There was are different possible effects of the big amounts of dust, ash, CO_2, water vapour and fire itself. May be, there will be light cooler, may be - slight warmer, but nothing really strange for the such zone of the risky agriculture, as Russia. And what is more important - nothing strange for the worlds number one in the export of the wheat, with the big stores of food and with the big forests. Do you know how to make porridge with the cork of oaks and birches? Russians know. In fact, even in the fantastic scenario of the temperature fall to -70 C most of Russians will survive without really seriouse problems at least for few years.
All this rubbish about Russians having some kind of superhuman ability to resist the cold - I have observed your subspecies in the cold and you lot seem to require the same cold weather gear that we do