More than half of the world's oceans have changed color in the past 20 years, becoming more green than blue. The culprit? Climate change. In a study published Wednesday in Nature, decades of research showed that 56 percent of the world's oceans experienced a color change between 2002 and 2022. The ocean changes color for many reasons, such as the reflection of light from particles and sediment in the water and decaying organic matter, but the main factor in the color change is the varying populations of phytoplankton: tiny plant-like microbes that capture and store carbon dioxide and are considered the base of the marine food chain. Phytoplankton contain chlorophyll, like land plants, and scientists involved in the study were able to monitor the health of the oceans by studying changes in chlorophyll in phytoplankton and measuring how much blue and green light was reflected from the surface to satellites in space. (