Water in the Atmosphere Page 2

Additional Resources

Climate

Precipitation

Temperature

A great many substances can be carried in the atmosphere besides its constituent gases. Mushroom spores, for instance, are so light that they can float high above the surface and serve as nuclei around which water droplets can condense. Human civilization sends metals, pesticides, chemicals, nutrients and other contaminants aloft, which can be blown around the Earth by the wind. When water droplets form around oxides of sulfur or nitrogen given off by the burning of fossil fuels, they form acidic droplets that can contribute to acid rain.

Several manmade chemicals in the atmosphere can deplete the amount of ozone high above the Earth. Ozone, three oxygen molecules bound together, is Earth's sunscreen, blocking ultraviolet radiation from reaching the skin of our planet. When such chemicals as chlorofluorocarbons (CFCs) from spray cans and refrigerants, nitrous oxides from fertilizers, or halons from fire extinguishers interact with atmospheric ozone, ozone is destroyed. A 1% loss of ozone allows 2% more ultraviolet radiation to reach the Earth, where it can damage molecules in living cells.

Being largely invisible, the atmosphere seems simple enough that we can take it for granted, as people have been taking it for granted for thousands of years. But scientists now find that atmospheric chemistry and currents are extremely complex because they are affected by so many factors. If the atmosphere is indeed holding more heat close to Earth's surface, and the global climate is growing warmer, then no one knows exactly how changes resulting from human activities will change life and its habitats for millennia to come. As the global climate changes for whatever reason, local weather patterns will be affected, some regions becoming drier, some wetter, and unsettled conditions will prevail.