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Global Warming Facts
Global warming,
or climate change, is a subject that shows no sign of cooling down.
Here's the lowdown on
why it's happening, what's causing it, and how it might change the planet.
Is It Happening?
Yes. Earth is already
showing many signs of worldwide climate change.
• Average
temperatures have climbed 1.4 degrees Fahrenheit (0.8 degree Celsius) around
the world since 1880, much of this in recent decades, according to NASA's
Goddard Institute for Space Studies.
• The rate of warming
is increasing. The 20th century's last two decades were the hottest in 400
years and possibly the warmest for several millennia, according to a number of
climate studies. And the United Nations' Intergovernmental Panel on Climate
Change (IPCC) reports that 11 of the past 12 years are among the dozen warmest
since 1850.
• The Arctic is
feeling the effects the most. Average temperatures in Alaska, western Canada,
and eastern Russia have risen at twice the global average, according to the
multinational Arctic Climate Impact Assessment report compiled between 2000
and 2004.
• Arctic ice is
rapidly disappearing, and the region may have its first completely
ice-free summer by 2040
or earlier.
Polar bears and indigenous
cultures are already suffering from the sea-ice loss.
• Glaciers and
mountain snows are rapidly melting—for example,
Montana's Glacier National Park now has
only 27 glaciers, versus 150 in 1910. In the Northern Hemisphere, thaws also
come a week earlier in spring and freezes begin a week later.
• Coral reefs, which
are highly sensitive to small changes in water temperature, suffered the
worst bleaching—or die-off in
response to stress—ever recorded in 1998, with some areas seeing
bleach rates of 70 percent. Experts expect these sorts of events to increase
in frequency and intensity in the next 50 years as sea temperatures rise.
• An upsurge in the
amount of extreme weather events, such as
wildfires,
heat waves, and
strong tropical storms, is also attributed
in part to climate change by some experts.
Are Humans Causing
It?
"Very likely,"
the IPCC said in a February
2007 report.
The report, based on
the work of some 2,500 scientists in more than 130 countries, concluded that
humans have caused all or most of the current planetary warming. Human-caused
global warming is often called anthropogenic climate change.
• Industrialization,
deforestation, and pollution have greatly increased atmospheric concentrations
of water vapor, carbon dioxide, methane, and nitrous oxide, all greenhouse
gases that help trap heat near Earth's surface. (See an interactive feature on
how global warming works.)
• Humans are pouring
carbon dioxide into the atmosphere much faster than
plants and oceans can absorb it.
• These gases persist
in the atmosphere for years, meaning that even if such emissions were
eliminated today, it would not
immediately stop global warming.
• Some experts point
out that natural cycles in Earth's orbit can alter the planet's exposure to
sunlight, which may explain the current trend. Earth has indeed experienced
warming and cooling cycles roughly every hundred thousand years due to these
orbital shifts, but such changes have occurred over the span of several
centuries. Today's changes have taken place over the past hundred years or
less.
• Other recent
research has suggested that the effects of
variations in the sun's output are
"negligible" as a factor in warming, but other, more complicated solar
mechanisms could possibly play a role.
What's Going to
Happen?
A follow-up
report by the IPCC released in
April 2007 warned that global warming could lead to large-scale
food and water shortages and have catastrophic effects on wildlife.
• Sea level could
rise between 7 and 23 inches (18 to 59 centimeters) by century's end, the
IPCC's February 2007 report projects. Rises of just 4 inches (10 centimeters)
could flood many South Seas islands and swamp large parts of Southeast Asia.
• Some hundred
million people live within 3 feet (1 meter) of mean sea level, and much of the
world's population is concentrated in vulnerable coastal cities. In the U.S.,
Louisiana and Florida are
especially at risk.
• Glaciers around the
world could melt, causing sea levels to rise while creating water shortages in
regions dependent on runoff for fresh water.
• Strong hurricanes,
droughts, heat waves, wildfires, and other natural disasters may become
commonplace in many parts of the world. The growth of deserts may also cause
food shortages in many places.
•
More than a million species
face extinction from disappearing habitat, changing ecosystems,
and acidifying oceans.
• The ocean's
circulation system, known as the ocean conveyor belt, could be permanently
altered, causing a mini-ice age
in Western Europe and other rapid changes.
• At some point in
the future, warming could become uncontrollable by creating a so-called
positive feedback effect.
Rising temperatures could release additional greenhouse gases by unlocking
methane in permafrost and undersea deposits, freeing carbon trapped in sea
ice, and causing increased evaporation of water.
What is Climategate?
In late November
2009, hackers unearthed hundreds of emails at the U.K.'s University of East
Anglia that exposed private conversations among top-level British and U.S.
climate scientists discussing whether certain data should be released to the
public. [Do we know who the hackers were? Were they skeptics? Might be worth
noting]
The email exchanges
also refer to statistical tricks used to illustrate climate change? trends,
and call climate skeptics idiots, according to the New York Times.
One such trick was
used to create the well-known hockey-stick graph, which shows a sharp uptick
in temperature increases during the 20th century. Former U.S vice president Al
Gore relied heavily on the graph as evidence of human-caused climate change in
the documentary An Inconvenient Truth.
The data used for
this graph come from two sources: thermostat readings and tree-ring samples.
While thermostat
readings have consistently shown a temperature rise over the past hundred
years, tree-ring samples show temperature increases stalling around 1960.
On the hockey-stick
graph, thermostat-only data is grafted onto data that incorporates both
thermostat and tree-ring readings, essentially presenting a seamless picture
of two different data sets, the hacked emails revealed.
But scientists argue
that dropping the tree-ring data was no secret and has been written about in
the scientific literature for years.
Climate change
skeptics have heralded the emails as an attempt to fool the public, according
to the Times.
Yet climate
scientists maintain that these controversial points are small blips that are
inevitable in scientific research, and that the evidence for human-induced
climate change is much broader and still widely accepted.
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