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Transcript
Teaching Climate Change
EPO Special Interest Group
Aileen O’Donoghue
Priest Associate Professor of Physics
St. Lawrence University, Canton, NY
Emphases for the Public
 Earth Will Be FINE!
 it’s been much hotter and much colder
 the 6.8 billion people won’t be fine
 nor will the polar bears, pikas, and other megafauna
 What we know: Data & Theories
 Not NEW!
 “amplified warming” since 1850 (John Tyndall)
 Data carefully collected & analyzed for decades
 requires careful study
 understanding before dismissal!
 How we know it: Process of science
 peer review: trying to insure honesty, not orthodoxy
What do we know
 Past climates
 how do we know of past climates?
 Variations in climate
 how does climate vary naturally?
 Predicting the future
 how do we model inputs & feedbacks?
 IPCC
 UCC
 Skeptics
Past Climate Records
 Instrumental
 18th – 21st centuries with increasing accuracy
 Best in Europe, N. America, Australia
 Very little data over oceans, 70% of surface
 Keeling Curve: 1957 - present
 CO2 in air over Mauna Loa, Hawaii
Northern Winter: CO2
builds up from decay.
Northern Summer:
Plants absorb CO2
Past Climate Records
 Proxy (indirect natural) Records
 Tree rings
 Temperature, precipitation, fire, insects, etc.
 Depends on area, species level of stress
 best near stress limit
 Back to ~1000 years (bristlecone pine in CA)
 plus overlapping with structures
Past Climates
 Proxy (indirect natural) Records
 Palynology (pollen) from sediments
shrub
 Accumulated in peat bogs & lakes
 Must be independently dated (cross-matched or 12C)
 Local influences complicate records
 eg. Fire, flood, etc.
 Types of pollen vary in uniqueness
 eg. Pine pollen everywhere … even ice caps!
birch
sedge
spruce
oak
Pine
Past Climates
 Vostok, Antarctica & Greenland Ice Cores
Greenland Ice Core
Summers indicated by
arrows.
Past Climates
 Vostok, Antarctica & Greenland Ice Cores
 Show annual* variations of atmosphere
 Bubbles of air contain old atmosphere
 Variations in CO2, CH4 Give
Comparisons to today,
Correlations with temperature
 Ice crystals vary in composition
 Different Isotopes of Oxygen, Hydrogen, etc.
 Dust
 Volcanos, Impacts, Winds, Organic Matter
*Where annual layers unclear, chronology is reconstructed from other annual variables
Isotopes
 Number of neutrons in nuclei varies
 eg. Oxygen 16 (16O) & 18 (18O)
16O
8 protons
8 neutrons

18O
18O
8 protons
10 neutrons
heavier than
16O
On average:
1 18O for 1000 16O
 harder to evaporate
 Ice Cores
 High ratio of 18O/16O for warm globe
 Deep Sea Sediments
 High ratio of 18O/16O for cool globe
Isotopes
 Variations indicate temperature
 Higher 18O/16O in ice  warmer
 Lower 18O/16O in ice  cooler
18O/16O
Arctic & Antarctic show
same variations 
variations are global
2H/1H
Isotopes
 Sea Temp.
 Higher 18O/16O
 cooler
 Lower 18O/16O
 warmer
Sea surface
temperature
18O/16O
C. R. W. Ellison et al., Science
312, 1929 -1932 (2006)
Isotopes
 Variations track
with GH gases
Methane
2H/1H
Carbon Dioxide
now
www.realclimate.org/index.php?p=221
2H/1H
then
Temperature & GH Gases
Temperature
tracks with
gases …
Carbon Dioxide
Temp (°C)
Which drives
which?
Methane
now
then
Ice Core Contributions to Global Change Research: Past Successes and Future Directions
National Ice Core Laboratory Ice Core Working Group, May, 1998.
Global CO2
CO2 from Ice Cores & Mauna Loa
Isotopes
 Necessary to understand ice core data!
Allows reconstruction of temperature
 Only way to get to last curve!
 Respects the audience
 Demands they respect the science
Discussion: How much should
we simplify?
Modeling the Climate
 Climate Systems
 Sun – source of (almost) all energy
 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, Surface and Atmosphere (CO2)
 insolation (incoming sunlight varies)
 reflection, absorption, re-radiation by surface, air
 Water cycle
 evaporation, precipitation, runoff
 Land surface
 soil moisture, vegetation, topography, snow & ice
 Ocean
 surface currents, deep currents, chemistry (salinity)
 Sea Ice
 strongly affected by feedbacks
Carbon Dioxide
 Long-term sources: Volcanoes & Humans
 Long-term sinks: Chemical Weathering
 H2O + CO2  H2CO3  H+ + HCO3
Carbonic Acid
 CaCO3 + H+  Ca + HCO3
Bicarbonate can combine
with many compounds eg.
