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How Does Solar Energy Move? Energy comes to Earth by RADIATION... Then gets transferred all 3 ways: Radiation (energy that travels from a source) Conduction (energy that’s transferred by contact) Convection (energy transfer in moving fluids)
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Global Warming
Learning goal: determine the long term impact of humans on weather and
vise versa
What is Global Warming?Increasing air temp because of heat being trapped in the atmosphere caused by greenhouse gases, such as CO2
Earth is starting to warm because less heat is being released back into space
Humans burning fossil fuels such as gas and coal are primarily responsible
CO2 is released in huge amounts when we drive cars, burn coal to generate electricity, and produce goods in factories
How Does Solar Energy Move?Energy comes to Earth by RADIATION . . .
Then gets transferred all 3 ways:
Radiation (energy that travels from a source)
Conduction (energy that’s transferred by contact)
Convection (energy transfer in moving fluids)
Insolation FactsOnly 51% of solar energy reaches Earth’s surface
Much of that is radiated back into atmosphere through infrared radiation
CO2 absorbs much of this infrared radiation, trapping the heat in our atmosphere
This is called the Greenhouse Effect
Without natural Greenhouse Effect Earth would be freezing (60 degrees F cooler)
Enhanced Greenhouse Effect makes temps increase with possibly disastrous results
Factors Affecting Insolation
Tilt of the Earth (23.5 deg)
Earth is heated unevenly, causing temp to vary around the world
Different latitudes receive more or less energy
Equator hottest – Poles the coldest
Time of Day
Closest to 90° at noon, warmest in afternoon, coldest just before sunrise
Factors Affecting Insolation
Season (time of year)
Northern Hemisphere has highest temperature just after time of maximum insolation
June 21 (summer solstice – longest day)
Lowest temp at time of minimum insolation
December 21 (winter solstice – shortest day)
Factors Affecting Insolation
Cloud Cover
Clouds reflect insolation back into space
More solar energy reaches Earth on clear days
More infrared radiation (from the surface) travels back into space on clear nights
Heating of Water and LandWater and Land heat up and cool off at different rates
Water heats more slowly than land
Why?
Heat goes deeper in water than land
Water spreads heat easily by convection
Some solar radiation is used in evaporation
Water needs more energy than land to raise temperature
Heating of Water and LandVarying types of land absorb heat differently
Dark surfaces absorb more energy
Rough surfaces absorb more energy
Wet ground warms more slowly
Meadows are warmer than forests
Cities typically have higher temps than forests
Why?
Building materials like concrete & asphalt absorb & radiate enormous amount of heat (urban heat island)
The Effects of IceIce reflects sunlight, and thus radiation, back into space
Cooler temperaturesCooler temperaturesMore snow coverMore snow cover
Less energy absorbed from the sunLess energy absorbed from the sun
Warmer temperaturesWarmer temperatures
Less snow coverLess snow cover
More energy absorbed from the sunMore energy absorbed from the sun
The Effects of WaterHonolulu, HawaiiLatitude: 21 18Jan temp: 73 F
San Diego, CaliforniaLatitude: 32 42Jan temp: 57.8 F
Latitudes are different but temps are moderate because they are surrounded by or next to the ocean
San Diego
Heating of LandSan Diego, CaliforniaLatitude: 32 42Jan temp: 57.8 F
Phoenix, ArizonaLatitude: 33.29Jan temp: 54.2 F
Latitudes are very similar but temperatures over land masses can vary greatly
July temperaturesSan Diego: 70.9 FSeasonal change: 13.1 deg F
Phoenix: 92.8 FSeasonal change: 38.6 deg F