Emission estimate is probably right
China has apparently exceeded the United States as the world's number one emitter of greenhouse gases. But how do they know? To really determine that properly, would you not have to measure emissions from every landfill, vehicle, production plant and animal in a country?
Not necessarily. When the United Nations reported this week that Kyoto Protocol signatory countries and jurisdictions had reduced greenhouse gas emissions to 5 per cent below 1990 levels, its public relations office also helpfully provided an explanation as to how such numbers were produced. These are actually estimates, not measurements.
Common greenhouse gases include carbon dioxide, methane, nitrous oxide, perfluorocarbons and sulfur hexafluoride. Regulators and scientists track input rather than output by using internationally accepted models to estimate how much greenhouse gas is produced by a nation's fuel consumption, industrial production and livestock.
Luckily, the production of carbon dioxide is relatively easy to determine and it is the dominant gas responsible for global warming. So, the good news is, the estimates are pretty accurate. The bad news is, they are probably right about China.