Real data — temperature, for instance — are almost always the combination of signal and noise, which we could also refer to as trend and fluctuation. Fluctuations are ubiquitous, they happen all the time. Sometimes they go up, sometimes down, sometimes a little and sometimes a lot, but the one thing they don’t do is stop.
That’s why, even in a stable climate, we’re sure to see extremes. Heat waves will happen. So will floods, drought, and giant storms. It’s the nature of the beast, those things can happen for no apparent reason — for no reason at all, really, just because they are random fluctuations. When extremes arrive, they often bring trouble with them. It’s good to be prepared for such fluctuations, because they’re unavoidable.
How extreme they are, and how often they occur, depends on the nature of the fluctuations. By measuring conditions over long periods of time, we not only get to know what the average conditions are, we also learn about the fluctuations. That enables us to define climate as the mean (average) and variation (fluctuations) of weather.
It can even happen, for no apparent reason, that we suffer an extreme extreme, a fluctuation so severe it’s unlike anything we’ve seen for a very long time, maybe even ever. Such events often bring, not just trouble, but disaster. Maybe even disaster more severe than we’ve seen for a very long time, maybe even ever.
Life can be dangerous, that too is the nature of the beast, and extreme extreme weather fluctuation is one of the greatest dangers. Fortunately such fluctuations are exceedingly rare. A once-in-a-thousand-years heat wave only happens, well, once in a thousand years. On average, that is … we could get two such events in rapid succession just because of (very very) bad luck. Fortunately, such concordances of extreme extremes are very very exceedingly rare.
In just the last decade we’ve seen a number of extreme extremes. Even if we only count the heat waves, recent history is remarkable. Europe in 2003, Australia in 2009 (not once but twice in a single year), Russia in 2010, the U.S. in 2012. And now Australia (again!) in 2013. All these heat waves were extreme, some were extreme extreme, and they all brought disaster. Their frequency is just as remarkable as their severity, having come one after another in rapid succession.
That could be just a coincidence — one hell of a whopper of the worst weather luck imaginable. Thing is, we have this mathematical science called statistics, and it tells us that the odds of that happening just by chance is small. Really really small. Miniscule. Sub-microscopic.
We also have this physical science called climate science. It tells us that we’re changing the climate itself, due to a lot of man-made causes but chiefly dumping immense quantities of greenhouse gases in the atmosphere. Because of that, the average temperature is changing. Temperature (and other weather variables), in addition to undergoing never-ending fluctuation, is also showing a trend — so the mean itself is changing. When that happens, a big fluctuation — not an extreme extreme, just an “ordinary” big one — gets added onto a higher mean value.
Consider the following fluctuations:
The value in 2012 (circled in red) is big. It’s the 2nd-biggest fluctuation of the last 118 years, but it’s just a little bigger (by 0.06 degrees) than the fluctuation in 1934 and quite a bit smaller (by 0.5 degrees) than the fluctuation of 1921. All by itself, that fluctuation is bound to bring trouble — a heat wave, possibly an extensive one, and maybe drought as well. It’s the kind of trouble that we are well advised to be prepared for, because it’s the kind of fluctuation that is sure to happen again and again.
But all by itself, that kind of fluctuation isn’t a disaster. We are prepared for it because we have seen it before. It was, effectively, just as big in 1934 and a lot worse in 1921, which is not so long ago that we’ve forgotten how bad it can get just from random fluctuation. We don’t like it, but we muddle through and recover because just as fluctuations can go far up and can also go far down (which is a different kind of trouble), most of the time they’re near the middle so conditions are near average.
Fluctuation is only part of the story. When we add in the effect of trend, we get annual average temperature for the 48 contiguous states of the U.S.
The 2012 value is now like nothing we’ve seen before. The fluctuation alone was big, but hardly extreme. All alone it was trouble, but not disaster. But when that big fluctuation is added to the substantial trend, it is extreme. It’s more than trouble, it’s disaster. It’s crippling drought, deadly heat wave, a big dent in the corn crop, and terrible wildfires raging out of control.
