(1) Ambient temperature is not very important. In a data center, you want to cool large arrays of small machines -- for that purpose, whether it's cold or hot outside the building doesn't matter very much. The 10-degree difference in outside air temperature is basically irrelevant you're trying to stop components from overheating.
(2) If you want places that are substantially colder, then you're looking at places that are far more "off-grid" i.e. remote. That may create substantial infrastructural difficulties (internet access, hardware supply, electrical supply, etc.). There's a reason why Google hasn't put all their datacenters on Antarctica.
(3) Denmark and Ireland already have good environmentally sustainable energy sources in place, more so than many other alternative locations. This move is about environmental policy.