US president Donald Trump's global tariffs have stunned the international markets.Donald Trump’s global tariffs have “screwed” the international markets, according to the head of an economic think tank.The US president unveiled sweeping levies on all foreign goods going into the States last week, on top of a global 25% tax on cars and steel products.While the UK received one of the lower tariffs, with just a 10% tax on all exports to the States, the stock market is still reeling.The FTSE index of the top 100 companies in the UK plummeted to a one-year low in value when the stock markets opened on Monday.On