Climate Modeling of the Early Earth: What Do We Know and How Well Do We Know It? James Kasting Department of Geosciences Penn State University.

Slides:



Advertisements
Similar presentations
CO2 and Long Term Climate GEOL 1130 Spring Earth-Venus contrast Which planet receives more incoming solar radiation? Which planet absorbs more solar.
Advertisements

CO2 and Long-Term Climate
The syllabus says: Atmosphere and change  Describe the functioning of the atmospheric system in terms of the energy balance between solar and long- wave.
1.Greenhouse Effect 2.The CO 2 Cycle, Long-Term Climate Change 3.Ice Ages and Short-Term Climate Change 4.Human-Induced Climate Change.
Climate over the long term (Ch highlights)
Reading: Chapter 4 Lecture 25. Snowball Earth vs. Slushball Earth..
The Early history of Earth! After the Earth formed…about 4.6 Billion years ago… …The Earth melted and differentiated into Core, Mantle, and Crust.
Climate Forcing and Physical Climate Responses Theory of Climate Climate Change (continued)
Greenhouse Effect. Thermal radiation Objects emit electromagnetic radiation –The hotter they are, the faster the energy output (  T 4 ) –The hotter they.
PTYS 214 – Spring 2011  Homework #5 available for download at the class website DUE Thursday, Feb. 24  Reminder: Extra Credit Presentations (up to 10pts)
Past Climate.
Astronomy190 - Topics in Astronomy Astronomy and Astrobiology Lecture 10 : Earth History Ty Robinson.
Many past ice ages were caused by… 1.Volcanic activity 2.Photosynthesis 3.Prehistoric humans 4.Changes in the earth’s orbit 5.Sun spots.
Astronomy190 - Topics in Astronomy Astronomy and Astrobiology Lecture 11 : Earth’s Habitability Ty Robinson.
Generalized diagram of the Earth system
Astronomy190 - Topics in Astronomy Astronomy and Astrobiology Lecture 13 : Life’s History Ty Robinson.
Greenhouse Effect: The heating of the surface of the earth due to the presence of an atmosphere containing gases that absorb and emit infrared radiation.
Essential Principles Challenge
Radiation’s Role in Anthropogenic Climate Change AOS 340.
Sustained Habitability on a Dynamic Early Earth James Kasting Department of Geosciences Penn State University.
Average Composition of the Troposphere Gas Name Formula Abundance (%) Residence time (approx) Nitrogen N %42,000,000 years Oxygen O %5,000.
Air Quality and Climate Change. Coal and Oil Formation Both are Fossil Fuels: remains of plants and animals that died anywhere from 400 million to 1 million.
Goals for this section 1.EXPLAIN the feedback mechanism believed to have maintained Earth's average temperature within the range of liquid water over 100s.
Review Climate Change. Weather vs Climate Weather is the daily atmospheric conditions including temperature and precipitation Climate is the average weather.
CH 24.3 Solar Radiation, Pressure, & Wind. Earth’s Energy Balance Input = Sun’s Energy = (Visible light + some UV) REFLECTED: ~ 25 % by clouds, dust,
Unit 18: Natural Climate Change. OBJECTIVES: Explore the origin and nature of climate change Present Earth’s climatic history prior to the industrial.
Chapter 12 Long-Term Climate Regulation Sun about 30% less luminous than today - Ts would have been below freezing - Earth seems to have had liquid water.
Early Earth’s Atmosphere. The First Atmosphere The early (first) atmosphere would have been similar to the Sun--mainly hydrogen and helium, but this atmosphere.
CESD 1 SAGES Scottish Alliance for Geoscience, Environment & Society Observing and Modelling Climate Change Simon Tett, Chair of Earth System Dynamics.
