86. Lesson 4. Well-designed policies and programs, to adapt to climate change, must be flexible. At the policy-level, the nature of climate change and adaptation is an area of great uncertainty. Studies only give a sense of the range of possible outcomes of climate change. For Viet Nam, the biggest uncertainties concern changes in the level and seasonal pattern of precipitation at a regional level. Well-designed policy to adapt to climate change must therefore be flexible, so that the policies can be modified as more information about the direction of climate change is collected. That is an important reason for making a strong commitment to research, development, and extension activities, since the focus of such efforts can be shifted as more is learned about the extent and impacts of climate change (World Bank, 2010b). Similarly, the bulk of the analysis in Viet Nam on climate risk and climate change threats has pointed out the diversity of risks and threats and contexts in which they play out. Because much of the focus of planned adaptation should be on providing farmers and others with the tools and resources that will enable them to respond to climate change itself and to the new risks that will accompany climate change, this will require that the tools and resources be readily adaptable to local needs, conditions and opportunities. This leads to the conclusion that one-size-fits-all approaches will be largely doomed to failure. Flexibility to learn, experiment and adapt to local and regional conditions will be essential for climate change response investment programs to be successful. This is both a policy and program design issue.