigan researchers, may allow the climate-anxious brain to process worrisome information more effectively, facilitating rapid communication between the midcingulate and other regions involved in threat anticipation and response. In other words, they write, the climate-anxious midcingulate might be characterised by ‘more efficient wiring’.
This neural sensitivity to potential dangers could be both a blessing and a curse. On one hand, it may attune some people to the very real perils of the future. The midcingulate is critical for anticipating future threats, and meta-analyses have found the region to be consistently activated when people contemplate unpredictable negative outcomes. Given the looming spectre of climate catastrophe, a hair-trigger threat-detection system could be an adaptive asset.
Climate anxiety is not just a sociocultural phenomenon. It has a theoretically identifiable neural correlate
On the other hand, argue the researchers:
[T]he complexity, uncertainty, as well as temporal and geographical distance of the climate crisis, in addition to its global nature, may lead individuals to deprioritising the risks associated with climate change, or becoming overwhelmed and disengaged – a state sometimes referred to as ‘eco-paralysis’.
An overactive midcingulate has been implicated in clinical anxiety disorders, and the new findings suggest that climate anxiety shares some of the same neural underpinnings. (It’s important to recall that climate anxiety seems to be distinct from generalised anxiety, though, as the brain differences observed in the Michigan study couldn’t be explained by overall anxiety levels.)
Ultimately, while speculative, these findings suggest that climate anxiety is not merely a sociocultural phenomenon, but one with theoretically identifiable neural correlates. They provide a potential biological framework for understanding why some people may be more psychologically impacted by climate change than others. And they raise intriguing questions about whether the brains of the climate anxious are particularly well-suited for confronting the existential threat of a warming world – or whether they are vulnerable to becoming overwhelmed by it. In all cases, though, they illustrate that world reaching inward.
There is perhaps a flipside to be realised here. A changing climate is seeping into our very neurobiology. What might it mean to orient our neurobiology toward climate change?
Such is the premise of a 2023 article in Nature Climate Change by the neuroscientist Kimberly Doell at the University of Vienna in Austria and her colleagues, who argue that the field is well positioned to inform our understanding of climate-adaptation responses and pro-environmental decision-making. In the decades since Ruskin shook his fists at the sky, environmental neuroscience has begun to probe the reciprocal dance between organisms and their ecological niches. We know now that the textures of modern environments – green spaces, urban sprawl, socioeconomic strata – all leave their mark on the brain. Climate change is no different.
Accordingly, argue Doell et al, scientists and advocates alike can integrate findings from neuroscience to improve communications strategies aimed at spurring climate action. They want to turn the tables, taking advantage of insights from neurobiology and cognitive neuroscience to more effectively design climate solutions – both within ourselves and for society as a whole.
The Anthropocene’s fever dream is already warping our wetware
We have models for this type of approach. Poverty research, for instance, has long implicated socioeconomic conditions with subpar health. In more recent years, neuroscience has reverse-engineered the pathways by which poverty’s various insults – understimulation, toxic exposures, chronic stress – can erode neural architecture and derail cognitive development. Brain science alone won’t solve poverty, yet even a limited understanding of these mechanisms has spurred research in programmes like Head Start, a family-based preschool curriculum that has been shown to boost selective attention (as evident in electrophysiological recordings) and cognitive test scores. While the hydra of structural inequity is not easily slain, neuroscientists have managed to shine some light on poverty’s neural correlates, flag its reversible harms, and design precision remedies accordingly. This same potential, argue Doell and her colleagues, extends to the neuroscience of climate change.
To realise this potential, though, we need to further understand how the Anthropocene’s fever dream is already warping our wetware. Social and behavioural science have begun cataloguing the psychological fallout of a planet in flux, but a neural taxonomy of climate change awaits. The field’s methodological and conceptual arsenal is primed for the challenge, but honing it will demand alliances with climate science, medicine, psychology, political science and beyond.
Some are trying. For example, the Kavli Foundation in Los Angeles, US, recognising a need for answers, last year put out a call for scientists to investigate how neural systems are responding to ecological upheaval. With a trial $5 million, the foundation aims to illuminate how habitat loss, light pollution and other environmental insults may be influencing the molecular, cellular and circuit-level machinery of brains, human and otherwise. The central question is: in a biosphere where change is the only constant, are neural systems plastic enough to keep pace, or will they be left struggling to adapt?