NaHCO3, Ca(HCO3)2
 Variable storage: Biosphere
 plants absorb CO2 to grow
 trees make wood out of air!
 plants make us … we’re made of air!
 decay releases CO2
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
Greenhouse Effect Concept
Inventory
 Dr. John Keller, Cal Poly
 Poster C24
Feedbacks
 Feedback Mechanism: Evaporation
 Clouds shade surface, cool it, warming stops?
 H2O vapor absorbs more IR, more warming
Runaway Greenhouse … Venus!
 Feedback Mechanism: Plant Growth
 More CO2 increases plant growth
 More plant growth is good!!
www.co2science.org
 Plants absorb CO2 (Keeling curve annual cycles)
CO2 is Reduced
BUT … why isn’t it working yet?
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
 Feedback Mechanism: Evaporation
 More clouds & cooling, snow comes back
 Warming halted
 H2O vapor absorbs more IR, more warming
“Hot House Earth”
Climate Variations
 Due to
 Atmospheric variations
 Pacific Cycles
 El Niño Soutern Oscillation (ENSO)
 Pacific Decadal Oscillation
 Atlantic Cycles
 North Atlantic Oscillation
 Atlantic Multidecadal Oscillation
Variations in the Atmosphere
 NAO Negative Phase mid 1950’s - 1970
It WAS
colder
when we
were kids!
Variations in the Atmosphere
 NAO Mostly positive since mid-70’s
Skeptics
use cooling
of eastern
Canada to
dispute
global
warming
Variations in the Atmosphere
 Atlantic Multidecadal Oscillation (AMO)
 Sea Surface Temperature in North Atlantic
Variations in the Atmosphere
 AMO
 Correlates with numbers of major hurricanes
… and southwestern droughts!
Not perfect
correlation … what
else is going on?
Variations in the Atmosphere
 Drought
 Correlation with PDO and AMO
Current
Conditions
Droughts
more severe &
widespread
when AMO is
positive
oceanword.tamu. edu
Variations in the Atmosphere
 Insolation Variations
 Solar brightness variations
 sunspots & other stellar variations
 Earth orbital variations (Milankovitch)
 other planets’ gravity vary Earth’s orbit
 Solar system environmental variation
 Sun moves through galactic environment
Insolation
 Varies with Milankovitch Cycles
 Last million years for 65 N (Berger (1991))
9,000 years ago, ice age ended!
Some argue this is the cause of ALL
climate change … so we can ignore our CO2
Milankovitch and Temperatures
Vostok Core Data
Temperature from 18O/16O
Milankovitch Insolation
Connection apparent …
but can it explain current warming?
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
 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
IPCC ARF WGI
 Components of Climate Change
Accounts for natural processes
eg. Changes
in
evaporation
eg. Melting
permafrost
releasing
methane
IPCC Climate Drivers
 Greenhouse Gases: CO2, CH4, H2O, NOx
Grey Bars
= Natural
Variability
Radiative forcing is a
change in the radiation
balance at the top of the
atmosphere. Positive
increases warming.
Combined
rate of
change
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)
 A1B
IPCC Scenarios
 Very rapid economic growth
 Global population peaks mid-century then declines
 rapid introduction of new, more efficient technologies.
 A2
 Very heterogeneous world
 Continuously increasing global population
 Regionally oriented economic growth more fragmented
and slower than in other storylines.
 B2
 Same global population as in the A1
 rapid changes toward a service and information economy
 reductions in material intensity
 introduction of clean, green technologies.
IPCC ARF
 Continued Warming
What we’re committed
to by past behavior!
Union of Concerned Scientitsts
 Confronting Climate Change in the U.S.
Northeast: Science, Impacts and Solutions
http://www.ucsusa.org/global_warming/
UCC Northeast US
 Climate of New York State
IPCC ARF
 Effects of Changing Mean
Does not
mean it
never gets
cold!
The Skeptics
 Important voices!
 Skeptics keep science honest
 Agreements
 CO2 in atmosphere is increasing rapidly
 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!
Discussion
 What should we include & leave out?
 How much complexity to include?
 Should we confront politics directly?
 How do we handle hostility?