To me it is not warming, the last few winters in Europe have been colder than ever. Had to descend a few times to keep the fuel temps in the normal range during the winters of 2010 and 2011. At 39,000 -63c not unusual. This is what the temperature was over Poland early one morning and the BA 777 behind us was the one that suffered a double flame-out on short final into LHR. ( ice in the fuel). Everybody was asking to come down or go faster due to fuel temperatures that morning. I'm not convinced it's 'warming'. What I did notice over the years was the height of the pollution layer. It increased significantly, especially over China.
Climate changes naturally anyway, look what happened to the Hairy Elephants.