The Quiet Sun

Climate skeptics have been crowing lately over the less than broiling summer we've had this year and last. It's true that this summer has been average to slightly under in temperatures, and it's continued over into the Fall (Miami's current record setting heat wave notwithstanding). But to say this summer's temperatures disprove global warming is short-sighted at best, foolish ignorance at worst.

To assume that temperatures are going to conform to nice predictable graphs is a mistake. Temperatures vary. Even average temperatures. There's a parallel here to the stock market. Any investor who has a clue knows that the stock market is up one day and down the next. The key is to know what the long term trends are. There are up days in a bear market just as there are down days in a bull market. Earth's average temperatures and climate work in the same way.

There is no denying that the number one factor for Earth's climate is the sun. Were the sun to be 5% hotter, we'd all be clamoring for real estate in Antarctica. If the reverse happened, they'd be selling snow blowers in Rio.

People tend to think of the sun's output as constant, but it isn't. The sun's output varies along an 11 year cycle, known as the solar cycle. Over this period the sun's output will vary by 0.1% from average. The telltale sign of solar activity is the number of sunspots visible on its surface. At its most vigorous, sunspot sightings are numerous and frequent. When the sun is quiet, sunspots are few and far between. Sometimes days will pass between sightings.

What does that mean for us? Well, during the years of high activity, the Earth receives more energy and is warmer than in years of little activity. And we can chart it with a roughly sinusoidal curve. If you guessed that we're currently in the quiet part of the cycle, you're a smart cookie.



That doesn't mean carbon dioxide levels don't matter. They do. We know from the fossil record that CO₂ levels have varied throughout history. When levels are high, average temperatures rise and when they fall so do temperatures. Combine this with the solar cycle and you can get some serious highs and lows. What high levels of carbon dioxide do is shift the temperature curve up.

Let's say that normal temperature variation is plus or minus 2 degrees over the span of a solar cycle. What high levels of carbon dioxide do is change that variation. Instead of being +2, you're now looking at +3. Instead of -2, you're looking at -1. And if those levels continue to rise, they shift upward again. +4 and 0.

Now those numbers aren't exact by any stretch of the imagination. I'm just trying to illustrate a principle here. There are plenty of other factors involved. Our atmosphere is awfully turbulent and complex. Volcanic eruptions, dust storms and pollution complicate things. What climate scientists are trying to accurately predict are the long term trends.

Being a Weather Channel junkie, I've noticed that a lot of record high temperatures took place in the late 50's. It just so happens that at this time we were going through a solar maximum. And we haven't had peaks quite that high since, though the late 90's came close.

As I mentioned above, we're currently in the quiet part of the solar cycle. The problem is, the sun seems to be stuck. The solar minimum has held sway for a couple of years now. The sun should've snapped out of it by now. Unfortunately, astronomers don't know why it hasn't.

While we don't have anything to worry about right now, if it continues for another year or two I'd be concerned. Why? Well, take a look at that chart again. Notice that section where the solar cycle all but flatlines? They call that the Maunder Minimum. It took place from 1645 to 1715, which coincides with the worst years of the Little Ice Age.

There's plenty of debate still going on as to the causes of the Little Ice Age. It could very well be the cumulative effect of several factors of which the Maunder Minimum is but one. But if we were to experience another one, I wonder how much CO₂ emissions would offset the diminished solar output.

If you're intrigued by our sun's quiet time, check out Solar Cycle 24 or NASA's Solar and Heliospheric Observatory (SOHO). In the meantime, better bundle up. I think it's going to be cold this winter.

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