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James Lovelock (b 1919)
• Independent scientist and inventor – PhD Medicine--- Developed instruments to measure atmospheric gases
• 1961 NASA consultant – working with Viking program to establish whether life forms exist on Mars
• Formulated “Gaia Hypothesis” (late 1960s)
Statement
The Earth’s atmospheric and geologic processes regulate theEarth’s temperature, climate and atmospheric content toproduce an environment conducive to life.
The Faint Sun Paradox
For over 4 BY the sun’s outputhas increased, but the Earth’sTemperature has remained constant
Ice Ages
The Greenhouse Effect --- How the Sun warms our planet
Greenhouse Gases (opaque to infra-red radiation)Carbon Dioxide, Methane, Nitrous Oxide
GAIA
Living organisms and geologic processes (Gaia) control the Earth’s temperature
--- Determine the atmospheric contentCarbon DioxideOxygenNitrogenSulphur DioxideMethane
--- Affect the amount of sunlight absorbed by the EarthAlbedo – the Earth’s reflectivity (Forest vs. ice)Cloud cover – influenced by living organisms
Carbon Dioxide Concentration
• Higher when the sun was younger (cooler)• At present --- low relative to geologic timescale• How much lower can it get???
X 100 ppm
Plate Tectonic Boundaries
Eurasian Plate
North American Plate
Mid Atlantic Ridge
Oceanic Crust (Basalt)
Continental Crust (Granitic)
Plate Tectonics and the Carbon Cycle
• Carbon dioxide is produced at spreading centres and volcanic arcs
• Carbonate rocks are removed and recycled in the Earth’s upper mantle
• Plate movements are driven by sinking slab (subduction)--- Water lubricates the process--- Basalt weathering makes the descending plate pliable
(Feedback to biosphere)
The Carbon Cycle
Source: Indiana University
CO2 Sources CO2 SinksVolcanic activity Granite/Basalt rock weatheringMetamorphism + carbonate depositionRespiration Marine organism deposition Photosynthesis + organic burial
Living Organisms --- Regulators of the Carbon CycleSilicate Rock WeatheringCO2 + H2O -> H2CO3 (carbonic acid)
H2CO3 + H2O + silicate minerals -> HCO3- + cations (Ca++, Fe++, Na+, etc.) + clays
Ca++ + 2HCO3- -> CaCO3 + CO2 + H2O
In rock weathering, 2 molecules of CO2 are absorbed and one released
Plant Life• Sink for CO2 (Over geologic time plant burial results in CO2 removal) • Plant roots break up rock: enhance weathering• Marine plants (algae, corals) store CO2 as Calcite in their skeletons
Emiliana huxleyiConverts sunlight, CO2 into
Calcite -- CaCO3
Unregulated, CO2 removal would increase greenhouse effect and lead to “snowball Earth”
75% of Carbon deposited in ocean is Calcite
Clouds and Gaia
--- Without clouds, the Earth would be 20 degrees hotter
--- Dimethyl sulphide, produced by marine algae reacts in the atmosphere with oxygen to form sulphuric acid aerosols, the nuclei of clouds.
--- Increasing temperature more algal blooms increasing clouds
Ice Age Cycles --- Antarctica --- Vostok Core DataIs Gaia struggling to maintain a cool temperature??
1979
Arctic Ice ExtentMass loss of Greenland andAntarctic sheets due to melting
Ice Issues
Oceanic Acidification --- Due to more CO2
Change in Oceanic pH 1900s to 1990
Acidification Effects• dissolution of crustacean shells CO2 released into atmosphere
• cocolythophores, corals threatened less CO2 bound up as calcite• food supply (fishing) adversely affected
Dead zones --- oxygen starved*** On continental shelves due to pollution*** Oceanic --- due to warming, less mixing with deeper layers
(nutrient rich)
Biodiversity --- Why it matters
Gaia• Every species has a preferred, optimum climate Losing species impairs the Earth’s ability to respond to environmental changes• Models (Daisyworld) show that the Earth’s temperature is most stable with a large number of species Food Production / Plant and animal Uses• Diverse flora/fauna are more resistant to disease, drought and other environmental changes
The great extinction --- 21st century
Today’s species loss is 10,000 times the natural rateIUCN’s Red List, of Threatened Species, year 2000,1% of birds, 18% of mammals, 7% of fish and 8% of plants were threatened with extinction.Causes • Overharvesting/ fishing• Pollution• Intrusive species• Habitat destruction due to human activity, encroachment and climate change
GAIA’S RESPONSE TO THE PRESENT CRISIS
• Raised temperature. (A sick patient fighting for their life) ***Positive feedbacks activated (melting ice sheets) *** Extra CO2 will be removed through weathering and
burial. (Long term)
• Gaia needs the ice ages--- Tropical biotic communities regenerate (greater landmass)
--- Colder oceans favour plankton growth--- More CO2 is locked up. Keeps Earth cool in the long term
• Gaia’s options are limited because of: *** Loss of biodiversity *** Oceans are less able to absorb excess CO2 (acidification)
*** The sun’s output (at an all time high) *** Loss of broadleaf trees (cooling effect) ---- Reflect sunlight from ground ---- Transpiration (cooling by evaporation of water)
---- Cloud seeding
POSSIBLE HUMAN RESPONSES
• Limit greenhouse gas emissions *** Requires international agreements (Difficult!)• Protect biodiversity• Tree planting (restoration of indigenous ecosystems)
Geo-engineering *** Carbon Capture/Storage (expensive!) --- CO2 injection --- Bio-char *** Artificial volcanoes (Sulphuric acid spray into stratosphere) ----Inexpensive but increases oceanic acidification *** Increase vertical circulation in oceans
Eocene Optimum
•CO2 and Methane concentrations, 2-3x normal (volcanic activity? Release of hydrates?)
Proxy measurements from Alkenones (produced by algae)
• Temperature stabilized, but over > 10my period.
Small perturbations in CO2 can have large consequences
---- release of gas hydrates (Methane stored beneath ocean floor) ---- melting of polar ice decrease in albedo (reflectivity) ---- more sunlight absorbed by Earth
---- CO2 released from oceans due to higher temperature
Removal of CO2 by increased rock weathering is a long term process
---- Earth responds to CO2 changes over geologic time
The Carbon Cycle and the Greenhouse Effect
Increase in rock weathering