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.