Radiative Forcing of Climate Change and Hydrological Cycle

Satellite observations over the past two decades indicate an increase in the Earth’s Energy Imbalance (EEI), which comprises signatures of radiative forcing and feedback factors. What is driving the trend? We utilize climate models used for the IPCC AR6 assessment to investigate the roles of the plausible causal factors, including the internal variability of the climate system and natural and anthropogenic drivers of climate change. The contrasting radiative effect of aerosols relative to greenhouse gases becomes evident in the evolution of the climate forcers, thermodynamical and dynamical changes, and the concomitant change in surface temperature. The contrast between greenhouse gas and aerosol radiative effects is also manifest in the perturbations to the surface energy balance and hydrological cycle. Attribution of the past (20thcentury) becomes essential for assessing the future climate states, in particular expectations of the frequency of heat and hydrological extremes. The growing capability to model the climate system seamlessly from seasonal to multidecadal timescales yields the prospect of improved understanding and actionable information on water extremes across timescales under forced climate change.

Speaker: V. Ramaswamy, Princeton University