Climate change is a significant and lasting change in the distribution of weather patterns over periods of time ranging from decades to millions of years. What differentiates today’s climate is the fact thatthe Earth is warming at a faster rate than ever before and humans have played a major role in the change.
The projected increase of up to 11˚F over the next century would dramatically alter the stable climate in which human civilization developed. Consider that the difference between today’s climate and the ice age, when massive glaciers covered the northern hemisphere, was a mere 9˚F.
Carbon dioxide is one of multiple greenhouse gases (GHGs) which trap heat in the atmosphere. These gases are necessary for sustaining life on earth because they trap energy from the sun. The greenhouse effect is the process by which the earth retains heat.
While carbon dioxide (CO2) levels have varied over time, there is compelling evidence that the current trends are both unprecedented and man-made.
This rise in temperature corresponds directly with a global surge in CO2 emissions beginning during the Industrial Revolution. Levels are up almost 40% since then, from approximately 285 ppm in the late 1800s to over 396 parts per million (ppm) in August 2012. CO2 levels have been rising at an average annual rate of about 2.0 ppm per year over the past decade.
Total carbon dioxide emissions doubled between 1900 and 1950. They increased nearly four-fold between 1950 and 2000. Today, human activity is responsible for producing nearly 20 billion tons of carbon dioxide annually. The earth’s temperature has fluctuated naturally over time but has increased rapidly with the rise in CO2 emissions, specifically after 1970.
It is important to understand that climate change will affect different regions in different ways.
Global temperatures are rising but this does not mean that every region is affected in the same way. This rise in temperature also does not mean that global warming and climate change are synonymous. Some regions of the world are experiencing extreme heat and droughts while others may be experiencing unseasonably cold weather.
Temperature change is not the most severe aspect of climate change. It is also causing the ice to melt in the Arctic, droughts in the Sahel (south of the Sahara), wildfires, and concerns of energy shortage in the United States.
Climate change also presents deep and broad challenges to U.S. security including unprecedented levels of drought, extreme flooding, wildfires, food security and water availability.
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