U.S. and European natural gas prices are sliding as warmer weather reduces demand for the heating fuel, and storage levels remain high. Risks of a global energy crisis are diminishing for now -- well -- that's until the next cold blast strikes. The polar vortex that sent much of the Lower 48 into a deep freeze at the end of 2022 ended last week. Now, much of the US will see warmer-than-normal temperatures through mid-Jan. The National Oceanic and Atmospheric Administration's latest 6-10 Day Temperature Outlook shows that…