Ice core samples dating back hundreds of thousands of years ago have given scientists a look into the past. As layers of ice accumulated on the Antarctic ice sheet, they preserved pockets of air with various concentrations of greenhouse gases from the atmosphere during a particular time. By comparing atmospheric concentrations before and after the Industrial Revolution, scientists are able to discern that human activity has caused a dramatic increase in greenhouse gases. Carbon dioxide, for instance, has increased 36 percent in the last 200 years. Methane concentrations have increased more drastically – 148 percent since the Industrial Revolution.

Elevated levels of greenhouse gases have contributed to the overall warming of the earth and troubled ecosystems around the world. Currently, global temperatures are rising 0.32 degrees Fahrenheit every ten years. Evidence of warming is seen most notably at the poles where ice caps and glaciers are melting, causing sea levels to rise more than five inches in the last century. Glaciers alone make up 10 percent of the Earth’s landmass, 75 percent of Earth’s freshwater. If they all melt, sea levels can rise 70 percent, creating a drastic change in the Earth’s landscape.

Global warming has also been blamed for unusual weather patterns. Heat waves and droughts plague lands that rely on agriculture, and rainfall patterns have been disrupted in a number of cities throughout the United States. Although scientists are still studying the actual affect of climate change on the occurrence of storm systems, there is some indication that warming has contributed to severe weather. In 2005, the Atlantic hurricane season set a record with 27 storms.