From tracking water using isotope hydrology, to understanding oceans thanks to radiotracers, nuclear science and technology is playing a big part in tackling climate change. Climate change is the greatest environmental challenge of our time. If the world is to meet the agreed climate goals within the available time frame, we need mature, readily deployable solutions. As the only world forum in the nuclear field, the IAEA will continue to contribute to an informed debate on the benefits of nuclear power and applications in the many international events that will take place, including COP26, where political leaders, industry, scientists and civil society will discuss the way forward.