Prior learning –There are 3 kinds of rock – sedimentary, metamorphic and Igneous –Igneous rocks form crystals depending on the length of time it takes.
The Atmosphere and the Water Cycle. Earth’s system’s have two sources of energy Internal External.
Atmosphere Chapter 11 Notes. Composition of the Atmosphere Currently: – Nitrogen (N 2 ): 78% – Oxygen (O 2 ): 21% – Argon (Ar) – Carbon dioxide (CO 2.
Lecture 35. Habitable Zones. reading: Chapters 9, 10.
Gaia Revisited: The Interplay Between Climate and Life on the Early Earth James F. Kasting Department of Geosciences Penn State University.
Global Energy Balance and the Greenhouse Effect What determines Earth’s surface temperature? What is the history of CO 2 on Earth? ultravioletinfrared.
Lecture Outlines Physical Geology, 14/e Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Plummer, Carlson &
Warm-Up Word Splash- Take a few minutes to think about the following words and tell me what they mean to you. Global Warming Climate Change.
Lecture 6: The Faint Young Sun Problem, Part 1-- Solar evolution/CO 2 feedbacks/Geochemical constraints Abiol 574.
Pre Test 1. True or False. Earths Surface tempature has been constantly changing in geological time. 2. How does earth exchange energy with the enviroment?
Evidence of Global Warming and Consequences
The Faint Young Sun Problem. Systems Notation = system component = positive coupling = negative coupling.
Long-term Evolution of Earth’s Atmosphere and Climate James Kasting Department of Geosciences Penn State University.
Modeling the Earth System: Different Approaches for Different Problems James Kasting Department of Geosciences Penn State University.
Evolution of Earth’s Atmosphere and Climate
Heat in the Atmosphere The sun’s energy is transferred to earth and the atmosphere three ways Radiation, Convection and Conduction.
Chapter 12—Part 1: The faint young Sun problem
Chapter 11—Part 2 Cyanobacteria and the Rise of Oxygen and Ozone.
How’s it going to end? Climate evolution on Mars and Venus and its bearing on the very long term fate of the Earth’s climate system.
Global Warming: the history Why should we be worried about overall global climate change?
Green House Effect and Global Warming. Do you believe that the planet is warming? 1.Yes 2.No.
Snowball Earth History of Glaciation. Main Periods of Glaciation Huronian glaciations billion years ago Late Proterozoic glaciations million.
Earth and sky, woods and fields, lakes and rivers, the mountain and the sea, are excellent schoolmasters, and teach some of us more than we can ever learn.
Habitability: Making a habitable planet 26 January 2016.
The Evolution of Earth’s Atmosphere and Surface James F. Kasting Department of Geosciences Penn State University.
Earth’s Early Climate Jim Kasting Meteo 470. Solar luminosity versus time See The Earth System, ed. 2, Fig The fundamental problem of long-term.
Goal: To understand the climate of the earth. Objectives: 1)To understand the Greenhouse effect. 2)To compare Greenhouse effect vs the climate. 3)To learn.
Atmospheric Composition and Climate on the Early Earth
Climate feedbacks: Water vapor, snow/ice albedo, and clouds
How the Greenhouse Effect Works/Feedback factors
The Greenhouse Effect 8.6 The greenhouse effect is a natural process whereby gases and clouds absorb infrared radiation emitted by Earth’s surface and.
8.10 Feedback Loops and Climate
Earth’s history.
The Evolution of the Atmosphere
Chapter 19 Global Change.
Greenhouse Gases and Climate Modeling
Patterns in environmental quality and sustainability
Habitability: Making a habitable planet
Paleo Climate Change.
Why is carbon dioxide so important? Examining the evidence
Global Warming.
Presentation transcript:

