Not true! In 1000 AD, the Norse grew barley in Iceland and grazed cattle in mid-Greenland.
Warmists prescribe (or proscribe!) arguably Draconian government actions. To accept these prescriptions, one HAS to get a YES answer to ALL the following questions: 1) Is there climate change?, 2) is there secular global warming?,3) is global warming a bad thing? 4) is global warming 'antropogenic'? 5) is stopping global warming technically feasible?, 6) is stopping global warming economically feasible? 7) is stopping global warming politically feasible?
I repeat: Yes is required for all of those questions. And consider question 3: Canada, Russia, Manchuria have vast areas of potentially arable land with a warmer climate.