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Abstract

In this study we discover that the recent Northeast Pacific multi-year persistent marine heatwaves (MHWs), which caused devastating marine ecological impacts with socioeconomic implications, are superimposed on a systematically-forced warming pool. The Pacific warming pool is marked by concurrent and pronounced increase in annual mean, and variance of sea surface temperature (SST), decrease in cold-season low cloud's cooling effect, and strengthened atmospheric ridge of high-pressure system. Our bi-variate attribution analysis reveals that forcing by elevated greenhouse gases (GHG) levels and the recent industrial aerosol-load decrease are the key causes for the configuration of the here-detected Pacific warming pool (P < 0.05). We further utilize extreme event attribution technique, which quantifies the additional risk of an event’s occurrence due to GHG forcings from that due to natural forcings alone, and provide a quantitative assessment of whether GHG forcing was necessary for the high-impact MHWs to occur, and whether it is a sufficient cause for such events to continue to repeatedly occur in the future. Results show that forcing by elevated GHGs levels has virtually certainly caused the multi-year persistent 2019–2021 MHW. The Pacific warming pool is coincided with a powerful ridge of high-pressure, which has recently emerged from the natural internal variability, indicating that it will provide conducive conditions over the Northeast Pacific for even more severe MHWs in the near future.Barkhordarian et al. (2022) Recent marine heatwaves in the North Pacific warming pool can be attributed to rising atmospheric levels of greenhouse gases. Communications Earth & Environment, 3, 131. https://doi.org/10.1038/s43247-022-00461-2