New research shows winter waves off California’s Pacific coast are swelling in size as the planet warms. Oceanographer Peter Bromirski at Scripps Institution of Oceanography used a unique approach to gather historical data from the past 90 years to track the increasing height of the surf. His team analyzed records from seismographs dating back to 1931 that picked up ripples of energy on the seafloor from crashing waves. That data was used to measure how they have increased over time. Bromirski’s research shows average winter wave heights have grown by as much as a foot since 1970, when global warming is believed to have started accelerating.