AGW Critics: Short Term Trends Are Not Your Friends

I ran across a nice post on the excellent Open Mind blog that shows with absolute clarity why the "cooling trend" of the last decade or so has no relevance to global warming. I've posted about this before, using a similar technique, but Open Mind goes into considerably more detail.

What's nice about these analyses—Open Mind's and, humbly, my own—is that the demonstrations have nothing specifically to do with global warming. The data are not climate data, and it doesn't matter what you think about climate change. They're just common-sense math. They can't be obfuscated with charges of sensor data inaccuracy or urban heat island effects or global conspiracies of grant-happy scientists or any of that. They are what they are.

Here the Cliff's Notes version of the Open Mind post.

Open Mind's author, Tamino, programs a set of data points to have a small upward trend (simulating global warming) and then superimposes on that a bit of "noise" (random upward and downward deviations, simulating weather). If you look at the whole graph, you can see the trend clearly, despite the noise:


Then he steps into the role of Global Warming Critic and takes a subset of the data, starting with "1998" (see the blog for why Tamino labels this data point as "1998"):


Presto! An instant decade-long cooling trend! Global warming is a hoax!

Well, of course not. The long-term upward trend can't possibly be wrong, because it's built in. It's literally programmed into the model. It's as real as it gets.

What does this show? It shows very, very clearly that noise can easily hide a trend if you choose the right time span. In the case of weather "noise", it takes longer than a decade to average out and give you a true picture of the climate trend.

So, the next time your friendly neighborhood GW critic trots out "It's actually been getting cooler since 1998", you have even better information on your side. Nice job, Open Mind.

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P.S.: For yet another take on the same concept, Andy Revkin of the New York Times has a good post on his Dot Earth blog.

April's Fool

Good ol' George Will, he's back for another try. Sort of like Charlie Brown and his neverending but hopeless quest to kick that football. And, just like C.B., he's never going to get it.

In his latest Washington Post windmill tilt, he goes after, of all things, compact fluorescent light bulbs (CFLs). Turns out that "some" of them—he doesn't bother with any numbers— don't last very long. Well, George, I have had "some" incandescent bulbs that didn't last very long either. I've had "some" of them blow out the first time I turned them on. Have you considered a column about that scandal?

He's also discovered that they contain mercury and should be disposed of properly. Apparently he's very concerned about the environment, so he worries about this. Some people might not do it right. There's no word, however, on whether or not he's equally concerned about the mercury that's been in all those fluorescent tubes that have been lighting offices and—gasp!—hospitals for so many decades. Or on whether he's worried about the mercury that goes into the air when you burn all the extra coal needed to run your inefficient, power-hungry incandescent bulb (which turns about 90% of its energy into heat)—mercury that gets dispersed into the landscape and is virtually impossible to clean up.

George seems unaware, too, that CFLs represent a transitional technology, one that will save energy until LED bulbs, which have all the benefits of CFLs but none of the drawbacks, are ready for home use.

While he's at it, George simply can't resist abusing the UN World Meteorological Office's data just one mo' time. He's a little more subtle about it than in his earlier columns; maybe he read one of the hundreds of blog entries that pointed out just how utterly wrong he was. Or the letter from the the head of the WMO itself that said the same. So this time he shoots for misleading instead of wrong—and he scores! Where he used to say that the WMO's data show no global warming since 1998, this time he goes with the more clever thought that, according to the WMO, "there has not been a warmer year on record than 1998." Well done! This one is technically true, but wholly misleading. He implies rather than states something that's factually incorrect. Brilliant!

Of course, it still doesn't mean anything. As Chris Mooney notes, "It’s absurd to assume that we’ll set a new temperature record each year, and that if we don’t, there’s nothing to worry about."

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The brilliant cartoon is by Tom Toles of the Post. It's a Web-only cartoon that unfortunately did not appear in the newspaper.

Hume-an Error

I didn't intend for this to be a climate blog. It was just supposed to be a place where I could note odd stuff that I run across and to let off steam about foolishness that I see.

But people will keep spouting the most ignorant crap about global warming, so here we go again.

