*ahem*
First, just a slight correction: we had snow in May no more than fourteen years ago, TRD, we're not seeing anything unique this year. Weather varies from year to year, and just because this winter was cold it doesn't mean it's because of the Global Warming. Heck, the fact that it was this cold fifty years ago is data enough to raise doubt. It has not gotten any colder nor any warmer in fifty years, one could claim.
I'm not trying to say we shouldn't do anything, nor am I claiming that Global Warming is true or false, I'm just throwing some data out here, 'cause you can't really discuss a topic without any data - not to mention knowing both (or all) sides of the matter. Claiming Global Warming is true because we haven't had such a cold winter in fifty years, is completely absurd. What did we do, during these fifty years, that kept Global Warming from progressing? What are we doing right now that is making sure it does progress? Are we not trying to prevent Global Warming by reducing emission of climate gasses? If that's what makes this winter colder, then we're doing it wrong. Keep in mind all these questions and conclusions are based on this winter being proof of Global Warming. As far as I'm concerned, it is not. This year's winter is nothing but how nature is, it is fluctuating. You have to consider the whole progression through all the years Earth has existed, at least since the last major Ice Age, and then calculate how much change human actions have brought into that. I have no data on that, but there's probably enough to fill years of study out there. Therefore I'll just make examples of how I think it should be interpreted, as a non-expert.
If we assume the Earth's average global temperature rises with one degree Celsius every hundred years by default, then we could assume that the temperatures in year 0 should be 20.1 degrees lower than what the average is today (probably an absurdly exaggerated growth, but let's go with it). Are you with me on that? Two thousand and ten years, twenty hundred and one tenth of a hundred, right?
Let's say the temperature today had grown by 25 degrees, that means there's four point nine degrees that nature has not caused itself (following our example). Then we'd have to find out whether this change has occurred over the course of two thousand and ten years, only a year or a period of several years. This is significant why? Because obviously, we would have to compare it to what humans have done during these years where the change is prominent. Let's assume the temperature jumped three degrees more than default during a course of ten years, and the first of those ten years was the birth of a new technology that probably resulted in a larger growth of climate gasses in our atmosphere. That would be a quite clear indication of human involvement in Global Warming.
I'd love to go on, but I don't really have time for this right now, and you guys won't read it if it exceeds a certain length. Have fun with it, and remain civilized.