Climate deniers don’t just want to deny global warming and its danger. They want you to deny it too.

But man-made climate change is real, the danger is extreme, so they have to use guile to persuade you otherwise. There are three tried-and-false tactics they use often, and to great effect. Let’s take a close look at these misdirection methods, so you can arm yourself for defense against the dark arts.

#3: REJECT THE DATA

Climate deniers don’t like what the data say. What they probably hate most is the temperature data — especially at Earth’s surface (where we live) — because it shows so plainly and obviously that the world is heating up. Here are the three best-known global-average surface temperature data records (yearly averages since 1880), from NASA, NOAA (the National Oceanic and Atmospheric Administration), and HadCRU (the Hadley Centre/Climate Research Unit in the U.K.):

They all tell pretty much the same story: Earth is heating up.

Pinning down global average temperature change is a complicated business. You have to gather data from around the world, including thermometer readings from thousands of surface stations for land areas and sea surface temperature measurements from ships and from satellites. You have to average them properly, in a way that doesn’t over-emphasize regions with lots of observations but underplay regions more sparsely observed (a process sometimes called “area-weighting”). You need to remove the seasonal cycle, because we’re not interested in whether summer is hotter than winter, we want to know whether the world as a whole is heating or cooling. You have to watch for things like station moves where temperature seems to change only because the station was moved to a hotter or colder location. Truly, it’s a complicated business.

The longer they’ve been doing it, the better they’ve gotten at it. In particular, they’ve learned to spot the signs of data problems and make adjustements to compensate. As a result, they’re a lot better at it now than they were just a few decades ago.

But because there are “adjustments” — whose only purpose is to make thing better by compensating for known problems — deniers have seized on that word to claim that the scientists doing it were perpetrating a fraud, that adjustments were only to introduce false warming into the record.

Richard Muller, a physicist at Berkeley University, thought that maybe they were right about that — he was highly suspicious of the surface temperature data. He decided to find out for himself, by organizing a team to go back to the original, unadjusted data, and use the most sophisticated and mathematically sound procedure for estimating a world-wide average, one which didn’t allow any way to make the results “lean” one way or the other to introduce a bias toward cooling or warming. The effort is called the Berkeley Earth Surface Temperature project.

Climate deniers were thrilled — they waited in anticipation of genuine scientists, using the best available methods, finally showing that the existing records were wrong.

The admiration of climate deniers for the Berkeley Earth Surface Temperature project didn’t last long. It vanished into thin air as soon as the results were announced. That’s when the climate denier community turned on Richard Muller like a pack of wolves, because the Berkeley Earth Surface Temperature project, the fakeproof method, showed that the existing data sets got it right all along. Muller himself had this to say in a 2012 op-ed in the New York Times:



CALL me a converted skeptic. Three years ago I identified problems in previous climate studies that, in my mind, threw doubt on the very existence of global warming. Last year, following an intensive research effort involving a dozen scientists, I concluded that global warming was real and that the prior estimates of the rate of warming were correct. I’m now going a step further: Humans are almost entirely the cause.



And how does the new Berkeley Earth data set compare to the others? Like this:

Climate deniers don’t just use this tactic on temperature records; when data disagree with their narrative they’ll attack the data. Far too often, they won’t just say the data are mistaken, they’ll accuse the scientists who put it together of fraud. It’s reprehensible.

Climate deniers like to call themselves “skeptics,” but they’re not. What’s the difference? I think Neil deGrasse Tyson said it best:



“A skeptic will question claims, then embrace the evidence. A denier will question claims, then reject the evidence.”



#2: DISTRACT FROM THE TREND WITH FOCUS ON FLUCTUATIONS

Almost all data is a combination of trend, which has persistence, and fluctuation, which doesn’t last. The trend reveals how climate is changing, but the fluctuations are weather, and just because climate changes, doesn’t mean we won’t still have weather. Fluctuations go up and down and down and up — they just won’t stop — but they never really get anywhere.

