Four Global Cities Ban Diesel Cars

The mayors of four of the world's major cities say they will ban the use of all diesel-powered cars and lorries by 2025. The leaders of Paris, Mexico City, Madrid and Athens say they want to improve poor air quality, which has been linked to three million deaths a year.

US President-elect Donald Trump has named General James Mattis as his defence secretary. Mr Trump has previously described Gen Mattis, 66, as "a true general's general". Gen Mattis, who is known as "Mad Dog", was an outspoken critic of the Obama administration's Middle East policy, particularly on Iran.

Scientists in the US have created a chemical sniffer modelled on the nose of a Labrador, which has been shown to massively improve detection of vapours. The researchers were attempting to mimic the highly effective way dogs sniff, which they do by exhaling and inhaling to "sample" the air.