Misconception Monday: Whether Weather or Climate

Okay, people, we’re getting back to the basics. After my (frankly) exhausting exasperation with Nicholas Wade, I need a palette cleanser. So what’s the most basic misconception I have on my to-do list? This one:

Misconception: Weather and climate are the same thing.

Correction: Weather and climate are related, but different, things.

In Massachusetts, we have an elementary school science standard that reads, “Differentiate between weather and climate.” One way to assess mastery of this skill is to present statements and ask whether they represent a statement about weather or a statement about climate. Want to try it?

  1. It is snowing today.
  2. This month has been very snowy.
  3. The average snowfall for the last three Januaries is 11.1 in..
  4. The snowiest January in the last century was in 2005, when it snowed 43.3 in.
  5. The average snowfall for January over the last century is 12.6 in..

So which statements are about climate? I’ll give you a hint—I should have asked which statement (singular) is about climate. The answer? It’s statement 5. How’d you do? Are you smarter than a 5th grader, or not?

There are two “tells” in Statement 5 that give it away: “average” and “last century.” Basically, statements about climate describe long-term patterns in the weather, and thus should reflect a ton of data. The official definition of climate, according to NOAA, is “The average of weather over at least a 30-year period.” Why 30? Who knows? I’m sure a committee at some point decided that 30 seemed right. I’m sure the process was totally scientific. Maybe.)

NOAA’s helpful glossary goes on to mention that climate considered over different periods of time (30 years; 1000 years) may be different—a very good point. Climate isn’t a static thing, there isn’t one set climate. You can tinker with the variables of time, geography, and conditions, and always be talking about climate. For example, look up each of these—the average snowfall of Januaries in Boston over the last century, the average temperature of January 1sts in the United States over the last 30 years, the average global carbon dioxide content of the air over the last millennia—you’ll get very different answers, but they’re all aspects of climate.

So, if climate is the average weather over at least 30 years, what is weather? Says NOAA: “The state of the atmosphere with respect to wind, temperature, cloudiness, moisture, pressure, etc…at a given point in time.” It’s a pretty fuzzy definition, I grant you, but the ever-trusty NOAA offers a pretty great distinction in the form of an adage: climate is what we expect and weather is what we get.

Weather! (Serge Melki via Wikimedia Commons) I admit that for me, however, it’s often easier to think of weather as “not climate.” To illustrate, let’s go back to the statements above. Remember, to be about climate, a claim needs to encompass the average of at least 30 years’ worth of weather. The first statement, “it is snowing today,” is pretty obviously weather. It’s a statement about the conditions right now, in a particular 24-hour period. No average; no 30 years. The next one, “this month has been very snowy,” may begin to feel more climate-like, and “very snowy” is kind of a statement about averages, but it’s definitely not a statement about climate because it just refers to one month’s worth of weather. Even the next statement doesn’t represent enough information to be about climate. Yes, it’s about an average condition, but it’s only the average of three years’ worth of weather. The next statement involves 100 years’ worth of weather—definitely enough to be about climate—but then it isolates just one year, the maximum, so it’s not a statement about climate because it’s only telling us about one year, not the average over the entire 100 years. (Now, the super-nerd inside me can’t help but point out that there is a statement of climate that can be inferred from Statement 4, namely that the average snowfall in January over the last century is less than 43.3 in., but the original statement, as written, isn’t about climate.)

Anyway. You get the difference between weather and climate, right?Climate! (NASA via Wikimedia Commons) But why is it important? If you don’t know the difference, it can be really easy to think that the climate isn’t changing. Scientific claims about global climate take into consideration all kinds of weather data from around the planet averaged over a very, very long time. So when scientists say that global climate is warming, they don’t mean that every day in every place on the planet will be warmer than the day before. They mean that the average temperatures, from around the globe, are warmer now than then have been in a long time.

So how can we help students (and the public) understand this? It's not as easy as drilling the definitions into their heads. There is so much material out there along the lines of “how to talk about climate” and “how to deal with denial” that I can’t possibly be more thorough here—so I won’t try to offer comprehensive advice. But I will tell you what I’d do if I were a teacher and a student expressed skepticism about global warming because it’s so cold out or because this year is colder than last year. I’d get them to explain to me the difference between a single data point and an average, and I’d ask them something like: “If you got 99s on all of your assignments in this class and one F, does the one F mean you’re not an A-student?” (How better to get the attention of a student than hinting that the teacher might give an unfair grade?) Is it guaranteed to work? No. But it’s something. How would you approach it? Leave your comments below.

Have an idea for a future Misconception Monday or other post? See some good or bad examples of science communication lately? Drop me an email or shoot me a tweet <at>keeps3.