Fig: 1: IMME global SSTA forecast identifying a strong El Nino and many ongoing marine heat waves.
Discussion: Many scientists are stating that 2023 could be the globally warmest year on record. Climate Impact Company agrees. Why? Take a look at the International Multi-Model Ensemble (IMME) September 2023 global sea surface temperature anomaly forecast. The projection indicates evolution of a strong El Nino, at least 4 large marine heat waves (MHW), and a large swath of warmer than normal water just south of the polar ice cap. The El Nino forecast is not certain yet. Climate Impact Company is indicating the MHW north of Hawaii needs to shift to the West Coast of North America (similar to 2015) to justify the intensity of the IMME El Nino projection. So…El Nino may not be as strong as shown. However, new to modern-day climate is the emergence of MHW’s and not just the Northeast Pacific present since 2013 but added to New Zealand waters, east of Argentina, and a new MHW southwest of Africa for 2023. MHW’s are adding heat to the troposphere which strengthens subtropical ridging leading to warmer/hotter subtropical ridging increasing hot and dry summer climate risk to land masses. Interestingly, MHW’s also add moisture to the low-level atmosphere which means when a synoptic scale storm or tropical system comes along to entrain that buoyant moisture unusual intensification occurs spawning extreme rain. In our view, MHW’s are a climate diagnostic characteristic of climate change: Causing long duration regimes such as drought which can be briefly interrupted by the opposing extreme, flash flooding.