When I was an astronaut, one of my favorite things to do was to float over to one of the small windows in the space shuttle and look down on Earth. From space, Earth's atmosphere looks like a fuzzy blue line ringing our planet--like someone took a blue crayon and drew a blue line all around it. But that thin blue band--our air--is Earth's space suit. It's all that protects us from the extreme conditions of space. It keeps us warm. It shields us from the Sun's harmful rays. It provides us with the oxygen we breathe. Without our atmosphere, life wouldn't be possible!
Yet over the past two centuries, people have been changing the atmosphere. We've been adding gases to the air that are making our planet warmer. This is changing Earth's climate. And, in one way or another, this is affecting our whole planet.
There are things you should know about Earth's changing climate--you can read all about these in Mission: Planet Earth. And there are things you can do--you can learn all about these in this book. So keep reading!
Until relatively recently, people didn't have much of an effect on Earth. This is because there weren't many of us on the planet. In 1750, there were fewer than one billion people on our planet. Today, there are nearly seven billion of us. And every single one of us needs water, food, clothing, and shelter.
Humans are a very creative, caring, and resourceful species. As our population has grown sky high, we've developed agricultural methods to feed billions of people. We've built villages, towns, and cities to live in. We've crisscrossed the countryside with roads to transport food and other goods. We've made ships, cars, trains, and airplanes to travel in. We've invented technologies to light our cities, heat and cool our homes, and bring radio, telephone, television, and the Internet to people around the globe. But as we've advanced our civilization, we've used more and more and more energy.
Where does all of this energy come from? It comes from fossil fuels--oil, coal, and natural gas. For the past 200 years, these are the sources of energy we've come to depend on. The problem--and it's a whopper!--is that when fossil fuels are burned, they send carbon dioxide (CO2) and other greenhouse gases into the air. Year after year for the past two centuries, carbon dioxide has been piling up in our atmosphere. And more is added every day. Carbon dioxide billows out of smokestacks and wafts out of tailpipes around the world--from Los Angeles and London to Moscow and Mumbai and from Beijing and Bangkok to Caracas and Khartoum.
The buildup of carbon dioxide is changing our air. And this is making our world warmer.
Take a deep breath. Feel the air rushing into your nose and lungs? It is so wispy and light that it seems weightless. But, of course, it isn't. We aren't aware that air has weight because we're surrounded by it--fish probably aren't aware that water has weight, either. The gases in the air around us can be weighed. Here's a simple experiment, so you can see for yourself.
First, get three balloons and a meter stick or yard stick. Tape an empty balloon to each end of the meter stick. Try to balance the meter stick on one finger. What happens to it? Now blow up the third balloon. Leave one of the original, deflated balloons on one end of the meter stick, and attach the blown-up balloon to the other end. Try to balance the meter stick on your finger again. What happens this time? Why?
EVEN MORE CO2?
For the last few centuries, people have been cutting down trees all over the world. We use wood for fuel and lumber. We clear the land to build towns, grow food, and give animals a place to graze. About 90 percent of the forests that once grew in the United
States have been cut down. About 20 percent of the Amazon rainforest has been cleared.
Huge patches of tropical rainforest in Asia and South America are chopped down and burned every day. When trees are burned for fuel or to clear the land, carbon dioxide is released into the air. And with fewer trees around, less carbon dioxide is soaked up from the air for photosynthesis. So, deforestation is double trouble--it just adds to the problem of global climate warming.
You've probably heard about fossil fuels. They come from the remains or "fossils" of prehistoric plants and animals that lived in swamps and oceans. Since all living things are based on carbon, their remains are mostly carbon, too. When these trees, algae, and small animals died, they decayed under layer after layer of sediments. They were buried deep inside Earth. Over millions and millions of years, intense pressure and heat cooked these fossils until only carbon and hydrogen were left--fossil fuels. And when fossil fuels are burned, the carbon is released into the air as carbon dioxide.
About 200 years ago, people started burning fossil fuels for energy. At first, it didn't seem like such a bad idea. A little bit releases a bunch of stored up energy when it's burned. For instance, burning a pound of coal produces a lot more energy than burning a pound of wood. So the idea really caught on.
But like burning wood in a campfire, burning fossil fuels sends carbon dioxide and other greenhouse gases into the air. This made scientists worry. They knew the gases wouldn't just disappear ... instead, they'd pile up in the air.
HOW DO WE USE ENERGY TODAY?
Everything we do takes energy--including driving cars, lighting homes, and making things in factories. Here's how it breaks down across the globe.
