dr. michael maccracken is climate enginering an option for dealing with climate change? 9/25/09 ...
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Dr. Michael MacCracken
Is Climate Enginering an Option for Dealing with Climate Change?
9/25/09
http://www.colby.edu/sts/20090925MaccrackenGeoengineeringColby.pdf
Seasons
A season is a period of time during the calendar year characterized by or associated with a set of coherent weather or climate phenomena.
Seasons are terrestrial responses to solar heating inequalities that are governed by the tilt of the Earth’s axis and the shape of its orbit around the Sun.
Angle and Duration of Sunlight
Angle of the sun’s rays changes over the course of the year.
In our latitude, the noontime sun angle varies from 68.5o on June 21 to 21.5o on December 21
Duration of the day changes over the course of the year.
Above the Arctic circle, the duration of the day on June 21 is 24 hours; on December 21 it is 0 hours.
Other FactorsThe fact that the Earth’s orbit is not a perfect circle makes little difference at
all.The Earth is farther from the Sun in summer in the Northern Hemisphere
(aphelion on July 5) and closer to the Sun in the Winter (perihelion on Jan. 5).
The difference of 3.5% in distance results in 7% greater solar insolation in Winter than Summer.
Overall, the angle and duration factors far outweigh this difference in distance.
Moreover, Summer is actually longer than Winter! There are 185 days between March 21 and Sept. 22 but only 180 days between Sept. 22 and March 21.
Why?
Greenhouse Effect Greenhouse Effect Climate Change Climate Change Global WarmingGlobal Warming
READ Somerville Chapter 3READ Somerville Chapter 3
Is the Greenhouse Effect Real?
YES! Without greenhouse gases in the atmosphere (CO2 and H2O) the Earth would be about 33 degrees cooler than at present
The average global temperature is now 287 KWithout greenhouse gases it would be 254 K
We would have an ice-covered planet!
Is the Climate Changing?YES!YES!
It has always been changing!It has always been changing!
And it is expected to continue to changeAnd it is expected to continue to change
What is Humanity Doing to Enhance the What is Humanity Doing to Enhance the Natural Greenhouse Effect?Natural Greenhouse Effect?
The composition of the earth's atmosphere The composition of the earth's atmosphere is undergoing a major global change is undergoing a major global change
Human activities, such as air pollution, Human activities, such as air pollution, deforestation, the burning of fossil fuels, and deforestation, the burning of fossil fuels, and even agricultural practices are now starting even agricultural practices are now starting to alter the balance of radiatively active to alter the balance of radiatively active gases in our atmospheregases in our atmosphere