At a time when the world’s top climate experts agree that carbon emissions must be rapidly reduced to hold down global warming, Italy’s major electricity producer, Enel, is converting its massive power plant here from oil to coal, the dirtiest fuel on earth.

Over the next five years, Italy will increase its reliance on coal to 33 percent from 14 percent. Power generated by Enel from coal will rise to 50 percent.

And Italy is not alone in its return to coal. Driven by rising demand, record high oil and natural gas prices, concerns over energy security and an aversion to nuclear energy, European countries are slated to build about 50 coal-fired plants over the next five years, plants that will be in use for the next five decades.