Weather changes all the time. The average pattern of weather, called climate, usually stays the same for centuries if it is undisturbed. However, Earth is not being left alone. People are taking actions that can change Earth and its climate in significant ways.

Carbon dioxide is the main culprit. Burning carbon-containing "fossil fuels" such as coal, oil and gas has a large impact on climate because it releases carbon dioxide gas into the atmosphere. Since the early 1800s, when people began burning large amounts of coal and oil, the amount of carbon dioxide in the Earth’s atmosphere has increased by nearly 30 percent, and the average global temperature appears to have risen between 1 and 2 degrees Fahrenheit, say scientists at the NSF-funded National Center for Atmospheric Research.

Carbon dioxide gas traps solar heat in the atmosphere, much as glass traps solar heat in a greenhouse. This is why carbon dioxide is called a "greenhouse gas." As more carbon dioxide is added to the atmosphere, heat from the Sun is trapped close to the Earth, so the temperature rises. If this goes on long enough, scientists predict major changes to the Earth's average temperatures, followed by its climate and ultimately its life, will happen.

Warming will change the length of growing seasons, the frequency and severity of storms, and sea level, which will rise as polar ice caps melt. Such changes will affect farms, forests and plants and animals in the natural environment.

Scientists calculate the Earth will warm about 2.5 degrees Fahrenheit (1.4 degrees Celsius) by the year 2050, although some predict almost no change and others a warming of more than 4 degrees Fahrenheit. All agree, however, that humans are having a never-before-seen affect on Earth, and the planet’s innate ability through natural processes to tolerate these changes, in the short time periods they are occurring, may be overwhelmed.

For example, scientists funded by NSF discovered that a vast blanket of particles stretching across South Africa damaged agriculture and modified rainfall patterns, including those of the mighty monsoons. Researchers dubbed this build-up of ash and other airborne substances the "Asian brown haze." Studies are underway to unravel the effect the miles-thick particle cloud may have on the region’s climate, and on world climate. The brown haze, researchers believe, could travel halfway around the globe in as little as one week.

To learn more:
www.ncar.ucar.edu/
www.abc-asia.ucsd.edu/ABCconceptFinal23May01.pdf

What can rock layers tell us about Earth's history? [Next]