Each day, Reint Jan Renes commutes from Amsterdam's regal main station to his office, weaving through the city's tree-lined canals on foot. He often finds the walk frustrating.  "We have this very, very beautiful old city, and you really have to look past all those signs that try to sell you something," said Renes, a behavioral psychologist researching sustainability in cities.   It's not just that advertisements can be an eyesore in an otherwise picturesque place. For Renes, there's an inherent tension between Amsterdam's ambitious climate policy of becoming fully carbon neutral by 2050, and the ads for cars and burgers, among other products, that crowd city streets.   Burning fossil fuels is one of the key drivers of climate change , with transport, including cars , aviation and shipping, accounting for about a quarter of global emissions.…