Climate Modeling of the Early Earth: What Do We Know and How Well Do We Know It? James Kasting Department of Geosciences Penn State University

Phanerozoic Time First shelly fossils Age of fish First vascular plants on land Ice age First dinosaurs Dinosaurs go extinct Ice age (Late Cenozoic) Warm

Geologic time Warm (?) Rise of atmospheric O 2 First shelly fossils (Cambrian explosion) Snowball Earth ice ages Warm Ice age Origin of life (Ice age)

G.M. Young et al., J. Geol. (1998) Evidence for 2.9-Ga glaciation One finds diamictites and dropstones in the 2.9-Ga Mozaan Group in South Africa, within the Pongola Basin Diamictites are called tillites once their glacial origin is established Diamictites are also found in the Belingue Greenstone Belt in Zimbabwe (E. M. Nisbet et al. Geology, 1993), although they were not identified as glacial by the authors

2.9-Ga dropstone Dropstones are fist- sized (or larger) chunks of rocks found in laminated marine sediments that are thought to have been deposited by melting icebergs This one was found in the muddy upper layers of the diamictites shown in the previous slide G.M. Young et al., J. Geol. (1998)

Oxygen isotope evidence for a hot early Earth? The geologic data suggest that the Archean was cool (but not frozen), at least some of the time By contrast, oxygen isotope data from cherts (SiO 2 ), appear to indicate that the Achean Earth was hot, 70  15 o C, at 3.3 Ga Indeed, data from carbonates (not shown) suggest that the Earth remained warm up until ~400 Ma These isotopic data have multiple interpretations, some of which will come up during Paul Knauth’s talk Warm Cold (SMOW) P. Knauth, Paleo 3 219, 53 (2005)

Surface temperature vs. pCO 2 and fCH 4 Kasting and Howard, Phil. Trans. Roy. Soc. B (2006) 3.3 Ga S/S o = 0.77 Getting surface temperatures of ~70 o C at 3.3 Ga would require of the order of 3 bars of CO 2 (10,000 times present), possibly more, as the greenhouse effect of CH 4 was overestimated in these calculations pH of rainwater would drop from 5.7 to ~3.7 Would this be consistent with evidence of paleoweathering?

From a theoretical standpoint, it is curious that the early Earth was warm, because the Sun is thought to have been less bright 

Why the Sun gets brighter with time H fuses to form He in the core Core becomes denser Core contracts and heats up Fusion reactions proceed faster More energy is produced  more energy needs to be emitted Figure redrawn from D.O. Gough, Solar Phys. (1981)

Various astronomers have come up with proposals for altering the standard solar evolution model, and we will hear about that at this meeting For now, I will assume that the young Sun was indeed faint This has big implications for planetary climates, as first pointed out by Sagan and Mullen (1972)…

The faint young Sun problem Kasting et al., Scientific American (1988) T e = effective radiating temperature = [S(1-A)/4  ] 1/4 T S = average surface temperature

Feedbacks are important in the climate system One way to describe these is with systems diagrams 

Systems Notation = system component = positive coupling = negative coupling

Positive Feedback Loops (Destabilizing) Surface temperature Atmospheric H 2 O Greenhouse effect Water vapor feedback (+)

The faint young Sun problem The best solution to this problem is higher concentrations of greenhouse gases in the distant past (but not H 2 O, which only makes the problem worse) Less H 2 O More H 2 O

Greenhouse gases Greenhouse gases are gases that let most of the incoming visible solar radiation in, but absorb and re- radiate much of the outgoing infrared radiation Important greenhouse gases on Earth are CO 2, H 2 O, and CH 4 –H 2 O, though, is always near its condensation temperature; hence, it acts as a feedback on climate rather than as a forcing mechanism The decrease in solar luminosity in the distant past could have been offset either by higher CO 2, higher CH 4, or both. Let’s consider CO 2 first 

The carbonate-silicate cycle (metamorphism) Silicate weathering slows down as the Earth cools  atmospheric CO 2 should build up This is probably at least part of the solution to the faint young Sun problem

Negative feedback loops (stabilizing) The carbonate-silicate cycle feedback (−)(−) Surface temperature Rainfall Silicate weathering rate Atmospheric CO 2 Greenhouse effect

CO 2 vs. time if no other greenhouse gases (besides H 2 O) J. F. Kasting, Science (1993) In the simplest story, atmospheric CO 2 levels should have declined monotonically with time as solar luminosity increased Geochemists, however, insist on making the story more complicated…

