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Clayton Page Aldern has a stark message about climate change and one the world knows hardly anything about.
Rising sea levels, superstorms, droughts and wildfires are well understood. But a burgeoning field of research is revealing a more immediate threat.
Climate change is disrupting how our brains work.
Aldern, who is a neuroscientist and environmental journalist, has digested a panoramic range of studies in his book The Weight of Nature, which looks at how climate change is affecting human neurochemistry, decision-making, responses and brain health.
The field is in its infancy – Aldern suggests calling it “climatological neuroepidemiology” – but it synthesises neuroscience, psychology and behavioural economics. “It is the job of your brain to model the world as it is,” he says. “And the world is mutating.” He adds that we are witnessing “a rapidly changing environment directly [intervening] in our brain health, behaviour, cognition, and decision-making in real time”.
Often, people’s decisions are informed partly by their emotions and by their embodied actions to the world. But when people get hot, their brains and bodies must also work to cool down. That takes energy. Under heat stress, the most overworked parts of the brain’s prefrontal cortex are those that correspond to rational decision-making. “Temperature spikes drive surges in everything from aggravated assault to domestic violence to online hate speech. Surging carbon dioxide levels and heatwaves diminish problem-solving abilities, cognitive performance and our capacity to learn,” Aldern says.
Take the relationship between heat and cognition. At higher temperatures, people’s feelings of hostility often increase and escalate as they “over-interpret” other people’s behaviour. “Higher temperatures prime people to understand one another’s actions as more aggressive. And then they’re more likely to reciprocate.” Such impulses can in turn lead to more aggression and even violence.
He cites Finnish researchers who collected blood samples from violent offenders at a high-security psychiatric hospital. They discovered that high temperatures heavily suppress the brain’s serotonin function, which is “wildly important in regulating violent behaviour”. The results were similar for non-violent offenders – so much so that the findings explained huge fluctuations in the country’s crime rate. A 2°C rise in ambient temperature potentially increases crimes by more than 3%, they concluded.
Aldern points to projections by the economist Matthew Ranson in the US, which indicate that between 2010 and 2099 climate change will cause “an additional 22,000 murders, 180,000 cases of rapes, 1.2 million aggravated assaults, 2.3 million simple assaults, 260,000 robberies, 1.3 million burglaries, 2.2 million cases of larceny, and 580,000 cases of vehicle theft”.
Aldern says: “Nobody can divine the future with that degree of accuracy. But pay attention to the number of zeros in each figure.”
Less dramatically, he details the impact of temperatures on student performance. During a heatwave in Boston in 2016, Harvard epidemiologists found that college students living in dormitories without air conditioning performed standard cognitive tests 13% more slowly than their contemporaries living in air-conditioned buildings. A UCLA study of one million students in New York City calculated that higher temperatures on exam days led to at least half a million failed tests over a 15-year period.
Indeed, for the average student, testing on a 90° Fahrenheit day decreases the likelihood of passing any subject by about 10%. In the US, hot school days are a particular concern for poorer school districts without access to air conditioning and home to higher concentrations of non-white students. Studies show this accounts for around 5% of the racial achievement gap.
Meanwhile, Chinese economists found that students who took mathematics tests on days above 32°C performed as if they had lost the equivalent of a quarter of a year of education, compared with test days when temperatures ranged between 22 and 24°C.
It’s not just students. Canadian members of parliament produce simpler speeches during scorching days with higher air pollution – literally, the words they bring together are less complex. Even judges are not immune, as Ottawa researchers discovered. They surveyed 200,000 court decisions on asylum applications over a four-year period and found that for every 10° Fahrenheit rise in outdoor temperature during a hearing, the probability of a judge handing down a decision in favour of the applicant fell by almost 7%. “Temperature made a complete mockery of objectivity,” says Aldern.
The book abounds with a “Pandora’s box of horrors”. What he describes as “vectors of brain disease” – mosquitoes, ticks and other pests – are seeing their habitats expand as the world roasts. This is leading to increasing risks of cerebral malaria and Powassan virus, a nasty pathogen that assaults the nervous system. Deforestation and urban sprawl mean “creatures great and small are forced to eke out an existence on the margins, close to human habitats”, allowing pathogens to transfer from animals to humans.
Readers would be forgiven for reaching for the Prozac. Yet Aldern is surprisingly optimistic. Ultimately, he wants to see climatological neuroepidemiology as a new unified field of research that we need “to be investing in as a society”. Understanding the scale and range of climate change impacts on the brain is a key first step.
“We’re talking about some scary stuff but this doesn’t need to be a story of fear,” Aldern told a Royal Society of Arts event in April. “This needs to be a story of awareness. If we can look into this future with open eyes, we will have a much better chance of confronting it accordingly and I mean that at a personal and at a societal level.
“What that means is looking at the potential influence of environmental change on ourselves in a manner that acknowledges that change but is responsive to it with something like a practice of mindfulness. Noticing and checking in with yourself is what allows us as people to respond to emotions, feelings and decision with a certain agency. Mindfulness tends to boost these measures of functional connectivity in the brain that are ultimately diminished by environmental stress.
“At a policy level, it’s taking these threats seriously. There is no policy-making institution in the world that is at this moment pricing the neurological costs of a changing climate and thinking rigorously about the fact that the public health concerns are very real.
“We ought to be walking into this future with open eyes and a cohesive research agenda or else by definition we’re turning a blind eye to many of these neurological effects that are just as, if not more, pressing than some of the other public health concerns we have with changing climate such as malaria, respiratory disease and cardiovascular conditions.”
The Weight of Nature – How a Changing Climate Changes Our Minds, Brains and Bodies is published by Allen Lane.
Huw Morris is a freelance journalist
Hurricane Sandy’s psychological legacy
Climate change affects humans before they are born, Aldern discovered. Queens College CUNY psychology lecturer Yoko Nomura was investigating the effects of prenatal stress on the unborn.
She was particularly interested in the impact of environmental stress on genes, a factor linked to attention deficit hyperactivity disorder (ADHD), autism and schizophrenia. Then Hurricane Sandy – the largest Atlantic storm on record – struck New York in 2012.
A subset of her patients were pregnant women. A decade later, Nomura found that girls who were exposed to Sandy in the womb experienced a 20-fold increase in anxiety and a 30-fold increase in depression later in life. Boys had 60-fold and 20-fold increased risks of ADHD and conduct disorder respectively.
“People do not need to experience war to suffer from post-traumatic stress disorder,” Aldern says. “The violence of a hurricane, a wildfire or drought will do that.”
