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Another Earth Day came and went this year and one thing stayed the same: Most Americans still aren’t overly worried about climate change.

Just 37 percent say they worry a great deal about it—a fraction that's barely budged from the 35 percent who said so nearly two decades ago, according to Gallup Inc.'s annual environmental poll.

That got me worried. Then my worry turned to guilt. And that guilt, as guilt often does, turned to a real hankering for some pizza.

Later, a takeout pizza, much to my relief, didn't turn into anything other than a tasty meal.

As for the cardboard box it came in, that's another story. It turned into a real eye-opener.

See, the pizza box was one of the best examples I'd seen in a long time of the neglected second of the three R's—you know, Reduce, Reuse, Recycle.

On the outside, the box was plain cardboard brown. Inside, it was a riot of color. It seemed fishy, though fruity was more like it. Here and there, I could make out an off-register picture of an apple.

It took unfolding the box—and a moment or two—before I could figure it out. My pizza box was made of juice boxes—or rather, four or so flattened juice boxes stamped on a single sheet of cardboard.

Of course, the juice boxes—which aren't an environmentally-smart choice in the first place—never had held juice. They hadn't even been punched out and shaped into individual boxes. The sheet of cardboard was a printer's goof—a misprint. The blurry pictures of apples made that clear.

Rather than toss out the poorly printed but otherwise pristine cardboard, someone enterprising had decided to reuse it by turning it inside out and folding it into a pizza box—one less pizza box the world needed to create from scratch. To my mind's eye, each box represented a tiny gesture—but a useful one. And by useful, I really mean reuseful. It's not a word, but it should be.

Once I'd gotten to the bottom of my pizza box mystery (and the end of my pie), I thought again about the Gallup results. It struck me that maybe it is a good thing so few of us worry a great deal about climate change. Worry only begets worry, after all. There are better ways to use our time. The three R's are one place to start.

Every cloud does have its silver lining. It's just sometimes you have to open a pizza box to find it.

Andrew Bridges is a science journalist and author who has written several books for Sally Ride Science, including Earth's Precious Resources: Clean Air.

I'd like to recant what I said a few posts ago about my backyard not being the place to cut global warming. Looking back, it's now clear I missed the peas for the forest.

I still maintain that reforesting my backyard would barely dent my overall emissions of carbon dioxide and other greenhouse gases. I just couldn't plant enough trees. But sinking some peas—and tomatoes and carrots and zucchini—into the soil just might do some real good.

That would mean recycling a concept that's nearly a century old: planting a victory garden.

Victory gardens first took root during World War I and blossomed anew during World War II. The government promoted the homegrown vegetable patches to free up additional resources for the war effort. Having ordinary citizens grow more of the food they ate also engaged them in that effort.

By 1943, there were 20 million victory gardens under cultivation, producing an estimated 40 percent of the nation's fresh vegetables, according to the Department of Agriculture.

I have seen a flurry of recent media coverage about a revived interest in victory gardens. Nothing I have read suggests it has anything to do with the war. (Unless you’re talking about the battle of the bulge: increasingly overweight Americans eat on average just 1.7 cups of veggies a day, or less than the recommended 2.5 cups.) Instead, this time around, it's all about the environment.

That's because every bushel of veggies harvested from a backyard garden is another bushel that didn’t have to hop on a truck, train or plane to make it to your kitchen door. That means cutting out a farm-to-fork trip that, for fresh produce, averages about 2,400 kilometers (1,500 miles), according to one widely quoted estimate.

Talk of "food kilometers" (or "miles," if that's your preference) is gaining currency in discussions about food and the environment. That's because the distance food travels is a proxy for its environmental impact—or is at least suggestive of the volume of greenhouse gases emitted during transit.

For instance, by the time a bunch of asparagus grown in Peru lands on a dining room table in, say, Springfield, Ill., it will have logged more food kilometers than would a bunch grown in California.

Of course, asparagus grown in a victory garden in the backyard of a home in the Illinois capital would be the real green choice. That’s because those hyper-local spears would rack up no food kilometers (and generate no related greenhouse gas emissions) on their short, post-harvest trip across the yard.

