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
Carbon Dioxide Has doubled to 350 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 Oxygen 18 Fossils Evaporites Glacial Indicators Air bubbles in amber
Earth’s Climatic History Faint Early Sun Anoxic Atmosphere Advent of Life – UV Protection? 2.3 by Glaciation 2 b.y. Oxygen Threshold End of Iron Formations First Red Sandstones Snowball Earth
Earth’s Climatic History Cambrian Explosion Ordovician Ice Age Advent of Forests Permian Ice Age Cretaceous Warm Period Eocene Warm Period Pleistocene Ice Age
Recent Paleoclimatology 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 Recovery 1550-1800 Little Ice Age II
Effects of Global Warming 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? Reduced Energy Demands Longer Growing Seasons More Biomass More Habitable Land
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) 360 Cl – CCl3 (Carbon tetrachloride) 294 Cl – H(Hydrochloric Acid)431
Long-Term Climatic Trends Brightening of the Sun Capturing of CO2 by carbonate rocks? Moist greenhouse effect Runaway CO2 Greenhouse Effect Venus conditions
The Goldilocks Problem Venus is too hot Mars is too cold Earth is Just Right
Planetary Habitable Zones Primarily in the Liquid Water Zone Can’t be too warm Water Vapor in upper atmosphere broken down by solar UV and charged particles (photodissociation) Hydrogen escapes to space
The Ultimate Long-Term Forecast Slow warming trend for the next billion years Increasing humidity CO 2 decrease leads to extinction of plants? Boiling and evaporation of the oceans
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