Remember the ‘Smoking Might Cause Lung Cancer’ campaigns of the 1970s and 1980s? Of course you don’t, because nobody ever used the word ‘might’, either in a public-health campaign or in a news headline (Tobacco executives said, more or less, ‘don’t’, but that’s another story altogether.)
Yet the whole truth is that smoking doesn’t necessarily cause lung cancer. Many people who smoke don’t get lung cancer. Some people who get lung cancer have never smoked in their lives. And in a case where someone does smoke and does get lung cancer, you can’t actually prove that the smoking caused the cancer. It might have happened anyway. But nobody even considered the possibility of headlining the whole truth about smoking, because that could have muddied the essential, and utterly valid message: smoking is really dangerous, and you’re crazy to do it.
Thanks largely to the constant repetition of that message, smoking rates have dropped in the developed world, and not even the tobacco execs are foolish enough nowadays to say that’s a bad thing.
So that brings me to climate change. The essential and utterly valid message, based on the best available science, is that the Earth is warming; it’s largely due to us; it’s going to keep warming unless we do something, and there’s a significant chance that the consequences will be disastrous.
But is that the whole truth in every detail? No. Some of the details are yet to be settled. How much more warming are we going to get by, say, the end of this century? The best estimate is between 3.2ºF and 7.2ºF above where things stood in 2000, but a few scientists say it could even be lower than 3.2ºF.
This isn’t entirely crazy: global warming causes more water to evaporate into the atmosphere, leading to more clouds. The balance of evidence suggests that the result will be to increase warming, because water vapor is itself a heat-trapping greenhouse gas. But a small minority of scientists thinks things might go the other way, and the answer isn’t really certain yet.
So should the overall message be that nobody knows anything? I don’t think so. We would never want to pretend the uncertainty isn’t there, since that would be dishonest. But featuring it prominently is dishonest too, just as trumpeting uncertainty in the smoking-cancer connection would have been.
Another source of uncertainty comes in making the human-warming connection. “Maybe it’s the sun,” say some skeptics, and while the sun hasn’t brightened at all during the most recent half-century when the warming has been greatest, there are plausible, though not proven, ways the sun could cause global warming without itself warming up.
So does it make us intellectually dishonest not to be trumpeting this potential challenge to conventional ideas? Not really: it would be dishonest to suppress this argument, but since it’s a long way from being even weakly established, and because abandoning the idea of human-influenced climate change would mean abandoning an awful lot that has been firmly established, the most honest thing to do is not to go into a tizzy about a very preliminary result.
There’s a flipside to keeping the message simple, though. ‘The Earth will keep warming if we don’t do anything about it,’ is true, but it might seem to imply that temperatures will literally be higher each year than they were the year before. That’s false: all sorts of natural climate variations operate to slow the warming down for a while, or speed it up. Temperatures go up over the long-term, but over periods of a few years, or even a couple of decades, the warming can flatten. Anyone who imagined it would be otherwise might think that the relatively slow warming of the past decade means the whole theory is debunked.
So where’s the right balance between telling the whole truth and being truthful in an effective way? At this point, a columnist is supposed to offer a tidy prescription. Sadly, I don’t have one. But NPR does: the US radio network just updated its guidelines to reflect a commitment to fairness and truthfulnessin reporting. That doesn’t mean telling the whole truth in every last detail. It does mean giving readers and listeners an honest take on critical issues.
For climate change, here’s my take (you already saw it above): The Earth is warming. It’s largely due to us. It’s going to keep warming unless we do something. And there’s a significant chance that the consequences will be disastrous.