Chapter16b - Climate Change I I Mid-chapter summar y •...

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Unformatted text preview: Climate Change - I I Mid-chapter summar y • The Earth’s climate is constantly undergoing change. Evidence suggests that throughout much of the Earth’s history the Earth’s climate was much warmer than it is today. • The most recent glacial period (or I ce Age) began about 2 million years ago. During this time, glacial advances were interrupted by warmer periods ( interglacial periods ). I n North America, glaciers reached their maximum thickness and extent about 18,000 to 22,000 years ago and disappeared completely from North America by about 6,000 years ago. • Over the last 100 years, the the Earth’s surface temperature has increased by about 0.6 o C (about 1 o F). Possible Causes of Climatic Change • External : changes in the 1. incoming solar radiation 2. composition of the atmosphere 3. Earth’s surface • Natural phenomena may contribute to all three ( 1-3 ) • Human activity may contribute to 2 and 3 • I nternal : changes in the circulation patterns of the ocean and the atmosphere, etc. Climate Change and Feedback Mechanisms • The climatic elements are intertwined: feedback • Negative feedback : counteracts changes, stabilizes climate ♦ Thermal (I R) radiation of the planet: increased temperature leads to increased I R emission from the planet -> the planet cools and the temperature drops. ♦ Cloud negative feedback : higher temperature leads to more water vapor and therefore more clouds. The clouds increase the planet’s albedo and less solar light reaches the surface -> planet cools and the temperature drops....
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Chapter16b - Climate Change I I Mid-chapter summar y •...

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