Unfortunately, relying on a Springfield (or Salem or Salt Lake City) victory garden to keep your family in vegetables is only going to work in season, unless you gear up a home-canning operation to tide over your loved ones during the winter months. But even purely seasonal gardens, multiplied by a few tens of millions, could play a part in cutting global warming.

That means victory gardens are still a good idea, even if they no longer have anything to do with war. If we'd just give peas a chance.

Andrew Bridges is a science journalist and author who has written several books for Sally Ride Science, including Earth's Precious Resources: Clean Air.

One of the pleasures of parenthood—and it must the same for teaching—is the wonderful excuse it provides to dip back into one’s favorite books from childhood. For me, Shel Silverstein’s Where the Sidewalk Ends is one of those books.

I happily rediscovered my copy recently, 30 years after receiving it, while browsing the shelves for something to read to our young son. I quickly alighted on an old favorite, “Lazy Jane.”

 If you’ve never read the poem or don’t remember it, Lazy Jane wants a drink of water, so she “waits and waits and waits for it to rain.” In Silverstein’s accompanying drawing, there Jane lies, flat on her back, her mouth open to the sky.

Of course, we can’t be like Jane. Relying on gravity to drop rain in our parched mouths just isn’t practical or feasible.

Instead, it’s much easier to tilt back our heads to take a swig of water. More and more, that water comes from a bottle.

Worldwide, we guzzle more than 175 billion liters (46 billion gallons) of bottled water a year, according to recently published tallies. Since one-liter and half-liter bottles are fairly standard, I have to think all that water comes packaged in a comparable number of bottles.

Recently, I saw first-hand where some of those bottles end up—and no, it wasn’t a clean, well-lighted recycling center. It was a small but fast-flowing river in Eastern Europe. Here’s a picture I took.

Earlier in the day, I’d been to the river’s pristine source, below a medieval monastery just 16 kilometers (10 miles) upstream. From there, the river snaked down a narrow valley, flowing past at least two impromptu garbage dumps and an abandoned trout farm.

Over the years, I later thought while snapping my picture of the gyre of plastic, the farm probably emptied of fish as the river filled with trash.

After I put away my camera, I started thinking of ways to clean up all the bottles bobbing in the swirling eddy. More than a few of my ideas centered on Rube Goldberg-type arrangements that involved stringing up nets to snare the bobbing bottles as they floated downstream.

Then Lazy Jane, fresh from my recent rereading of the poem, popped into my mind.

Good old Jane helped me see a practical solution to the bottle problem. And it had everything to do with her lazy reliance on the force that drags rain from the clouds.

That force is called gravity, and it’s what municipal water systems harness to make the water flow.  All we have to do is turn the tap.

Andrew Bridges is a science journalist and author who has written several books for Sally Ride Science, including Earth’s Precious Resources: Clean Air.

A tidbit of 40,000-year-old archaeology news, coupled with a little virtual digging of my own, got me thinking recently that the electric car could soon be back from the dead—this time, for good.

European scientists who had examined the isotopic makeup of an ancient tooth found in Greece announced in February they’d found the first direct evidence that Neanderthals ranged 20 or more kilometers (12-plus miles) over the course of their lifetimes. Previously, some had suggested the dead-end species were nothing but homebodies.

I’m not sure why we should be surprised to learn the Neanderthals got around. After all, our cousins-of-the-prominent-brow presumably could have easily covered such a distance in a day’s walking. Why shouldn’t we assume the Neanderthals traveled at least that far—and more?

Then again, a similar assumption—this one about how far we modern-day humans travel—helped bury the electric car, including the EV1 from General Motors. The car’s ability to go just 80 to 160 kilometers (50 to 100 miles) before needing a recharge put a stake in its battery-powered heart. Drivers just weren’t comfortable with that limited range, GM said in pulling the car from the market.

You can’t argue with that—or can you? If we can profess surprise at learning how much ground the Neanderthals covered then maybe we should brace ourselves to learn how little we do.

I got digging and tracked down the most recent National Household Travel Survey, which provides a lot more detailed data than can any old molar. The latest survey, released in 2004, shows U.S. drivers travel on average just 53 kilometers (33 miles) a day. That’s certainly more than your average Neanderthal covered in day’s shuffle. But it’s clearly less, by a comfortable margin, than what an electric car like the EV1 could cover before it ran out of juice.

