CH4 and N2O Permanent agricultural associates

Dansgaard-Oeschger events are rapid climate fluctuations that occurred 25 times during the past glacial period. The processes behind the timing and amplitude of these events (as recorded in ice cores) are still unclear. 

Column-averaged infrared solar measurement between 1983 and 2003 at Kit Peak Observatory (2090 m a.s.L, Colorado, United States) resulted in an averaged tropospheric volume mixing ratio of 1814 48 ppb with trend equal to 8.3 2.2 ppb yr i in 1983 decreasing to 1.9 3.7 ppb yr in 2003 (Rinsland et al. 2006). A similar trend has been observed in the lower stratosphere where at the 120-10 hPa ( 16-30 km altitude) at 25°N-35°N from 2004-2008 a value of 1370 ppb was estimated using spectroscopic measurement (Rinsland et al. 2009). In 1985, this value was estimated to be 1151 ppb. 

The seasonal amplitude between 1977 and 1995 was 30 ppb, very close to the peak-to-peak seasonal cycle found at Cape Grim. It is obvious that the NH concen- 

The results from weekly global measurements of nitrous oxide from 1981 to 1996 show that there is more N2O in the northern hemisphere by about 0.7 0.04 ppb, and that the Arctic to Antarctic difference is about 1.2 0.1 ppb (Khalil et al. 2002 Fig. 2.75). Concentrations at locations influenced by continental air are higher than at marine sites, showing the existence of large land-based emissions. For the second period (Fig. 2.75), N2O increased linearly at an average rate of about 0.73 ppb yr (r = 0.99), although there were periods when the rates were substantially different. 

---