Transcript What is Climate? Temperature near the surface of Earth: • Seattle Annual Mean: 52˚F, 11˚C • Global Annual Mean: 57˚F, 14˚C Precipitation of water: •

What is Climate?
Temperature near the surface of Earth:
• Seattle Annual Mean: 52˚F, 11˚C
• Global Annual Mean: 57˚F, 14˚C
Precipitation of water:
• Seattle Annual Sum: 37 inches
• Global Annual Sum: 39 inches
Washington State Annual Precipitation
Western Regional
Climate Center
Annual Variation of Climate: The Annual Cycle
Temperature
Precipitation
Temperature Extremes
Maximum
100˚F July 1994
Mean
1949-2000
Minimum
0˚F Jan. 1950
1948-2000
“The Instrumental Record”
?
2001 Value = 371
0.45% per year
increase recently
35% increase
Since Industrial
Revolution
Pre-industrial Value = 275
Greenland Ice Core
Mauna Loa
•
Vostok
3,623 meters of Ice Core
~2 Miles of Ice Core
~400,000 years of Earth History
USGS
Data from Petit,et al. (1999), and GISS (2003)
Previous
Warm
Periods
2000
Previous
1990
Glacial
1980
Periods
1970
1960
1750
Vostok, Antarctica Ice Core
What is causing the CO2 increase in the Atmosphere?
A: Fossil Fuel Burning: Coal, Oil and Natural Gas.
How do we know that?
A1: Circumstantial Evidence of timing of
increase with rise of fossil fuel use.
A2: Smoking gun evidence of isotopic studies.
The Carbon 14 Evidence
• Carbon 14 is produced in the atmosphere
by cosmic rays.
• 14C is incorporated into CO2 and taken up
in plants during photosynthesis
• Dead plant matter is used to make Fossil Fuels
• 14C is radioactive and decays with a half life of
~5,700 years
Since the plant matter in fossil carbon fuels is
millions of years old, it contains no 14C.
The Carbon 14 Evidence
14C
is decreasing with time in the atmosphere
at about the right rate to be explained by
fossil fuel burning.
This is strong evidence that the new carbon
in the atmosphere in the form of CO2
is coming from fossil fuel burning.
The Carbon Budget
PgC/yr in 1990’s
Emissions (fossil fuel, cement)
6.3 ± 0.4
Atmospheric Increase
3.2 ± 0.1
Ocean uptake
1.7 ± 0.5
Land uptake
1.4 ± 0.7
In the 1990’s about half of the CO2 produced by
human activities stayed in the atmosphere
and the other half was stored in the ocean and land.
Energy Flow in the Climate System
Morocco
Saharan Dust
over the
Eastern Atlantic
Ocean
Stratocumulus
Canary Islands
Saharan Dust
NASA Image
from MODIS
Cape Verde Islands Senegal
Clean Air
Fires in Oregon
Ship
Tracks
Marine
Stratocumulus Clouds
Smoke from Fires
NASA MODIS Image July 29, 2002
Forcing Climate Change
Change between 1750 and present
Greenhouse Gases
(CO2, CH4, CFC, N2O)
+2.4 ± 0.2 Wm-2
Direct Aerosol Forcing
-1.0 ± 1.0 Wm-2
The forcing of climate change by humans is
Uncertain primarily because of the aerosol portion.
Relaxation Time Scales
Carbon Dioxide: A couple hundred years.
Aerosols:
A couple weeks.
Eventually the warming effect of CO2
and other greenhouse gases will
overwhelm the cooling effect of aerosols.
Climate Sensitivity
Classic Climate Sensitivity Question:
If we doubled the atmospheric CO2, and then waited
for the climate to come into a new equilibrium,
by how much would
the global mean surface temperature increase?
Answer:
1.5˚C to 4.5˚C or 3˚F to 8˚F
Uncertain to a factor of 3! Why?
Natural Feedbacks within the Climate System
Water Vapor Feedback
Increase CO2
+3CIncrease
~ +20% H2O
Temperature
Increase
Water Vapor
Water Vapor
Feedback Loop
Water Vapor Feedback Approximately Doubles
the Sensitivity of Climate ~1 to 2 ˚C warming
Greenhouse Effect = Surface Emission - Outgoing Energy
155 Wm-2
=
390 Wm-2
- 235 Wm-2
Natural Feedbacks within the Climate System
Ice-Albedo Feedback
Increase
Temperature
Melt Surface
Ice
Increase Solar
Absorption
Ice-Albedo
Feedback Loop
Ice-Albedo Feedback increases
the Sensitivity of Climate by 30% or so
Natural Feedbacks within the Climate System
Cloud Feedback
Increase
Temperature
Change Cloud
Properties
Change Earth’s
Energy Balance
Cloud
Feedback Loop
?
