Abstract:
As the main long-lived greenhouse gases, CH
4 and N
2O are included in the Kyoto Protocol, and countries are required to limit the rapid increase in their emissions since the Industrial Revolution. In this work, a radiative transfer model with a high resolution of 998 bands is used to calculate the instantaneous radiative efficiencies, stratospheric- adjusted radiative efficiencies, and lifetime-adjusted radiative efficiencies of CH
4 and N
2O for clear and cloudy skies, as well as their global warming potentials (GWPs) and global temperature potentials (GTPs). Simple fitting formulas for calculating the adjusted radiative forcing due to CH
4 and N
2O are given on the basis of the model results in this work. It is shown that the radiative efficiencies of CH
4 and N
2O for cloudy skies are 4.142×10
-4 W m
-2 ppb
-1 (1ppb=10
-9) and 3.125×10
-3 W m
-2 ppb
-1 after stratospheric adjustment, and 3.732×10
-4 W m
-2 ppb
-1 and 2.987×10
-3 W m
-2 ppb
-1, respectively, after lifetime adjustment, which are highly consistent with those of the IPCC (2007). Moreover, the 100-year GWPs of CH
4 and N
2O are 16 and 266, respectively, and their corresponding 100-year GTPs are 18 and 268 for sustained emissions, and 0.24 and 233 for pulse emissions. These results indicate that CH
4 and N
2O will still play a critical role in future global warming, second only to CO
2.