SHARM EL-SHEIKH, Egypt, Nov 21 (Reuters Breakingviews) - Trade is a major cause of global warming. Think of all those goods travelling from far away on polluting ships – and raw materials and components whizzing across the world in complex supply chains. But the right trade policies can also do a lot to save the planet. The solution is to tax trade in carbon-intensive goods and get rid of tariffs on clean ones – while also subsidising green technologies and stopping aid to dirty ones. And to do all this fairly. Trade wasn’t prominent at COP27, the United Nations climate...