Climate scientists can tell you, it’s the trend that matters. Heat waves, flood, drought and the like are things we’ve always had to deal with, and they spell trouble. But when they get more frequent, and more severe, it can be disastrous. It costs money, it costs jobs, it costs lives.

Deniers don’t want you to know how the trend is going, so they go out of their way to shout about fluctuations that go the other way. Maybe the most infamous example is when Oklahoma senator James Inhofe carried a snowball onto the floor of the U.S. senate one day to try to ridicule global warming. He ended up ridiculing himself, because the idea that you can discredit global warming because you happened to find some cold weather — in winter, no less — is truly ridiculous. As in, worthy of ridicule.

Temperature is one of those things that fluctuates. It can show large swings from day to day, from month to month, even from year to year. But there’s also a trend, which is upward — it’s called global warming. Lately deniers have been taking temperature fluctuations that happen to go downward and braying about “global cooling.” Of course the fluctuations don’t last — but they still accomplish their goal of creating doubt in the minds of the scientifically naive.

Christopher Booker writes for the British newspaper The Telegraph. He recently included a comment about England’s meteorological office acquiring a new computer for their weather and climate simulations, in which he had this to say:



“Only gradually since 2007, when none of them predicted a temporary fall in global temperatures of 0.7 degrees, equal to their entire net rise in the 20th century, have they been prepared to concede that CO 2 was not the real story.” — Christopher Booker, U.K. Telegraph, 22 October 2016.



It that true? Did global temperature actually fall far enough to negate the entire 20th-century rise? Here’s Earth’s average temperature change each month from 1880, according to NASA:

If we zoom in on the last 40 years or so, starting about 1975, we can easily see what it is Christopher Booker is talking about:

He’s talking about a couple of fluctuations. If you compare an especially high fluctuation to an especially low fluctuation, you might convince yourself that temperature is falling fast.

But a fluctuation is not a trend. Trends have some persistence; fluctuations don’t last. Climate scientists tell us that it’s the trend that matters — that’s why it’s what they talk about:

Another example: about a week ago David Rose had an article in the U.K. Daily Mail with its focus on a “sudden drop” in global temperature. Rose searched far and wide to find a data set he could use to make that claim, and the best he could come up with was satellite data for the lower atmosphere (not at the surface) over land areas only (excluding the 2/3 of the world covered by ocean). His story was repeated by others in the U.K. Spectator and the alt-right propoganda-driven Breitbart News.

What’s fascinating is what they chose to focus on: some fluctuations which they seemed to think were worth shouthing about, with no mention of the trend. Here, in blue, are the fluctuations they made such a fuss about, and in red is the trend they didn’t want to discuss:

Fluctuations will always be with us, they’re part of nature. But the rising trend of global temperature that we’ve been seeing is man-made. According to the overwhelming majority of climate scientists, this trend spells trouble. And the reason? Mainly, it’s CO 2 .

We now come to the most common, most pernicious, and probably most effective climate denier tactic:

#1: CHERRY-PICKING

On April 15, 2013, Lawrence Solomon published a brief article in the Financial Post suggesting that sea ice in the Arctic wasn’t really declining, that there was no trend toward persistent long-term melting. He started with this:



Arctic sea ice back to 1989 levels Yesterday, April 14th, the Arctic had more sea ice than it had on April 14,1989 – 14.511 million square kilometres vs 14.510 million square kilometres, according to the National Snow and Ice Data Center of the United States, an official source.



His opening sentence is one of the most extreme examples of cherry-picking: showing or talking about some evidence that supports your claim, while ignoring or rejecting evidence that contradict you.

He went on to add a couple more cherry-picked “facts” for good measure. Then he ended with this:



“The only evident trend in the ice, as in the weather, is variability.”



It all sounds pretty convincing, doesn’t it? Arctic sea ice was no more extensive on that day than it was 24 years ago! Plus, he actually mentions the words “trend” and “variability” — how scientific.

