Topic 6

Insolation and the Seasons

Insolation(INcoming SOLar radiATION)

Intensity of Insolation depends on the angle of the Sun’s rays, which are due to:– Earth’s shape– latitude– season– time of day

Duration of Insolation (number of hours of daylight) is due to:

– latitude– season

Generally: intensity, temperature duration, temperatureWhich plays a greater role?

IntensityWhen are intensity & durantion greatest in New York?

June 21stWhen is our hottest day of the year?

end of JulyThese dates are not the same because the Earth has to

reach a balance between insolation and terrestrial radiation (the heat Earth is giving off to space)

(Likewise, the hottest time of day is not solar noon)

Effects of the Atmosphere on Insolation

Before radiation from the Sun can reach the Earth’s surface, it has to pass through the atmosphere… most of the “bad” stuff never reaches us.

The Greenhouse Effect

How does a greenhouse get heated?

Long wavelength visible light from the Sun passes through the glass, gets absorbed by objects inside the greenhouse and reradiated as short wavelength infrared (heat) energy.

Longer wavelengths are unable to pass through the glass, so the heat gets trapped inside, making temperatures rise.

“Greenhouse gases” in our atmosphere act just like the glass, trapping the heat in our atmosphere and increasing global temperatures.

What are the greenhouse gases?

Water Vapor Carbon Dioxide & Methane -- mostly from

the burning and production of fossil fuels (coal, oil, natural gas), destruction of rainforests, and decomposition of organic matter

Ozone -- smogChlorofluorocarbons (CFCs) -- aerosol

spray cans and refrigerants

What is “Global Warming?”

“Global Warming” is a term that combines the effects of greenhouse gases and loss of the ozone layer and their affects on our overall increasing temperatures.

The debate is not about the Earth getting warmer…it’s about whether or not human activities are causing it.

What are some possible effects of Global Warming?

• Melting of glacial ice and polar ice caps which further alters climate patterns and raises sea levels

• Growing seasons shift• Habitat loss/shift --

Will organisms adapt?