Shouldn't these countries benefit from it? Shouldn't they want heat to melt the ice?
Some short-term models of the economic effects of global warming do point to benefits for the Northern countries. In the long run however, the models tend to point to "everybody loses". But like with all long-run projections, it's harder to be certain of country-specific effects.
- shift of climate should move more productive climate zones to those countries
- the carbon dioxide does not simply increase temperature, but instead retains heat, thus result is disproportionally strong in winters and nights (seems fine...)
- Northern sea routes become viable, thus shortening the trade route between Asia and Europe
- one exports carbohydrates, they are being combusted, CO2 level increase, ice thaws, more more natural resources in Arctic become much easier to explore - well, cynically I'd say that in a way this business model is sustainable
- Rain is much harder to predict than temperature. It applies both to weather reports and IPCC models. I'm not saying that those countries would be afflicted by unfavourable change of rain patterns, I'm just saying it's a lottery.
- even in the biggest approximation shift of climate zones is not so unquestionably desirable for Russia, as its southern regions (ex. Caucasus) would actually lose their favourability
- Those sparsely populated countries are not even close to utilising all arable land they have right now, so that getting more of it would not change much
- Infrastructure build for different conditions. Let's say there is an inhospitable place with permafrost that each summer turns in to mud. Warmer climate would be theoretically highly desired, just if it actually started to thaw all those buildings may sink a bit. (which is slightly bad for a building and disaster for a railway line)
- People mention global disruption, which is a bit tricky. Sure, an economic crisis may harm seriously such countries. Nevertheless, I'm somewhat sceptical about climate refugees. We haven't been accepting so far people from Arab peninsula on the grounds that temperature there can exceed 50 Celsius. Even if the climate become really nasty - Russia is not the most welcoming place for refugees, Canada would be indirectly shielded by US, while in Scandinavia it may be a serious problem, but it depends on future political climate (depends at which moment imported political instability makes local population go berserk)
This is partly why some people have switched to "climate change". Warming sounds good, but the transition in the ecosystem can be pretty rough. For example, much worse forest fires in Russia.
Russia also built cities and resource extraction infrastructure on permafrost. This is now melting, causing considerable damage.
I live in Northern Canada, so I have a dog in this hunt, so to speak.
We already see effects of global warming, and while some of them are presumably more pleasant (no, we don't see as much extreme cold in the winter anymore), you might be surprised at some of the unexpected consequences.
We are seeing milder winters, but they're also much snowier and cloudier, since we no longer see the massive Arctic High Pressure systems that used to sit over us for weeks to give us cold, clear, calm (but sunny!) winter weather.
We are seeing more invasive insects coming up from the south. These would normally be killed off in severe winter weather but now range further than ever before. A pine beetle infestation killed thousands of hectares of trees not far from where I live. Those dead trees now pose a massive fire hazard.
You'd think that warmer weather would open up agricultural opportunities, too, but in Canada that is limited; much of the area that's warming the most sits in the Canadian Shield, an area of solid rock that comprises most of the country. The lack of arable soil is a much greater challenge to overcome than just the temperature itself. I believe much of Siberia faces that same issue.
Even on top of that, the towns in the far north are all built on permafrost, and as we lose that the towns are slowly sinking into the ground. The airport in Inuvik, Northwest Territories recently had to spend CDN$22 million to replace a runway that had become unusable because parts of it had sunk due to melting permafrost. That's a dramatic example but many towns are facing similar issues.
Russia and Canada do support global warming, as shown in Crude Oil Production - Countries - List
At 10 million barrels per day, Russia is second only to the US (12 million) in terms of daily extraction of crude oil. Canada is in 5th place with 4 million barrels per day.
Most of that oil is used as fuel, generating atmospheric CO₂.
According to World Beef Production: Ranking Of Countries - Beef2Live | Eat Beef * Live Better, Russia and Canada are only 11th and 12th in beef cattle, well behind the US, which produces 5 times as much as the other two countries combined. Obviously these two countries need to improve their methane gas emissions.