WHERE DOES OUR ENERGY COME FROM?
About 85 percent of the energy the world consumes comes from fossil fuels ...
Here are some of the ways we use fossil fuels today.
OIL is turned into
• gasoline for cars, diesel fuel for trucks, and jet fuel for airplanes;
• fertilizers for farms and backyards;
• synthetic fabrics for clothes and carpets; and
• plastic for bottles, toothbrushes, guitar strings--you name it!
COAL is burned in power plants to make electricity.
NATURAL GAS is piped into homes to heat and cool them.
And, yes, each time we refine or burn these fuels or make products from them, carbon dioxide is added to the air.
By the way ...
Most coal is burned in power plants to make electricity. A coal plant that produces electricity to power a city of about 140,000 people (such as Syracuse, NY; Hayward, CA; or Kansas City, KS) for a year, gives off 3.7 millon tons of carbon dioxide. The giant ocean liner Queen Mary II weighs about 150,000 tons. That means the weight of coal's carbon dioxide emissions equals more than 24 ocean liners.
4 U 2 Do
Be an electricity sleuth. Find out how the electricity that flows into your home is generated. How much is produced by coal or other nonrenewable fossil fuels? How much is made by energy sources like solar energy, wind power, and other renewable energy sources? Start your investigation by going online to your local electricity provider or by calling them.
EARTH, THE GREENHOUSE
Earth's atmosphere is like a greenhouse--it lets sunshine in but doesn't let much heat out. This greenhouse effect is a natural process that warms Earth. Here's how it works. As sunlight falls on the oceans and lands, it is absorbed at the surface and warms our planet. The warm water and ground cool down by radiating the heat away. Most of the gases in our air, like oxygen and nitrogen, let the heat pass through. But a few gases--called greenhouse gases--such as carbon dioxide and water trap some of the heat before it seeps into space. They make our planet a pleasant place to live. If there were no heat-trapping gases in our air, Earth would be a cold, desert world much like our Moon. So the natural greenhouse effect is a good thing.
What's happening today as people send ever more greenhouse gases into the air? The greenhouse effect is getting stronger and stronger and our planet is getting warmer and warmer. This human-magnified greenhouse effect--definitely not a good thing!
TOO MUCH CO2
Once we began burning fossil fuels for energy, we started adding carbon dioxide to our air. Burning coal, burning oil, and burning natural gas send tons and tons of carbon dioxide into our air. How much? So far, we've added 26 billion metric tons. And every day we add more.
For a long time, no one knew how much carbon dioxide was in the atmosphere. Then in 1958, a young scientist named Charles Keeling set up a monitoring station near the top of Mauna Loa, the biggest volcano in Hawaii. He measured the amount of carbon dioxide in the air continuously for many years. His graph, called the Keeling Curve, is one of the most famous graphs in science. Today, monitoring stations all over the world still record these measurements.
CARBON DIOXIDE IN THE AIR
The Keeling Curve shows that the amount of carbon dioxide in the air has been going up every year. In 1958, there were about 315 molecules of carbon dioxide out of every one million molecules of air (called parts per million or ppm). Today there are about 385 ppm of carbon dioxide! That's a mega increase in just 50 years.
As carbon dioxide builds up in the air, it magnifies the greenhouse effect. This means our world is getting warmer. In the last century, Earth's average temperature has risen about 1.5°F. This may not sound like very much, but it is. Already scientists have measured changes all over the globe. Oceans are warmer. Mountain glaciers are melting. Ice shelves are crumbling into the sea. Sea levels are rising. Weather patterns are different. And from the rainforests and dry deserts to the icy poles and salty seas, animals and plants are struggling to beat the heat.
WHAT CAN WE DO?
What can we do? We can work together. And that's just what people all over the world are doing. People are working fast and furiously to come up with solutions to stop the buildup of heat-trapping gases in our air. We need energy, but we need to use energy sources that emit little or no carbon dioxide. The good news is that they already exist--as sunshine, wind, water, fuels made from plants, and more. And people all over the globe are already using them. Once we scale up the use of these clean-energy sources, we'll be on our way to taking better care of our planet. Switching to clean energy is important. But there's something more all of us can do. We can do it right now, right this minute and it will take a big bite out of global warming. Conserve energy! Just use less of it. This is the fastest, cheapest, and easiest thing to do. You've probably heard the expression "go green." It means living in a way that lessens our impact on Earth. In the next chapters you'll find ideas to help you live a greener life.
Copyright © 2009 Sally Ride and Tam O'Shaughnessy Illustrations copyright © 2009 by Andrew Arnold