Rapid Attribution of 2022 and 2023 Marine Heatwaves

The science of climate change attribution has progressed to the point where the influence of climate change on weather events can be calculated consistently and rapidly. Here, we extend methods developed for attributing daily air temperature to calculate how climate change has altered the likelihood of sea surface temperatures. Using the results of this analysis, we examine various notable events in sea surface temperature from 2022 and 2023. These include the unprecedented global heat of July 2023, the 2022 northwest Atlantic marine heat wave (MHW), the Caribbean 2023 MHW, and some timely events from the end of 2023. For each of these events, we quantify the climate fingerprint (i.e. the increase in likelihood for these events to occur) by computing a novel metric called the Change in Information due to Perspective (ChIP). Because of the strong influence of climate change on the ocean, we contextualize these events by computing the ChIP with respect to alternative baselines - not just the preindustrial period. We show that these events stand out as having exceptional climate fingerprints, even above generally high attributability of ocean temperatures.