For 2.5 million years, the earth’s climate has fluctuated, cycling from
ice ages to warmer periods. But in the last century, the planet’s temperature
has risen unusually fast – about 1.2 to 1.4 degrees Fahrenheit. Scientists
believe it’s human activity that’s driving the temperatures up; a process
known as global warming. Ever since the industrial revolution began, factories,
power plants, and eventually, cars, have burned fossil fuels such as oil
and coal...releasing huge amounts of carbon dioxide and other gases into
the atmosphere. These greenhouse gases trap heat near the earth through
a naturally occurring process called the greenhouse effect. The greenhouse
effect begins with the sun and the energy it radiates to the earth.
The earth and the atmosphere absorb some of this energy, while the rest
is radiated back into space. Naturally occurring gases in the atmosphere
trap some of this energy and reflect it back, warming the earth.
Scientists now believe that the greenhouse effect is being intensified
by the extra greenhouse gases that humans have released. Evidence for global
warming includes a recent string of very warm years. Scientists report
that 1998 was the warmest year in measured history, with 2005 coming in
second. Meanwhile, readings taken from ice cores...show that the
greenhouse gases, carbon dioxide and methane have hit their highest levels
in the past 420,000 years. Arctic sea ice is also shrinking. According
to NASA studies, the extent of Arctic sea ice has declined about 10% in
the last 30 years. As long as industrialized nations consume energy and
developing countries increase their fossil fuel consumption...the concentration
of greenhouse gases in the atmosphere will continue to rise. Researchers
predict that temperatures will increase about 2 to10 degrees Fahrenheit
by the end of the century. What’s less certain is what rising temperatures
mean for the planet. Some climate models predict subtle changes.
Others forecast rising sea levels which could flood coastal areas around
the world. Weather patterns could change, making hurricanes more
frequent. Severe droughts could become more common in warm areas
and species unable to adapt to the changing conditions would face extinction.
Although much remains to be learned about global warming...many organizations
advocate cutting greenhouse gas emissions to reduce the impact of global
warming. Consumers can help. By saving energy around the house, switching
to compact fluorescent light bulbs...and driving fewer miles in the car
each week. These simple changes may help keep the Earth cooler in the future.