Today’s main points:

1) Earth’s atmosphere has an unusual, biologically influenced chemistry

2) Oxygen concentrations link the biota to the climate through direct and indirect negative feedbacks involving both O2 and the greenhouse (trace) gases.

3) James Lovelock and the Gaia Hypothesis

4) Problems with the Gaia H.

5) Some solutions to these problems

6) Introducing Daisyworld

Earth: biota control some major components of

Earth’s atmosphere

Mars & Venus: strictly abiotic processes in

control

Earth’s atmosphere has an odd chemical composition

Comparisons with other rocky planets reveal the influences of biota on Earth’s atmosphere

Atmospheric ChemistryIstván LagziRóbert MészárosGyörgyi GelybóÁdám Leelőssy

Copyright © 2013 Eötvös Loránd University

Earth has had 4 different climatic regimes

By 3.2-3.5 billion years ago, bacteria had already

invented most forms of metabolism found on Earth today.

Earth forms 4.5 billion years ago

?

eukaryotesarchaeabacteria

endosymbiosis:

mitochondria added

nucleus evolves

4 billion years ago

oxygenic

photosynthesis

1.8 billion years ago

2.8 billion years ago

Proterozoic : Era of Banded Iron

2.5 billion

to 540 million

photosynthetic bacteria (and

archaea) produce O2 as

waste product

stromatolites

banded iron

Photosynthetic bacteria (and archaea) produce O2 as

waste product

Abundant iron binds oxygen, becoming insoluable in

sea water, deposited on sea bed

Banded iron formations result.

Fe2++ (ferrous iron) buffers

atmosphere from

poisonous O2

Earth today………………

What roles do biota play in Earth’s atmospheric chemistry today?

21%78%

0.3%

R G Prinn, and , B Fegley, Jr

Annual Review of Earth and Planetary SciencesVol. 15, 1987

78% of Earth’s atmosphere is N2

Most of this N2

comes from denitrifying bacteria in soils and oceans

Today’s denitrification rates could produce the present amount of N2 in Earth’s atmosphere in ca. 17 myr

Earth’s atmosphere has an odd chemical composition

Comparisons with other rocky planets reveal the influences of biota on Earth’s atmosphere

Perhaps there was abundant life once, but Mars’ present atmospheric chemistry consistent with abiotic equilibria.

0.13%

Mars: no biology involved in composition of this atmosphere

Martian atmosphere exists in a stable condition close to chemical equilibrium, with very little oxygen, methane, or hydrogen, but an overwhelming abundance of carbon dioxide (95%).

= no LIFE, not really.

Venus: N2 is 2.6% of atmosphereCO2 is 96%

462 degrees Centigrade

Venus: no biology involved in composition of this atmosphere

Surface of Venus from the Russian Venera 13 lander in 1982. Note the flat basaltic rocks

that are still sharp and un-eroded. Venera 13 lasted for 127 minutes before the extreme heat overcame the electronics.

shrouded in sulfuric acid fog

How might the biota impose negative feedbacks on Earth’s climate?

remember: homeostasis needs negative feedbacks

Earth’s atmosphere:

O2 levels tightly controlled by biota (photosynthesis).

Bacteria control or at least strongly influence N2 levels.

CO2 and CH4 under strong biological control (though some of these always present….volcanism)

Review: How exactly does LIFE influence O2 and CO2 (and CH4 too)?

Photosynthesis (using solar energy to build energy-rich carbon compounds)

CO2 + H2O + sunlight -> CH2O + O2

photosynthesis: removes CO2 from atmosphere, produces O2 as byproduct

O2 + CH2O -> energy + H2O + CO2

Respiration (burning energy stored in carbon compounds)

lowers O2 levels,returns CO2 to atmosphere

respiration: the Krebs (Citric Acid) Cycle

How might the biota impose negative feedbacks on Earth’s climate?(remember: homeostasis needs negative feedbacks)

Processes affecting volatiles in planetary atmospheres(Prinn and Fegley, 1987) Earth Planet Sci Reviews

SCIENCE 2015

Finally, a direct negative feedback between photosynthesis and Earth’s climate?

