Ebola is genuinely scary.
Of course, some of the fear is unfounded, since Ebola actually isn’t that contagious,but its symptoms are horrific and it kills most of the people it infects, and we all know our hyperconnected society makes us vulnerable to contagion, so, frankly, we’re jumpy. Panic is understandable now, if not very helpful. So when I saw the Bloomberg News article, “Climate Change May Kill More [people] Than Ebola, UK Doctors Say,” I immediately saw the value of the title; climate change is so bad, it’s even worse than Ebola. You can read the article yourself, of course, but an expert’s estimates always seem a little remote. To get a feel for the situation, let’s try doing our own comparison.
First, how bad is Ebola?
According to CNBC’s website, as of the 17th of September:
- 4,985 Ebola cases have been reported, according to UN officials
- 2,461 deaths from Ebola have been reported
- If the current outbreak isn’t controlled, various sources project anywhere between 20,000 to 250,000 will die of the disease.
CNBC says half of these cases had been reported in the previous three weeks, which explains why the number of deaths is only half the number of infections; a lot of the reported infections had not killed yet. About 90% of those who are infected die. It’s not clear to me whether these numbers include cases from previous outbreaks, but since almost 2,500 cases were reported in the weeks before September 17th, and since many cases must have gone unreported, it seems reasonable to estimate that at least 3,000 people died from Ebola this summer. This thing is undeniably scary and tragic.
Coming up with equivalent numbers for climate-related mortality is harder, because virtually every way global warming can kill is mixed in with a lot of other dangers. It’s hard to tease out who died from a changed climate and who would have died anyway if we still had the climate we had before.
Scientists have ways of sorting through this morass, of course. They can use various statistical methods to come up with reasonable estimates for increased mortality risk in various climate scenarios, but we’re trying to do this on our own. So, let’s start by looking at how many people already die of the kinds of things climate change influences. That will at least put us in the right ballpark of the mess we’re looking at as these dangers get worse.
Every summer, about 2,000 people die from heat related causes in the United States alone. The US has less than 5% of the world’s population, isn’t a very hot country, relatively speaking, and a lot of us can and do use air conditioning freely, so the worldwide figures are probably somewhere in the tends of thousands. How many of those heat-related deaths can be attributed to climate change is, of course, complicated, but clearly some of them are, since climate change has already dramatically increased extreme heat world-wide.
About 10,000 people die every year from tropical cyclones (the type of storm that includes hurricanes), worldwide. Although it isn’t yet clear whether tropical cyclones are getting more frequent or more windy due to climate change, they are getting more dangerous–both sea level rise and a warmer atmosphere’s greater ability to hold water increase the flooding associated with these storms–and the flooding is by far more dangerous than the wind. So some of these deaths, too, are climate-related.
There are other climate-related dangers, such as drought or non-hurricane flooding, or greater risk of insect-borne diseases. There are even more complicating factors for these, but they do probably add some people to the death toll for climate change. But there is another way that climate change can kill: through violence. According to a study released a year ago, higher temperatures make people behave very badly.
The causal mechanism doesn’t seem clear, here–I expect there are several causes involved–but the study established that above-average temperature spikes are strongly associated with increased violence. Scientists analyzed the results from 60 other studies and found that the association is consistent in all 27 countries studied and applies to both interpersonal violence (murder, rape, assault), and larger-scale horrors, like war and institutional collapse. This doesn’t mean that all violence is climate-related, but that some number of the people who die by the hands of other people wouldn’t if our climate weren’t being warped.
To give an idea of the scale we’re looking at, almost 15,000 were murdered in the US in 2012, a rate that is somewhat high compared to other industrialized countries. That doesn’t count war dead, and of course the US has lost comparatively few people that way in recent years.
So each of these climate-influenced causes have a worldwide death-toll in the tens of thousands to hundreds of thousands. Combined, that’s something like a few million deaths a year, some number of which can be laid at the doorstep of global warming. And what is that number? I do not know. But Let’s say it’s 1%. That’s a nice, small, cautious figure. Let’s say that out of every hundred people who die from something climate-related, only one actually died from climate change itself. Well, one percent of a million is still ten thousand, which is over three times our loss to Ebola this summer.
No, this isn’t a scientifically rigorous estimate–but you can see how climate change can indeed kill more people than Ebola. The article title is certainly plausible.
Yes, the Ebola pandemic could continue to mushroom and spread for a while. Things could get much worse before they get better. But the fact of the matter is that disease outbreaks end. Eventually, everybody who is vulnerable to the disease gets it and either dies or develops immunity. Remember that the worst-case scenario estimates cap the Ebola death-toll at somewhere around 250,000 people, world-wide. Other experts put that number as low as 20,000. In contrast, there is no acquired immunity to climate change, so however many people died from it this year, the same number–or more–is likely going to die of it next year and the year after, too. We are only seeing the beginnings of the climate chaos we could be in for.
The death toll from Ebola is going to start coming down eventually. Our losses to climate change are probably lower now than they’ll ever be again. How high those numbers go is in our hands.