Transcript Brief Overview of Climate Change

Climate Change
Brett Weimer
INTB-3000
July 20, 2011
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What is Climate Change?
 Climate change refers to any significant change
in measures of climate (such as temperature,
precipitation, or wind) lasting for an extended
period (decades or longer).
Climate change may result from:
 natural factors, such as changes in the sun's
intensity or slow changes in the Earth's orbit
around the sun;
 natural processes within the climate system
(e.g. changes in ocean circulation);
 human activities that change the atmosphere's
composition (e.g. deforestation, reforestation,
urbanization, desertification, etc.).
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http://www.epa.gov/climatechange/basicinfo.html#science
7/20/2011
History
The Earth's climate has changed many times during the planet's history,
with events ranging from ice ages to long periods of warmth. Historically,
natural factors such as volcanic eruptions, changes in the Earth's orbit,
and the amount of energy released from the Sun have affected the
Earth's climate. Beginning late in the 18th century, human activities
associated with the Industrial Revolution also began to contribute to
changes in the composition of the Earth’s atmosphere and influencing its
climate.
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Brett Weimer – Climate Change
http://www.epa.gov/climatechange/basicinfo.html#science
7/20/2011
http://climate.nasa.gov/evidence/
Primary Causes
For over the past 200 years, the burning of fossil fuels, such as coal and oil, and
deforestation have caused the concentrations of heat-trapping "greenhouse gases" to
increase significantly in our atmosphere. These gases prevent heat from escaping to space,
somewhat like the glass panels of a greenhouse.
Greenhouse gases are necessary to live as we know it, because they keep the planet's
surface warmer than it otherwise would be. But, as the concentrations of these gases
continue to increase in the atmosphere, the Earth's temperature is climbing above past
levels. According to NOAA and NASA data, the Earth's average surface temperature has
increased by about 1.2 to 1.4ºF in the last 100 years. The eight warmest years on record
(since 1850) have all occurred since 1998, with the warmest year being 2005. Most of the
warming in recent decades is very likely the result of human activities. Other aspects of the
climate are also changing such as rainfall patterns, snow and ice cover, and sea level.
If greenhouse gases continue to increase, climate models predict that the average
temperature at the Earth's surface could increase from 3.2 to 7.2ºF above 1990 levels by
the end of this century. Most climate scientists agree that human activities are changing the
composition of the atmosphere, and that increasing the concentration of greenhouse gases
will change the planet's climate. But they are not sure by how much it will change, at what
rate it will change, or what the exact effects will be.
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Brett Weimer – Climate Change
http://www.epa.gov/climatechange/basicinfo.html#science
7/20/2011
The Greenhouse Effect
A layer of greenhouse
gases – primarily water
vapor, and including
much smaller amounts
of carbon dioxide,
methane and nitrous
oxide – act as a
thermal blanket for the
Earth, absorbing heat
and warming the
surface to a lifesupporting average of
59 degrees Fahrenheit
(15 degrees Celsius).
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http://climate.nasa.gov/causes/
Evidence
Sea level rise
Global sea level rose about 17 centimeters (6.7
inches) in the last century. The rate in the last
decade, however, is nearly double that of the
last century.
Republic of Maldives: Vulnerable to sea level rise.
Global temperature rise
All three major global surface temperature
reconstructions show that Earth has warmed since
1880. Most of this warming has occurred since the
1970s, with the 20 warmest years having occurred
since 1981 and with all 10 of the warmest years
occurring in the past 12 years. Even though the
2000s witnessed a solar output decline resulting in
an unusually deep solar minimum in 2007-2009,
surface temperatures continue to increase.
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Brett Weimer – Climate Change
http://climate.nasa.gov/evidence/
7/20/2011
Evidence (cont.)
Warming oceans
The oceans have absorbed much of this
increased heat, with the top 700 meters (about
2,300 feet) of ocean showing warming of 0.302
degrees Fahrenheit since 1969.
Shrinking ice sheets
The Greenland and Antarctic ice sheets have
decreased in mass. Data from NASA's Gravity
Recovery and Climate Experiment show
Greenland lost 150 to 250 cubic kilometers (36
to 60 cubic miles) of ice per year between 2002
and 2006, while Antarctica lost about 152 cubic
kilometers (36 cubic miles) of ice between 2002
and 2005.
Flowing meltwater from the Greenland ice sheet.
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Brett Weimer – Climate Change
http://climate.nasa.gov/evidence
7/20/2011
Evidence (cont.)
Declining Arctic sea ice
Both the extent and thickness of Arctic sea ice
has declined rapidly over the last several
decades.
Visualization of the 2007 Arctic sea ice minimum.
Glacial retreat
Glaciers are retreating almost everywhere
around the world — including in the Alps,
Himalayas, Andes, Rockies, Alaska and Africa.
The disappearing snowcap of Mount Kilimanjaro, from
space.
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Brett Weimer – Climate Change
http://climate.nasa.gov/evidence
7/20/2011
Evidence (cont.)
Extreme events
The number of record high temperature events
in the United States has been increasing, while
the number of record low temperature events
has been decreasing, since 1950. The U.S. has
also witnessed increasing numbers of intense
rainfall events.
Ocean acidification
Since the beginning of the Industrial Revolution,
the acidity of surface ocean waters has
increased by about 30 percent. This increase is
the result of humans emitting more carbon
dioxide into the atmosphere and hence more
being absorbed into the oceans. The amount of
carbon dioxide absorbed by the upper layer of
the oceans is increasing by about 2 billion tons
per year.
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Brett Weimer – Climate Change
http://climate.nasa.gov/evidence
7/20/2011
Forecasted Effects
Regional impacts of global change forecast by the IPCC (Intergovernmental Panel on Climate Change):
 North America: Decreasing snowpack in the western mountains; 5-20 percent increase in yields of rainfed agriculture in some regions; increased frequency, intensity and duration of heat waves in cities that
currently experience them.
 Latin America: Gradual replacement of tropical forest by savannah in eastern Amazonia; risk of
significant biodiversity loss through species extinction in many tropical areas; significant changes in water
availability for human consumption, agriculture and energy generation.
 Europe: Increased risk of inland flash floods; more frequent coastal flooding and increased erosion from
storms and sea level rise; glacial retreat in mountainous areas; reduced snow cover and winter tourism;
extensive species losses; reductions of crop productivity in southern Europe.
 Africa: By 2020, between 75 and 250 million people are projected to be exposed to increased water
stress; yields from rain-fed agriculture could be reduced by up to 50 percent in some regions by 2020;
agricultural production, including access to food, may be severely compromised.
 Asia: Freshwater availability projected to decrease in Central, South, East and Southeast Asia by the
2050s; coastal areas will be at risk due to increased flooding; death rate from disease associated with
floods and droughts expected to rise in some regions.
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Brett Weimer – Climate Change
"Taken as a whole," the IPCC states, "the range of
published evidence indicates that the net damage costs
of climate change are likely to be significant and to
increase over time."
http://climate.nasa.gov/effects/
7/20/2011