Analyzing the Atmosphere and Informing Action

Spotlight: Randall Martin, PhD | Dept. of Energy, Environmental, and Chemical Engineering

Contributed by Bennett Rosenberg on October 1, 2020.

Climate news is often confusing. New scientific findings are amplified and often distorted in the media. An article may champion a novel point of view on anthropogenic impacts, but rarely without scrutiny and counterarguments containing denial or claims that climate change is natural. We need more data, more direct proof, and more accurate predictions.

Washington University professor Randall Martin sets out to find these answers. Using a combination of observations and advanced computer modelling, he seeks to understand the distributions of atmospheric composition, both locally and globally, and the intricate processes that create and connect them.

Martin highlights three major components to the atmosphere, all of which define our climate. Firstly and most famously, we have greenhouse gases. These gases, although the principal cause of our climate crisis, are integral to Earth systems because they trap essential energy needed to sustain higher life. Secondly, suspended liquids and solids called aerosols drift through the air. There are innumerable classifications of aerosols, such as dust, smoke, and myriad chemicals released by humans. While they do disseminate and are usually filtered from the atmosphere within a few weeks, aerosols may travel around the globe. Finally, the atmosphere contains dispersed trace gases, which include everything except nitrogen and oxygen. Martin and his group are part of a global network monitoring these components and modelling predictions.

There are three major thrusts to the work by the Atmospheric Composition Analysis Group: satellite remote sensing, ground-based measurements, and global chemical transport modelling. The first two involve collecting raw data on the atmosphere. In orbit, satellites measure optical and physical qualities in the atmosphere, recording light scattering, colors, and radiation through imaging and spectroscopy. On the ground, Martin’s group takes in situ atmospheric samples alongside a global community, including governmental and post-secondary institutions. Finally, the group both utilizes and advances a complex, international modelling software called GEOS-Chem. Together, this model and the raw data recorded by the group generate inferences and predictions for practical applications.

A GEOS-Chem simulation of global aerosols. Source: Melanie Hammer and Aaron van Donkelaar.
An artist’s rendering of NASA’s Aqua Satellite Orbiting Earth. Source: NASA.

The Atmospheric Composition Analysis Group’s work serves to test our understanding of our atmosphere, generate predictions and projections, and inform policy. Some examples of the group’s contributions include assessing the distribution of atmospheric air quality, its effects on human and ecosystem health, and its sensitivity to emissions.

This informing process follows three steps. It starts with a question. Then, the group gathers measurements to evaluate and improve the model’s ability to address the question. Important developments are submitted to an international steering committee. The final step is to run the model, address the question, and communicate the findings to lawmakers and the general public. Essentially, the group helps define the very science that is the backbone of environmental policy. In Martin’s words, his work “stirs human action with a quantitative foundation.”

Martin’s work is global by nature and points to the need for an international push for effective climate policy. He hopes that by continuing his research, he may provide clear science that clarifies confusing climate news and generates intelligent climate policy.

…human action with a quantitative foundation.

Relevant Publications:

Cooper, M. J., R. V. Martin, C. A. McLinden, J. R. Brook, Inferring ground-level nitrogen dioxide concentrations at fine spatial resolution applied to the TROPOMI satellite instrument. Environ. Res. Letters, doi: 10.1088/1748-9326/aba3a5, 2020.

Croft, B., Martin, R. V., Leaitch, W. R., Burkart, J., Chang, R. Y.-W., Collins, D. B., Hayes, P. L., Hodshire, A. L., Huang, L., Kodros, J. K., Moravek, A., Mungall, E. L., Murphy, J. G., Sharma, S., Tremblay, S., Wentworth, G. R., Willis, M. D., Abbatt, J. P. D., and Pierce, J. R.: Arctic marine secondary organic aerosol contributes significantly to summertime particle size distributions in the Canadian Arctic Archipelago, Atmos. Chem. Phys., 19, 2787–2812,, 2019.

Hammer, M. S., A. van Donkelaar, C. Li, A. Lyapustin, A. M. Sayer, N. C. Hsu, R. C., Levy, M. Garay, O. Kalashnikova, R. A. Kahn, M. Brauer, J. S. Apte, D. K. Henze, L. Zhang, Q. Zhang, B. Ford, J. R. Pierce, R. V. Martin,  Global Estimates and Long-Term Trends of Fine Particulate Matter Concentrations (1998-2018). Environ. Sci. Technol. doi:10.1021/acs.est.oco1764, 2020.

Xu, J.-W., Martin, R. V., Morrow, A., Sharma, S., Huang, L., Leaitch, W. R., Burkart, J., Schulz, H., Zanatta, M., Willis, M. D., Henze, D. K., Lee, C. J., Herber, A. B., and Abbatt, J. P. D.: Source attribution of Arctic black carbon constrained by aircraft and surface measurements, Atmos. Chem. Phys., 17, 11971–11989,, 2017.