According to the United States Environmental Protection Agency (“EPA”), the increase in anthropogenic CO2 emissions has led to the increase in global temperatures in the past century . Because of the preponderance of evidence linking greenhouse gases and climate change, governments worldwide are developing policy to reduce CO2 emissions.
CO2 can enter the atmosphere by burning fossil fuels, in manufacturing processes, and other energy-reliant activities. However, not all emitted carbon remains in the atmosphere; oceans and plant matter absorb some, and some escapes the atmosphere. It is the remaining CO2 in the atmosphere that is causing climate change. To illustrate, the following diagram depicts the cycle of carbon in the atmosphere.
The effect of carbon emissions on the atmosphere can be seen by observing increasing CO2 levels. From the Intergovernmental Panel on Climate Change Working Group I (“IPCC WGI”):
“The global atmospheric concentration of carbon dioxide has increased from a pre-industrial value of about 280 ppm to 379 ppm in 2005. The atmospheric concentration of carbon dioxide in 2005 exceeds by far the natural range over the last 650,000 years (180 to 300 ppm) as determined from ice cores. The annual carbon dioxide concentration growth rate was larger during the last 10 years (1995–2005 average: 1.9 ppm per year), than it has been since the beginning of continuous direct atmospheric measurements (1960–2005 average: 1.4 ppm per year) although there is year-to-year variability in growth rates .”
Other greenhouse gases, such as Methane and Nitrous Oxide, have also been increasing in recent years: “Methane has increased from pre-industrial levels of 715 ppb to 1774 ppb in 2005. Nitrous oxide has increased from 270 ppb to 319 ppb over the same time period (IPCC WGI SPM).” Still, CO2 is the focus of most global warming policies because it accounts for the majority of greenhouse gas emissions. The following diagram illustrates
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