Now, if we could get over being surprised about how much—or little—we really travel in our everyday lives, it won’t bring back the Neanderthals. But I think it could restore the electric car to life, albeit with a major tweak that would provide the range—and peace of mind—that drivers clearly crave. With gas prices at record highs, and global warming a major concern, more electric cars could be a good thing.

Even though a car than runs on gasoline can travel, say, 600 kilometers (375 miles) on a full tank, the federal data show we rarely go so far in any one fell swoop. Instead, on an average day of driving, we make three or so car trips, each just 16 kilometers (10 miles) or so in length.

Yet we still demand the option of traveling even farther should we be so inspired (or compelled). That’s an important point. Even if the limited range of an electric car more than adequately covers our daily driving needs, it remains severely inadequate when it comes to the—how should I say it?—hypothetical driving we just might do.

That could soon change.

Carmakers are promising to debut a new generation of electric cars, called plug-in hybrids, as early as 2010. The cars will be hybrids, like Toyota’s Prius, in pairing a battery-powered electric motor with a traditional gas- (or diesel-) burning internal combustion engine. What’s different is the batteries are rechargeable—hence the “plug-in” part.

The cars should be able to travel in all-electric mode for an estimated 65 or so kilometers (roughly 40 miles). As the batteries dwindle, it’s back home for a recharge. Or, should you want or need to travel even farther, you can let the internal combustion engine take over.

In that mode, a full tank of gas can keep things rolling for hundreds of kilometers (miles) more. That should provide the range and comfort that drivers demand—and that older, purely electric cars just couldn’t offer. But I have a suspicion those gas tanks will go largely untapped.

I bet when folks start driving their plug-in hybrids, they’ll find battery power alone suffices most days (as long as they keep those batteries topped off). That’ll cut gas consumption and tailpipe emissions.

And maybe we’ll finally get over being surprised by what science tells us: Even though we’ve come a long way since the days of the Neanderthals, most days we just don’t go that far.

Gas prices have lots of us thinking about every drop of fuel that goes into our cars. But what about every puff of carbon dioxide that comes out?

That’s not something we dwell on much. That’s because a vehicle’s CO₂ emissions aren’t easy to quantify while sitting behind the wheel—much less visualize, since the gas comes out the tailpipe and is invisible anyway.

Sitting in front of a computer with Internet access, it’s a different matter. That’s because the government’s done almost all the work for us.

Overall, each and every American is responsible for emitting 20.15 metric tons of carbon dioxide a year, according to 2005 Department of Energy statistics. Transportation—think planes, trains, automobiles and the like—accounted for about one-third of that per capita total. The average passenger vehicle alone is responsible for 5.2 metric tons of carbon dioxide emissions a year, according to the Environmental Protection Agency (EPA).

It’s easy to calculate a vehicle’s carbon dioxide emissions, though I wouldn’t recommend trying it while driving. First off, the EPA tells us that a gallon of gasoline produces 8.8 kilograms, or 19.4 pounds, of CO₂ when combusted. And that same gallon carries the average American passenger vehicle an EPA-estimated 20.3 miles, though your own set of wheels may have better or worse fuel economy.

Since the EPA also estimates that the average vehicle travels 12,000 miles a year, it’s a snap to calculate how much gasoline it burns to do so:  about 591 gallons (that’s 12,000 miles traveled in a year ÷ 20.3 miles per gallon = 591 gallons of gasoline burned).

From there, it’s just as easy to calculate CO₂ emissions:  5,201 kilograms or 5.2 metric tons per vehicle (that is, 591 gallons of gasoline burned in a year × 8.8 kilograms of CO₂ produced per gallon = 5,201 kilograms CO₂ emitted).

I freely mixed English and metric units in the above calculations but that’s because gasoline’s typically sold by the gallon and CO₂ emissions are counted up by the metric ton. If we stick to just English units, a good rule of thumb is that driving produces slightly less than a pound of carbon dioxide per mile traveled. That’s assuming 20.3 miles per gallon. If your vehicle gets 10 MPG, then it’s roughly two pounds a mile. If it gets 40 MPG, then it’s about a half-pound.

