Increases in Future AR Count and Size: Overview of the ARTMIP Tier 2 CMIP5/6 Experiment
The Atmospheric River Tracking Method Intercomparison Project (ARTMIP) team ran multiple objective atmospheric river (AR) detection tools (ARDTs) on future climate simulations, showing for the first time that (a) most ARDTs detect more ARs and larger ARs as the climate warms, and (b) uncertainty associated with the ARDTs themselves is much larger than the uncertainty associated with future climate simulations.
In addition to revealing a previously-ignored, but large, source of uncertainty—uncertainty associated with the detection of atmospheric rivers—this effort produced a publicly-accessible database of atmospheric river detections in multiple future climate change simulations. This dataset will be central to future efforts to develop a basic understanding of atmospheric rivers and climate change.
An international, grassroots team of researchers consisting of participants from national laboratories, universities, and research centers worked together on the Atmospheric River Tracking Method Intercomparison Project (ARTMIP) Tier 2 CMIP5/6 experiment: a controlled experiment designed to understand how the use of different objective atmospheric river (AR) detection tools (ARDTs) impact our understanding of future climate change and ARs. This initial paper on the ARTMIP Tier2 CMIP5/6 experiment outlines the experimental design and shows some significant new results that immediately emerged from the experiment. A key finding is that most ARDTs detect more ARs and larger ARs as the climate warms, which implies an increase in impacts from these extreme storms. This study also revealed that there is substantial uncertainty in projections of future ARs, and that the uncertainty associated with how ARs are objectively identified is much larger than the uncertainty associated with different climate model simulations. This paper underscores the need for more basic research on atmospheric rivers and how they might be impacted by climate change.