学英文4

A carbon footprint takes into consideration many harmful gases, and the average size varies around the world.

These days, you don’t have to be an environmental scientist to have heard the term carbon footprint. It gets used a lot in discussions about global warming or climate change and refers to the amount of carbon dioxide (CO₂) that gets released during certain processes, whether by a corporation or just one person.

However, carbon dioxide is but one of many gases that contribute to global warming and a carbon footprint. Such harmful emissions are known as greenhouse gases and some of them are far more damaging than CO₂. Methane (CH₄), for example, is twenty-five times as harmful as CO₂, and nitrous oxide (N₂O) is three hundred times worse. And then there are refrigerant gases, which are used in cooling systems and can be several thousand times more potent than CO₂.

In the United Kingdom, CO₂ accounts for 86 percent of its greenhouse gas output, while methane accounts for 7 percent, nitrous oxide 6 percent and refrigerant gases 1 percent.

Since we know how potent all these other gases are in relation to CO₂, a carbon footprint provides an accurate reading on all the major harmful emissions being released. This conversion method is known as carbon dioxide equivalent, or CO₂e.

The average size of a carbon footprint varies from country to country, but it tends to be bigger in the developed world. In Malawi, for example, the average carbon footprint of a person is around 0.1 metric tons of CO₂e per year. The average person in the United Kingdom, however, measures up at around 15 metric tons per year, while the average North American comes in at around 28, and Australians at 30 metric tons. As for the planet as a whole, in 2007 we produced around 49 billion metric tons of CO₂e.

Being British, the author hopes to help the United Kingdom reduce harmful emissions by a significant yet reasonable amount. Berners-Lee has laid the groundwork for such a reduction through what he calls the 10-tonne lifestyle, which would result in the average person going from 15 to 10 metric tons per year – a one-third reduction of each person’s carbon footprint.