In recognition of fundamental changes to the way governments approach energy-related environmental issues, the International Energy Agency (IEA) produces each year a report on CO2 emissions from fuel combustion.

The report started publication in 1997 and is designed to help people understand the evolution of CO2 emissions sector-wise and by fuel in more than 140 countries and regions. It has ever since become an essential tool for analysts and policymakers.

In the 2008 edition, the IEA said China's CO2 emissions volume totaled 5.649 billion tons, second to the 5.697 billion tons of emissions by the United States, the world's biggest CO2 emitter.

The publication however noted that China's per capita CO2 emission volume was 4.28 tons, less than 23 percent, 39 percent and 45.1 percent respectively that of the US, Russia and Japan.

Undoubtedly, the calculation, both on a per capita and national basis, indicates that the IEA attaches importance not only to a country's whole CO2 emission volumes but also to its per capita emissions.

The agency has however failed to clarify whether its per capita data is based on a country's citizens or on its residents, no matter whether they are citizens or non-nationals. The two different statistical methods will lead to two distinctive statistical results.

Of a country's nationals, some possibly live and engage in certain kinds of production activity not in their own country, which will cause some CO2 emissions in other countries or regions. Similarly, for a specific country, there are surely some non-national residents living and engaging in production activity that lead to increased CO2 emissions within the country's territory.

As economic globalization deepens, it has become very common for a country's gross national product (GNP) to often diverge from its gross domestic product (GDP). That is partly the result of globalization, which has facilitated the flow of people among different countries and their production activity in non-native soil. As a result, some parts of a country's final product and labor value, although still belonging to its GNP, are calculated as forming other countries' GDP value.

Given that any production activity will unavoidably cause some CO2 and other greenhouse gas emissions, it has become an obvious fact that all countries' gross national emission (GNE), a CO2 emission statistical data directly based on production activity of their own nationals, is always different from their gross domestic emission (GDE), the volume of CO2 emissions caused by all their residents, including nationals and non-nationals, within their territories.

There may be some who argue that there is not much difference between a country's GNE and its GDE. For a majority of countries, this is likely the case. But for those that have absorbed a large amount of foreign direct investment (FDI), the situation is completely different.

If a number of foreign-funded and joint venture companies set up production bases in a country, its CO2 emissions volume caused by these foreign producers would be quite significant.