Just this month, Australians experienced a similar large upward fluctuation in nationwide temperature. Again, all by itself that’s not such a big deal. Heat waves and wildfires happen, and since Australia is a pretty hot place anyway those who live there are well prepared for such fluctuations. But when they are added on top of a substantial trend
it becomes like nothing they’ve seen before. These data only go through 2011, they don’t include 2012 and certainly don’t show the astounding heat of early 2013. But they do reveal the trend, the increase in the average which makes every upward fluctuation far worse than it would have been.
The lesson is this: when trend and fluctuation collide, it creates unprecedented extremes. While extremes are trouble, unprecedented extremes are disaster.
Australia has survived their latest heat wave, albeit with much suffering and horrific wildfires. The U.S. survived our hottest year ever, albeit with much suffering, substantial crop damage, and horrific wildfires. But harken back to the opening paragraph, and recall that fluctuations are ubiquitous, they happen all the time, the one thing they don’t do is stop.
So, extremes are inevitable. That’s a problem, but we already knew that and for the most part we’re prepared. The extreme problem, the one we’re not prepared for, the deadly threat we face, is that the trend isn’t going to stop either. If the post-1975 trend continues in the U.S., this is the future we face:
The dot with a red circle around it is the temperature in 2012. That was a national disaster. Now imagine that the endpoint of the red line, so much hotter than what brought about a national disaster, becomes the norm.
What will life be like when unprecedented disaster becomes the norm? We are not prepared.
Alas, “the post-1975 trend continues in the U.S.” is an optimistic forecast. It only leads to an average temperature anomaly of about +6°F by the year 2100. That’s on the low side of actual forecasts by legitimate climate scientists:
Suppose the average temperature anomaly in the U.S. climbs over 11°F by the year 2100. Consider how bad it already was in 2012. Consider how terrible it will be if we get to 6°F. Now, double that. The devastation boggles the mind.
Now imagine all of that plus one of those big upward fluctuations. The kind that is ubiquitous, the kind that just won’t stop.
Whether we, as a civilization, can even survive such a debacle is in doubt.
WHEN FOOLS FOOL
Perhaps you’re thinking that when fluctuation and trend collide, it creates the kind of event that will motivate people to do something about global warming. Indeed it does.
But as bizarre as it may seem, it also helps deniers who want to deny the problem push their denial story. Let’s take the “post-1975 trend continues in the U.S.” and add some fluctuation onto that trend. I added random noise, with the same standard deviation (the same size) as the actual fluctuations of U.S. temperature. This was the result:
The trend keeps rising, and the fluctuations keep fluctuating, but since they go sometimes up and sometimes down, and since they don’t go as far as the 2012 fluctuation very often, in this particular future scenario the temperature didn’t get as high as it was in 2012 for eighteen years, not breaking the 2012 record until 2031. If this is how the future unfolds — and it could well do so, although it could also reach a new record high well before that — we’ll hear proclamations of “No warming in the U.S. for 18 years!” Oklahoma senator James Inhofe will declare that we’re in a cooling period. Anthony Watts will host a guest article by Chip Knappenberger that U.S. temperature data indicate nothing to worry about. Fox News will give them, and a lot of other crackpots, a national televised forum to spread their propaganda. Imagine if you will, the hubbub in 2022 when, just by accident, the fluctuation goes in the opposite direction to the trend and the so-called “Heartland Institute” buys print ads in the New York Times declaring that the whole global warming idea is a scam, climate scientists are a bunch of frauds, and we should really be worried about the next ice age.
Climate scientists will talk about signal and noise, about how ubiquitous is random fluctuation, about the long-term trend, about fundamental physics. They’ll talk about how bad it’s going to get and how it affects such fundamental issues as food and water. It doesn’t get any more fundamental than that.
Meanwhile, the trend will continue. The fluctuations will continue. Sooner or later, the two will collide. Again.