and environmental challenges. Action at the advance during the next 20 years, resilience local level has already increased, and a grow- mechanisms may become more sophisticated. ing number of companies have pledged to go Calls for Geoengineering carbon neutral. Some large asset managers As warming gets closer to exceeding the Paris have concluded that climate change threat- Agreement goals, it is increasingly likely that ens their long-term returns and are requiring states and nonstate actors will more aggres- carbon emissions disclosures from 昀椀rms in sively research, test, and possibly deploy geo- their portfolios or declining to invest in some engineering measures—deliberate large-scale fossil fuel projects. In 2018, nearly 10,000 cities interventions in the earth’s natural systems— and municipalities in 128 countries took some to try to counteract climate change. Current form of climate action, as did 6,225 companies research is largely focused on solar radiation headquartered in 120 countries, represent- management (SRM), an e昀昀ort to cool the ing $36.5 trillion in revenue, larger than the combined gross domestic product (GDP) of the planet by re昀氀ecting the suns energy back into United States and China. Public-private part- space. Stratospheric aerosol injection (SAI), a nerships are becoming a preferred operating form of SRM that sprays particles in the strato- framework, partly a recognition that nonstate sphere to cause global dimming, has attracted funding by those who fear the worst of climate e昀昀orts are most e昀昀ective when linked to change. Proponents argue that the needed state action. energy transformation will happen too slowly GROWTH OF RESILIENCE AND ADAPTATION and that SAI can buy the planet time because In addition to e昀昀orts to reach net zero emis- it is technologically feasible and less expensive sions, many countries and local communities than mitigation. will expand investment in adaptive infrastruc- Current research is almost entirely in comput- ture and resilience measures. Some measures er models with academia, nongovernmental are as inexpensive and simple as restoring organizations, and private companies playing mangrove forests or increasing rainwater stor- a leading role. However, there will be in- age; others are as complex as building mas- creased calls for countries to begin engaging sive sea walls and planning for the relocation in the dialogue and possibly take leadership to of large populations. A key challenge for these develop international agreements that could e昀昀orts will be funding for vulnerable commu- help set research standards, ensure transpar- nities—particularly as governments face com- ency in live tests, determine the legal frame- peting 昀椀scal and political challenges and have work around if, how, and when to deploy SRM to choose which communities to support. technologies, and monitor the e昀昀ects. The Public-private partnerships are innovating possibly catastrophic unintended side e昀昀ects new insurance approaches aimed at building are not well understood, and some scientists resilience to climate risks, such as insuring fear that SRM, while keeping temperatures down, would create unexpected and devastat- natural assets like the Mesoamerican reef o昀昀 ing changes in weather systems and rainfall Mexico or index-based weather insurance for patterns. Countries and nonstate actors de- local farmers in Kenya. These approaches rely on new data and machine learning technolo- ploying it alone will increase the risk of con昀氀ict gies—suggesting that as these technologies and blowback, especially when others blame A MORE CONTESTED WORLD 39