Getting that information to drivers in the United States could get them thinking about the real-world effect their vehicles have on CO₂ emissions, the atmosphere and, ultimately, climate change.  It’s information that would fit neatly on the window labels that now list a new car’s fuel economy.

That information is already is on labels in  Europe, where they must display both a new car’s fuel economy and its carbon dioxide emissions. The latter, expressed in grams of CO₂ per kilometer traveled, also is used as a regulatory benchmark. The European Commission recently proposed requiring automakers to drop their average CO₂ emissions to 120 grams/kilometer by 2012. That’s 0.42 pounds a mile.

Maybe the U.S. could require a similar amount of disclosure, but do Europe one better, too. It could further require the instrument panels of our cars, trucks and sport utility vehicles to include a gauge that displays a running average of the vehicle’s carbon dioxide emissions, as expressed in pounds per mile traveled. Such an instrument, call it the “carbonometer,” would give drivers a clear view of the CO₂ coming out the tailpipe—even if it is invisible.

March marks 50 years of nearly uninterrupted measurements of the rising carbon dioxide levels in the atmosphere from Hawaii's Mauna Loa.

When the Mauna Loa measurements began in March 1958, the atmosphere already contained about 315 parts per million CO₂. It has since risen to 383 parts per million. That's a nearly 22 percent increase, driven by the burning of fossil fuels.

When displayed in graph form, the Mauna Loa record steadily curves upward from 1958 to the present. Within that curve, though, there are plenty of squiggles.

Those regular squiggles represent the dip in CO₂ levels that coincides with the greening of the northern hemisphere each spring and summer.

There is more land, and as a consequence, more vegetation, in the northern hemisphere. So when things are green north of the equator, there is a slight drawdown in the amount of CO₂ in the atmosphere. After things turn brown again in the northern fall and winter, CO₂ levels again pick up their upward climb.

On one hand, the squiggles remind us that vegetation, through photosynthesis, each year scrubs the atmosphere of at least some of its surfeit of CO₂.

On the other hand, the overall curve shows we still have the upper hand. Simply put, humans are pumping CO₂ into the atmosphere much, much faster than nature's greenery (and the oceans) can take it out.

Take the United States, where forests absorb the equivalent of just 14 percent of the nation's CO₂ emissions. That means those trees offset just one-seventh of the country's overall carbon dioxide emissions. So my question is this: Could more trees make a difference?

Not in my backyard.

Don't get me wrong, I'm all for trees — and for more trees. But if I look at how much CO₂ I put into the atmosphere by driving, doing laundry, cruising the internet, cooking and reading by the light of my bedside lamp, there’s no way I could offset those emissions by reforesting my modest little backyard.

Hence my NIMBYism.

The numbers tell the full story. Annual U.S. per capita emissions of CO₂ equal 20.15 metric tons, according to 2005 Department of Energy statistics. That comes out to roughly 44,425 pounds a person.

Now, if that’s the problem, let's look at the solution trees can offer. What they can do to help sop up my CO₂ emissions? The Department of Energy has a simple spreadsheet available online that allows users to figure that out.

I picked two common trees to see what they could do to offset my emissions. One species was the slow-growing white oak and the other the rapid-growing loblolly pine.

Now suppose I planted one of each in my backyard, which is about all that would fit, and left them to grow for 15 years.

By 2023, the oak would have absorbed just 138 pounds, or roughly 63 kilograms, of CO₂. That's just a tad more than I exhale in two months of breathing.

The faster-growing loblolly would do a lot better, absorbing 314 pounds, or 142 kilograms of CO₂, in 15 years. Still, that's about as much carbon dioxide I release to the atmosphere by burning through a tank of gasoline in my station wagon — something that can take just a couple of weeks.

So, should I conclude that any stab I might make at slowing, stopping or even reversing the growth in atmospheric CO₂ levels is useless? No, not if I use less.

Rather than a plant a tree every time I fill 'er up, maybe I could not burn that gasoline in the first place. Maybe I could walk, bike or ride the bus a little more than I do already.

