Climate change seems to be a long term trend, with hardiness zones moving northward, etc. Differentiatining that from Anthropogenic Global Warming for the moment, since some people dispute the veracity of that theory, it is indisputable that the northern hemisphere is warming; if this continues even longer term and accelerates it will disrupt agriculture.
While more land may become available further north, the most fertile and arable land-at least in the United States, which produces a very large share of the world's food, is in the area presently being farmed. If this land becomes less viable because of warming, it will be extremely difficult to adapt the less arable land to the north to food production, and as a consequence world hunger will increase.
So warming, whether influenced by mankind or natural, regional or global, is shaping up to be a major issue...but we won't know how major for some time to come or how to address it. World hunger is a different problem set, with distribution being more of a factor than actual production.
I don't think it is a choice between one or the other though, as both are interrelated but separate issues that need to be addressed by different policies. If it is a matter of cost and we have to choose between addressing world hunger or global warming-however you define it-I maintain that the methodology of risk management is the best way of addressing both issues. For example, alternative energy is becoming more beneficial in undeveloped nations as it becomes more affordable; you can't build a multi-billion dollar electrical grid in a short period of time, but you can put a solar panel on a building and provide electricity immediately. This strategy can be applied to food production in a variety of ways and provides the multiple benefits of addressing both warming, assuming mankind is accerating it-and providing a source of energy that can help produce food. Risk management-you put your money where it will generate the most immediate and obvious benefits, and if it also provides another benefit, so much the better. But you are generating your 'profit' (in this case, energy to produce food) first, and the risk of addressing a problem that may not be as dire as some suggest is absorbed. I don't have a position in terms of global warming; the evidence to date indicates that mankind is accelerating global warming but there is a lot of additional research needed to adequately define the impact, so if we are going to try to address the problem based on what we do know now vs. the uncertainty of what is to come, put the money where we will benefit regardless.
This strategy also benefits distribution-we produce enough food, but we can't get it where it needs to be, and the costs of distribution also include energy and the increasing competition for oil. We take multiple military actions to defend our supply lines, and these military actions also disrupt distribution and food production in the countries that are caught in the crossfire. Result: more hunger of displaced populations. One solar panel is not going to make a huge difference in either food production or mitigating global warming, but it and other sources of alternative energy broadly applied can have even more benefits than those already mentioned. Get distribution more cost effective, decrease dependence on foreign oil and reduce the military actions and costs to maintain it, and put the tools for local production in the hands of the people who can use it.