I set off for London at an early hour this morning. The air had a crisp autumn bite. As the train headed north of Basingstoke and the sun rose above the low lying mist in the fields a striking criss-cross matrix of contrails became increasingly visible across the skyline – some from planes that had long since left UK airspace or landed at the big London airports and a load more from planes still in view. At one point I counted 10 aircraft at varying altitudes adding their fresh white trails to the blue canvas.

Aside from being a reminder of just how busy the skies are above us, particularly in the South East of England, it was also an illustration of how issues around climate change are not as straightforward as sometimes thought. On my way home this evening I read a couple of articles concerning climate change and air travel, both of which were calling for a dramatic cut in the number of flights in and out of the UK to reduce carbon emissions. This reminded me of some research that was conducted following the 9/11 terrorist attacks when the entire US fleet was grounded for several days.

Observers at the time said how abnormally clear and bright the sky seemed over the US during those days and those monitoring atmospheric temperatures noticed a sudden and dramatic rise across the US not seen in research before. It became apparent that contrails and air particles associated with air travel and long suspected as being a large contributing factor in global dimming were doing more than imagined to keep the opposite effects of global warming at bay.