Tropospheric O3 damage to plants significantly affects global vegetation productivity, yet accurately predicting this damage remains challenging. This study develops a parameterization to globally predict ozone damage by integrating a combination of factors: cumulative uptake of ozone (CUO), O3 concentration, stomatal conductance (Gs), and total exposure time. We compiled experimental data from over 200 peer-reviewed publications spanning 50 years, focusing on the responses of various crops and trees to chronic ozone exposure. Our analysis reveals that while CUO alone has a weak relationship with changes in photosynthesis and stomatal conductance under O3 stress, combining CUO with O3 concentration, Gs, and total exposure time significantly strengthens the predictive power. This combined approach was validated across diverse categories from experimental data, including plant types, tree age, exposure systems, types of control air, rooting environments, and ozone concentration bins. We found photosynthesis exhibited a weaker response relationship than stomatal conductance, indicative of underlying responses to O3 stress that could not be captured by the variables and methods used in this study. Our results underscore the complexity of predicting O3 damage and highlight the importance of synthesizing multiple predictors. Future research should incorporate other environmental stressors, e.g., heat, drought, and elevated CO2 levels, to enhance the accuracy of O3 damage models. This study provides a significant advancement in incorporating O3 damage parameterization for global crop and land surface modeling.

There are many ethical issues that come up in geoscience research, and here I use my own experience to illustrate two of them. Ethics, unlike science, is based on values and not testable hypotheses. My values include justice and sustainability for all rather than increasing wealth for a few. One of the most important ethical issues is choosing what topics to research. In 1982 when I first heard about nuclear winter, I started work in that area. Soon thereafter, Presidents Reagan and Gorbachev ended the nuclear arms race, informed by matching scientific results from both US and Russian scientists. I continue to work in this area, because the greatest threat we pose to ourselves remains nuclear war, and the world still has enough weapons to produce nuclear winter. I think the second greatest threat is global warming. I do research on proposed interventions such as creating a cloud in the stratosphere to mimic large volcanic eruptions, which, if it proves to be technically feasible, could reduce some of the impacts of global warming. But this technique, sometimes called solar radiation management (SRM), would come with many risks. I have been working in this area for the past decade to try to better understand the potential benefits and risks, so that society, if it is tempted to consider SRM in the future, will be able to make an informed decision. I continue to work on the impacts of volcanic eruptions on climate, so we can better separate natural from anthropogenic impacts on climate, and so that we can have better seasonal forecasts after the next large eruption. I have stopped working on soil moisture, as I do not find it as ethically compelling, and I only have time for so many topics. Another ethical issue is whether to communicate policy recommendations. If you are seen to advocate a particular policy, will it tarnish your reputation as a scientist? I say, as long as you make your values clear, who better to make policy recommendations? You are the most knowledgeable on the subject. So I say that the US needs to sign the 2017 UN Treaty on the Prohibition of Nuclear Weapons, to save us and the world from nuclear annihilation. I say that the US needs to get back into the Paris Accords and increase our pledge to rapidly eliminate our greenhouse gas emissions, to save us and the world from environmental catastrophe. This is the behavior of an ethical scientist.