Stratospheric Forcing and Climate

Group Leader: Claudia Timmreck

The overarching goal of the Stratospheric Forcing and Climate (SFC) group is to substantially advance our current scientific understanding of stratospheric forcing and its role in past, present, and future climate variability. SFC will primarily concentrate on stratospheric aerosol (volcanoes, SAM) but also consider other factors, i.e. solar and orbital forcing. Close collaboration to the other AES groups is envisaged . SFC is focusing on two specific aspects:

1.    Constraining uncertainties in stratospheric aerosol forcing

At present a large multi-model spread in stratospheric aerosol radiative forcing estimates related to both, large volcanic eruptions, and SAM, exist. This spread results from the different evolution of the stratospheric sulfur layer in different models due to differences in particle size, transport, and aerosol-radiation coupling. Of special importance is the scale dependency of microphysical processes and their parameterizations in models. In SFC, we plan to treat volcanic processes from spatial scales, required to simulate the evolution of the volcanic plume, up to global climate effects using the nesting option of ICON. SFC will also participate in the interactive stratospheric aerosol model intercomparison (ISA-MIP) which will help to improve the understanding of volcanic and SAM related sulfur evolution and transport processes.

2.    Understanding the stratospheric aerosol impact on seasonal and regional climate

An ability to reliably anticipate future changes to the climate rests on understanding of the processes involved in climate change. Explosive volcanic eruptions are unique natural experiments that provide unprecedented insights into many of these processes. Understanding the climate system response to volcanic forcing improves our understanding of processes relevant to climate change. Another important motivation comes from climate engineering discussions. The arguably most discussed method is artificial stratospheric sulfur injection (SAM) to mimic volcanic surface cooling. The analogy may be limited, but volcanoes are the only natural experiment that allows studying potential consequences of such climate engineering.

The "Stratospheric Forcing and Climate" group exists since August 2018. Some of its members were in the "Middle and Upper Atmosphere"  group before. For past scientific activities see the legacy website of this group.