Where can I cut global warming? Not in my backyard — just a few feet over, in my driveway.

Andrew Bridges is a science journalist and author who has written several books for Sally Ride Science, including Earth’s Precious Resources: Clean Air.

From carbon credits, to compostable latte cups, to dresses made of recycled plastic bags (yes, really), society’s environmental consciousness has reached fashionable proportions.

Naturally we want to help. But we’re grown-ups, already entrenched in our lifestyles, just happy to have small ways of assuaging our impact-related guilt. Sure, I’ll recycle. How hard is that?

Kids are different. Their world is smaller, and so they feel their impact on it can be greater. Grade-school projects to plant a tiny garden made me feel like I was changing my whole town.

When recycling came onto my radar, I embraced it with the same zeal. After all, who could say that that one extra paper towel roll wasn’t going to put my hometown landfill over the top?

It is easy to view this sort of youthful enthusiasm for doing the right thing as a cute diversion, like the school play. But the truth is that it matters, for two reasons.

The first reason is developing a lifelong good-for-everyone habit. Brush your teeth. Read a lot. Recycle. It isn’t how many paper towel rolls I saved as a 6th grader. It’s the fact that I still recycle and re-use, as a matter of course. I’ve even talked my five-year old into letting me tuck away some of his (many) extra toys, and pretend they’re new later instead of buying him quite so many new ones.

Second, kids really can make a difference. There are a lot of them, and recycling works. For example, Seattle now recycles or composts nearly half of its garbage.

Of course the fewer new things we buy in the first place, the less we consume, too. When I was still in high school I discovered the thrill of finding used clothes and books in thrift stores. What kid doesn’t love a treasure hunt? And buying used is of the most environmentally friendly ways to shop. Bonus!

So, let your kids’ enthusiasm for living green go wild. For example, let them help design their next birthday party or family gathering to be eco-friendly. They are sure to think of creative fun: re-gift well loved books and toys, do a thrift store fashion show, make and wrap presents from used materials, and invent experiences to give instead of giving stuff. For kids these ideas are fresh, fun, and within their budget.

However you do it, don’t let your child’s marvelous I-can-change-the-world-to green optimism fade. You are setting the tone for an earth-friendly adulthood. Participate. Encourage them. You’ll probably get as excited as your kids.

In fact, if my kid can ever make me a dress out of used plastic bags, I promise I’ll wear it.

Beth Geiger is an award-winning author of science books for young adults. She contributed to several books in Sally Ride Science’s Earth's Precious Resources Classroom Set, including authoring Clean Water.

Day in and day out, no country uses more energy than America. Individual Americans, however, are far from being the world's biggest energy hogs.

How can that be? Simple: Size matters. There are a lot of Americans using a lot of energy. Some countries use more on a per capita basis, but have smaller populations.

Each year, the average American uses in energy the equivalent of nearly 59 barrels of crude oil, according to the Department of Energy. Other countries are more profligate. Cold climates often explain the difference. Canadians, for example, use the equivalent of 72 barrels of oil per person a year.

But other nations are far more frugal. Each German gets by with the equivalent of just 30 barrels a year. That's about half the energy an average American uses. So how do we explain that?

For sure there are lots of virtuous Germans, for whom living green is a fact of life. That might mean making the choice to bike instead of drive to the post office, for example.

But I'd wager Germans overall spend little more time each day choosing how much energy to use than do their American counterparts. I'd even venture to say that in a lot of ways that really matter, neither Germans nor Americans make that sort of choice at all on a daily basis. Yet Germans still manage to use just half as much energy.

Does that mean they somehow glide thoughtlessly, effortlessly — magically? — through each day using less energy? Not quite.

It's more likely Germans wake up in homes, neighborhoods and cities set up from the get-go to use less energy. It's the clotheslines hanging off their balconies and the tankless water heaters in their bathrooms that provide hot water only as it's needed. It’s also the fuel-efficient cars in their driveways, and a thousand other things. Germans don’t choose each day to use less; they can't help but use less.

