Dr. Bernstein focuses on the health impacts of the climate crisis on children's health and advancing solutions to address its causes to improve the health and wellbeing of children around the world.

In 2019, Dr. Bernstein testified before Congress on the child health impacts of climate change, drawing from his personal experience as a pediatrician having to treat children with breathing difficulties, vector-borne diseases, and trauma from natural disasters.

Dr. Bernstein leads Climate MD, a Harvard Chan C-CHANGE program to encourage physicians to transform climate change from an issue dominated by politics and concerns about the future to one that matters to every person's health now. He is the course director for Human Health and Global Environmental Change and created the HarvardX course "The Health Effects of Climate Change" which explores how climate change influences health through its effects on air quality, nutrition, infectious diseases, and human migration as well as solutions to the climate crisis.