Greenhouse gases include gases such as carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), ozone (O3), and fluorinated gases. These greenhouse gases allow the sun's light to shine onto Earth's surface. Then the gases, such as ozone, trap the heat that reflects back from the surface inside Earth's atmosphere. The gases act like the glass walls of a greenhouse. In other words, they are warming.
The greenhouse effect happens when these gases gather in Earth's atmosphere. According to scientists, without the greenhouse effect, the average temperature of Earth would drop from 57 degrees Fahrenheit (14 degrees Celsius) to as low as negative 0.4 degrees F (minus 18 degrees C).
Do We Blame the Industrial Revolution?
Some greenhouse gases come from natural sources. For example, evaporation adds water vapor to the atmosphere. Animals and plants release carbon dioxide when they breathe. Methane is released naturally from decomposition, when soils and living things break down. Volcanoes—both on land and under the ocean—release greenhouse gases.
The Industrial Revolution happened in the late 1700s and early 1800s, when factories began producing more. Since then, people have been releasing larger quantities of greenhouse gases into the atmosphere. Greenhouse gas emissions increased 70 percent between 1970 and 2004. Emissions of carbon dioxide (CO2), rose about 80 percent during that time.
The amount of CO2 in the atmosphere far exceeds Earth's natural amount seen over the last 650,000 years.
Most of the CO2 that people put into the atmosphere comes from burning fossil fuels. Cars, trucks, trains and planes all burn fossil fuels. Many electric power plants do, as well. Another way humans release CO2 into the atmosphere is by cutting down forests, because trees contain large amounts of carbon.
Human Activity + Greenhouse Gases = A Warming Earth
People add methane to the atmosphere through livestock farming, landfills and fossil fuel production such as coal mining and natural gas processing. Nitrous oxide comes from agriculture and fossil fuel burning.
Fluorinated gases include chlorofluorocarbons (CFCs), hydro chlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs). They are produced during the manufacturing of refrigeration and cooling products. Some come through aerosol cans, such as some hairsprays or spray paint.
As greenhouse gases increase, so does the temperature of Earth. The rise in Earth's average temperature contributed to by human activity is known as global warming.
The Greenhouse Effect and Climate Change
Even slight increases in average global temperatures can have huge effects.
Perhaps the biggest effect is that glaciers and ice caps melt faster than usual. The meltwater drains into the oceans, causing sea levels to rise.
Glaciers and ice caps cover about 10 percent of the world's land. They hold between 70 and 75 percent of the world's freshwater. If all of this ice melted, sea levels would rise about 70 meters (230 feet).
The Intergovernmental Panel on Climate Change says that the global sea level rose about 1.8 millimeters (0.07 inch) per year from 1961 to 1993. It rose about 3.1 millimeters (1/8 inch) per year since 1993.
This seems like only a tiny bit, but rising sea levels can cause flooding in cities along the coasts. This could force millions of people in low-lying areas out of their homes, such as in Bangladesh, the U.S. state of Florida, and the Netherlands.
Millions more people in countries such as Peru and India depend on water from melted glaciers. They use it for drinking, watering crops and hydroelectric power. Rapid loss of these glaciers would greatly hurt those countries.
Predictable Rain is Important to Many
Greenhouse gas emissions also affect changes in precipitation, such as rain and snow.
In the 20th century, precipitation increased in eastern parts of North and South America, Northern Europe, and northern and Central Asia. However, it has decreased in parts of Africa, the Mediterranean, and southern Asia.
As climates change, so do the habitats for living things. Animals that are adapted to a certain climates might become threatened. Many humans depend on predictable rain patterns to grow specific crops. If the climate of an area changes, the people who live there may no longer be able to grow the crops they depend on for survival.
Scientists aren't the only Ones Who Can Help
- Drive less. Use public transportation, carpool, walk, or ride a bike.
- Fly less. Airplanes produce huge amounts of greenhouse gas emissions.
- Reduce, reuse, and recycle.
- Plant a tree. Trees absorb carbon dioxide, keeping it out of the atmosphere.
- Use less electricity.
- Eat less meat. Cows are one of the biggest methane producers.
- Support alternative energy sources that don’t burn fossil fuels.