Every time you exhale, you are pumping out what the EPA has determined to be a pollutant “reasonably anticipated to endanger public health or welfare.” Carbon dioxide (CO₂) has an impact on global temperature and weather patterns and, along with water vapor, methane, nitrous oxide, and chlorofluorocarbons, is considered a “greenhouse” gas. CO₂ comes from a variety of sources, ranging from animals to cars, factories, and other sources of carbon combustion. The concentration of CO₂ currently in the atmosphere is higher than it has been in the last 650,000 years, according to the National Oceanic and Atmospheric Administration (NOAA).

The effects of CO₂ are not all bad. Plants breathe it like we breathe oxygen, so increased levels can cause crops and other plants to grow more vigorously and absorb water more efficiently. As a greenhouse gas, it traps heat on the surface of the earth thus warming the planet. This can lead to longer growing seasons and increased precipitation. But with these benefits come other dangers, many which are difficult to control and predict.

Rising global temperatures mean that the polar ice caps and other major ice sheets will continue to melt. Greenland lost 150-250 cubic kilometers of ice (36-60 cubic miles) from 2002 to 2005 and Antarctica lost about 152 cubic kilometers (36 cubic miles). This, in turn, leads to rising ocean levels. Global Sea levels rose about 17 centimeters (6.7 inches) in the last century. Coastal areas are put at a high risk of floods as a result.

The increased precipitation caused by higher global temperatures also results in more intense storms. The 2007 Intergovernmental Panel on Climate Change (IPCC) summary predicts that the intensity of tropical cyclones (such as hurricanes) will increase. Since water vapor is also a greenhouse gas, some scientists think that more precipitation and evaporation will create a feedback loop, further warming the planet. The extent of this, however, is still unknown.

In response to fears of these negative effects, policymakers have taken steps to curb the amount of CO₂ and other greenhouse gasses that are released into the atmosphere. The United Nations recently held a United Nations Framework Convention on Climate Change in Doha which amended the Kyoto Protocol. The protocol is an international agreement to reduce greenhouse gas emissions. The U.S. signed the treaty, but it was never introduced in congress for ratification.

In the U.S., the EPA released the Tailpipe rule, Timing rule, and Tailoring rule to control CO₂ emissions. These regulations set limits on the amount of carbon based emissions that factories, cars, and other industries can emit annually. The rules were upheld by a Federal Circuit Court in Coalition for Responsible Regulation, Inc. v. EPA.

Still, global emissions increased 3% in 2011 and are expected to increase another 2.6% in 2012. The continuing difficulty of curbing the use of the world’s primary source of energy (carbon based fuel) has led to another scientific field attempting to control the weather: Geoengineering.

Geoengineering is concentrated on two fronts: Fertilizing the oceans to promote the growth of algae that soak up carbon from the air and injecting sun-reflecting chemicals to the upper atmosphere. Both of these have the intention of cooling the planet. However, the side effects of these processes are still unknown in a chaotic weather system. Consequently, this field has been met with skepticism until more information can be obtained.

Additional Resources

The New York Times, Global Warming & Climate Change: http://topics.nytimes.com/top/news/science/topics/globalwarming/index.html

The U.N. Framework Convention on Climate Change, Doha Climate Change Conference: http://unfccc.int/2860.php#decisions

NASA, Global Climate Change: http://climate.nasa.gov/evidence