Meanwhile, Americans rely on clothes dryers, conventional water heaters with tanks kept brimming with hot water around the clock, gas-guzzling SUVs and other conveniences of life in the U.S. of A. that often aren't very energy efficient. And so, Americans don't choose each day to use more; they can’t help but use more.

Sure, daily decisions can and do have an effect on energy use – like choosing to bike instead of drive. But I doubt they have as large an effect as do the types of decisions made, say, once a decade or more.

Take the refrigerator, which runs around the clock and uses more electricity than any other appliance in the American home. The country's 126 million fridges used 156 billion kilowatt-hours of electricity in 2001. That's the energy equivalent of 92 million barrels of oil.

We don’t wake up each morning and decide how much energy our fridges will use that day. Instead, that's a decision we make on average just once every 13 years. That’s how long fridges typically last.

Ever more strict U.S. government standards ensure when we do pick out a new fridge, it's bound to be far more efficient than models from even a few years before. In 2001, those standards dictated that the average new fridge use 476 kilowatt-hours of electricity a year, or half as much as just a decade earlier.

However, as of 2001, the fridge in the average American kitchen was using 1,239 kilowatt-hours a year. Why so much more? Because America was then, and still is today, saddled with a lot of old and inefficient fridges.

Americans buy about 10 million new refrigerators a year. At that clip, it takes more than a dozen years to swap out every fridge in America (assuming each old fridge is replaced once during that time).

So by the time 2013 or so rolls around, the average kitchen fridge should be a lot closer to the 476 kilowatt-hours-a-year standard than it was in 2001. The average fridge can’t help but use less energy at that point. But it still won’t turn its American owner German.

The government can tell us how efficient our refrigerators should be. But it can't tell us how big. Peek inside an average German kitchen and chances are you won't find a hulking, American-style fridge. Instead, much smaller models that use far less electricity are common. A quick check of a German online retailer recently found plenty of under-the-counter models that use between just 150 and 225 kilowatt-hours a year.

That's a reminder there's still a lot of room for personal choice when picking out a new fridge – or car or home, for that matter. And when it comes to energy efficiency, choosing small can make a big difference.

Andrew is a science journalist and author who has written several books for Sally Ride Science, including Earth’s Precious Resources: Clean Air.

Okay, I know what you may be thinking...a line from a cheesy Elvis song? What does that have to do with climate change? Well, let me explain...

I am a 7th grade life science teacher. Yesterday, I arrived on campus and opened my email where I found two messages from the National Science Teachers' Association, both of which referred to climate change.

Next, I traveled to my teacher mailbox. Lo and behold, what did I see waiting for me there, a magazine all about the melting polar ice caps, and of course, climate change.

When I walked back to my classroom, I noticed that the film, An Inconvenient Truth, waited on my desk. I lent this movie to one of my colleagues so that she could send her students off on their winter break, thinking and talking about the all important topic du jour, climate change.

It seems to me that the phrase, 'climate change,' often dances across our lips and through our thoughts these days. As a matter of fact, when you Google the phrase, it provokes over 22 million hits! If that isn’t proof that 'climate change' is a topic worth talking about, I don’t know what is.

Don’t get me wrong, I am glad everyone is talking about it. Climate change to me seems unbelievable, scary, and necessary to understand. In fact, I believe that it is vital to our own survival to know the causes and effects of what is happening on our planet today.

But, I also wonder if we couldn't learn a thing or two from the "King."

As a 7th grade science teacher, I realized that I should talk about climate change with my students. They are the future, and will ultimately be responsible for cleaning up the mess left by past generations.

But, as a citizen, and Elvis fan, I realized that I should do more than talk. And as a teacher, I can inspire and facilitate change within my students.

While Elvis calls this "action," and Jim Cummins, notable educational researcher, calls it transformative pedagogy, I call it responsibility. So, I decided that today, I will be responsible. I will begin to put into action what everyone has been talking about, and I will do it as an example for my students.

Eventually, transformative pedagogy will lead to major projects and community-wide action by my 7th graders, but today, I will start small. Al Gore suggests 'Ten things you can do to help solve the climate crisis.' I am adapting that into 'Ten things you can do in your classroom TODAY to help solve the climate crisis.'

Today I will put the "King's" advice into action. I hope you will too.

