The document discusses the environmental impacts of emissions from airplane vapor trails, also known as contrails. It notes that the 35 million commercial airline flights each year produce a lot of carbon dioxide and greenhouse gases. Vapor trails are particularly problematic when they form at high altitudes where airplanes fly, as this thin air allows thick smoke to linger. Studies show vapor trails can contribute up to 8% of global warming, and as much as 20% of warming over the Arctic. Reducing the amount of soot in vapor trails could help lessen their impacts and may even help cool the earth by preventing the formation of cirrus clouds. However, politicians are often reluctant to introduce taxes on airlines that could reduce emissions.