In every province, the chief occupations, in order of importance, are lovemaking, malicious gossip, and talking nonsense.
— Voltaire, Candide
Whether we refer to the subject as “climate change” or “global warming,” it’s a good idea to know what it is we’re talking about. Yet true to Voltaire’s form, we indulge in a great deal of talking nonsense about it. Therefore let me say a few things about what it is not.
Global warming is NOT the end of weather
In February 2015, senator James Inhofe (R-OK) brought a snowball onto the floor of the U.S. Senate. He talked about how cold it was outside, calling the temperature “unseasonable,” and cavalierly tossed the snowball to the senate president with the words “catch this.” It was his attempt to ridicule those who call global warming a problem.
He succeeded in bringing down ridicule — on himself. That’s because, implicit in senator Inhofe’s criticism is the idea that we can discount global warming because he found some cold weather (in winter). Of course the idea is silly, but it’s surprising how many people think that global warming must spell the end of cold. Everywhere. All the time.
Just because climate changes, it doesn’t mean we won’t still have weather. We will, of all kinds: hot, cold, wet, dry, windy, calm. The days will continue to bring a never-ending variety of temperatures, from bitter cold to oppressive heat, because nothing will stop them fluctuating from day to day. But if you track temperature every day, you’ll find that the hots are a little hotter and a little more frequent, the colds not quite so cold nor quite so common.
Global warming is NOT the fluctuations — it’s the trend
One of the most common misconceptions is that if global warming is really happening, each year must be hotter than the one before.
Temperature (and other weather variables) fluctuate, always have, always will. Global warming doesn’t change that (although it might change the essential nature of the fluctuations). What counts is the trend. We’ll still have colder days and hotter days, colder and hotter months, years. But the average, what we expect to happen over long periods of time, is changing persistently.
Global warming is NOT a “little” change
Some make hay of the fact that the average temperature change over the whole globe caused by mankind so far, has only been about 1C (one degree Celsius, equal to 1.8 degrees Fahrenheit). How can that matter, they ask, when temperature may change by 30 degrees or more within a single day? If you raise the temperature of the room you’re sitting in by a “mere” 1C, you might not even notice.
It’s no surprise if a single day is one degree hotter, or even ten. But if temperature is persistently just a little bit hotter on average, the extra heat adds up day in and day out, and the effect can be profound.
Tens of thousands of years ago global average temperature was “only” about five degrees colder. To many, that hardly seems enough to bring about a cataclysm. But Earth was in the grip of a great glaciation, with miles-thick sheets of ice covering what are now the locations of great cities. So much of the world’s water was frozen that the sea stood 400 feet lower than it does today, uncovering great tracts of land.
We’re witnessing big changes already, from only one degree of change. Bayfield, Wisconsin, is a small town on the shore of Lake Superior, best known for its natural landscape and outdoor activities. Every year the lake freezes over, and locals have kept track of how long it stayed that way for over a century. Back in the 1850s and 1860s it was typically ice-covered for about 118 days, but now that the 2000s are here the lake is typically ice-covered for only 53 days. That much decrease — nine weeks, so today’s typical lake ice season is less than half what it used to be — isn’t “little” by anybody’s definition.
Many other huge changes (“you can’t miss it” as opposed to “you might not even notice”) have taken place, due to the 1C we’ve warmed the planet so far. The consensus of climate scientists is that if we go twice as far, up to 2C, the cost (in lives lost, refugees, crop failures, drought, flood, sea level rise, and more) will be far more than we want to face. Noone knows how bad it will get beyond that, 3C or even more, and nobody in his right mind wants to find out.
Global warming is NOT the same everywhere
Many believe that global warming is uniform, i.e. that every place on Earth will warm at the same rate. But the differences between regions have caused them to warm by different amounts.
The oceans have huge “thermal inertia,” so it takes more heat to warm them than it does the land. Since the northern hemisphere has so much more land than the southern (most of the world’s land is in the northern half of the globe), it has warmed considerably faster. The Arctic is warming most quickly, about 3 1/2 times as fast as the globe as a whole.
This figure (from NASA) shows how much different parts of
the world have warmed, by comparing the 2005-2015 average to the 1951-1980 average.
Global warming is NOT the same at all times
We’ve already emphasized that temperature is always fluctuating as heat moves from land to air to sea; even when averaged over an entire year, fluctuation persists. But it’s also important to realize that the trend hasn’t been the same at all times either.
As figure this graph shows, not only has there been a pattern to the world’s temperature changes, there are year-to-year fluctuations which can make one year cooler than the previous, even in a warming world:
It also reveals unsteadiness of the trend itself; the early 20th century saw a period of warming which was followed by several decades of none. Since about 1970, however, the trend has been steadily upward. The overall pattern is found not only in the temperature at Earth’s surface (where we live), but in the depths of the oceans as well.
Global warming does NOT cause all extreme weather — but it causes more
Lately, whenever extreme weather brings disaster someplace, two reactions are common. Some will talk about how this may be directly related to climate change. Others will retort that extreme weather has been happening always, and you can’t prove this particular event was caused by anything unnatural.
It’s true that you can’t prove any single event was caused by global warming. It’s also true you can’t prove any home run in a baseball game was “caused by” steroids. Major leaguers have been hitting home runs as long as we’ve played baseball — but when steroid use became endemic, the number of home runs went up. By a lot — enough that we could tell, steroid use might not have “caused” any particular home run, but it was causing more than we got without.
Climate change has been likened to “weather on steroids.” We can’t blame it for that particular heat wave, but we can definitely blame it for the increase. And, like steroids, it doesn’t just cause extreme events to be more common, it make them more extreme.
Global warming did NOT recently “pause”
Even when the trend is steadily upward, fluctuations can make it seem otherwise. That’s the nature of fluctuations; by going down they can mask a trend in the opposite direction.
One of the most persistent, and most effective, talking points of those who deny the reality of global warming is that temperature increase recently showed a “pause” or “hiatus.” Such claims usually start with the year 1998 because that was when the fluctuation was exceptionally high, so much so that it took years for the upward trend to overtake it. A favorite trick is to show a graph of global temperature like this:
It shows the period of the so-called “pause” but not what came before. Including context would cast doubt on the “pause” claim, and might even reveal that short periods of time — less than about 30 years — aren’t enough to reveal the genuine climate trend, they’re dominated by weather fluctuations.
Some context is necessary, like this:
It makes plain the lack of support for the “pause” idea. Not only does what came before show this, what has happened after 2013 makes the idea look rather silly. Since 2014 was a new record hottest year, and 2015 broke the record again, talk of the “pause” has shifted to other strategies, including casting doubt on the data itself, and pointing to different data as though it were better when in fact it’s not.
When someone shows a graph which doesn’t start until 1997 or 1998, refusing to show what came before, ask yourself why they’re not telling the whole story.
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