Geoengineering has been proposed as a possible response to ocean acidification. These processes are sometimes considered variations of sinks or mitigation, and sometimes as geoengineering. Geoengineering is the application of planetary engineering techniques to Earth. IPCC (2007b&colon;15) concluded that reliable cost estimates for geoengineering options had not been published. Many critics and concerned scientists are whole-heartedly against the idea of solar geoengineering. Ocean iron fertilization is an example of such a geoengineering technique. Liao argues that human engineering is less risky than geoengineering. Techniques to remove from the atmosphere, carbon dioxide removal, are a form of geoengineering. Enhanced weathering is considered one of the least expensive geoengineering options. He also supports nuclear power and rejects geoengineering. The Convention on Biological Diversity of 2010 banned some forms of geoengineering. The Royal Society (2009) published the findings of a study into geoengineering. It was judged that reliable cost estimates for geoengineering had not yet been published. It was judged that reliable cost estimates for geoengineering had not been published. He has also contributed to assessments focused on geoengineering.