lec-2-3-slides-09 - Lectures 2-3 week 1-2 2009 HAS222d...

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Unformatted text preview: Lectures 2-3 week 1-2 2009: HAS222d Solar radiation, the greenhouse, global heat engine http://en.wikipedia.org/ The 4 streams of this course (see syllabus) 1.Energy forms of energy concetrated, diluted conservation transmission/movement transformation efficiency of transformation heat engines degradation (and entropy) storage ‘utilization’ by plants and animals carbon cycle, photosynthesis 3.Humans and energy history of energy demand and development ….fossil fuels connections with evolution alternative energies 2.Global Environment physical, chemical, biological atmosphere, ocean, land surface energy, air, water, ice, carbon the sun-atmosphere-ocean heat engine fluid circulations in which protective ‘niches’ of life develop 4.Arctic populations natives: settlement Europeans: exploration assimilation, exploitation shaping of their lives by energy and food resources in a harsh environment amplified global warming in the Arctic Let’s start with the sun diameter: 1.38 million km distance from Earth (mean): 149.6 million km (93 million miles)* tilt of Earth’s rotation axis relative to its orbit round the sun: 23.5 0 the orbit is an ellipse, but only about 2% different from a circle: the oribital eccentriciy**= 0.017 rotation period: 23.9 hours length of day: 24 hours On July 4 this year the Earth is farthest from the sun (aphelion); on Jan 4 it was closest (perihelion); about 7% more sunlight (rate of energy falling on Earth) in Jan than in July. As Northern Hemisphere goes, so goes climate! The eccentricity shifts with 100,000 year period from 0.05 to nearly zero. perihelion shifts with 21,000 year period obliquity (tilt of axis) shifts with 41,000 year period …..all these slight changes alter the amount of sunshine and its distribution at the Earth’s surface, somehow leading to ice ages….cycles of cold and warm climate. Averaged over the globe, sunlight falling on Earth in July (aphelion) is indeed about 7% less intense than it is in January (perihelion)." That's the good news. The bad news is it's still hot. "In fact," says Spencer, "the average temperature of Earth at aphelion is about 4o F (2.3o C) higher than it is at perihelion." Earth is actually warmer when we're farther from the Sun ! ========================================================================================= www.cwru.edu , http://science.nasa.gov/headlines/y2001/ast03jul_1.htm *(these two numbers together tell us how big the disc of the *(these two numbers together tell us how big the disc of the sun appears in the sky sun appears in the sky ….the relationship is .the relationship is....
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lec-2-3-slides-09 - Lectures 2-3 week 1-2 2009 HAS222d...

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