Transcript Phys. 102: Introduction to Astronomy

SOAR 2007
Current Changes and
Future Climates
Predicting the Future
 Climate Systems
 Atmosphere – changes over hours
 Oceans – surface changes over weeks
– depths change over millennia
 Biosphere – changes annually to centuries
 Cryosphere – ice, glaciers permafrost, snow
– various change scales
 Geosphere – volcanos, continental drif
– long time scales, large changes
Modeling the Climate
 Systems & Feedbacks Among
 Radiation
 insolation (incoming sunlight varies)
 reflection, absorption, re-radiation by surface, air
 Water cycle
 evaporation, precipitation, runoff
 Land surface
 soil moisture, vegitation, topography, snow & ice
 Ocean
 surface currents, deep currents, chemistry (salinity)
 Sea Ice
 strongly affected by feedbacks
Feedbacks
 Positive
 Any change leads to further change
 eg. Ball on a hill
 Negative
 System always returns to equilibrium
 eg. Ball in a bowl
 Neutral
 System stays in new state
 eg. Ball on a plain
Feedbacks
 Greenhouse Effect: Warming
 Good … makes Earth inhabitable!!
 Ground absorbs sunlight
Ground heats (parking lots in summer)
Ground radiates heat (Infrared, IR)
Atmosphere absorbs (some) IR
Atmosphere heats
 Feedbaack Mechanisms
 Evaporation
 Plant growth
 Ice-Albedo effect
Feedbacks
 Feedback Mechanism: Evaporation
 H2O vapor absorbs more IR
 warming increases?
Clouds shade surface, cool it, warming stops?
 warming decreases?
 Feedback Mechanism: Plant Growth
 More CO2 increases plant growth
 More plant growth is good!!
 Plants absorb CO2 (Keeling curve annual cycles
 CO2 is Reduced
Feedbacks
 Feedback Mechanism: Ice Albedo Effect
 Warming melts glaciers, sea ice
 Ground warms more than snow/ice
Ground warms, radiates more IR
Atmosphere warms
More ice melts
 warming increases
 Cooling increasing glaciers
More sunlight reflected
Ground Cools
 cooling increases
Feedbacks
 Feedback Mechanism: Ice Albedo Effect
 Warming melts glaciers, sea ice
 Ground warms more than snow/ice
Ground warms, radiates more IR
Atmosphere warms
More ice melts
 warming increases
 Cooling increasing glaciers
More sunlight reflected
Ground Cools
 cooling increases
IPCC
 Intergovernmental Panel on Climate Change
 Established in 1988
 World Meteorological Org. (WMO)
 UN Environment Programme (UNEP)
 Mandate
“The role of the IPCC is to assess on a
comprehensive, objective, open and transparent
basis the scientific, technical and socioeconomic information relevant to understanding
the scientific basis of risk of human-induced
climate change, its potential impacts and
options for adaptation and mitigation.”
http://www.ipcc.ch/about/about.htm
IPCC
 Intergovernmental Panel on Climate Change
“The IPCC does not carry out research nor does
it monitor climate related data or other relevant
parameters. It bases its assessment mainly on
peer reviewed and published
scientific/technical literature. Its role,
organisation, participation and general
procedures are laid down in the ‘Principles
Governing IPCC Work’“
http://www.ipcc.ch/about/about.htm
IPCC
 Working Groups
 I: Science
 knowns, unknowns & projections
 II: Impact and Adaption
 vulnerability: natural and human
 consequences: + and –
 III: Mitigation
 options for changing human
behavior and impact
 Task Force on National
Greenhouse Gas Inventories
IPCC
 Intergovenmental Panel on Climate Change
 View of the bulk of the scientific community
 Computer models estimate feedbacks
 Reports every 5 years
 2007 report available in print & electronic
 3rd Assessment report gave “Hockey Stick”
IPCC
 4th Assessment
 Released 2007
 WGI = 701 pages!
