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Earth’s Climate System

Explore the dynamics of Earth's climate system, causes of climate change, feedback loops, and natural influences like solar activity and orbital variations. Understand the impact of greenhouse gases, human-induced climate change, and historical climate data.

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Earth’s Climate System

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  1. Earth’s Climate System • Climate – long term atmospheric conditions in a region • Earth’s climate includes interactions of: • Atmosphere • Hydrosphere • Geosphere • Biosphere • Cryosphere • Climate system – exchanges of energy and moisture between these spheres

  2. Earth’s Climate System

  3. Earth’s Climate System • Feedback loops – modify atmospheric processes • Positive feedback loops – enhance initial change • Negative feedback loops – counteract initial change

  4. Determining Causes of Earth’s Climate Change • Paleoclimatology • Proxy data – indirect evidence using natural recorders of climate variability • Sea floor sediments • Coral deposits • Glacial ice rings • Tree rings • Pollen • Historical documents

  5. Temperature: the last 400,000 years From the Vostok ice core (Antarctica)

  6. External Forcing: Internal Forcing: Natural Climate Change The agent of change is outside of the Earth-atmosphere system • The agent of change is within the Earth-atmosphere system itself

  7. Variations in solar output Orbital variations Meteors External Forcing

  8. Natural Causes of Climate Change • Solar energy changes • Variable energy from the Sun over time • Luminosity • Sunspots

  9. Sunspots are the most familiar type of solar activity. Solar Variations • Sunspots correlate with solar activity • More sunspots, more solar energy

  10. SOLAR ACTIVITY • Sunspots are the most familiar type of solar activity.

  11. THE SOLAR CYCLE • Sunspot numbers increase and decrease • over an 11-year cycle • Observed for centuries. • Individual spots last from a few hours to months. • Studies show the Sun is in fact about • 0.1% brighter when solar activity is high.

  12. The Seasons • The Earth has seasons because the axis is tilted. • Earth rotates on its axis as it orbits the Sun. • Earth’s axis ALWAYS points in the same direction… • but Earth’s location in its orbit around the Sun determines whether the NH or SH is pointed toward the Sun.

  13. The Seasons • NH Summer Solstice • June 20-21 • NH Autumnal Equinox • September 22-23 • NH Winter Solstice • December 21-22 • NH Vernal Equinox • March 20-21

  14. Earth’s orbit: an ellipse • Perihelion: place in the orbit closest to the Sun • Aphelion: place in the orbit farthest from the Sun

  15. Earth’s orbit: an ellipse • Perihelion: place in the orbit closest to the Sun • Aphelion: place in the orbit farthest from the Sun

  16. THE MAUNDER MINIMUM • An absence of sunspots was well observed • from 1645 to 1715. • The so-called “Maunder minimum” coincided with a cool climatic period in Europe and North America: • “Little Ice Age” • The Maunder Minimum was not unique. • Increased medieval activity • correlated with climate change.

  17. Natural Causes of Climate Change • Variations in Earth’s Orbit • Milankovitch Theories • Eccentricity of Earth’s orbit • Obliquity of Earth’s axis • Precession of Earth’s axis

  18. Milankovitch theory: Serbian astrophysicist in 1920’s who studied effects of solar radiation on the irregularity of ice ages Variations in the Earth’s orbit Changes in shape of the earth’s orbit around sun: Eccentricity (100,000 years) Wobbling of the earth’s axis of rotation: Precession (22,000 years) Changes in the tilt of earth’s axis: Obliquity (41,000 years) Orbital changes

  19. Eccentricity: period ~ 100,000 years

  20. Natural Causes of Climate Change Volcanic eruptions Volcanic ejecta may block sunlight Need many eruptions in short time period Not observed in recent history

  21. Natural Causes of Climate Change • Movement of Earth’s Plates • Change ocean circulation • Extremely slow process • Climate change would be very gradual over millions of years • Linked to Pleistocene Ice Age, Little Ice Age, Medieval Warm Period

  22. Documenting Human-Caused Climate Change • Intergovernmental Panel on Climate Change (IPCC) • Global group of scientists • Published assessments since 1990 • Predict global temperature changes of 1.4–5.8°C (2.5–10.4°F) • Climate change models can mimic modern conditions only if human emissions are taken into account.

  23. Atmosphere’s Greenhouse Effect • Global warming – increase in Earth’s global temperatures • Greenhouse effect – keeps Earth’s surface habitable • Incoming heat energy is shorter wavelengths • Longer wavelengths – some trapped, some escape, net warming effect

  24. Earth’s Heat Budget Addition to or subtraction from heat on Earth Incoming radiation from Sun shorter wavelengths Outgoing radiation from Earth longer wavelengths Rates of energy absorption and reradiation must be equal

  25. Earth’s Heat Budget

  26. Greenhouse Gases • Water vapor • Most important • 66–85% of greenhouse effect • Carbon dioxide • Natural part of atmosphere • Greatest relative contribution from human activities • Burning of fossil fuels

  27. Atmospheric Carbon Dioxide

  28. Greenhouse Gases • Methane • Second most abundant human-caused greenhouse gas • Great warming power per molecule • Landfill decomposition • Cattle • Other trace gases • Nitrous oxide, CFCs, ozone

  29. Human-Caused Greenhouse Gases

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