Climate and Climate Change
Essential Points
1. Climate and weather prediction are completely
different
2. Detecting climate change is very complex
3. The main greenhouse gas on Earth is water
vapor
4. A little greenhouse effect is a good thing
5. Many things have affected earth’s past climate
6. Gradual brightening of the sun will eventually
make the earth too hot for life
Climate Versus Weather
Climate is what you expect and
weather is what you get
Green Bay 1977-2002
Green Bay 1887-2002
Green Bay 1887-2002
Green Bay 1887-2002
Long-Term Trends
Long-Term Trends
Long-Term Trends
Long-Term Trends
Long-Term Trends
Some Conclusions
• This is not as easy as the media make it seem
• The fact that it’s not easy doesn’t excuse us
from dealing with it
• The fact that something can’t be proven
conclusively doesn’t protect you if you make the
wrong decision
• Don’t confuse reasoning with reality. Just
because you can justify believing something
doesn’t make it true.
Greenhouse Effect
Negative Greenhouse Effect
Positive and Negative Greenhouse
Effects
Positive Greenhouse Effect
• Light enters
• IR trapped: Warming
Negative Greenhouse Effect
• Light Blocked
• IR can leave: Cooling
• Titan
Greenhouse Gases
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Water Vapor
Carbon Dioxide
Methane
Nitrous and Nitric Oxides
Ozone
• Transparent to visible light but
absorb infrared
What Color is Water?
What Color is Ice?
Infrared Absorption
Carbon Dioxide
• Has doubled to 380 ppm since start of
Industrial Revolution
• Coupled to Temperature Rise?
• More Cloud Cover?
• Taken up by biomass?
• Taken up by oceans?
Paleoclimatology
• The present is the key to the past – but
• The past is also the key to the present
• Study of ancient climates
• Have to rely on proxy measurements
• How to convert qualitative data to
numbers?
Ancient Paleoclimatology
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Oxygen 18
Fossils
Evaporites
Glacial Indicators
Air bubbles in amber
Earth’s Climatic History
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Faint Early Sun
Anoxic Early Atmosphere
Advent of Life – UV Protection?
2.3 b.y. Glaciation
2 b.y. Oxygen Threshold
– End of Iron Formations
– First Red Sandstones
• 900-600 m.y. Snowball Earth
Earth’s Climatic History
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600-500 m.y. Cambrian “Explosion”
450 m.y. Ordovician Ice Age
350 m.y. Advent of Forests
350-250 m.y. Permian Ice Age
100 m.y. Cretaceous Warm Period
50 m.y. Eocene Warm Period
Pleistocene Ice Age
Recent Paleoclimatology
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Historic Records
Tree Rings
Pollen Studies
Oxygen 18
Ice Cores
Holocene Climate
• 11,000 Younger Dryas Cooling
• 9,000-6,000 Mid-Holocene Warm Period
(“Climatic Optimum”)
• 900-1300 AD – Medieval Warm Period
• 1300-1450 Little Ice Age I
• 1450-1550 Partial Recovery
• 1550-1800 Little Ice Age II
Possible Effects of Global Warming
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More Heat Extremes
Drought
Rise in Sea Level
Temporary Severe Cold Spell?
Rapid Migration of Ecological Zones
More Biomass but Lower Nutritional Value
Not a Bad Thing?
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Reduced Energy Demands
Longer Growing Seasons
More Biomass
More Habitable Land
What We Know and Don’t Know
• Certain: Carbon Dioxide Increase
• Nearly Certain: Climate is Warming
• Debatable (Legitimately)
– How much is of human origin?
– Permanent or temporary warming?
• Uncertain:
– Can we do anything?
– Will benefits exceed costs?
– Risks of premature policy decisions?
The Spectrum of Skepticism
Concerns about failure to modeled features like cloud cover
Too many assumptions have to be built into climate models
Concerns about the way global climate data are measured
How to link recent instrument data with older historical and prehistoric
climate indicators?
Concerns about the validity of computer modeling of climate in
general
Are recent climate changes man-made, or natural?
Claims that warming of the climate might actually be beneficial
Claims that climatic change is too far along to reverse or mitigate
Claims that attempts to control climate change would be too costly
Claims that human activities have no effect on climate
Claims that no long term climate changes are occurring at all
Claims that the earth is actually cooling
Ozone
Stratosphere – Good
• Absorbs solar ultraviolet
Troposphere – Bad
• Toxic
• Contributes to air pollution
Ozone Depletion
• Cl stripped off synthetic molecules by solar
ultraviolet
• Cl reacts with ozone, acts as catalyst
• Cl – CF3 (Freon)
• Cl – CCl3 (Carbon tetrachloride)
• Cl – H (Hydrochloric Acid)
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Smog
Particulate Matter
Long-Term Climatic Trends
• Brightening of the Sun
• Capturing of CO2 by carbonate rocks?
– Extinction of plants
• Moist greenhouse effect
• Runaway CO2 Greenhouse Effect
• Venus conditions
The Ultimate Long-Term Forecast
• Slow warming trend for the next billion
years
• Increasing humidity
• Boiling and evaporation of the oceans,
accompanied by extinction of life
The Goldilocks Problem
• Venus is too hot
• Mars is too cold
• Earth is J-u-st Right
Planetary Habitable Zones
• Primarily in the Liquid Water Zone
• Ice is OK but planet can’t be too warm
• Water Vapor in upper atmosphere broken
down by solar UV and charged particles
(photodissociation)
• Hydrogen escapes to space
• Can lose oceans in 100 m.y.
Planetary Habitable Zones
Future of Life
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Plants need > 10 ppm CO2
Animals and plants die around 50 C
Micro-organisms can tolerate 130 C +
But biology seems to like heat and we have
a billion years to experiment
Pressurized cells?
Anti-boiling fluids?
Problem is breakdown of organic molecules
200 C (380 F) max?
The Oreo Model of Life History
Micro-organism
Earth (0-3 billion
years)
Multicellular Earth
(3-5 billion years)
Micro-organism
Earth (5-6 billion
years)
“The white creamy
middle”
Essential Points
1. Climate and weather prediction are completely
different
2. Detecting climate change is very complex
3. The main greenhouse gas on Earth is water
vapor
4. A little greenhouse effect is a good thing
5. Many things have affected earth’s past climate
6. Gradual brightening of the sun will eventually
make the earth too hot for life