The authors of this letter are a group of  scientists from different disciplines united by a concern over one-sided consideration of SRM. We believe that reducing greenhouse gas concentrations is the safest and most important tool to combat climate change and hope that humanity manages to avert climate catastrophes. But while hoping for the best, we believe it is prudent to prepare also for less favourable scenarios by researching and deliberating on various aspects of SRM. The international community needs to be ready to deal with a range of possible developments including illegitimate use as well as a potential future desire for coordinated legitimate use. We do not promote the eventual use of SRM: there is currently insufficient evidence to either confirm or refute its usefulness or desirability in absolute terms. What we do promote is balanced, insight-based deliberation, research and assessment with careful weighing of risks and potentials at every stage of governance.