The latest loony tirade comes from the mouth of the redoubtable Brit Hume (incidentally, I think this argues for an entirely new definition of redoubtable: someone you can doubt over and over again.) Talking about a recent demonstration in Washington, he said this on the March 2 edition of Fox News's Special Report:

[Y]ou have to give those global warming activists credit for pluck. Not only were they protesting warming temperatures in a city going through its coldest winter in recent memories—a city in the midst of a snow emergency and sub-freezing temperatures—they were also doing so on a planet that has seen no average warming for the past 10 years. But climate change alarmists are not easily fazed.
...
The problem with [scientists' climate models] is that when data from the past have been plugged into them, they have had trouble predicting today's temperatures. The climate alarmists certainly did not foresee the cooling trend of the past decade. No matter.

Let's skip over whether or not he should be using the loaded term "climate change alarmists" twice in something that they're calling a "report." I guess that's why Fox News's slogans are "Unfair and Unbalanced" and "We Spin, You Listen Up." (I got those right, didn't I?)

While we're at it, we can also skip the bit where he apparently just makes up the "coldest winter in recent memories" factoid: a full third of the previous nine DC winters were colder.¹ Maybe he has a really bad memory.

Nah. He just likes to make stuff up.

OK, that's enough Andy Rooney. Let's get to the serious issues.

"Coldest winter in recent memories"

Even if this were true—and it's not—this is a classic case of confusing weather and climate. Weather is something that happens day-to-day, month-to-month, year-to-year. There's a lot of variability—noise, if you will—in it. It's very hard to predict more than a couple of days in advance. Climate is, in essence, weather with the noise removed.

Climate information is obtained by averaging weather over a long period of time and observing trends. Suppose you were to graph annual temperatures over many years. If you observe the temperature trends and how they are changing, you are looking at climate; but if you observe the temperature spikes here and there, you are looking at weather.

This winter's average temperature is weather, not climate. (Whether or not there's a snowstorm that discourages global warming alarmists from demonstrating is really weather.)

Let's use a classic example: rolling dice. If you roll an ordinary six-sided die many times, you will find that it averages around 3.5. If you graph this, you'll find a lot of spikes for low and high rolls, but if you make a trend line, it will be more or less flat. Here's a little graph of a hundred simulated throws:



The trend line is in red. That is climate. The line is essentially flat because the dice rolls aren't trending up or down—there's no change in the average roll as we move along in time.

The actual throws are in blue. That is weather. These vary rather wildly. Some throws are near the trend line, some are way above it, and some are way below it.

Now here is another simulation. This time I've loaded the dice: as we go on, it gets progressively easier to roll higher numbers, so now the average roll is increasing as we move along in time (this simulates global warming):



The loading of the dice is clearly visible in the upward curve of the trend line. But notice where we rolled a 2 at the red arrow. It doesn't prove that the dice aren't loaded, right? In fact, we can't tell anything at all from the one data point.

If this were a graph of average DC winter temperatures instead of dice rolls, the arrow would point to our "cold winter" (and, yes, even with global warming, there will be relatively cold winters). Just as that one throw can't tell us anything about whether the dice are loaded, that one cold winter can't tell us anything about global warming.

Here's the key point: weather is, for all intents and purposes, random. Climate is not. And you can't look at that random weather for today or this month or this year and use it to say anything about climate.² You can't just look at a single point in time and say, "It's cold, therefore global warming is bunk." But that's what Brit did with his "it's cold this winter" comment. (Maybe he'll come back in August when it's 105° in DC and say, "It's really hot today. Looks like I was wrong about global warming.")


"Cooling trend of the last decade"

Brit simply asserts this, so we don't know where he got it from—but I think I can make a pretty good guess. A lot of people (including George Will, quite recently—coincidence?) have been saying the same thing, and it always seems to come down to this: it was a little cooler in 2008 than it was in 1998.

OK, let's go back to our loaded dice. Look at the green line I've added:



See that, loaded dice alarmists? The recent trend is downward!

Well, not really. I just drew a pretty line between two arbitrary rolls. It doesn't mean anything at all.

But that green line is what makes Brit (or whoever he got this nonsense from) say that there's been no warming for the last ten years: he picked two arbitrary years, drew a line between them, and said, "See? No warming!" Unfortunately for Brit, it doesn't work that way. The individual data points are random, and you can't draw any conclusions by comparing two random things. Just as the green line here doesn't show that the dice aren't loaded (because they are loaded), the fact that 2008 was a little cooler than 1998 doesn't mean that there's no climate warming going on (because climate warming is going on).

