Why Has the Summertime Central U.S. Warming Hole Not Disappeared?

• DOI: 10.1175/jcli-d-22-0716.1
• Publication Date: 2023-07-31T10:31:34Z
• Authors: J. K. Eischeid; M. P. Hoerling; X.-W. Quan; A. Kumar; J. Barsugli; Z. M. Labe; K. E. Kunkel; C. J. Schreck; D. R. Easterling; T. Zhang; J. Uehling; X. Zhang
• Keywords: Forcing (mathematics)

Abstract A cooling trend in summer (May–August) daytime temperatures since the mid-twentieth century over central United States contrasts with strong warming of western and eastern States. Prior studies based on data through 1999 suggested that this so-called hole arose mainly from internal climate variability thus would likely disappear. Yet it has prevailed for two more decades, despite accelerating global warming, compelling reexamination causes addition to natural could include anthropogenic aerosol–induced cooling, hydrologic cycle intensification by greenhouse gas increases, land use change impacts. Here we present evidence critical importance resulting ocean–atmosphere drivers. Observational analysis reveals hole’s persistence is consistent unusually high summertime rainfall region during first decades twenty-first century. Comparative large ensembles four different models demonstrates trends as observed can arise (although low probability) via atmospheric alone, which induce warming-hole-like patterns In addition, atmosphere-only model experiments reveal sea surface temperature changes have also favored U.S cool/wet conditions early We argue latter effect symptomatic external radiative forcing influences, which, constraints ocean patterns, likewise contributed U.S. roughly equal proportion contributions variability. These results important ramifications attribution extreme events predicting risks record-breaking heat waves region. Significance Statement Our paper makes a significant contribution States, contrasting remainder having assigning cause Observations simulations Precipitation increased substantially result circulation consisting generally lower pressure cooler air advection into The pattern rainfall/lower due near-equal (climate change)