Quantifying and Understanding Uncertainties in Regional Impacts of Solar Geoengineering 

Human-caused climate change is already happening across many regions of the world. In some places, the observed changes we see match what current, physics-based global climate models predicted. However, in other regions, the changes are the opposite of what those models predicted. These discrepancies, which are connected to physical-science uncertainties of our climate system, raise questions about the ability of current, physics-based global climate models to accurately predict regional climate changes.

These same climate models are also the primary tools used to predict and quantify the regional impacts of proposed solar geoengineering scenarios. If the emerging regional climate discrepancies raise questions about our ability to predict climate change, they also raise questions about our ability to predict regional impacts of solar geoengineering scenarios, particularly over land. So far, the impact of these uncertainties on predictions of regional climate impacts from solar geoengineering scenarios has not been fully quantified.

Some important questions include:

• Which regional impacts of solar geoengineering are consistent across current climate models?
• Do regional discrepancies in climate models make those impacts better or worse?
• How do known uncertainties—like small-scale parameterized physics (e.g., clouds and turbulence)—and emerging uncertainties—like atmosphere-ocean interactions—factor into our confidence in predicting the regional impacts of solar geoengineering?
• How does physical-science uncertainty impact the detectability (time of emergence) of regional impacts of solar geoengineering scenarios?

The overall scientific objective of this research is to better understand the uncertainties in regional impacts of solar geoengineering scenarios, particularly over land areas. This will be achieved through three main research tasks, leveraging the unique computational resources at the Max Planck Institute for Meteorology (MPI-M):

1. Quantifying uncertainty caused by atmosphere-ocean interactions
2. Quantifying uncertainty caused by small-scale, complex processes in the climate system (e.g., clouds, turbulence)
3. Assessing the reliability of results by reducing uncertainty in how the climate system works

The expected outcomes of this work include:

• Establishing clearer boundaries of the physical-science uncertainties related to the regional impacts of solar geoengineering
• Forming a better understanding of solar geoengineering’s land-based hazards, including heat waves, drought, and rainfall shifts
• Quantifying and understanding how much of the uncertainty in regional solar geoengineering impacts comes from well-known sources (e.g., small-scale physics, natural variability, etc.) and how much comes from emerging sources (e.g., atmosphere-ocean coupling).

Ultimately, this research will provide more reliable information related to the regional impacts of solar geoengineering scenarios.

Co-Principal Investigators: Sarah Kang, Professor and Director, Max Planck Institute for Meteorology; Ulrike Niemeier, Research Scientist, Max Planck Institute for Meteorology.