(By the way, 2008 was cooler than 1998 in large part because 1998 was an El Niño year, while 2008 was a La Niña year—El Niño has a warming effect, while La Niña has a cooling effect. But despite La Niña, 2008 was still the 10th warmest year on record. There's more about this claim in the George Will response.)

"They have had trouble predicting today's temperatures"

Well, this one is real easy. "Today's temperatures" is weather. You can't predict weather from climate models. Repeat after me, Brit: for all practical purposes, weather is random. Climate models do not try to predict weather. You can't predict today's weather—or this year's weather, for that matter—from any climate model. That's not what they're for. Climate models try to predict the red line, not the blue line.

And the climate models are, in fact, rather good at doing that. Scientists have gone back to look at some of the older models and have found that longer term temperature trends have been pretty much as expected. RealClimate (a great site run by actual climate scientists) has more information.

Brit, you're supposed to be a journalist. You got some splainin' to do.

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¹ Source: Weather Underground. The mean winter (December 1-February 28) temperatures for Washington, DC. in 2000, 2002, and 2003 were all lower than 2008.

² Even a decade is a bit dicey (sorry). For global surface temperatures, according to climate scientist Gavin Schmidt, 15 years is the point at which weather "noise" averages out. What this means is that, if the climate were not changing at all, the average temperature for any 15-year span would be about the same as that for any other 15-year span because weather averages out over a period that long. That is not be true for a shorter span such as a decade—two different decades could have significantly different average temperatures even with no climate change. So, 15 years is about the shortest time span you can use to say anything really meaningful about global climate trends.

Unless you account for noise.

If you do that, you can point to a shorter time period as being anomalously warm or cool. The weather noise for a decade has been calculated, and it's less that 0.1°C. So, in the absence of climate change, we would expect the average temperature for any decade to be within 0.1°C of the long-term average. If the average for a particular decade is more than 0.1°C different from the long-term average, we can say that it's an anomaly and possible evidence of a change in the climate.

Where There's a Will, There's No Way

George Will writes the most appalling drivel in his latest Washington Post column ("Dark Green Doomsayers", February 15, 2009). Here's a summary:

1. Scientists in the 1970s widely predicted severe global cooling.


2. The University of Illinois says that global sea ice levels now equal those of 1979.


3. The UN says that "there has been no recorded global warming for more than a decade".


4. Paul Ehrlich lost a 1980 bet that the prices of certain commodities would increase by 1990.


5. Ergo, there is no global warming.

The first three items are just plain wrong, and the fourth merits a resounding "Huh?". This seems to make his conclusion rather dubious. How's about we look at each of these.

1: Scientists in the 1970s were predicting global cooling

No, they weren't.

The quotes Will uses to buttress this assertion are generally from news and popular media. He doesn't bother to look at the scientific papers of the era because, if he had, it would have ruined his thesis. Among other things, he would have found this comprehensive study of peer-reviewed climate-related scientific articles from 1965 to 1979 (summarized nicely in USA Today). Of the 71 papers reviewed, fewer than 10% predicted global cooling, while over 60% predicted global warming (about 30% made no prediction).

Where he does quote scientific sources, he's less than candid about context or accuracy. Here's an example: he quotes a 1976 article in Science as predicting "extensive Northern Hemisphere glaciation". And Science did indeed predict that--but not in the way that George wants you to think. He quotes the prediction itself, but he doesn't bother with any of the fruity topping. Here's the bit he left out:

Having presented evidence that major changes in past climate were associated with variations in the geometry of the earth's orbit, we should be able to predict the trend of future climate. Such forecasts must be qualified in two ways. First, they apply only to the natural component of future climatic trends - and not to anthropogenic effects such as those due to the burning of fossil fuels. Second, they describe only the long-term trends, because they are linked to orbital variations with periods of 20,000 years and longer. Climatic oscillations at higher frequencies are not predicted. [Emphasis added]

George, this prediction doesn't take human activity into account. It's a very general forecast for the next 20,000 years in the absence of human activity.

There was no scientific consensus for global cooling in the 1970s; in fact, scientists were already tending, although not with today's near-unanimity, in the opposite direction.

Item 1 is wrong.

2: The University of Illinois says that global sea ice levels now equal those of 1979

No, it doesn't.

In fact, University of Illinois Arctic Climate Research Center immediately repudiated Will's statement:

In an opinion piece by George Will published on February 15, 2009 in the Washington Post, George Will states "According to the University of Illinois' Arctic Climate Research Center, global sea ice levels now equal those of 1979."

