I like your reference to other climate forcings...there are a great many that we know about, and they interact with each other in such a complex and chaotic web of feedback loops that nobody can predict weather, let alone climate. My bet here, if it was long term, which it isn't, would be based on an abundance of natural gas, not on any predictions of an unusually cool summer. Regarding factors that determine weather short term and climate long term, it seems lately all we ever hear about is carbon dioxide; that's real, of course, but despite the eco-freaks dire warnings, it happens to be very good news for Canadians long term. If it wasn't for human activities, the scientific consensus is we now would be heading back to where we've been several times before in the last couple of million years: ice ages, when locations like that of present-day Saskatoon were buried under a mile of ice.