If you reduce atmospheric density by removing O2, more radiation reaches Earth surface w/o scattering, surface warmer.

warmer surface causes increased latent heat flux, triggering more evapotranspiration, more water vapor in atmosphere, greenhouse accentuated, more precipitation, warmer planet

Poulsen et al (2015): manipulate O2 levels in a GCM:

RESULTS:

Poulsen et al (2015) GCM results:

adding O2 decreases precipitation

adding O2 cools Earth’s surface

more vegetation ->>>> more O2

less short-wave radiation reaches surface

planet’s surface cools, less water in atmosphere

less vegetation ->>>> less O2

planet’s surface warms, more H2O in atmosphere

more short-wave radiation reaches surface

How else does O2 affect Earth’s greenhouse?

1) Photoxidation of CH4

2) CO2 uptake by phytoplankton need water to be well-oxygenated

3) O2 level controls abundance of ozone (O3) 2O2 + uv radiation -> O3 + Oand O + O2 -> O3

Conclude:1) Over geological time, Earth’s biosphere has

“explored” several alternative states of climate-atmosphere-biota

2) Its present atmospheric chemistry (high N2 and high O2) is “biochemical” …… far from the state expected if it were at equilibrium with Earth’s physical chemistry.

3) Yes, there are negative feedbacks between Earth’s climate, biota, and greenhouse

These include:a) Silica-mineral weathering (Ruddiman textbook)

b) O2 conc.’s effect on shortwave scattering (Poulsen et al., 2015)

c) effects of O2 conc. of other greenhouse gases like CH4

d) Generic effects of O2 levels on C fixation by plants.

Today’s main points:

1)Earth’s atmosphere has an unusual, biologically influenced chemistry

2)Oxygen concentrations link the biota to the climate through direct and indirect negative feedbacks involving both O2 and the greenhouse (trace) gases.

The Gaia Hypothesis

James Lovelock, PhD in Medicine, an “independent scientist”

Lovelock’s mother started work at 13 in a pickle factory. His father, Tom, served six months hard labour in his teens for poaching and was illiterate until attending technical college. The family moved to London, where Lovelock's dislike of authority made him, by his own account, an unhappy pupil. (Wikipedia)

Is this what creates a creative thinker?

1961: Lovelock hired at NASA to develop instruments for the analysis of extraterrestrial atmospheres.

He became interested in the composition of the Martian atmosphere, reasoning that life on Mars would be obliged to use it and change it.

He concluded Mars was lifeless.

Gaia hypothesis : living and non-living parts of the Earth form a complex interacting system that can be considered a single organism.

Detour: But what is an “organism”?

Individual entity exhibiting the properties of life.

Gaia theory asserts that living organisms (Life)help stabilize the Earth’s surface environment in ways that make it favorable to Life.

James Lovelock

But what is “life”?

1) A life form is an entity (something singular)

2) Life has spontaneity: it just happens (no larger control required)

3) Life self-makes and self-maintains: it is autopoietic.

4) Life processes energy (it lives off cascades of entropy)

Lovelock’s initial observations:

Oxygen and methane exist together in Earth’s atmosphere at levels greater than expected given their reactivities. The high levels of both these gases are maintained through their continual production by organisms.

methane, CH4 has 70x the greenhouse effect as CO2

Other planets in our solar system - all of which are lifeless (?) - lack chemical disequilibria at scales comparable to what we find in Earth’s atmosphere.

Lovelock: presence of Life makes Earth’s biosphere “stably unstable”.

Impact crater with sand dunes, Mars

For instance:The lifespan of a typical oxygen molecule, from its origin when photosynthesis splits a water molecule to its burial in sediment as an oxide, is roughly 3.25 million years.

This means that the entire oxygen reservoir has been replaced roughly 100 times over the course of Earth’s history.Yet the level of oxygen has only varied between 15% and 25% over the last 250 million years.

atmospheric oxygen level

vs. time for the past 550

million years (Berner(1999) PNAS)

Coccoliths and the Cliffs of Dover

Lovelock also pointed out that Life does influence Earth’s atmosphere

organisms’ roles in carbon cycle

more vegetation ->>>> more O2

less short-wave radiation reaches surface

planet’s surface cools, less water in atmosphere

less vegetation ->>>> less O2

planet’s surface warms, more H2O in atmosphere

more short-wave radiation reaches surface

How else does O2 affect Earth’s greenhouse?

