Research focuses primarily on the interdisciplinary application of engineering feedback analysis, dynamics, and control tools to problems in climate; principally solar geoengineering and climate dynamics/variability.  Additional interests include control of fluid dynamics, vibration and noise, and telescope control.

Geoengineering refers to large-scale intentional intervention in the climate system as a possible additional tool to help manage some impacts of climate change; an example would be adding aerosols to the stratosphere to reflect some sunlight.  This doesn’t reduce the need to cut greenhouse gas emissions, nonetheless deploying some amount of geoengineering might reduce climate damages, and more research is needed to evaluate it.

Past projects:

  1. Holistic Assessment of SO2 injections into the stratosphere: can we combine aerosol injection at different latitudes to improve climate outcomes or meet specific goals?  (A start towards “well-designed” geoengineering!)  Joint with PNNL and NCAR.
  2. Geoengineering on a Regional Scale: With significant impacts projected from global warming and melting ice, the Arctic is a critical region for evaluating possible future global cooling techniques, such as injecting aerosols into the stratosphere to boost “albedo” and reflect some of the sun’s energy. Combining social science, engineering, and communication, this team will engage Arctic communities in a participatory discussion about these emerging technologies, identify public concerns, and evaluate regionally specific geoengineering strategies that address them.  (Atkinson Center for a Sustainable Future, Academic Venture Fund, 2015, with Bruce Lewenstein and Holly Buck)

Current projects:

  1. How Do You Construct a Strategic Approach to Climate Change by Coupling Geoengineering to Mitigation and Adaptation? (Atkinson Center Impact through Innovation Fund, with Environmental Defense Fund)
  2. Developing a research strategy for geoengineering

Potential research opportunities; come talk to me if any of these sound interesting or you’d like more than the terse description below!

  1. What would the first years of a stratospheric aerosol deployment look like?  What is the signal-to-noise ratio for detecting aerosol optical density; what is the smallest initial deployment that would provide useful information, and what observations would be required?
  2. What other experiments would be useful to understand stratospheric aerosol geoengineering?  (Note that this isn’t my expertise, just a question I’m interested in flushing out!)
  3. We have recently conducted a 20-member ensemble of geoengineering simulations to evaluate robust regional responses and variability.  A number of variables have been analyzed, some that haven’t been looked at in detail include sea ice, permafrost,…
  4. One of the next steps in research is to explore what happens if one only injected aerosols in a single season (and then use that information to combine injection at different seasons and latitudes to explore outcomes).  This is a bigger project that would require computational support; some initial NSF funding is pending.
  5. The other next step in research is to better assess the extent and impact of uncertainty, e.g., through perturbed physics simulations or multiple models.   (An example would be changing the parameters of the aerosol microphysical growth model and seeing how much of an impact that makes on surface climate.) This is also a bigger project that would require computational support.

(The ideas below aren’t current, though I’ll leave them here to spark ideas.)

  1. Using System identification to assess regional climate response to Marine Cloud Brightening (geoengineering by “brightening” clouds in particular regions and seasons).  Some preliminary simulations and analysis have been conducted, see paper here, but analysis so far has only scratching the surface.  Nothing like this has yet been done in climate science!
  2. “Big data” and climate science: can we use ARGO float data to understand ocean eddies?  The ARGO float trajectories provide massive (though sparse in space and time) data on currents, but most researchers have only looked at temperature/salinity profiles – can we build some spatiotemporal estimate of ocean eddies?
  3. Climate impacts of geoengineering in a moderate use “overshoot” scenario; a dynamic emulator (see paper here) can be used to assess climate response for a scenario different from what was simulated.  Example questions to ask are when would regional changes in precipitation be statistically significant over natural variability?  We have climate model output from multiple models that “turned down the sun” to simulate geoengineering, as well as recent analysis from one of the world’s most powerful models simulating aerosol injection at 4 latitudes; an 80-year simulation has been conducted but barely analyzed yet.
  4. Application of Engineering System identification tools to understand dynamics underlying ENSO or AMOC (requires funding for computational resources); a useful starting point is here.
  5. Geoengineering control design… papers such as this one (single input) and this one (multivariable) use a simple proportional-integral control; how should one design a strategy using more information about either the dynamics (requires estimating those from model output) or the state?
  6. Efficacy – how do we compare different forcing agents in the climate system, such as comparing CO2 versus methane?  One metric is how much of each cause the same change in global mean temperature; this can be efficiently computed with a feedback loop.  The concept has been written down here, but there’s a lot of different forcing to consider, and different metrics that could be evaluated.
  7. If we sprayed sea water on top of existing sea ice in late fall and early winter to generate a thicker layer of ice, would this extend the life of the ice through the following summer?