The 75th anniversary of India–China relations offers a rare diplomatic opening. In a world of strategic rivalry, climate change and air pollution represent a shared threat where national interests converge. Environmental cooperation provides a low-politics entry point for rebuilding trust—through joint work on crop-residue management, high-density air-monitoring networks, and clean-energy transitions. Moreover, the Himalayan region—the planet’s “Third Pole”—is acutely vulnerable to black carbon and atmospheric pollutants from both sides of the border. Cooperation on air quality is therefore an act of Himalayan stewardship, protecting the water security of over a billion people.