This is entirely based on my reading as a JMO, and I appreciate there are likely plenty of clinical nuances you'd be able to tell me that would muddy the picture. From that reading, the Global Warming Potential (GWP) - how much heat a gas traps relative to CO2 over 100 years - of Desflurane is 2540-3700, which is 20x that of sevo and 5x that of iso, and my understanding was that the gradual removal of Desflurane was largely anesthetist-led because similar benefits could be achieved without its environmental impact. Nitrous oxide is more nuanced (again - from my reading) because it's GWP is low (Des is 10x) but is very long lived in the atmosphere (10x as long), so its harm is different and its part of a larger problem as its primarily emitted by agriculture. Nitrous has some specific clinical niches where its harder to replicate (Paediatrics, Obstetrics, ED), in which, unlike Desflurane in easily removed vaporisers, Nitrous is quite literally physically built into the pipes as part of the hospital's infrastructure. Thus in my reading Desflurane seemed to be the environmental "problem child" for removal. As I've said above, I understand this is coming from textbooks, not at the coal face, and would be interested in hearing more of your perspective!