Gaseous Air Pollution Trends

Air pollution trends are well documented from the H. Akimoto's science paper, "The impact of global air pollution on climate and the environment is a new focus in atmospheric science. Intercontinental transport and hemispheric air pollution by ozone jeopardize agricultural and natural ecosystems worldwide and have a strong effect on climate. Aerosols, which are spread globally but have a strong regional imbalance, change global climate through their direct and indirect effects on radiative forcing. In the 1990s, nitrogen oxide emissions from Asia surpassed those from North America and Europe and should continue to exceed them for decades. International initiatives to mitigate global air pollution require participation from both developed and developing countries."

Figure 1 shows an example of the dramatic increase in air pollution in Asia over the lastquarter century (Akimoto, 2003). NOx emissions from North America and Europe have been nearly equal since the 1980s and decreasing trend after 1990 is thought to be due to stringent emission controls in Western European countries. In contrast, Asian emissions have increased rapidly.


Figure 1. Changes in anthropogenic NOx emissions over North America (United States and Canada), Europe (including Russia and the near and middle East), and Asia (East, Southeast, and South Asia) [from Akimoto, 2003].



Another sources are avaiable from the Nature paper written by A. Richter et al. (2005), they show NOx trends based on long-term (1996~2004) satellite measurements (GOME and SCIAMACHY).

"NOx is emitted from combustion processes and play a key part in the photochemically induced catalytic production of ozone, which results in summer smog and has increased levels of tropospheric ozone globally. Release of nitrogen oxide also results in nitric acid deposition, and—at least locally—increases radiative forcing effects due to the absorption of downward propagating visible light. Nitrogen oxide concentrations in many industrialized countries are expected to decrease, but rapid economic development has the potential to increase significantly the emissions of nitrogen oxides in parts of Asia."

Simmilar (with Akimoto's) results are shown that substantial reductions in NO2 over some areas of Europe and the USA, but a highly significant increase of about 50 per cent—with an accelerating trend in annual growth rate—over the industrial areas of China. Figure 2 shows the gradient obtained from a linear regression of the annual averages of tropospheric GOME NO2 vertical columns, retrieved close to 10.30 a.m. lt from 1996 to 2002 is shown. Reductions in NO2 are observed over Europe and the Central East Coast of the United States, while large increases are evident over China.




Figure 2. Average annual changes in tropospheric NO2 as observed by GOME from 1996 to 2002. [from Richter et al., 2005].