Gaia – A Planet in Crisis

By

Paul Kieniewicz

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??

Modern carbon dioxide atmospheric concentrations

2010 --- 389ppm

Effects of Global Warming

Sea Level Change

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

Extras

The Greenhouse Effect --- How the Sun warms our planet

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

The Goldilocks Zone

Venus: Temp: 460 C; 93 bars – too hotEarth: Temp: 14C ; 1000mb – just rightMars: Temp -20 C. 1 mb – too cold

Earth’s temperature isJust Right!