Transcript fundamentals of global climate change

LEARNING FROM GLOBAL
DISASTER LABORATORIES
PART 11A: FUNDAMENTALS OF
GLOBAL CLIMATE CHANGE
Walter Hays, Global Alliance for
Disaster Reduction, Vienna,
Virginia, USA
FUNDAMENTALS OF
GLOBAL CLIMATE CHANGE
WHAT DO WE NOT KNOW FOR
CERTAIN?
COULD human activities exacerbate
the “unnatural” Greenhouse effect by
increasing certain greenhouse gases
(e.g., CO2) above normal (i.e., safe)
levels; if so, can we do anything to
slow or reverse the undesirable trend?
THE ISSUE: HUMAN INFLUENCES
 Are humans exacerbating GLOBAL
WARMING by adding
too much carbon
dioxide to the normal
levels of greenhouse
gases in the
atmosphere through
rapidly increasing
global use of fossil
fuels.
HUMAN INFLUENCES
 Aerosols, smoke and
sulfates reflect
sunlight away from the
Earth, which outweigh
the temporary,
localized cooling
effects from aerosols
and the smoke and
sulfates from industry.
HUMAN INFLUENCES ON LAND
SURFACES
 Once tropical forests
(a carbon sink) are
cleared for cattle
ranching or community
development, the
cleared land can
becomes a major
source of methane, a
greenhouse gas.
FUNDAMENTALS OF
GLOBAL CLIMATE CHANGE
WHAT DO WE THINK WE
KNOW FOR CERTAIN?
THE EARTH’S GREENHOUSE EFFECT
OCCURS NATURALLY.
PLANET EARTH (THE BLUE PLANET)
AND THE SOLAR INPUT
PHYSICAL INTERACTIONS OCCUR
ON MANY DIFFERENT SCALES
• Propagation, reflection, and
refraction of light and EM
waves radiated from the sun
(i.e., the solar input to Planet
Earth)
ABOUT 33 PERCENT OF THE
INCOMING SOLAR INPUT IS
REFLECTED BACK TO SPACE
BY CLOUDS, SNOW, ICE,
AND, TO A LESSER DEGREE,
BY LAND AND WATER
SURFACES.
THE BALANCE (ABOUT 70
PERCENT) OF THE INCOMING
SOLAR INPUT IS ABSORBED
BY LAND, AIR, WATER, AND
ICE.
THE SOLAR SPECTRUM
INCLUDES: A) VISIBLE LIGHT
(ROYGBIV), ALONG WITH:
B) ULTRAVIOLET LIGHT
(SHORTER WAVE LENGTHS),
AND C) INFRARED LIGHT
(LONGER WAVE LENGTHS).
PHYSICAL INTERACTIONS OCCUR
ON MANY DIFFERENT SCALES
• Absorption, storage, and reradiation of light and EM waves
causes the “natural” greenhouse
effect).
THE GREENHOUSE EFFECT
OCCURS WHEN AN EARTH
WARMED BY THE SOLAR
SPECTRUM RADIATES
INVISIBLE INFRARED LIGHT
BACK, BUT…
CONTINUED
…INSTEAD OF GOING BACK
TO SPACE, IT IS PARTLY
ABSORBED BY
GREENHOUSE GASES IN THE
ATMOSPHERE
 NOTE: ABSORPTION MAKES
THE ATMOSPHERE WARMER.
GREENHOUSE GASES IN THE
ATMOSPHERE
 “Greenhouse"
gases include
water vapor,
carbon dioxide,
methane and
nitrous oxide.
WATER VAPOR
Water vapor is
the most potent
greenhouse gas
 Higher air
temperatures
increase the rate
of water
vaporization.
VOLCANIC ERUPTIONS
Volcanic
eruptions
add water
vapor and
ash to the
atmosphere.
PHYSICAL INTERACTIONS OCCUR
ON MANY DIFFERENT SCALES
• Absorption of heat by
greenhouse gases in the
atmosphere causes the
“unnatural” greenhouse
effect).
“UNNATURAL”GREENHOUSE
EFFECT
 Greenhouse gases
trap heat inside the
atmosphere.
 Too much trapped
heat increases
temperatures in the
atmosphere and on
the land and ocean
surfaces, which
causes climate
change.
WHAT DOES IT ALL MEAN?
