You'd think that if anywhere on Earth stands to benefit from global warming it's Canada.
So, in isolation you are correct, as higher average temperatures for cold places like Canada or the Scandinavian countries increase, they might actually increase productivity. However, this will be undermined by the instability and worsening productivity of the rest of the world.
We're all in this together.
[1] http://www.bloomberg.com/news/articles/2015-10-21/climate-ch...
Climate Change is intensifying the summers and winters in canada.
Notice the increased number of forest fires per year.
And the winters will also be worse.
Up north might get warmer but it would still be a huge undertaking to move impacted people from the south where they currently live.
Just because it's cold in the winter doesn't mean global warming will be good.
By September, hay was going for 50-60% more than it had been at the END of the previous year's season. There will probably be a dire shortage come February/March 2016. This will eventually translate itself into rising food prices. Normally, one would be able to import hay from Alberta or Washington, but they've also just come out of a poor growing season.