Magnitude potentially large,
but neither sign nor magnitude known.
Cloud Effects on Earth’s Energy Budget
1. Clouds reflect solar radiation - a cooling effect
2. Clouds emit less energy to space than clear skies
• Opaque to infrared radiation
• Colder than surface because air temperature
decreases with altitude.
GMS-5
IR image
20˚C
0˚C
-70˚C
NASA Shuttle Photo
Earth Energy Emission
150
200
250
300
Cloud Effects on the Global Energy Balance
Clouds double the Earth’s albedo from 15% to 30%
This results in a net loss of energy of 50 Wm-2
But cloud reduce emitted infrared radiation by 30 Wm-2
The net result of today’s clouds on the energy balance
is thus a loss of 20 Wm-2
Doubling CO2 changes the energy balance by +4 Wm-2
Cloud Forcing of the Energy Balance
• Cover a significant fraction of the Earth’s Surface
• Have a large effect on Earth’s Energy Budget
-70
-30
0
+30 Wm-2
Marine Boundary Layer Clouds
• Cover a significant fraction of the Earth’s Surface
0
20
40
60
80%
Marine
Stratocumulus
Reduce Energy
Budget of Earth
Reflect Solar
Radiation
Low, Warm,
emit like surface
Marine Boundary Layer Clouds
• Cover a significant fraction of the Earth’s Surface
• Have a large effect on Earth’s Energy Budget
• Are Potentially sensitive to both direct human
influences and to climate change.
• Contribute to uncertainty about how climate will
change in the future.
Angola
Namibia
How will the Climate Change in the future?
Best Available Data and Climate models
Intergovernmental Panel on Climate Change
IPCC
Intergovernmental Panel on Climate Change
Uncertain Forcing
Uncertain Feedbacks
5˚F
Intergovernmental Panel on Climate Change
15 Inches
What would a 5˚F warming mean?
What would a 5˚F warming mean?
+5˚F ~ +20% vapor
pressure
+20% precip?
What would a 5˚F warming mean?
Snowline up about 1000 Feet
Stevens Pass
4061 ft
Snoqualmie Pass 3022 ft
NASA MODIS Image July 20, 2002
NASA MODIS False Color Image July 20, 2002
Washington State in 2100
Warmer by 5˚F (more in winter, less in summer)
More rainfall, less snow pack
Longer, more severe summer drought
Challenges for local salmon runs
and local fresh water supplies
Probable Climate changes after 2050
Intergovernmental Panel on Climate Change, 2001
Cosmic Ray
Hits Nitrogen
in Air, frees
Neutron
Radiocarbon and Fossil Fuel
Neutron Hits Nitrogen
Radiocarbon
incorporated
into CO2
Molecule
CO2 taken up
by plant in Photosynthesis
to form hydrocarbon
with atmospheric ratio
of radiocarbon
Collision
Yields 14C or
Radiocarbon
Accumulation of plant
material in sediment
begins formation
process of fossil
carbon fuel
Downward trend in
radiocarbon is measured
and used to confirm
source of CO2 increase
in Atmosphere
Accumulated Plant
material slowly loses
radiocarbon by radioactive
decay, while forming coal,
oil and natural gas.
Atmospheric ratio
of radiocarbon declines
because of fossil-fuel
produced CO2, which has
no radiocarbon.
Fossil carbon fuel
is mined and combusted,
producing CO2 with
zero radiocarbon.
Credits
University of Wa shington
Department of Atmospheric Sciences
National Science Founda tion
Climate Dynamics Program
National Aeronautics and Space Administration
Earth Science Enterprise
Johnson Space Center
Goddard Space Flight C enter
MODIS Land Rapid Response Team
National Oceanographi c and Atmospheric Administration
Paleoclimatology Progr am
Office of Global Programs
Desert Research Institute
Western Region al Climate Center
US Geological Survey
Intergove rnmental Pan el on Climate Change
Photo and Image Credits
Tad Anderson
John T. Andrews
Kim Comstock
Jacques Descloitres
Kay Dewar
Grace Candace Gudmund son
Dennis L. Hartmann
Marc Michelsen
SHEBA Aerial Photography Project
Todd Sowers