Do you like warm weather? Do you wish it could be warmer still? Be careful what you wish for. The Earth may be moving in that direction. The trend is called global warming. Not all scientists agree that global warming is happening. Some say it is impossible to know if the climate is changing overall. After all, temperatures vary from day to day and year to year. Most scientists, however, say the trend is up. The warmest days are warmer, the coldest days not as cold. They point out that the ten warmest years of the last century happened after 1980. The three hottest came after 1990. The hottest year on record was 1998. These scientists say the Earth has warmed up about 1° Fahrenheit (0.6° Celsius) in the last 100 years. The rate of change, they say, is speeding up. A hundred years from now, the Earth may well be as much as ten degrees hotter!
WHAT CAUSES GLOBAL WARMING?
Sunlight brings energy to the Earth. This light turns to heat when it hits the ground. The heat in turn seeps away from the Earth, but the atmosphere slows the heat’s escape. The atmosphere is a layer of air around the planet. It holds in some of the warmth. The atmosphere is a mixture of many gases. In the last 250 years, this mixture has been changing. The amounts of gases such as methane and carbon dioxide have been rising. These gases trap heat more effectively than other gases. They make the Earth’s atmosphere act like the glass in a greenhouse. It lets sunlight in, but it doesn’t let heat out. As a result, heat is building up close to the surface.
WHY IS THE ATMOSPHERE CHANGING?
People are changing the atmosphere. The changes started hundreds of years ago when people began cutting down forests and burning the wood. The invention of cars and other machines greatly increased the amount of greenhouse gases released into the atmosphere. Such machines burn fuels like wood, coal, oil, and natural gas. When these fuels burn, they add carbon dioxide to the atmosphere. Methane comes from producing coal. Today, the air contains almost one-third more carbon dioxide than it did in 1750. The amount of methane has doubled.
IS GLOBAL WARMING DANGEROUS?
Global warming could melt the ice at the poles. This would raise the level of the oceans. Water would then cover all the flat coastal lands. People would have less land on which to live and grow food. Plants and animals are adapted to their climates. If the climate changes rapidly, many may not be able to adapt. Some species will simply die out. Others may spread to cooler climates. There, however, they will be struggling with species already in place.
CAN GLOBAL WARMING BE STOPPED?
Burning less wood, coal, oil, and natural gas will help stop global warming. Scientists recommend that people get more energy from sunlight, wind, tides, nuclear energy, and other sources that don’t burn fuel. Energy sources like these put little or no greenhouse gases into the air. Scientists say trees can help prevent global warming. All growing plants take carbon dioxide out of the air. Trees do this especially well. They turn the carbon part of carbon dioxide into wood. They release the oxygen. In recent years, people have been cutting down forests all over the world. Scientists say vast new forests must be planted.
WHAT IS BEING DONE?
In 1997, officials from 160 countries met in Kyoto, Japan . They wrote an agreement called the Kyoto Protocol. Countries that sign this agreement promise to burn 5 percent less fossil fuel (coal, oil, and natural gas) by 2012. In 2002, however, the United States decided not to sign the treaty. Russia also has not signed the treaty. Without the United States and Russia , the treaty can’t work.
Pollution
In the mid-1900s, a biologist named Rachel Carson was afraid that some day there might be no more birds. Farmers were spraying a chemical called DDT on their fields to kill insects. But DDT was also keeping birds such as the bald eagle and peregrine falcon from having babies. DDT prevented the babies from hatching. She wrote a book called Silent Spring to warn about the dangers of DDT. Pollution happens when chemicals that are harmful to living things get into the environment. Rachel Carson feared that DDT would get into the food people ate. Her book scared a lot of people. Governments banned the use of DDT. People then began to worry about other kinds of pollution. They worried that pollution could harm people’s health.
WHAT DOES POLLUTION DO?
Pollution can kill or sicken plants, animals, and people. Pollution can change the environment. Things that cause pollution are called pollutants. Pollution can get into the air. Air pollution can irritate people’s lungs. Polluted air can mix with rain to make acid rain. Acid rain kills trees and harms fish in lakes. Pollution can also get into soil and water. From there, pollutants can get into the food chain. Plants take in the pollution from the ground. Animals that eat the plants can be harmed, too. Bigger animals and even people might eat the damaged animals.
WHERE DOES POLLUTION COME FROM?
Air pollution comes from factories and power plants that burn coal and oil. Smoke from factories and power plants can mix with water in the air to make acid rain. Air pollution also comes from cars and other vehicles that burn gasoline. Soil pollution can come from chemicals used on farms to kill insects and other pests. Pollutants can also seep from garbage dumps into the nearby soil and water.
Water pollution comes from factories that dump poisonous chemicals into lakes and rivers. Water pollution can also come from farms. Farmers put chemicals on the ground to help crops grow and to kill insects. Rain can wash these chemicals into lakes and rivers. Big ships called oil tankers can pollute the ocean if the oil leaks out of the tankers. There can be a huge oil spill if a tanker has an accident and sinks at sea. A special kind of pollution comes from nuclear power plants. Nuclear power plants produce radioactive waste. This waste lasts for thousands of years and can cause cancer and other deadly illnesses if it is not properly stored.
IS POLLUTION CHANGING EARTH’S CLIMATE?
Many scientists think that pollution is changing Earth’s climate. They think the change is coming from gases in the air called greenhouse gases. Carbon dioxide and other gases trap heat from the Sun. They trap heat the way glass walls and ceilings in greenhouses trap heat. It stays warm inside a greenhouse even when it is cold outside. Greenhouse gases in the air make Earth warm enough for life. But scientists think that people are putting too much carbon dioxide and other greenhouse gases into the air. These extra greenhouse gases come from burning coal and oil in factories and power plants. They come from burning gasoline in cars. Too much of them will make Earth warmer. This warming could cause disastrous changes on the planet.
HOW CAN WE STOP POLLUTION?
Chemicals that cause pollution are not easy to get rid of. They stay in the air and ground and water for a long time. The best way to fight pollution is to stop producing it in the first place. Governments can pass laws that forbid or limit the use of chemicals that cause pollution. Laws can stop factories from dumping poisonous chemicals in lakes, rivers, and the ocean. Factories and power plants can clean up the smoke that they give off.
Engineers can build cars that burn less gasoline. They can find ways for cars to give off cleaner exhaust gases. Scientists are looking for fuels to replace coal and oil. They are looking for ways to use the power in wind and in rays from the Sun. They are also looking for safe ways to get rid of nuclear waste. You can help cut down on the amount of garbage you make. You can recycle paper, plastic, glass bottles, and metal cans. Recycled material gets used over again. Recycling helps cut down on pollution.
