Our phones and gadgets are now endangering the planet | John Harris

The energy used in our digital consumption is set to have a bigger impact on global warming than the entire aviation industry

It was just another moment in this long, increasingly strange summer. I was on a train home from Paddington station, and the carriage's air-conditioning was just about fighting off the heat outside. Most people seemed to be staring at their phones - in many cases, they were trying to stream a World Cup match, as the 4G signal came and went, and Great Western Railway's onboard wifi proved to be maddeningly erratic. The trebly chatter of headphone leakage was constant. And thousands of miles and a few time zones away in Loudoun County, Virginia, one of the world's largest concentrations of computing power was playing its part in keeping everything I saw ticking over, as data from around the world passed back and forth from its vast buildings.

Most of us communicate with this small and wealthy corner of the US every day. Thanks to a combination of factors - its proximity to Washington DC, competitive electricity prices, and its low susceptibility to natural disasters - the county is the home of data centres used by about 3,000 tech companies: huge agglomerations of circuitry, cables and cooling systems that sit in corners of the world most of us rarely see, but that are now at the core of how we live. About 70% of the world's online traffic is reckoned to pass through Loudoun County.