Theme 1 – The seasons of the Earth1. Seasons of the year. (nd). Retrieved December 9, 2011, from the National Aeronautics and Space Administration website: http://www-istp.gsfc.nasa.gov/stargaze/Sseasons.htmIf the Earth's axis were perpendicular to the ecliptic (the trajectory orbital of the Earth around the Sun), the trajectory of the Sun the position relative to the Earth would always be halfway between the North and South poles; its view from any point on Earth would be the same every day; and every point on the Earth, except the poles, would be in shadow (night) half the time and in the sun (day) half the time. Because the Earth's axis of rotation is tilted away from the perpendicular, the Earth experiences seasons. The spring equinox occurs around March 21, and the autumnal equinox occurs around September 22. During this period, the length of day and night is equal. The summer solstice takes place around June 21 and the winter solstice around December 21. The North Pole is tilted toward the Sun during the summer solstice and faces the Sun during the winter solstice (Seasons, n.d.).2. Astronomical theory of climate change. (nd). Retrieved December 9, 2011, from the NationalOceanic and Atmospheric Administration website: http://www.ncdc.noaa.gov/paleo/milankovitch.htmlMilutin Milankovitch, a Serbian astronomer, developed an astronomical theory that explains climate change. As the tilt of the Earth's axis changes, the severity of the seasons changes; a greater degree of tilt means warmer summers and cooler winters, while a decrease in tilt means cooler summers and warmer winters. Since Earth wobbles in orbit, the tilt can vary from 22 degrees to 25 degrees over a 41,000 year cycle. Currently the inclination is 23.5 degrees. Other...... middle of paper......for marine life. During an El Niño event, westerly winds at the western end of the basin allow warm water to flow eastward and the trade winds weaken. The storm area and atmospheric convection move with the warm water, causing heavy precipitation and flooding along coastal areas of western South America. The thermocline (the boundary layer between warm surface waters and deeper, colder waters) deepens and cold water does not rise, depriving marine life of necessary nutrients. During a La Niña event, the trade winds become stronger and the warm pool shrinks, resulting in colder, drier weather off the U.S. coast. Atmospheric convection is limited to the western end of the basin and heavy rain falls over Indonesia. Cold waters along the west coast of South America are soaring and nutrients are abundant for marine life (El Niño, n.d.)..).