Sunlight varies over the Earth producing variations of temperature, density and pressure Sunshine and Temperatures on Earth Width of Sunbeam striking a specified area of ground

Direct Solar Irradiance Decreases as the distance from Earth to Sun Increases. This distance varies over the year and over long periods, causing climate cycles.

Terrestrial Radiation and Earth’s Temperature We can estimate the temperature of any planet with a simple law. Objects like the Earth radiate at a rate proportional to the 4 th power of their absolute temperature according to the Stefan-Boltzmann Law When incoming solar radiation equals outgoing terrestrial radiation, a planet’s equilibrium temperature is Since I avg = 342 W m -2 T equil = 280K = 7 o C For Radiation: What comes down must go up!

Complicating Factor #1: Albedo Since A = 30% T equil = 255K = -18 o C Albedo is the % of light that is reflected. Reflected light does not contribute to heating. Therefore white objects such as cloud tops and snow reinforce cold. 30 Nov 2006 Midwest Ice Storm

Extra Snow and Ice Perhaps by Chance More Light Reflected Less Absorbed Temperature Falls Even More Snow and Ice Ice Age Begins ?? Even More Light Reflected Less Absorbed Temperature Falls More Snow, Ice Albedo Positive Feedback Mechanism

Albedo Also Varies with Wavelength

Note that global climate cooled from 1940 to 1975!

1 metric ton = 2200 pounds This does not include 1500 to 2000 million metric tons of wood burning from forest clearing. So, given that emissions have increased with time, why did the climate cool from 1940 to 1975?

When T Rises by 10 o C Water Vapor Capacity Doubles Potential Evaporation Rate Doubles Potential Precipitation Rate Doubles

What will rising sea level do to Florida?

00.0 m

30.0 m At the present rate of sea level rise (3 mm/yr) this would take 10,000 years

Into the Future: Predicted Temperature Changes NASA GISS Climate Model Simulation for 2xCO 2.

How Long Have We Been Altering Climate? By 2000 BP, much Forest had Already Been Lost to Agriculture.

This site includes many detailed vegetation maps

During the Ice Age, Deserts spread and Tropical Rainforests shrank.

The melting ice raised sea level 120 m (400 ft). Remaining Ice on Antarctica and Greenland can raise sea level another 75 m (250 ft)

Graphic of Earth's orbit adapted from Pisias and Imbrie [1986/1987].

Zachos, et al. Trends, Rhythms in Cenozoic Climate, Science 292, pp (2004) Cenozoic Climate Overview

During the Carboniferous continents collided to form Pangea. The collision produced the Appalachian Mts, which were much higher than now

Ultimately, we are doomed by the Sun’s gradual brightening and eventual expansion.