manipulation of the natural environments of this planet, e.g., land, lakes, rivers, atmosphere, seas, oceans, and/or its physical, chemical, or biological processes. Plans to address climate change increasingly include proposals for geoengineering projects, which mostly focus on reducing the level1 or mitigating the consequences of rising atmospheric carbon dioxide (CO2). Their effects on natural environments and their processes are likely to be global, at best only partly predictable, and extend beyond their objective.2 Furthermore, even