We do not know where George Will is getting his information, but our data shows that on February 15, 1979, global sea ice area was 16.79 million sq. km and on February 15, 2009, global sea ice area was 15.45 million sq. km. Therefore, global sea ice levels are 1.34 million sq. km less in February 2009 than in February 1979. This decrease in sea ice area is roughly equal to the area of Texas, California, and Oklahoma combined.

It is disturbing that the Washington Post would publish such information without first checking the facts.

Plain enough? The very source that Will cites says, "We do not know where George Will is getting his information....".

Item 2 is wrong.

3: The UN says that "there has been no recorded global warming for more than a decade"

No, it doesn't.

Will references the UN World Meteorological Organization (WMO) but appears to be quoting a badly written BBC News article.

Here's the deal: In early 2008, the WMO noted that 2008 was likely to be cooler than 1998. Why? Because 2008 was going to be a La Niña year, while 1998 was an extreme El Niño year. La Niña has a cooling effect, while El Niño has a warming effect. Now, anyone who was old enough in 1997-1998 will remember the extraordinary weather of that period. Along with everything else, it was damned hot--hot enough that almost everyone who tracks these things ranks it as the warmest or second warmest year ever.

So, it's not surprising that 2008 would be cooler than 1998, and the WMO said so. But here's how the BBC News article phrases that:

This would mean that temperatures have not risen globally since 1998 when El Nino warmed the world.

Uh, no, it wouldn't mean that at all. It only means that the specific year 2008 would probably be cooler than the specific year 1998 due to La Niña/El Niño effects. This has nothing to do with global warming, and it is unequivocally wrong for Will to quote the WMO as having said anything even remotely like "there has been no recorded global warming for more than a decade." [Update: See Hume-an Error for more detail on why you can't do this.]

In fact, the WMO says this in the next paragraph of the same article that Will is quoting:

"When you look at climate change you should not look at any particular year," [WMO secretary-general Michel Jarraud] said. "You should look at trends over a pretty long period and the trend of temperature globally is still very much indicative of warming.

"La Nina is part of what we call 'variability'. There has always been and there will always be cooler and warmer years, but what is important for climate change is that the trend is up; the climate on average is warming even if there is a temporary cooling because of La Nina."

So when Will says that

[A]ccording to the U.N. World Meteorological Organization, there has been no recorded global warming for more than a decade....

what the WMO actually says is that

[T]he trend of temperature globally is still very much indicative of warming....

Item 3 is wrong.

4: Paul Ehrlich lost a 1980 bet that the prices of certain commodities would increase by 1990.

Wow, this one is true. But I'm still trying to figure out how it's relevant. The fact that an individual scientist made a foolish bet thirty years ago and lost is supposed to somehow prove that the understanding of climate change that is now accepted by 97% of climatologists is wrong? Seriously?

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Now, Will's column is an op-ed piece. He's entitled to his opinion (however wrong-headed it may be). But here's the thing: it doesn't matter what your view of climate change is--these "facts" are simply wrong. Opinion is opinion. Facts is facts. If your facts are wrong, your opinion is of no value.

It gets worse: not only is the column wrong on facts, it is fundamentally dishonest. Will had to know that everything he wrote was wrong (well, except for the part that's irrelevant). If he read enough of the BBC News article to find the WMO "statement" he used, then he had to have also read the WMO's refutation of that point--it's the next paragraph. Furthermore, Will was taken to task on the 1970s global cooling myth (and much more) when he wrote the same thing at least three times before.

George Will is a professional writer with a professional research staff. He is paid top dollar to write these pieces. It is inconceivable to me that he was unaware of the factual inaccuracy of this column. If he was, then he is grossly incompetent and shouldn't be writing for a top newspaper like the Post. If he wasn't, then he is lying.

I do not see a third alternative.

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Update: We now know for a fact that Will was previously apprised of his misuse of a Science News article--but the current column misuses the same quote in the same way. Journalist and science writer John Fleck reveals in the Albuquerque Journal that he sent a copy of the complete article to Will in 2008:

When George Will last wrote about this subject, in May 2008, I sent him a copy of the 1975 Science News article, hoping he might get a fuller picture of what was going on at the time. I got a nice note back from him thanking me for sharing it. It doesn't seem as if he read it, which would have been nicer.