The Pacific Ocean off the California coast was experiencing record-high temperatures well before the National Oceanic and Atmospheric Administration declared the onset of El Niño this month. The El Niño, now stirring offshore, will collide with the marine heat wave to create a rare convergence of warming conditions—the most powerful in decades, and one whose consequences are already unfolding.
A group that monitors waters off Marin County, Point Blue Conservation Science, recorded a 2°C…