Air travel has long been lambasted, particularly by environmental groups, for the amount of gas emissions that flights release into the atmosphere, and contributing to global warming. There is a growing movement to make a smaller environmental imprint, by becoming carbon neutral - effectively paying for the pollution we cause by contributing to projects that do not contribute noxious gas and toxins into the environment. The air travel industry has begun to join this trend.
Global warming is believed to be mainly caused by carbon dioxide emissions that are released when using fossil fuels such as coal, gas and oil. You heat your home; keep your perishables in the fridge; drive your car; take a flight, and are thus contributing carbon dioxide to the atmosphere. As things stand, most of the things we do that pollute the environment cannot by completely avoided. Hence the idea of becoming carbon neutral - of figuring out how much pollution we each cause and then neutralizing that by paying back to the environment so to speak.
Becoming carbon neutral means purchasing carbon offsets to neutralize the pollutants added to the environment. Because global warming is a problem across the planet, it doesn't matter where the carbon offset is located - if you contribute to wind turbines thousands of miles away it has a beneficial effect - local or abroad as climate change affects every part of the world.
Essentially, carbon offsets are credits you purchase to apply to the emissions you put into the environment, and you effectively reduce your net impact on the environment. Carbon offsets include programs such as wind power, solar power, and other such projects that focus on energy efficiency and renewable resources.
But how does all of this apply to air travel? Flights burn a lot of fuel, and put those emissions right into the atmosphere. The air travel industry is seeking more fuel efficient planes, but any gain in efficiency seems offset by the increase in the numbers of passengers traveling by air. The next page goes into more detail on climate change and air travel, and choices we have as consumers.