1) Photoxidation of CH4

2) CO2 uptake by phytoplankton need water to be well-oxygenated

3) O2 level controls abundance of ozone (O3) 2O2 + uv radiation -> O3 + Oand O + O2 -> O3

Summary of circumstantial evidence for Gaia

1) Oxygen levels are (somehow) homeostaticallymaintained

2) Biota are crucial in carbon and methane biogeochemical cycles, hence in greenhouse effect

3) Earth’s climate has persisted within life-supporting parameters for >540 mya

The Problems with Gaia

1)It is interdisciplinary (so specialist avoid dealing with it)

2) No mechanism for Gaia to develop: The Problem of One

3) Just another manifestation of the dreaded Anthropic Principle

Problem #4) A terrible name

The name “Gaia” immediatelyput the hypothesis into the same category as:

2) No mechanism for Gaia to develop:

The Problem of One: There cannot be any sorting for an optimal, self-maintaining biosphere if there is only one biosphere to choose from.

These (and other) critics questioned how natural selection operating on individual organisms can lead to the evolution of planetary-scale homeostasis.

Stephen J. Gould

Richard Dawkins

Lovelock and the Gaia H. did not stand a chance….except for Lynn Margulis, microbiologist, University of Massachusetts.

Her enemies called her “Attila the Hen” ….but they feared her.

In fact, the Gaia hypothesis had an explanation that Lovelock ignored.

?academic amnesia?

W. Ross Ashby, pioneer British cyberneticist and psychiatrist

“Design for a Brain”

Environment

Kitten

S

Sensory andmotor channels

All possible behaviors

Essential variables(must stay within kitten’sphysiological limits)

Ashby’s canonical example: a kitten first learning about fire.

One planet exposed to multiple “experiments” over geological time ……in search of a stable biosphere

Microbes: > ½ of O2, most of N2, most CH4, indispensable for all “higher” life forms

Higher plants rely heavily on symbioses with microbes

Streptococcus mitis survived several years in the space environment inside a contaminated Surveyor spacecraft on the surface of the Moon.

Atmospheric ChemistryIstván LagziRóbert MészárosGyörgyi GelybóÁdám Leelőssy

Copyright © 2013 Eötvös Loránd University

Microbes will always survive, regardless of how the biosphere’s latest biosphere experiment turns out.

Environment

Kitten

S

Sensory andmotor channels

All possible behaviors

Essential variables(must stay within kitten’sphysiological limits)

Microbes, not cat.

more vegetation ->>>> more O2

less short-wave radiation reaches surface

planet’s surface cools, less water in atmosphere

less vegetation ->>>> less O2

planet’s surface warms, more H2O in atmosphere

more short-wave radiation reaches surface

"...if a system as large as the surface of the

earth...is kept gently simmering dynamically for

five thousand million years, then nothing short of

a miracle could keep the system away from

those states in which the variables are

aggregated into intensely self-preserving forms.

" W.R. Ashby, 1962, Design for a Brain, p. 233.

I agree with Ashby’s extremum principle of least change:

These (and other) critics questioned how natural selection operating on individual organisms can lead to the evolution of planetary-scale homeostasis.

Stephen J. Gould

Richard Dawkins

3) Our perception of “Gaia” could be a manifestation of the Weak Anthropic Principle

(“Conditions in the Universe must allow observers to exist, otherwise, we would not be here observing it”).

In other words, Earth is inevitably motherly.

“nice by luck”

If Earth had not been equable and Life-friendly for 100s of millions of years, we humans would never have evolved to observe it …..and to argue about things as confusing as the Weak Anthropic Principle.

The Weak Anthropic argument fails to explain why the biota living on our planet in fact play such strong roles in creating and maintaining the conditions necessary for their continued existence here.

Lovelock took a more mechanical approach to defending the Gaia Hypothesis.

He invented a mathematical model of an imagined world, Daisyworld.

Telletubbies have no known connection with Daisyworld.

Daisyworld supports two different types of daisies: black daisies and white daisies. They differ in their albedo. White daisies have a high albedo and thus reflect light and heat, thus cooling the area around them.

guaranteed to rankle establishment scientists

Daisyworld is interesting, imaginative, but fails to circumvent either the Problem of One or implications of the Weak Anthropic Principle.