How do we know IF the climate is changing?
i.e., Can human activities cause a change in climate by increasing the
concentration of greenhouse gases in the atmosphere?
First, let’s see how do we measure the earth temperature and CO2
concentration?
• Records of temperatures on land come from weather stations around the
world. Scientists use the instruments to track temperatures, rainfall and
other precipitation, wind speed, and barometric pressure.
• Air bubbles inside of ice core samples from Greenland and Antarctica tell
researchers about the long-term history of the planet’s climate.
• Tree rings are another way to reveal past trends in temperature and
periods of drought and rainfall.
• Tree rings and ice cores show that concentrations of carbon dioxide in the
atmosphere have been going up.
Our Effects are….
o During the last two centuries, humans have used these fossil fuel
resources at an increasing rate. In 1996, humanity released about 23
billion tons of carbon dioxide to the atmosphere every year by burning
fossil fuels. The U.S. alone released 5.3 billion tons in 1996 from fossil fuel
combustion.
o Some developing countries like China and India have been increasing
their use of fossil fuels a lot faster than industrialized nations like the U.S.
So….
Ø Over the past century, CO2 levels in the atmosphere have increased from
280 parts per million to nearly 360 ppm. During the same time, global
temperatures have risen nearly 1 OF. (if that doesn’t sound like much,
consider that the average global temperature during the Ice Ages was only
about 9-12 OF colder than today, and the world has a very different climate
today than it had then)
Ø Recent studies indicate that in the northern hemisphere, spring is arriving
sooner and fall later
Ø Melting glaciers worldwide (e.g., glaciers in Montana’s Glacier National
Park are now one-third the size they were in 1850).
Ø Sea level has risen, indicating that ocean temperatures have increased
(water expands as it warms).
Ø In 1995, a panel of 2,000 scientists concluded that “the balance of
evidence suggests a recognizable human influence on global climate.”
Ø Most scientists believe that global warming is happening and will continue.