1. The Atmosphere: An Introduction to Meteorology, 12th
Chapter 14: The Changing Climate
The Atmosphere: An Introduction to Meteorology, 12th
Lutgens • Tarbuck
Lectures by:
Heather Gallacher,
Cleveland State University
Copyright © 2013 Pearson Education, Inc.

2. The Climate System
The climate system involves exchanges of energy and moisture among five spheres.
Atmosphere
Hydrosphere
Biosphere
The solid Earth
Cryosphere, the Earth’s surface that is solid water

3. The Climate System

4. How is Climate Change Detected?
Proxy data comes from sea floor sediments, glacial ice, fossil pollen, and tree growth rings, as well as from historical documents.
Paleoclimatology:
Scientists who analyze proxy data and reconstruct past climates are engaged in paleoclimatology.

5. How is Climate Change Detected?
Sea floor sediment—a storehouse of climate data:
This sediment consists of dead, near-surface organisms that accumulate on sea floor.
Oxygen-isotope analysis:
This analysis measures the ratio between 16O (common) and 18O (heavier) in ocean water.
There is more 18O in water during glacial times.
There is more 16O in water during interglacial times.

6. How is Climate Change Detected?
Climate change recorded in glacial ice:
Scientists collect ice cores with a drilling rig.
Ice cores contain a detailed record of changing air temperatures and snow fall.
They also contain air bubbles trapped in the ice, which contain a record of variations in atmospheric composition.

7. How is Climate Change Detected?
Tree rings provide archives of environmental history.
Dendochronology is the dating and study of tree rings.
Thick tree rings indicate favorable conditions for growth.
Thin tree rings indicate unfavorable conditions.

8. How is Climate Change Detected?
Other types of proxy data:
Analyzing fossil pollen makes it possible to obtain high-resolution records of vegetational changes in an area.
Corals exhibit seasonal growth bands.
The accuracy and reliability of climate data extracted from corals has been established when compared to recent instrumental records.
Historical data sometimes will contain information, but do not readily lend themselves to climate analysis.

9. Natural Causes of Climate Change
Plate tectonics
Volcanic activity
Variations in Earth’s orbit
Solar variability

10. Natural Causes of Climate Change
Plate tectonics and climate change:
Tectonic plates move very slowly and produce very gradual changes.

11. Natural Causes of Climate Change
Volcanic activity and climate change:
Major eruptions eject material into atmosphere.
This material filters out solar radiation.
It also lowers the temperature in the troposphere.
The Mount St. Helens eruption lowered the temperature 0.1°C.
El Chichon, in 1982, lowered the temperature 0.3–0.5°C.
Mount Pinatubo, in 1991, lowered temperature 0.5°C.

12. Natural Causes of Climate Change
Variations in Earth’s orbit
The Milankovitch mathematical model is based on several elements.
Variations in shape (eccentricity) of Earth’s orbit about the Sun.
Changes in obliquity—that is, changes in the angle of axis.
Precession, the wobbling of Earth’s axis.

13. Natural Causes of Climate Change

14. Natural Causes of Climate Change
Solar variability and climate:
Sunspots are huge magnetic storms on the Sun’s surface.
They eject large numbers of particles that interact with gases in the Earth’s upper atmosphere.
They are on, approximately, an 11-year cycle between high and low activity.

15. Natural Causes of Climate Change
Sunspots and temperature
Low sunspot activity has been identified with colder periods in North America and Europe.
Sunspots and drought
Periods of drought in the western United States coincide with the 22-year magnetic cycle of the Sun.

16. Human Impact on Global Climate
Addition of carbon dioxide to the atmosphere.
Altering amount of ground cover:
Changes albedo
Evaporation rates
Surface winds

17. Carbon Dioxide, Trace Gases and Climate Change
Rising CO2 levels:
Higher levels are due to burning fossil fuels and deforestation.
Some of the excess is taken up by plants or is dissolved in the oceans.

18. Carbon Dioxide, Trace Gases and Climate Change
The atmosphere’s response
Global Warming

19. Carbon Dioxide, Trace Gases and Climate Change
Role of trace gases:
Methane (CH4), nitrous oxide (N2O), and chlorofluorocarbons (CFCs) all absorb wavelengths of outgoing radiation from Earth.

20. Carbon Dioxide, Trace Gases and Climate Change

21. Climate-Feedback Mechanisms
When one or more component of climate system is altered, scientists must consider many possible outcomes.

22. Climate-Feedback Mechanisms
Types of feedback mechanisms:
The effects of positive-feedback mechanisms reinforce the initial change.
Negative-feedback mechanisms produce results that are just the opposite of the initial change.

23. Climate-Feedback Mechanisms

24. Climate-Feedback Mechanisms
Computer models of climate: Important yet imperfect tools.
Mathematical models are simplified versions of the real climate.
Earth’s climate system is very complex.
It is difficult to model all variables.

25. How Aerosols Influence Climate
Aerosols are tiny, liquid and solid particles that are suspended in the air.
Natural sources include wildfires, dust storms, breaking waves, and volcanoes.
Human-generated aerosols come from the combustion of fossil fuels and burning vegetation.
Black carbon is soot generated by combustion processes.

26. Some Possible Consequences of Global Warming
Sea-level rise

27. Some Possible Consequences of Global Warming
The changing Arctic:
The loss of Arctic sea ice is occurring and represents a positive-feedback mechanism.
Permafrost has decreased, which also represents a positive-feedback mechanism.
Increasing ocean acidity is caused by CO2 being absorbed by oceans, which decreases pH.
The potential for “surprises”
Climate change can bring unexpected results.

28. End Of Chapter 14