“Warm is warm,” says Simple Sam. “How can you say it’s warm because of the greenhouse effect and not the sun? The sun shines everyday….”
And it’s been getting warmer since the beginning of time because of it, Sam? Maybe not. Come into my classroom, and we’ll talk. …
“But it’s Saturday.”
Not to worry. Sit down for a while. –You see, Sam, it’s all about fingerprints. You’ve got to get your Sherlock glass out of your detective bag, and track down the fingerprints.
“Warmth has fingerprints?”
Yes, it does, Sam. It’s got to come from somewhere, and it leaves a trail.
“Are you going to pick up its trail with your tricorder.”
My goodness, Sam. I didn’t know you were a Trekkie. Never mind. You don’t need to live in a fictional universe to detect these fingerprints. Just round up the suspects. You named one. The sun. I named the other. The greenhouse effect. Each has a distinctive signature.
The sun warms directly, Sam. Its influence will be direct. It will warm the upper atmosphere as well as the lower atmosphere, because sunlight needs to pass through both. The day would show the added warmth more than the night, since the day is when the sun is actually shining.
“Yes, the sun shines during the day. Noted. I’d like to remind you again that we’re having a lesson on Saturday here.”
Is that right, Sam? Nice day, too. –Now the greenhouse effect warms by trapping heat, primarily heat given off by the earth at night as low intensity infrared light. Without the presence of greenhouse gases in the atmosphere, this heat would escape into space. Now since greenhouse gases trap the heat from below, we would expect the lower atmosphere to gains more heat while the upper atmosphere actually becomes cooler. The greenhouse effect being strongest at night, we would expect the night to be proportionately warmer than the day. And …
“Let me guess, the upper atmosphere ….”
… is actually cooling so much it’s shrinking. Remember my piece Space Litter? No?
“And the night ….”
….you guessed it, is warming faster than the day.
“You’re going to have to show some evidence for this.”
Of course I am. But today, I just wanted to go through the basic idea of climate fingerprints, so you know what to look for, you know, when you’re glancing over your climate datasets.
By the way, Sam, the sun would not be a strong suspect anyway. We’ve just gone through the warmest decade in probably 2000 years, and the sun has actually been going through a cool period.
“I’ll need evidence for the cool sun, too.”
Patience, Sam. You do know it’s Saturday?