European stock markets opened significantly lower as tensions between the US and Europe escalated over potential tariffs. The Euro Stoxx 50 index fell 1.7% at the open, while Germany's DAX index dropped 1.3%. The UK FTSE 100 index decreased by 0.4%, France's CAC 40 index declined 0.7%, and Italy's FTSE MIB index was down 1.6%. This market reaction follows Trump's threat to impose tariffs on eight European countries related to the Greenland issue.