1. Switch to a more energy efficient bulb. Change the bulb in your classroom in front of your students. Discuss why you are doing this. Encourage them to share what they learned with their families.
2. Don't waste paper. Ask students to turn in an essay electronically. Do not require a paper copy. Provide students with feedback via email.
3. Switch to a thermos. Students watch you. They see you with your plastic water bottle. Today, bring a reusable thermos. Be explicit about what you are doing and why.
4. Recycle.
5. Start an 'ecology club' at your school.
6. Plant a tree. Make it a class project. Watch it grow. Measure it. Collect data.
7. Ride your bike to work. Students will be impressed and inspired!
8. Re-use old project materials. Encourage students to do the same.
9. Support an environmental group. Organize a fundraising drive on campus.
10. Turn off computers and lights when they are not in use.
11. Ask students to be the "climate police" of the class. Students can point out when energy saving efforts are not being made. They love to tell you when you are doing something wrong!

When I was a child in the early 1970s, every classroom light switch in my elementary school bore a bright orange-and-black sticker reminding us to turn out the lights when they weren’t in use. The stickers worked then and work today: I still can’t walk out of a room — an empty room — without killing the lights. Old habits die hard.

In the years following the 1973 energy crisis, the message implicit in each sticker was clear without being preachy: save energy. Clear too was the impact the stickers could have, later research showed. Two Canadian studies, carried out in the 1980s and 1990s, found that introducing the stickers into an office environment could prod workers into cutting their use of electric lights by about 15%.

The stickers work because they remind us the lights are on in the first place. Most of us are perfectly capable of turning on a light, and leaving it on, without giving that flick of the switch a moment’s thought. Sometimes a simple message emblazoned on a bright sticker is all it takes to get us to change our behavior for the better.

The stickers also work because they restore in our minds the connection between the lights overhead and the fossil fuels burned to make the electricity they draw. Typically, power plants are miles and miles from the home, office or school. That ensures the smokestacks stay well out of both sight and mind.  A sticker can’t close that physical distance, but it can narrow any mental gap and get us thinking about the real world consequences of our actions.

I don’t know how common light-switch stickers are in classrooms these days. But I rarely see them in places where promoting a little thrift couldn’t hurt. Maybe it’s time to bring them back en force, this time with a more explicit message—like “SAVE ENERGY”.

Energy conservation is still a laudable goal, for sure, and the stickers could still push that message. Today, though, we’re just as worried about greenhouse gas emissions. Whenever we burn oil, gas or coal to make electricity, more greenhouse gases, carbon dioxide chief among them, enter the atmosphere. But just how much is neither obvious nor well understood.

Take the electric light example. If you live in the United States, there’s a good chance the electricity you use came from a coal-fired power plant. Coal generates half the nation’s electricity, after all.

Say you keep a 100-watt bulb burning in your classroom for eight hours a day, five days a week. By the time Friday afternoon rolls around, that light bulb will have used four kilowatt-hours (kWh) of electricity.

On one hand, that electricity is cheap: about 36 cents, at an average U.S. retail price of 8.9 cents per kilowatt-hour. Its cost to the atmosphere is something else.

That is because it takes a little more than a pound of coal to generate a kilowatt-hour’s worth of electricity. And in burning coal, a power plant also generates about 2.1 pounds of carbon dioxide for each kilowatt-hour it produces. (How can the mass of the CO2 be greater than the mass of the coal? Don’t forget that a lot of oxygen gets consumed in the process.)

So that little light bulb, at the end of a 40-hour work week, will have gobbled up four pounds of coal and released another 8.4 pounds of carbon dioxide into the atmosphere. Over the course of a 180-day school year, that’s 302 pounds of CO2.

Now, what if that light bulb took recess and lunch along with your students, and stayed off an extra 72 minutes or 15 percent of the school day? That would reduce its annual CO2 emissions by 45 pounds— about what a kindergartner weighs.

That’s a whole lesson’s worth of information and way too much to cram on a small sticker. Maybe just adding “CUT EMISSIONS” would do the trick. It’s less of shock but it’s a message that still sticks.

For more information about Andrew Bridges, click here.