Changing
Earth’s
Climate
1
`The balance of evidence
suggests that there is a
discernible human
influence on global
climate '
Intergovernmental Panel on Climate Change (United
Nations), Second Assessment Report, 1996
`There is new and stronger
evidence that most of the
warming observed over
the last 50 years is
attributable to human
activity'
Intergovernmental Panel on Climate Change (United
Nations), Third Assessment Report, 2001
`Most of the observed increase
in globally averaged
th
temperatures since the mid-20
century is very likely due to the
observed increase in
greenhouse gas concentrations.'
Intergovernmental Panel on Climate Change (United
Nations), Fourth Assessment Report, 2007
`Warming of the climate system is
unequivocal, as is now evident
from observations of increases in
global average air and ocean
temperatures, widespread melting
of snow and ice, and rising global
mean sea level.'
Intergovernmental Panel on Climate Change (United
Nations), Fourth Assessment Report, 2007
Greenhouse Gasses
• Sunlight heats up
Earth’s surface
• Earth radiates heat back
into the air
• Greenhouse gasses
absorb this heat and
don’t let Earth’s heat out
Increased Greenhouse Gases
Earth’s “cooling” system is “clogged”
Evidence from the Earth
Observations of recent climate change
Global mean
temperature
Global average
sea level
Northern
hemisphere
snow cover
9
Global Instrumental Temperature Record
10 warmest years
10
390
Carbon Dioxide Concentration (ppmv)
380
Carbon Dioxide Concentration
370
360
350
340
330
320
310
1960
1970
1980
1990
2000
2007
Reconstructing past climates
How we get data from the past
Deep ocean cores
Tree rings
Historical documents
Coral cores
Ice cores
–
–
–
–
–
12
Reconstructed Surface Temperatures
Past CO2 concentrations
Carbon Dioxide Concentration (ppmv)
380
370
360
350
340
Mauna Loa, Hawaii (1958 - present)
330
Siple Station (1750 - )
320
310
300
290
280
270
1750
1800
1850
1900
1950
2000
CO2 concentration
after 50 years of
unrestricted fossil
fuel burning (600
ppmv)
Present CO2
concentration
(383 ppmv)
270
240
210
180
Temp.
Proxy
CO2 (ppmv)
300
800
600
400
200
Thousands of Years Before Present
Petit et al., 1999; Siegenthaler et al., 2005; EPICA Community members, 2004
0
Signs that global warming is underway
•
•
•
•
•
•
•
Sea level rising
• by thermal expansion AND ice melt
Sea ice melting (Arctic and Antarctic)
Glaciers melting worldwide
Arctic and Antarctic Peninsula heating up fastest
Melting on ice sheets is accelerating
More severe weather (droughts, floods, storms,
heat waves, hard freezes, etc.)
Bottom line:
• These changes do not fit the natural patterns unless we
add the effects of increased Greenhouse gasses
Some climate change facts
• Earth is 1°F warmer than 100
years ago
• Not equally distributed
– Some areas have warmed 11°F
• Weather becoming more
variable and more severe
Scientists have no doubt
18
Glaciers fluctuate with climate
18,000 years ago
Present
Glacier ice
Sea ice
Predicted changes of human climate change
•
•
For over 30 years, scientists have predicted
increased greenhouse gasses will cause
unnatural changes
By 2000 we have seen:
 Antarctic sea ice break-ups
 Antarctic Peninsula warming
 Arctic sea ice melting
 Faster Arctic warming (11°F!)
 Melting of small glaciers and ice caps
 Sea level rise
Antarctic Sea Ice Break-ups
21
Antarctic Sea Ice Melting
22
23
Arctic Sea Ice Melting
24
Ice Extent Anomaly (106 km2)
Arctic sea ice extent
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
1980
1985
1990
1995
2000
2005
25
Melting of small glaciers and ice caps
2004
1941
26
Carroll Glacier
1906
2004
27
McCarty Glacier, Alaska
28
Muir and Riggs Glaciers
29
1993
2000
Kilimanjaro
1970
2005
31
Qori Kalis
1978
2002
32
Patagonia
1928
2004
33
Who cares about glaciers?
•
•
•
•
~80% of world’s water supply
Rapidly retreating worldwide
Glaciers and ice caps gone by 2100 or sooner
Major ice sheets also retreating
1941
2004
Sea-level rising
• Thermal expansion (warmer water
expands and needs more space)
• Addition of water from melting ice
• Melting ice sheets
– Greenland: 7.4 m (25’) potential
– Antarctica: 74 m (250’) potential
Greenland satellite melt record
1992
2005
36
This is how much ice
melted in just one
year.
1 year of melt!
R. Huff, J. Box, S. Starkweather, T. Albert
Sea Level Rise
• Areas in red
will be
under water
if all
Greenland
melts.
38
Earth if Antarctica melts
39
Sea-level rise
Additional consequences
•
•
•
•
•
Fastest extinction rate of life on Earth in 65
Million years (1000x normal rate)
Increased disease (e.g. asthma, malaria)
Increased poverty and hunger
Sea level rise
More extreme weather
–
–
–
–
Droughts
Flooding
Heat-waves
Storms