• THE “NATURAL” GREENHOUSE
EFFECT KEEPS THE EARTH WARM AT
ABOUT 57.9 DEGREES F, AND
• THE “UNNATURAL”GREENHOUSE
EFFECT CAUSES THE ATMOSPHERE’S
TEMPERATURE TO RISE, FOLLOWED
BY A RISE IN LAND AND OCEAN
TEMPERATURES, CAUSING CLIMATE
CHANGE ON A GLOBAL SCALE
SATELLITE MEASUREMENTS
INDICATE THAT THE TROPOSPHERE IS WARMING FASTER
THAN THE EARTH’S SURFACE.
 NOTE: THIS INDICATES THAT
GREENHOUSE GASES IN THE
ATMOSPHERE ARE ABSORBING
TOO MUCH HEAT.
2005 - HOTTEST YEAR ON RECORD
• According to NASA and other
organizations, 2005 was the
hottest year on record for the
Northern Hemisphere.
• Temperatures were about 1.4
degrees Fahrenheit above the
historical average.
A WARMING EARTH: SEPT 25, 2007
THE AVERAGE GLOBAL
TEMPERATURE HAS RISEN 1.7
DEGREES F IN PAST 150 YEARS
AVERAGE GLOBAL SEA
LEVEL HAS INCREASED BY
4.7 INCHES SINCE THE
LAST ICE AGE.
SEA LEVEL RISES FOR TWO
REASONS:
 WATER EXPANDS WHEN IT
IS WARMED, AND
 WATER VOLUME
INCREASES AS MELT
WATER IS ADDED.
•
•
IF THE FLOATING ARCTIC ICE
CAPS MELT, GLOBAL SEA
LEVEL WILL NOT BE AFFECTED.
IF ALL THE SNOW AND ICE IN
GREENLAND MELTED, GLOBAL
SEA LEVEL WILL RISE 24 FEET.
CLOUDS CAUSE BOTH
COOLING AND WARMING
 Clouds cool Earth by
reflecting incoming
solar energy.
 Clouds cool Earth by
slowing evaporation.
 Clouds warm Earth by
trapping heat being reradiated upward from
the Earth’s surface.
LAND SURFACES AFFECT
TEMPERATURES AND MOISTURE
Mountain ranges
can block clouds,
creating "dry"
shadows
downwind.
 Sloping land
facilitates water
runoff, leaving
the land and air
drier.
ROLE OF ICE AND SNOW
Ice and snow
reflects heat
outward into space,
cooling Planet Earth
in the process.
When ice melts,
ocean water looses
some of its stored
heat.
THE OCEANS ARE A
NATURAL CARBON SINK
The oceans and
marine life
remove and/or
consume huge
amounts of
carbon dioxide.
THE OCEANS STORE HEAT
BETTER THAN LAND DOES
Oceans, the source
of moisture in the
air, store heat more
effectively over the
long term than land
and transports it
efficiently over
distances of
thousands of miles.
THE ALBEDO (PERCENT OF
LIGHT REFLECTED) FOR
FRESH SNOW IS 80-90
PERCENT,
 BUT IT IS ONLY 50 – 60
PERCENT FOR MELTING ICE.
CARBON DIOXIDE ENTERS
THE ATMOSPHERE
NATURALLY, AND IT LEAVES
THE ATMOSPHERE
NATURALLY.
•
AS THE GREENHOUSE
EFFECT INCREASES,
TEMPERATURES IN THE
ATMOSPHERE INCREASES
AND THE REMOVAL RATE OF
CARBON DIOXIDE
DECREASES.
SUMMARY
•
WITHOUT THE “NATURAL”
GREENHOUSE EFFECT,
PLANET EARTH WOULD BE
MUCH COLDER; E.G., A
TEMPERATURE OF ABOUT
MINUS 2 DEGREES F.
•
IF THE “UNNATURAL”
GREENHOUSE EFFECT
WERE TO GET OUT OF
CONTROL, PLANET EARTH
WOULD BE WARMER THAN
THE CURRENT AVERAGE
TEMPERATURE OF 57.9
DEGREES F.
THE WORLD IS DEBATING THE
TIPPING SCENARIO ISSUE
• The “Tipping Scenario Issue”
is: “Within a few decades, will
humans be virtually helpless
to slow the perceived risks
associated with global
climate change?