Trace gas the relationship can be used to estimate tropospheric residence-times of gases. Trace gas The most abundant gases in the atmosphere are nitrogen (78.1%), oxygen (20.9%), and argon (0.934%). Combined, oxygen, argon, and nitrogen make up 99.934% of the gases in the atmosphere (not including water vapor). The other gases that are not part of the 99.934% of the atmosphere are called trace gases. The abundance of a trace gas can range from a few parts per trillion (ppt) by volume to several hundred parts per million by volume (ppmv). When a trace gas is added into the atmosphere, that process
Regulation of greenhouse gases under the Clean Air Act in the climate system. Once emitted into the atmosphere, GHGs influence the Earth's energy balance for a period of decades to centuries. Consistent with their long-lasting impacts, the IPCC found that even if the concentrations of all GHGs had been kept constant at year 2000 levels, a further warming of approximately 0.1C per decade would be expected. The fact that GHGs are long-lived in the atmosphere also means that they become well mixed across the globe – hence the global nature of the problem. After considering the scientific evidence before her, Administrator Jackson found that greenhouse gases could be reasonably