Sheldon’s pCO 2 estimate from paleosols First published estimate of Archean CO 2 from paleosols came from Rye et al. (1995) (probably incorrect) Sheldon presented an alternative analysis of paleosols based on mass balance arguments (efficiency of weathering) Sheldon’s calculated pCO 2 at 2.2 Ga is also about bar, or 28 PAL, with a quoted uncertainty of a factor of 3 New estimate for pCO 2 at 2.7 Ga (Driese et al., 2011): PAL N. Sheldon, Precambrian Res. (2006) Driese et al., 2011

Rosing et al.: CO 2 from BIFs J. F. Kasting Nature (2010) Rye et al. (old) Ohmoto Sheldon von Paris et al. More recently, Rosing et al. (Nature, 2010) have tried to place even more stringent constraints on past CO 2 using banded iron-formations (BIFs) I have argued with these estimates, but I’ll let the authors present them first, and then we can argue.. (pCO 2  3 PAL)

Sagan and Mullen, Science (1972) Sagan and Mullen liked ammonia (NH 3 ) and methane (CH 4 ) as Archean greenhouse gases As a result of Preston Cloud’s work in the late 1960’s, they were aware that atmospheric O 2 was low on the early Earth

But Sagan and Mullen hadn’t thought about the photochemistry of ammonia 

Problems with Sagan and Mullen’s hypothesis Ammonia is photochemically unstable with respect to conversion to N 2 and H 2 (Kuhn and Atreya, 1979) There may be ways to salvage this hypothesis, or part of it, by shielding ammonia with fractal organic haze (see talk by Feng Tian)

CH 4 as an Archean greenhouse gas CH 4 is a better candidate for providing additional greenhouse warming Substrates for methanogenesis should have been widely available, e.g.: CO H 2  CH H 2 O Methanogens (organisms that produce methane) are evolutionarily ancient –We can tell this by looking at their DNA

Feedbacks in the methane cycle Furthermore, there are strong feedbacks in the methane cycle that would have helped methane become abundant Doubling times for thermophilic methan- ogens are shorter than for mesophiles Thermophiles will therefore tend to outcompete mesophiles, producing more CH 4 and further warming the climate

CH 4 -climate positive feedback loop Surface temperature CH 4 production rate Greenhouse effect (+) Methanogens grow faster at high temperatures

But, If CH 4 becomes more abundant than about 1/10 th of the CO 2 concentration, it begins to polymerize 

Titan’s organic haze layer The haze is formed from UV photolysis of CH 4 It creates an anti- greenhouse effect by absorbing sunlight up in the stratosphere and re- radiating the energy back to space This cools Titan’s surface Image from Voyager 2

Possible Archean climate control loop Surface temperature CH 4 production Haze production Atmospheric CH 4 /CO 2 ratio CO 2 loss (weathering) (–)

CH 4 /CO 2 /C 2 H 6 greenhouse with haze The Archean climate system would arguably have stabilized in the regime where a thin organic haze was present We don’t quite make it to 288 K, using pCO 2 from Driese et al. (2011) Possible additional warming from higher pN 2 or from albedo feedbacks? Late Archean Earth? Water freezes J. Haqq-Misra et al., Astrobiology (2008) (Old—Rye et al.) Driese et al. (2011) (10-50 PAL, 2.7 Ga)

In any case, the climate crashed when pO 2 rose at 2.4 Ga, wiping out much of the methane greenhouse and triggering glaciations 

Huronian Supergroup ( Ga) Redbeds Detrital uraninite and pyrite Glaciations S. Roscoe, 1969 Low O 2 High O 2

Conclusions The Sun really was ~30% dimmer during its early history, at least after the first 200 m.y. CO 2, CH 4, and C 2 H 6 may all have contributed to the greenhouse effect back when atmospheric O 2 levels were low –Higher pN 2 and lower planetary albedo could also have helped warm the climate, but these mechanisms (in my view) are more speculative High atmospheric CH 4 /CO 2 ratios can trigger the formation of organic haze. This has a cooling effect. –Stability arguments suggest that the Archean climate may have stabilized when a thin organic haze was present The Paleoproterozoic glaciation at ~2.4 Ga may have been triggered by the rise of O 2 and loss of the methane component of the atmospheric greenhouse