Dr. Hess is a lead author on several national and international climate assessments, including the Intergovernmental Panel on Climate Change Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation and the Sixth Assessment Report. He is also an author on the annual Lancet Countdown on Health and Climate Change.

He is the principal investigator of an NIH-funded grant supporting work in India on the epidemiology of extreme heat and strategies for developing, implementing and evaluating heat early-warning systems.

Dr. Hess is also a consultant for the Climate and Health Program at the US Centers for Disease Control and Prevention, where he previously worked as a medical adviser on the health effects of climate change and evidence-based interventions to enhance preparedness and promote climate change adaptation at the state and federal levels. He is a section editor at the Western Journal of Emergency Medicine and a recipient of the Presidential GreenGov award. His work has received funding from the National Institutes of Health, NASA, the Wellcome Trust and the Robert Wood Johnson Foundation, among other funders.