In this chapter, we focus specifically on agricultural risks and uncertainties related to climate variability and global climate change from a policy viewpoint. Policymakers have little control over the weather, which is driven by very short-run (hourly to daily) patterns in atmosphere and ocean circulation. With good scientific information, however, policymakers in many regions can anticipate longer-run (monthly, yearly, decadal) climate variability and climate change reflected in patterns of temperature and precipitation. Such climate fluctuations involve structural dynamics in the physical system that can be modeled and projected with varying degrees of certainty over different spatial and temporal scales. To the extent that climate variability and change in the mean state can be projected, governments can then facilitate adaptation; that is, they can augment markets by implementing policies to promote domestic food security via trade (e.g., arrange for food imports when crop production is expected to decline domestically), investments (e.g., fund crop research or improvements in irrigation infrastructure), and early-warning systems or safety-net programs for vulnerable populations within their countries.