It’s been a scary year for what must now be called, not global warming (as if temperatures were creeping up of their own accord) but , as if someone was doing this deliberately.
Because we are. This year, scientists stopped pussyfooting around with statistical niceties and firmly linked the abnormal storms, wildfires and melting to our greenhouse gases. They warned in October that we have 12 years to take drastic action or court unstoppable disaster.
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We know what to do – we just aren’t doing it. In November, greenhouse emissions reached record highs. Yet the US joined big oil producers in blocking even meaningful statements, never mind action, at a top-level meeting in Poland even as its own researchers warned we were on course for more wildfires and storms, drought and crop failure.
We are also on course for more disease. In Poland, Maria Neira, head of public health at the World Health Organization (WHO), said that “the true cost of climate change is felt in our hospitals and in our lungs”. Air pollution, notably with greenhouse gases, directly kills 7 million people a year, and crop failure and heat stress as temperatures rise takes a huge medical and economic toll. “The evidence is clear,” said Tedros Ghebreyesus, head of the WHO, “that climate change is already having a serious impact on human health.”
The trouble is that most surveys of climate change and health emphasise diseases that don’t much affect the rich countries most able to do something. Warmer weather and changes in rainfall can boost insects and waterborne bugs, so the diseases they carry have received most attention. A in November totted up the usual suspects: risks of waterborne bacteria that cause diarrhoea, algal blooms that carry cholera, and diseases like malaria carried by insects or ticks, are already rising in line with temperatures.
But those diseases are overwhelmingly those of the poor, and tropical. They don’t threaten places like London or Washington with chlorinated water and long-banished malarial mosquitoes – and people care about things that threaten them.
So how about chickenpox? At a meeting in Washington in December, Rachel Baker of Princeton University reported that, when you control for the social drivers of chickenpox outbreaks (mainly, when kids go back to school), you can see clearly that the weather affects it too.
Her team found that climate changes forecast for Mexico (which has lots of chickenpox and good statistics) will shift outbreak timing in some places, and slightly boost the number of cases.
Underwhelming, maybe: chickenpox rarely kills, and rich countries mostly vaccinate against it. But, says Baker, the model is revealing similar things for, a virus that kills 160,000 babies a year worldwide, a toll second only to malaria. A few dozen of those deaths, and thousands of hospitalisations, happen each year in the UK, and in the US.
The big news here is that, except maybe for flu, no one really knew climate affects viruses that spread directly from person to person. It turns out it does. Who knows how many other viruses change with the weather?
Admittedly the impacts Baker’s team found aren’t dramatic: Mexican states that get drier will have more chickenpox cases in summer. But the inescapable limitation in all these studies is that they isolate one variable – in this case a disease – and ask what climate does to it, all other things being equal.
There’s the rub: all other things are not going to be equal. A vast number of things will change all at once, in a global system that is entirely interlinked and enormously complex. In any complex system, change one small thing, and big, unexpected changes can appear somewhere else. All sorts of changes, even small ones, happening at once, will have outcomes we cannot predict.
If patterns of common illnesses change with climate, then the people affected will also be more likely to be heat-stressed, poorer, maybe displaced or malnourished, as crops fail, cities flood, and health and sanitation systems struggle.
We all live at the end of fragile global supply chains of everything from food to vaccines. As global heating bites across the planet, it will create mass migration, economic losses and political instability in various places. Trading and financial systems will totter, or collapse. Viruses subject to new conditions evolve and adapt, just as our capacity to respond weakens.
Meanwhile, the impact of disease itself on civilisation can snowball out of control. And it is simply not the case that something called “Western civilisation” might collapse under these strains while some other civilisation soldiers on. We are all far too interconnected. Even small changes in common diseases could well add to a mess that will be global, complex and unpredictable.
Happy holidays.
