Oh dear, this is a classic example of what happens when we focus on a single issue and fail to understand that there are many factors involved in an economy. Were this not the case, much of the developing world would already be far wealthier and more equitable than is the case. Russia is a declining kleptocracy and when Putin leaves the stage will likely break up into quasi-independent feudal areas ruled by ex-siloviki. Climate change will have essentially zero impact either way. As for the idea that the USA will lose 30%+ of its economy, this is highly amusing as agriculture accounts for only 0.6% of its GDP. So even if the USA ceased all agricultural production (crops, livestock) no one would notice the economic difference. Climate change will certainly bring alterations around the globe, but they will in no way resemble the predictions made in this article.