
50 Engineering Response to Climate Change
changes occur on a 100,000-year cycle. When the earth is closest to the sun
(perihelion), more solar radiation reaches the surface of the planet, resulting
in a warmer planet. When the earth’s orbit is farthest from the sun (aph-
elion), colder temperatures are observed. However, looking at today, the orbit
is closer to circular. The earth travels in a loop around the sun each year,
while it additionally rotates on its tilted axis. The hemisphere tilted toward
the sun experiences summer, while the hemisphere facing away experiences
winter. The severity of the seasons changes when the angle of the til