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The global average
temperature in 2011 was 14.52 degrees Celsius (58.14
degrees Fahrenheit). According to NASA scientists, this
was the ninth warmest year in 132 years of recordkeeping,
despite the cooling influence of the La Niña atmospheric
and oceanic circulation pattern and relatively low solar
irradiance. Since the 1970s, each subsequent decade has
gotten hotter -- and 9 of the 10 hottest years on record
have occurred in the twenty-first century.
Each year’s average
temperature is determined by a number of factors,
including solar activity and the status of the El Niño/La
Niña phenomenon. But heat-trapping gases that have
accumulated in the atmosphere, largely from the burning of
fossil fuels, have become a dominant force, pushing the
Earth’s climate out of its normal range. The planet is now
close to 0.8 degrees Celsius warmer than it was a century
ago. Hidden within annual averages and expected
variability are startling instances of new temperature and
rainfall records in many parts of the world -- weather
extremes that would once be considered anomalies but that
now risk becoming the new norm as the Earth heats up.
Worldwide, 2011 was the second wettest year on record over
land. (The record was set in 2010, which also tied 2005 as
the warmest overall.) Heavier deluges are expected on a
warmer planet; each temperature rise of 1 degree Celsius
increases the amount of moisture the atmosphere can hold
by about 7 percent. Higher temperatures also can fuel
stronger storms.
Brazil started the year with the deadliest natural
disaster in its history: in January, a month’s worth of
rain fell in a single day in Rio de Janeiro state, leading
to floods and landslides that killed at least 900 people.
That same month, flooding in eastern Australia covered an
area nearly the size of France and Germany combined.
Overall, it was the third wettest year in Australia since
recordkeeping began in 1900.
The most expensive weather disaster of 2011 was the
flooding in Thailand in the second half of the year, which
ultimately submerged one third of the country’s provinces.
At $45 billion worth of damage -- equal to 14 percent of
Thailand’s gross domestic product -- it was also the
costliest natural catastrophe the country ever
experienced.
In October, more than 100 people died as two storms -- one
from the Pacific and the other from the Caribbean --
pounded Central America with rain. In western El Salvador,
nearly 1.5 meters of rain (almost 5 feet) fell over 10
days. And in December, Tropical Storm Washi hit the
Philippines, creating flash floods that killed more than
1,200 people.
The 2011 Atlantic hurricane season had 19 named storms.
Hurricane Irene brought extreme flooding to the
northeastern United States in August, with total damages
topping $7.3 billion. The year was the wettest on the
books for seven states in the country, while it was among
the driest for several others. Although the extremes
appear to balance out, making for a near-average year, in
fact a record 58 percent of the contiguous United States
was either extremely wet or extremely dry in 2011.
Indeed, as is expected on a hotter planet, while some
parts of the globe were overwhelmed by rain in 2011,
others were distinguished by dryness. A severe drought in
the Horn of Africa that began in 2010 devolved into a
crisis situation in 2011, characterized by crop failure,
exorbitant food prices, and widespread malnutrition.
Exacerbated by chronic political instability and a belated
humanitarian response, the death toll may have exceeded
50,000 people.
Back in North America, a drought that began in late 2010
and worsened over 2011 led hundreds of farmers from
northern Mexico to march to that nation’s capital in
January 2012 to draw the government’s attention to their
suffering. Nearly 900,000 hectares of farmland (some 2.2
million acres) and 1.7 million head of livestock were lost
due to the dryness -- the worst in Mexico’s 70+ years of
data collecting.
Scorching heat, drought, and wildfires across the U.S.
Southern Plains and Southwest caused farm, ranch, and
forestry damages that exceeded $10 billion in 2011.
Wichita Falls, Texas, experienced 100 days over 100
degrees Fahrenheit -- far more than the previous record of
79 days set in 1980. Oklahoma and Texas had the hottest
summers of any states in history, breaking by a wide
margin the record set in 1934 during the Dust Bowl. James
Hansen, director of NASA’s Goddard Institute for Space
Studies, writes that the likelihood of such extreme heat
waves “was negligible prior to the recent rapid global
warming.” Texas also had its lowest rainfall on record.
Invigorated by the heat and drought, wildfires burned
across an estimated 1.5 million hectares (3.7 million
acres) in the state.
For the continental United States, summer 2011 was the
second warmest in history. Nearly three times more weather
stations hit record highs than lows in 2011, in line with
a trend of increasing heat extremes. Whereas in the middle
of the 20th century there were close to the same number of
record highs and lows -- as would be expected absent a
strong warming trend -- in the 1990s highs began outpacing
lows. In the first decade of this century, there were
twice as many record highs as record lows.
Worldwide, seven countries set all-time temperature highs
in 2011: Armenia, China, Iran, Iraq, Kuwait, Republic of
the Congo, and Zambia. Interestingly, Zambia also was the
only country to experience an all-time low temperature
when it dropped to -9 degrees Celsius (16 degrees
Fahrenheit) in June. Kuwait experienced the year's highest
temperature, with thermometers measuring a searing 53.3
degrees Celsius (127.9 degrees Fahrenheit), the highest
temperature ever recorded on Earth during the month of
August. Even more threatening to health than daytime highs
are extra hot nighttime minimum temperatures, which do not
allow any respite from the heat. The world’s hottest
24-hour minimum ever -- 41.7 degrees Celsius (107 degrees
Fahrenheit) -- was recorded in Oman in June 2011.
Even the Arctic had a notably warm year, with the 2011
temperature a record 2.2 degrees Celsius (4 degrees
Fahrenheit) above the mean for 1951–80. Barrow, Alaska,
the northernmost U.S. city, spent a record-breaking 86
consecutive days at or above freezing, far more than the
previous record of 68 days set in 2009.
In fact, over the last 50 years temperatures in the Arctic
have risen more than twice as fast as the global average,
melting ice and thawing permafrost. Arctic sea ice has
been shrinking more rapidly, falling to its lowest volume
and second lowest area on record during the 2011 summer
melt season. With the summertime ice loss outpacing
wintertime recovery, Arctic sea ice has thinned, making it
increasingly vulnerable to further melting. Scientists
expect a completely ice-free summertime Arctic by 2030 or
even earlier.
As the reflective ice disappears, it exposes the dark
ocean, which more readily absorbs solar energy, further
warming the region. This sets forth a climate cascade,
accelerating ice loss both in the ocean as well as on
nearby Greenland, which contains enough ice to raise
global sea level by 7 meters (23 feet) if it completely
melted. The warming also thaws Arctic permafrost,
releasing carbon dioxide and methane, further accelerating
global warming.
Even without fully incorporating such climate feedback,
models show that continued reliance on fossil fuels could
raise the global temperature by up to 7 degrees Celsius
(over 12 degrees Fahrenheit) by the end of this century.
Such an elevated temperature would amplify temperature and
precipitation extremes enough to make the weather events
of recent years look tame in comparison. Only a rapid,
dramatic reduction of greenhouse gas emissions can hold
future temperatures in a range bearing any resemblance to
what civilization has known.
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