The first wave of researchers to take up Kavli’s challenge are studying a diverse array of creatures, each uniquely positioned to reveal insights about the brain’s resilience in the face of planetary disruption. Wolfgang Stein at Illinois State University in the US and Steffen Harzsch at University of Greifswald in Germany, for example, focus on crustaceans, seeking to understand how their neural thermal regulators cope with rising temperatures in shallow and deep waters. Another group has targeted the brains of cephalopods, whose RNA-editing prowess may be key to their ability to tolerate plummeting oxygen levels in their increasingly suffocating aquatic habitats. A third Kavli cohort, led by Florence Kermen at University of Copenhagen in Denmark, is subjecting zebrafish to extreme temperatures, scouring their neurons and glial cells for the molecular signatures that allow them to thrive – even as their watery world heats up.
These initial investments have sparked federal curiosity. In December 2023, the US National Science Foundation joined forces with Kavli, inviting researchers to submit research proposals that seek to probe the ‘modulatory, homeostatic, adaptive, and/or evolutionary mechanisms that impact neurophysiology in response to anthropogenic environmental influence’. We may not be in arms-race territory yet, but at least there’s a suggestion that we’re beginning to walk in the right direction.
The brain, that spongy command centre perched atop our spinal cord, has always been a black box. As the climate crisis tightens its grip, and the ecological ground beneath our feet grows ever more unsteady, the imperative to pry it open and peer inside grows more urgent by the day. Already, we’ve begun to glimpse the outlines of a new neural cartography, sketched in broad strokes by the likes of Sisodiya and his colleagues. We know now that the brain is less a static lump of self-regulating tissue than it is a dynamic, living landscape, its hills and valleys shaped by the contours of our environment. Just as the Greenland ice sheet groans and buckles under the heat of a changing climate, so too do our synapses wither and our neurons wink out as the mercury rises. Just as rising seas swallow coastlines, and forests succumb to drought and flame, the anatomical borders of our brains are redrawn by each new onslaught of environmental insult.
But the dialogue between brain and biosphere is not a one-way street. The choices we make, the behaviours we pursue, the ways in which we navigate a world in crisis – all of these decisions are reflected back onto the environment, for good or for ill. So, I offer: in seeking to understand how a changing climate moulds the contours of our minds, we must also reckon with how the architecture of our thoughts might be renovated in service of sustainability.
Bit by bit, synapse by synapse, we can chart a course through the gathering plague-cloud
The cartographers of the Anthropocene mind have their work cut out for them. But in the hands of neuroscience – with its shimmering brain scans and humming electrodes, its gene-editing precision and algorithmic might – there is something approaching a starting point. By tracing the pathways of environmental impact to their neural roots, and by following the cascading consequences of our mental processes back out into the world, we might yet begin to parse the tangled web that binds the fates of mind and planet.
This much is clear: as the gears of the climate crisis grind on, our brains will be swept along for the ride. The question is whether we’ll be mere passengers, or whether we’ll seize the controls and steer towards something resembling a liveable future. The weight of nature – the immensity of the crisis we face – is daunting. But it need not be paralysing. Bit by bit, synapse by synapse, we can chart a course through the gathering plague-clouds. It was Ruskin, at a slightly more legible moment in his life, who offered: ‘To banish imperfection is to destroy expression, to check exertion, to paralyse vitality.’ Even if we somehow could, we ought not banish the alleged imperfections of environmental influence on the mind. Instead, we ought to read in them an intimate, vital relationship between self and world.
In this, climatological neuroepidemiology – young and untested though it may be – is poised to play an outsized role. In gazing into the black box of the climate-altered mind, in illuminating the neural circuitry of our planetary predicament, the field offers something precious: a flicker of agency in a world that often feels as if it’s spinning out of control. It whispers that the levers of change are within reach, lodged in the squishy confines of our crania, waiting to be grasped. And it suggests that, even as the weight of nature presses down upon us, we might yet find a way to press back.
