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Response in climate and weather extremes to increasing atmospheric carbon dioxide in the High-Resolution Community Earth System Model (CESM)

Ryan Sriver, University of Illinois at Urbana-Champaign

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Ryan Sriver, Hui Li

Extreme weather and climate events pose serious risks to natural and human systems. Understanding how these events are changing with increasing CO2 is crucial to future planning. This collaborative research between the University of Illinois, Yale University, and the National Center for Atmospheric Research (NCAR) is aimed at using the Blue Waters petascale resources to address key uncertainties associated with the numerical modeling of the Earth’s climate system and the ability to accurately analyze changes in extreme weather/climate events due to extreme CO2 forcing. The project brings together a team of scientists to address these issues with well-recognized expertise in the study of past and future projections of climate and extensive experience in national and international assessments of climate change as well as experts in computer science and information technology.

We plan to expand on our previous CESM work by focusing on climate effects of idealized time varying CO2 experiments. Simulations will include ramped CO2 experiments (in which atmospheric CO2 is increased by 1% per year) and 4 x CO2 experiments (in which CO2 is instantaneously quadrupled and run forward to global equilibrium).

These idealized simulations will be performed in combination with the control experiments using constant pre-industrial climate conditions. We will analyze potential sensitivities of extreme events and damage metrics to CO2-induced changes in large-scale environmental factors, and we will assess potential biases based on model-data comparisons for current climate conditions.

Preliminary results already suggest significant changes in frequency and intensity of extreme precipitation events, droughts, and heat waves. We will also use these simulations to explore the potential for climate feedbacks under high CO2 scenarios within the coupled Earth system, including effects on tropical cyclones. The comprehensive suite of model experiments will provide us with thousands of simulated cyclone tracks for different climate and CO2 conditions using a dynamically consistent Earth system modeling framework, enabling robust assessment of cyclone activity and variability in response to changes in climate. A key outcome of these simulations will be gridded fields of storm tracks, winds, and other useful metrics that can be used to assess potential changes in storm-related damages under future global warming.