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MET 112 Global Climate Change - Lecture 4. Natural Climate Forcing Dr. Eugene Cordero San Jose State University. Outline – Earth’s early history Evolution of the atmosphere Temperature variations Activity. Articles we’ve been reading…. 0 of 5. :15.
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MET 112 Global Climate Change - Lecture 4 Natural Climate Forcing Dr. Eugene Cordero San Jose State University Outline – • Earth’s early history • Evolution of the atmosphere • Temperature variations • Activity MET 112 Global Climate Change
0 of 5 :15 In this weeks reading, the main topic of the article from New Zealand is about • Changes in CO2 • Changes in CH4 • Changes in solar radiation • Transport of oil • Transport of water • Changes in air pollution • Both 1 and 4 • Both 1 and 5 • Both 1 and 6 MET 112 Global Climate Change
0 of 5 :20 Who is the primary funder of the American Enterprise Institute (AEI) • NASA • ExxonMobil • Google • HP • PrimeAmerica • ESPN • CNN MET 112 Global Climate Change
Temperature Graph Source: http://www.ruf.rice.edu/~leeman/aNR.html
Water restrictions in Australia Source: http://www.melbournewater.com.au/content/water/water_storages/stage_3_water_restrictions_-_questions_and_answers.asp
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 MET 112 Global Climate Change
Variations in solar output Orbital variations Meteors External Forcing MET 112 Global Climate Change
Sunspots are the most familiar type of solar activity. Solar Variations • Sunspots correlate with solar activity • More sunspots, more solar energy MET 112 Global Climate Change
SOLAR ACTIVITY • Sunspots are the most familiar type of solar activity.
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.
SOLAR INFLUENCES ON CLIMATE • Solar activity appears to slightly change the Sun’s brightness and affect climate on the Earth...
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. MET 112 Global Climate Change
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 MET 112 Global Climate Change
Earth’s orbit: an ellipse • Perihelion: place in the orbit closest to the Sun • Aphelion: place in the orbit farthest from the Sun MET 112 Global Climate Change
Eccentricity: period ~ 100,000 years MET 112 Global Climate Change
Precession: period ~ 22,000 years MET 112 Global Climate Change
Axis tilt: period ~ 41,000 years MET 112 Global Climate Change
Temperature: the last 400,000 years From the Vostok ice core (Antarctica)
Fig 4.5 High summer sunshine, lower ice volume
Formation of Glaciers • Glaciers - composed of fallen snow that is compressed into a large, thickened mass of ice over many years • Glacier Growth: When over a year snowfall (winter) is larger than snowmelt (summer) • Glacier Decay: When over a year snowfall (winter) is less than snowmelt (summer) • Glacier growth and decay largely influenced by summer temperatures. MET 112 Global Climate Change
____________________________ ____________________________ Ocean changes Chemical changes in the atmosphere (i.e. CO2) Natural variations Internal Forcing Plate tectonics/mountain building Volcanoes MET 112 Global Climate Change
Activity Consider the fact that today, the perihelion of the Earth’s orbit around the sun occurs in the Northern Hemisphere winter. In 11,000 years, the perihelion will occur during Northern Hemisphere summer. A) Explain how the climate (i.e. temperature of summer compared to temperature of winter) of the Northern Hemisphere would change in 11,000 years just due to the precession. B) How would this affect the presence of Northern Hemisphere glaciers (growing or decaying)? Assume growth is largely controlled by summer temperature. MET 112 Global Climate Change
42 of 70 If the earth’s tilt was to decrease, how would the summer temperature change at our latitude • Warmer summer • Cooler summer • Summer would stay the same • Impossible to tell
42 of 70 A: How would climate change • Warmer winters, cooler summers • Warmer winters, warmer summers • Cooler winters, warmer summers • Cooler winter, cooler summer MET 112 Global Climate Change
42 of 70 B: How would glaciers change? • Glaciers would grow • Glaciers would decay • Glaciers would stay about constant MET 112 Global Climate Change