The following day (April 16, 2013) I posted this graph showing all the available “sea ice extent anomaly” data from the National Snow and Ice Data Center (yes, an official source):

In case you’re wondering what’s happened since then, it’s this:

The red line is an estimate the trend — the one that Lawrence Solomon said isn’t “evident.”

This particular example is also a case of tactic #2: distract from the trend by focus on fluctuation. It’s executed by the never-ending tactic of cherry-picking: discuss evidence that supports your claim while ignoring or concealing evidence that contradicts you.

The most frequent target of cherry-picking is temperature data. Here, for instance is senator Ted Cruz’s favorite temperature graph:

It certainly looks like there’s been no global warming! But remember that data is a combination of trend and fluctuation. Fluctuations sometimes go down, which can make an upward trend look downward, even when that trend — which we call global warming — hasn’t stopped or even slowed. What deniers do is cherry-pick — find a time span which starts with a large upward fluctuation, maybe even ends with a large downward fluctuation, to create the false impression of a downward trend.

In 1997-1998 we had a particularly strong el Niño, one of the factors that can cause an especially large upward fluctuation. That’s why climate deniers start so many temperature graphs with 1997-1998 — it’s the large upward fluctuation they need to give a false impression of trend.

But that’s not the only time span one can cherry-pick to show fluctuation and claim it’s a trend. There are many, which led to a now-famous animated graph from the website Skeptical Science:

No matter how temperatures change, as long as there are fluctuations deniers will be able to cherry-pick some time span to look like their false claim. And there will always be fluctuations.

What if we didn’t cherry-pick the time span? The data in Ted Cruz’s graph starts back in 1979, well before 1997, and we’ve got some more data since he showed it in his latest senate hearing. Here’s the whole story:

The red box shows the part included in Ted Cruz’s graph. The interesting part, that reveals the upward trend, is what Ted Cruz didn’t show.

Picking an outlier for your start and/or end points isn’t the only way to cherry-pick and hide the trend. Another is simply to pick a time span that’s way too brief for the trend to make itself clear.

Fluctuations can be large, especially for temperature data, and the trend can take years to accumulate enough warming to overcome them. That’s one of the reasons the typical time span to define climate instead of weather is 30 years. If all you show is a brief span of time, the trend doesn’t have long enough to “rise above the noise.” But it’s still there.

The Global Warming Policy Forum (GWPF) features a temperature graph in their logo. The data are yearly average temperature according to the Hadley Center/Climate Research Unit in the U.K. (HadCRU). Here’s the HadCRU data itself:

The year 2016 isn’t complete yet, but will be soon, so I’ve shown the average for the year-so-far.

Here’s the graph GWPF includes in their logo:

Notice how it doesn’t start until 2001? Notice that it doesn’t include 2016’s year-so-far value? I wonder what they’ll do when 2016 is complete and it’s harder to hide the temperature rise? Notice how squeezed the data is into a small space, so the total variation looks small? If they showed what came before, or what came after, or even on a scale that helped see the changes better, you might notice how clear the upward trend is.

There are many ways to cherry-pick. Choose a time span selected to give the wrong impression (start with 1997-1998); choose the one data set that supports your claim but not any of the others; choose a single event which bucks the trend (my grandmother smoked cigarettes and lived to be 98 years old).

Climate deniers use these tactics because they work. When they suggest that the temperature data are a fraud, it raises your suspicions. When they point out a “sudden drop” in temperature data while concealing the trend, it can be persuasive. When you hear that Arctic sea ice is no more extensive than it was on this date 24 years ago, it sounds convincing. When you see temperature data on a graph starting in 1997-1998, it looks convincing.

Even the best of us, even the smartest of us, are all too easily fooled by misdirection (stage magicians can use that fact to make a very good living). There’s no shame in being fooled by a charlatan, we’ve all been taken in at one time or another. My hope is that now that you’ve seen some of their tricks, when you run into them the next time you’ll recognize them for what they are: tricks.

Fool me once, shame on you. Fool me twice …

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