1. Some of the causes of past climate change are changes in the earth’s orbit, changes in the sun’s intensity, and volcanic eruptions causing aerosol and carbon dioxide emissions. The first cause, changes in the earth’s orbit, affects climate because it changes how much sunlight is received on the earth’s surface. The second cause, changes in the sun’s intensity, affects climate because the intensity of sunlight that reaches earth’s surface creates a warming or cooling effect depending on the intensity. The third cause, carbon dioxide emissions through volcanic eruptions, changes climate because of the warming effect that raises temperatures. The fourth cause, aerosol emissions through volcanic eruptions, changes climate because aerosols block sunlight and affect climate with short term cooling.
2. The following is a list of indicators that suggest global warming in the U.S.:
• U.S. Greenhouse Gas Emissions – Concentrations of greenhouse gases have risen greatly since the start of the industrial era.
• U.S. and Global Temperature – Average temperatures in the U.S. have risen exponentially with the greatest warming in states such as Alaska.
• U.S. and Global Precipitation - During the twentieth century, average precipitation in the U.S. has increased by six percent.
• Tropical Cyclone Intensity – The intensity of tropical storms has increased in the last 20 years and is closely related to warmer Atlantic sea surface temperatures.
• Sea Surface Temperature – Sea surface temperatures have been warmer over the past three centuries then any other three consecutive centuries.
• Sea Level – The average sea level rise has grown exponentially and in recent years has grown more then an inch per decade.
• Glaciers – Since 1960 the sizes of U.S. glaciers have shrunk and are shrinking exponentially quicker by each year.
• Length of Growing Season – The length of the U.S....