The risks and benefits of solar geoengineering, or solar radiation management (SRM), depend on assumptions about its implementation. Claims that SRM will reduce precipitation, increase ocean acidification or deplete stratospheric ozone, or that it must be continued forever once started, are not inherent features of SRM; rather, they are features of common scenarios for its implementation. Most analyses assume, for example, that SRM would be used to stop the increase in global temperature or restore temperature to pre-industrial values. We argue that these are poor scenario choices on which to base policy-relevant judgements about SRM. As a basis for further analysis, we provide a scenario that is temporary in that its end point is zero SRM, is moderate in that it offsets only half of the growth in anthropogenic climate forcing and is responsive in that it recognizes that the amount of SRM will be adjusted in light of new information.