Closed Circuit Greenhouse
With global warming not getting the serious treatment it needs, global food shortages are soon going to become a serious problem for all nations, not just in the developing world. Complete climate control for growing crops is only possible in a greenhouse, and even then modern greenhouses extract large amounts of water from their surrounding environment. In a warming world, crops will be needed most where water will already be scarce. What's needed, then, is a redesign of greenhouses in two ways.
Closed Water Cycle
To address the large water usage problem, all waste water should be reclaimed and reprocessed. This especially includes water in the air due to crop respiration, which would necessitate a lossless dehumidifier.
Greenhouses at present are small. If they are to grow sufficient crops for the surrounding population, they need to expand in size. There are two avenues for this: horizontally or vertically. Each comes with its own benefits and drawbacks.
Expanding horizontally will make the greenhouse cover more land area, allowing more sunlight to enter, and potentially even allowing its roof to become permeable during a beneficial precipitation event. However, structural problems abound. Presumably the greenhouse will need to be able to survive the expected as well as rare inclement weather of the area. A large physical footprint makes this more challenging.
Expanding vertically would make the greenhouse multistory. It would cover a smaller horizontal area for its crop output, however getting needed sunlight to the lower levels may require external solar reflectors. Vertical greenhouses would be the better choice for urban environments, where horizontal space is scarce but vertical space plentiful.