A great white shark. Liz Hellmers / California Department of Fish and Wildlife Southern California has seen a spike in great white shark sightings amid a spate of unseasonably warm spring weather. Experts expect to see more unusual heat, and more sharks, in the months ahead. Weather forecasters expect a warming El Niño to shape over the summer, and according to some experts , it may be one of the strongest ever recorded.  “The last time we had a strong El Niño was in 2015 and 2016, and we had a lot of juvenile white sharks hanging around early,” Chris Lowe, head of the Shark Lab at Cal State University, Long Beach, told the Los Angeles Times . “So I’m expecting this year to be a sharky summer.” Over the last two decades, sightings of juvenile great whites in Southern California have been trending up.…