Geoengineering is an ineffective and irresponsible approach to the challenges posed by climate change. Its risks and potential impacts are global and extend far beyond the climate discussion. All of the proposed technologies carry large-scale risks for biodiversity, ecosystems, food security, human rights, health and democracy. It creates new threats to peace and security at the national, regional and global scales, both through the unintended but foreseeable exacerbation of underlying conflicts and through the potential for weaponization of geoengineering technologies. And it would further entrench our dependence on a fossil fuel economy.