This article explores the nexus of international law on climate change and human rights, and argues that the numerous climate lawsuits around the world transform the application, implementation, and enforcement of international law on climate change. It describes how the two tracks of international law, on climate change and human rights, have developed and how they now converge, as revealed by the 2024 judgment of the European Court of Human Rights in the case Klimaseniorinnen Schweiz and Others v Switzerland. This ruling, as well as the numerous national climate lawsuits, show the dynamic and complexity of international law on climate change. They also show how international law is applied on several levels and at different scales simultaneously—not only in global contexts, but also in national cases, and not only top-down, but also from below. Thus, Klimaseniorinnen illustrates how different fields of international law—on climate change, human rights, and participatory rights in environmental matters—can be integrated, rather than fragmented.