I. Climate Change – Greenhouse Gases A. Background • Greenhouse Effect • Gases absorb heat • Natural Greenhouse Effect • Mean planetary temperature = 15 o C vs. -6 o C • Enhanced Greenhouse Effect • Due to GHGs emitted from human activity B. Greenhouse Gases • Most important GHG is water vapor • Accounts for ~50% of natural GHE
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I. I.Climate Change – Greenhouse Gases A. A.Background Greenhouse Effect Gases absorb heat Natural Greenhouse Effect Mean planetary temperature = 15 o.
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I. Climate Change – Greenhouse Gases
A. Background• Greenhouse Effect
• Gases absorb heat• Natural Greenhouse Effect
• Mean planetary temperature = 15 oC vs. -6 oC• Enhanced Greenhouse Effect
• Due to GHGs emitted from human activity
B. Greenhouse Gases• Most important GHG is water vapor
D. Volcanism• Affects water vapor, particles, sulfides, nitrates• Generally leads to planetary cooling
• Theory about extinctions at P/T & K/T boundaries• Mt. St. Helens and Mt. Pinatubo eruptions caused
planetary cooling, and those were small eruptions
E. Photosynthesis & Transpiration• Affect CO2, water vapor
• As [CO2] rises, some plants• Photosynthesize more rapidly• Grow faster• Incorporate more CO2 into biomass
• Keep their stomata open less
• Transpiration releases water vapor into atmosphere• Less transpiration when [CO2] is higher (stomata)
II. Climate Change – Other Factors
F. Soil Characteristics• Affect heat capacity and retention• More hydrated soil leads to
• Darker color (less reflective)• More heat capacity (high heat capacity of water)
G. Albedo (Reflectivity)• Earth’s surface varies considerably (mean = 0.30-0.36)
• Ice/Snow highly reflective (0.9)• Clouds vary in reflectivity• Land generally less reflective
• Changes in land use affect albedo• Desertification increases albedo• Forest – 0.12• Grassland – 0.19• Desert – 0.30
II. Climate Change – Other Factors
H. Wind Patterns• Affect atmospheric circulation and heat flux• Affect circulation of oceans and lakes
• Wind mixes warm water down and brings cooler, nutrient-rich water to surface
• May affect photosynthesis & removal of CO2 from atmosphere
• Ex – El Niño results from changes in wind patterns
I. Astronomical Factors• Earth’s axis precesses on a 26,000 year cycle• Axial tilt varies on a 41,000 year cycle• Orbital eccentricity has a 100,000 year cycle
• Correlated with glacial periods over past 750,000 years