Recent strengthening of the tropical Pacific zonal SST gradient is a dynamically consistent response to rising greenhouse gases

The tropical Pacific Ocean strongly influences regional climates and their variability worldwide and regulates the rate of global temperature rise in response to rising greenhouse gases (GHGs). The tropical Pacific Ocean response to rising GHGs impacts all of the world's population. With few exceptions, state-of-the-art climate models predict that positive radiative forcing reduces the west-to-east warm-to-cool sea surface temperature (SST) gradient across the equatorial Pacific. In nature, however, the gradient has strengthened in recent decades as GHG concentrations have risen sharply. This stark discrepancy between models and observations has troubled the climate research community for two decades. Here, by returning to the fundamental dynamics and thermodynamics of the tropical ocean-atmosphere system, and avoiding sources of model bias, we show that a parsimonious formulation of tropical Pacific dynamics yields a response that is consistent with observations and attributable to rising GHGs. The failure of state-of-the-art models to capture this response introduces critical error into their projections of climate change in the many regions sensitive to tropical Pacific SSTs