 available on line
ipcc-wg1.ucar.edu/wg1
 available in print
Cambridge U. Press
IPCC
 4th Assessment
 Released 2007
 WGI = 701 pages!
 available on line
ipcc-wg1.ucar.edu/wg1
 available in print
Cambridge U. Press
Assessment Report Four (ARF)
 Findings of Working Group I
 Summary for Policymakers (18 pages)
 Human & Natural Drivers of Climate Change
 Direct Observations of Recent Climate Change
 A Paleoclimatic Perspective
 Understanding and Attributing Climate Change
 Projections of Future Changes in Climate
Assessment Report Four (ARF)
 Findings of Working Group I
 Technical Summary (66 pages)
 Chamges in Human & Natural Drivers of Climate
 Observations of Changes in Climate
 Understanding and Attributing Climate Change
 Projections of Future Changes in Climate
 Robust Findings and Key Uncertainties
Union of Concerned Scientitsts
 Confronting Climate Change in the U.S.
Northeast: Science, Impacts and Solutions
http://www.ucsusa.org/global_warming/
IPCC ARF WGI
 Radiative Forcing
 “The change in net (down minus up) irradiance
(solar plus longwave; in W/m2) at the tropopause
after allowing for stratospheric temperatures to
readjust to radiative equilibrium, but with
surface and tropospheric temperatures and
state held fixed at the unperturbed values”
RF = net flux imbalance at tropopause
Atmospheric
Structure
 Layers (from surface)
 Troposphere –
sphere of weather
 Stratosphere –
sphere of ozone (O3)
 Mesosphere
 Ionosphere –
sphere of ions
RF = net flux
imbalance at
tropopause
IPCC ARF WGI
 Components of Climate Change
Accounts for natural processes
eg. Changes
in
evaporation
eg. Melting
permafrost
releasing
methane
IPCC ARF WGI
 Radiative Forcing 1750 - 2005
Carbon
Dioxide
Methane
“Ozone Layer”
absorbs UV, reduces
RF at tropopause
Buildings increase
surface albedo
relative to forests
Aerosols (particles)
reflect sunlight AND
increase cloud cover
(eg. Contrails)
Solar radiation has
increased since 1750
(Little Ice Age end)
IPCC Climate Drivers
 Greenhouse Gases: CO2, CH4, H2O, NOx
Grey Bars
= Natural
Variability
Combined
rate of
change
IPCC Climate Drivers
 Greenhouse Gases: CO2, CH4, H2O, NOx
Grey Bars
= Natural
Variability
Combined
rate of
change
IPCC Changes Since 1850
 Global Average
Temperature
 Global Average
Sea Level
 mostly thermal
expansion
 Northern
Hemisphere
Snow Cover
UCC Northeast US
 Climate of New York State
UCC Northeast US
100-yr
Flood
becoming
10-yr
Flood
UCC Northeast US
Snow cover decreasing
Combined
rate of
change
IPCC ARF
 Continued Warming
What we’re committed
to by past behavior!
IPCC ARF
 Effects of Changing Mean
Does not
mean it
never gets
cold!
IPCC ARF
 Location of Changes
Uncertainties
IPCC ARF
 Location of Changes
The Skeptics
 Important voices!
 Skeptics keep science honest
 Agreements
 CO2 in atmosphere is increasing
 CO2 levels correlate with temperature
 Arguments
 Climate is driven exclusively by insolation
 Milankovitch Cycles
 Sunspot Cycles
 Too expensive to reduce CO2: Adapt
 Global warming is good!
The Skeptics
 Journal of American Physicians & Surgeons 2007
 Mailed to all SLU Physics Professors Tuesday!!
The Skeptics
 Claims all warming due to solar activity
Scale minimizes
hydrocarbon use,
leaves out first
century.
The Skeptics
 Claims all warming due to solar activity
Scale minimizes
hydrocarbon use,
leaves out first
century.
What to Do?
 Complex system hard to model
 Experts don’t agree
 Could be global disaster
Ignore it?
Adapt?
Mitigate it? Kyoto + ?