January 18, 2011
2010 Hits Top of Temperature Chart
Alexandra Giese
Topping off the warmest decade in history, 2010 experienced a global
average temperature of 14.63 degrees Celsius (58.3 degrees Fahrenheit),
tying 2005 as the hottest year in 131 years of recordkeeping.
This news will come as no surprise to residents of the 19 countries
that experienced record heat in 2010. Belarus set a record of 38.7
degrees Celsius (101.7 degrees Fahrenheit) on August 6 and then broke it
by 0.2 degrees Celsius just one day later. A 47.2-degree Celsius
(117.0-degree Fahrenheit) spike in Burma set a record for Southeast Asia
as a whole. And on May 26, 2010, the ancient city of Mohenjo-daro in
Pakistan hit 53.5 degrees Celsius (128.3 degrees Fahrenheit)—a record
not only for the country but for all of Asia. In fact, it was the fourth
hottest temperature ever recorded anywhere. (See
data.)
The earth’s temperature is not only rising, it is rising at an
increasing rate. From 1880 through 1970, the global average temperature
increased roughly 0.03 degrees Celsius each decade. Since 1970, that
pace has increased dramatically, to 0.13 degrees Celsius per decade. Two
thirds of the increase of nearly 0.8 degrees Celsius (1.4 degrees
Fahrenheit) in the global temperature since the 1880s has occurred in
the last 40 years. And 9 of the 10 warmest years happened in the last
decade.
Global temperature is influenced by a number of factors, some natural
and some due to human activities. A phenomenon known as the El
Niño-Southern Oscillation is characterized by extremes in Pacific Ocean
temperatures and shifts in atmospheric patterns. The cycle involves
opposite phases, both of which have global impacts. The El Niño phase
typically raises the global average temperature, while its counterpart,
La Niña, tends to depress it. Temperature variations are also partly
determined by solar cycles. Because we are close to a minimum in solar
irradiance (how much energy the earth receives from the sun) and entered
a La Niña episode in the second half of 2010, we would expect a cooler
year than normal—making 2010’s record temperature even more remarkable.
Since the Industrial Revolution, emissions from human activities of
greenhouse gases such as carbon dioxide have driven the earth’s climate
system dangerously outside of its normal range. Carbon dioxide levels in
the atmosphere have risen nearly 40 percent, from 280 parts per million
(ppm) to almost 390 ppm. As the atmosphere becomes increasingly
overloaded with heat-trapping gases, the earth’s temperature continues
to rise.
Even seemingly small changes in global temperature have far-reaching
effects on sea level, atmospheric circulation, and weather patterns
around the globe. Climate scientists note that increases in both the
frequency and severity of extreme weather events are characteristics of
a hotter climate. In 2010, the heat wave in Russia, fires in Israel,
flooding in Pakistan and Australia, landslides in China, record snowfall
across the mid-Atlantic region of the United States, and 12 Atlantic
Ocean hurricanes were among the extreme weather events. The human cost
of these events was not small: the Russian heat wave and forest fires
claimed 56,000 lives, while the Pakistan floods took 1,760.
Although the weather of 2010 seems extreme compared with that of earlier
years, scientists warn that such patterns could become more common in
the near future. And while no single event can be attributed directly to
climate change, NASA climate scientist James Hansen notes that the
extreme weather of 2010 would “almost certainly not” have occurred in
the absence of excessive greenhouse gas emissions. Warmer air holds more
water vapor, and that extra moisture leads to heavier storms. At the
same time that precipitation events are becoming larger in some areas,
climate change causes more intense and prolonged droughts in others. By
some estimates, droughts could be up to 10 times as severe by the end of
the century.
Like a growing number of extreme weather events, an increase in the
number of record-high temperatures—and a concomitant decrease in the
number of record lows—is characteristic of a warming world. For
instance, while 19 countries recorded record highs in 2010, not one
witnessed a record low temperature. Across the United States, weather
station data reveal that daily maximum temperature records outnumbered
minimum temperature records for nine months of 2010. Over the last
decade, record highs were more than twice as common as record lows,
whereas half a century ago there was a roughly equal probability of
experiencing either of these.
Temperatures are rising faster in some places than in others. The
Arctic has warmed by as much as 3–4 degrees Celsius (5–7 degrees
Fahrenheit) since the 1950s. It is heating up at twice the rate of the
earth on average, making it the fastest-warming region on the planet.
Disproportionately large warming in the Arctic is partially due to the
albedo effect. As sea ice melts, darker ocean water is exposed; the
additional energy absorbed by the darker surface then melts more ice,
setting in motion a self-reinforcing feedback.
In 2010, Arctic sea ice shrank to its
third-lowest extent on record, after 2007 and 2008, and also reached
what was likely its lowest volume in thousands of years. At both poles,
the great ice sheets are showing worrying signs: recent calculations
reveal that Greenland is losing more than 250 billion tons of water per
year, and 87 percent of marine glaciers on the Antarctic Peninsula have
retreated since the 1940s. There is enough water frozen in Greenland and
Antarctica to raise global sea levels by over 70 meters (230 feet) if
they were to melt entirely.
Unless global temperatures are stabilized, higher seas from melting
ice sheets and mountain glaciers, combined with the heat-driven
expansion of ocean water itself, will eventually lead to the
displacement of millions of people
as
low-lying coastal areas and island nations are inundated. Sea level
rise has been minimal so far, with a global average of 17 centimeters (6
inches) during the last century. But the rate of the rise is
accelerating, and some scientists maintain that a rise as high as 2
meters (6 feet) is possible before this century’s end.
It is not only coastal populations that are threatened by rising
global temperatures. Higher temperatures reduce crop yields and water
supplies, affecting food security worldwide. Agricultural scientists
have drawn a correlation between a temperature rise of 1 degree Celsius
above the optimum during the growing season and a grain yield decrease
of 10 percent. Heat waves and droughts can also cause
drastic cuts in harvests. Mountain glaciers, which are shrinking
worldwide as a result of rising temperatures, supply drinking and
irrigation water to much of the world’s population, including hundreds
of millions in Asia.
More than any natural variations, carbon emissions from human activities
will determine the future trajectory of the earth’s temperature and thus
the frequency of extreme weather events, the rise in sea level, and the
state of food security. The 2007 report from the Intergovernmental Panel
on Climate Change projected that the earth would warm 1.1–6.4 degrees
Celsius (2–11 degrees Fahrenheit) by the end of the century. Yet a rise
of 2–3 degrees Celsius will make the earth as hot as it was 3 million
years ago, when oceans were more than 25 meters (80 feet) higher than
they are today. Subsequent research has projected an even larger rise—up
to 7.4 degrees Celsius–-if the world continues to depend on a
fossil-fuel-based energy system. But we can create a different future by
turning to a new path—one with carbon-free energy sources, restructured
transportation, and increased efficiency. By dramatically reducing
emissions, we could halt the rapid rise of the earth’s temperature.
Copyright ©
2011 Earth Policy Institute