Bree'sDontWorryPost

Why Worry...about airline carbon emissions?

Airline emissions are a huge contributor to the greenhouse effect. Aircraft pollution is particularly potent because it is directly emitted into the atmosphere’s upper troposphere and lower stratosphere. Commercial aviation began in the 1940s and has continued to grow ever since. Beginning as an extension of cargo transportation, commercial flights now account for over 80,000 flights per day worldwide. A product of technological advances, the industrial revolution, and understanding in the physics of flights, aviation has become a standard transportation option.

Aircraft engines produce emissions that are similar to other machines that use fossil fuel combustion. However, scientists estimate that “the effect of aviation emissions on the climate is up to five times the impact of emissions occurring on the ground” (sciencedaily.com). In general, aviation emissions affect how much solar energy reaches the Earth and how much radiation escapes into space. There has been evidence of net warming tendency in the last 40-50 years, correlated to post-industrial times. Aircraft emissions induce change in atmospheric chemical composition and cloudiness.
 * Environmental Impact:**

In climate science, radiative forcing is defined as the change in net irradiance, or the power of electromagnetic radiation, between different layers of the atmosphere. A key finding in the IPCC (Intergovernmental Panel on Climate Change) report of 1998 is that the radiative forcing due to aviation fuel use is 2-4 times that from carbon dioxide alone (aiaa.org). To put this in perspective, the average value radiative forcing for all other human activities is at most 1.5 times that of CO2 emissions alone. Emissions from aircrafts contribute to radiative forcing directly with CO2, H2O, soot, and sulfate aerosol, and also indirectly with NOx, ozone, and methane. These last three emissions react with water vapor for form contrails and additional cirrus clouds in the sky.

There has been some efforts internationally and on a country-wide level to reduce aviation emissions. The International Civil Aviation Organization (ICAO), formed by the UN, issued the Kyoto Protocol in 1997. With Japan being the first country to adopt the protocol, there are now 184 countries participating. The Kyoto Protocol set a binding target for 37 industrialized countries to reduce six major greenhouse gas emissions by 5.2% over the five-year period of 2008-2012. Heavier burden is placed on developed nations who are principally responsible for current high levels of emissions. However, countries like India and China who are contributing significantly to aircraft business but are still considered developing do not have to commit to specific reduction targets.
 * Proposed Solutions:**

Another effort to reduce emissions comes in the form of alternative fueling. Jet fuel is a refined petroleum product used in jet aircraft engines; the two major types of jet fuel used in the US are naphtha-based and kerosene-based (climatelab.org). Industry and the FAA (Federal Aviation Administration) established the Commercial Aviation Alternative Fuels Initiative (CAAFI) to explore potential alternative fuels. Biofuels, a blend of algae fuels with existing jet fuels, have been proposed as an option.

Supporting links: To learn more about the [|Kyoto Protocol], the Commercial Aviation Alternative Fuels Initiative [|CAAFI], and research in [|Jet Biofuels]

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