READING GLOBAL
WARMING
Global warming is the
unusually rapid increase in Earth’s average surface temperature over the past
century primarily due to the greenhouse gases released as people burn fossil
fuels. The global average surface temperature rose 0.6 to 0.9 degrees Celsius
(1.1 to 1.6° F) between 1906 and 2005, and the rate of
temperature increase has nearly doubled in the last 50 years. Temperatures are
certain to go up further.
Earth has experienced
climate change in the past without help from humanity. But the current climatic
warming is occurring much more rapidly than past warming events.
In Earth’s history before
the Industrial Revolution, Earth’s climate changed due to natural causes
unrelated to human activity. These natural causes are still in play today, but
their influence is too small or they occur too slowly to explain the rapid
warming seen in recent decades. Models predict that as the world consumes ever
more fossil fuel, greenhouse gas concentrations will continue to rise, and
Earth’s average surface temperature will rise with them. Based on plausible
emission scenarios, average surface temperatures could rise between 2°C and 6°C
by the end of the 21st century. Some of this warming will occur even if future
greenhouse gas emissions are reduced, because the Earth system has not yet
fully adjusted to environmental changes we have already made.
The impact of global
warming is far greater than just increasing temperatures. Warming modifies
rainfall patterns, amplifies coastal erosion, lengthens the growing season in
some regions, melts ice caps and glaciers, and alters the ranges of some
infectious diseases. Some of these changes are already occurring.
Earth’s temperature begins with the Sun. Roughly 30 percent of incoming
sunlight is reflected back into space by bright surfaces like clouds and ice.
Of the remaining 70 percent, most is absorbed by the land and ocean, and the
rest is absorbed by the atmosphere. The absorbed solar energy heats our planet.
As the rocks, the air, and the seas warm, they radiate “heat” energy (thermal
infrared radiation). From the surface, this energy travels into the atmosphere
where much of it is absorbed by water vapor and long-lived greenhouse gases
such as carbon dioxide and methane.
When they absorb the energy radiating from Earth’s surface, microscopic
water or greenhouse gas molecules turn into tiny heaters— like the bricks in a
fireplace, they radiate heat even after the fire goes out. They radiate in all
directions. The energy that radiates back toward Earth heats both the lower
atmosphere and the surface, enhancing the heating they get from direct
sunlight.
This absorption and radiation of heat by the atmosphere—the natural
greenhouse effect—is beneficial for life on Earth. If there were no greenhouse
effect, the Earth’s average surface temperature would be a very chilly -18°C
(0°F) instead of the comfortable 15°C (59°F) that it is today.
Earth has experienced climate change in the past without help from
humanity. We know about past climates because of evidence left in tree rings,
layers of ice in glaciers, ocean sediments, coral reefs, and layers of
sedimentary rocks. For example, bubbles of air in glacial ice trap tiny samples
of Earth’s atmosphere, giving scientists a history of greenhouse gases that
stretches back more than 800,000 years. The chemical make-up of the ice
provides clues to the average global temperature.
The impact of increased surface temperatures is significant in itself.
But global warming will have additional, far-reaching effects on the planet.
Warming modifies rainfall patterns, amplifies coastal erosion, lengthens the
growing season in some regions, melts ice caps and glaciers, and alters the
ranges of some infectious diseases. Some of these changes are already
occurring.
For most places, global warming will result in more frequent hot days
and fewer cool days, with the greatest warming occurring over land. Longer,
more intense heat waves will become more common. Storms, floods, and droughts
will generally be more severe as precipitation patterns change. Hurricanes may
increase in intensity due to warmer ocean surface temperatures.
The weather isn’t the only thing global warming will impact: rising sea
levels will erode coasts and cause more frequent coastal flooding. Some island
nations will disappear. The problem is serious because up to 10 percent of the
world’s population lives in vulnerable areas less than 10 meters (about 30
feet) above sea level.
The changes to weather and ecosystems will also affect people more
directly. Hardest hit will be those living in low-lying coastal areas, and
residents of poorer countries who do not have the resources to adapt to changes
in temperature extremes and water resources. As tropical temperature zones
expand, the reach of some infectious diseases, such as malaria, will change.
More intense rains and hurricanes and rising sea levels will lead to more
severe flooding and potential loss of property and life.
1 Part.
Answer in Spanish
the following question about the reading.
3. What is Earth’s
natural greenhouse effect?
5. How Will Global
Warming Change Earth?
8. How is Today’s
Warming Different from the Past?
