Brighter Planet

How is my carbon footprint calculated?

Your carbon footprint is calculated as:

emissions - offsets = footprint

In other words, your footprint is your net impact on the climate in terms of greenhouse gases. We currently take the following components into account when we calculate your emissions:

• Driving
• Flying
• Other transportation (public transportation, trains)
• Home energy use
• Consumables
• Shared services

When you create a new profile, your emissions in each of these components is assumed to be the default. When you add information to your profile, we estimate new values for the components. If you add a low-emissions vehicle and say you drive it less than the average American, for example, your driving component of emissions will be reduced and therefore your footprint will also be reduced.

When you earn offsets, we add this to your offsets total and subtract this from your emissions. Therefore your footprint is reduced by earning offsets.

What are shared services?

The shared services component of your emissions is divided equally among all U.S. residents and represents services from which we benefit, but that we do not control. Street lights and the Coast Guard are good examples of shared services. They will be active for you, even if you do not use them or control them. This portion of your footprint cannot be reduced except through political action to get organizations and government to systematically reduce carbon emissions.

Why did my footprint go down?

Sometimes when you enter data into your profile, your total estimated footprint drops, instead of getting higher. This may come as a surprise, but there is a simple reason for it. When you start out with an empty profile, we assume a default estimate for the components of your emissions: how much you drive, how much you fly, etc. These default estimates are based on U.S. Census and U.S. Environmental Protection Agency data represent the average American.

When you add a flight, for example, we stop assuming that you are an average flier, and your footprint total will actually be lower than the initial value. That is, at least until you have entered more or longer flights than the average American flies.