Global Warming = Record snow?

Great Debates
1

Rather than hijack the other Global Warming thread…

Can someone explain what people mean when they claim that global warming is responsible for both the slightly colder-than-normal weather and record snows we’ve been experiencing in the Northeast this year? Explain it rationally, I mean, not just wave hands and mumble that it is connected but too complicated to explain. (I’m not talking about dopers, but self-proclaimed global warming “experts” in real life. *They * are clearly incapable of explaining what they mean. Believe me, I’ve tried to get coherent arguments out of them)

The average snowfall a year, July to June, in my area is 67 inches. At this point we’re up to 118 inches, which is the second snowiest year on record over the past 140 years. That’s a lot more snow than normal, but we have proof that it’s been worse. The temperature variances aren’t nearly as great since November, two months being at about 2F and 3F above normal, the rest about the same below normal (-2, -3, -1.7). We did have a long beautiful fall, though, before being hammered by snow.

From my point of view there’s been no statistically significant change either way from average temperature this winter, since there are bound to be years that don’t squarely hit the averages. And as for the snowfall, I’ve anticipated that this would be a particularly snowy winter for a few years now; obviously I didn’t predict it would be this snowy, but I knew it’d be pretty snowy. What my astronomy professor taught us about the eleven year sunspot cycle’s effect on our winters seems dead-on accurate, and the warmest, least snowy winter came a few winters back just when that science said it would too.

Since the weather seems to be acting more or less as it should, I’m at a complete loss when it comes to understanding what people might mean when they cite our bad winter as further and sinister proof that global warming is going on. Does anyone know what they might possibly be drawing conclusions from? How can record snow be a proof that the planet is warming alarmingly? If anything, on the surface it seems like a counter-proof.

The only thing I can imagine they mean is that global warming means there are more days when it’s “warm enough” to snow, but that’s a weak argument because there are never days that the average temperatures normally are so cold snow is extremely unlikely to occur - we complain bitterly when it is in subzero temperatures, but it’s hardly a normal occurrence any day of the year. Being too warm to snow seems a far more likely result of global warming, doesn’t it?

2

I cannot explain the technical details, but I do remember Carl Sagan explaining that colder winters was an ironic consequence of global warming. Something about getting extremes at both ends of the scale. Perhaps you could google him.

3

The short answer is that the best phrase is not “Global Warming” but “Global Climate Change.” While an overall increase in mean temperatures is a feature of these changes, and a feature with very significant consequences, another possibly even more significant predicted feature is a greater volatility about the mean. The result is that the highs will be quite higher, the lows a bit lower, the snows snowier, the droughts drier, and the floods deeper. Why more severe snows (well precipitation in general)? Increased global mean temperatures means more water evaporates into the atmosphere eventually coming down somewhere. When it comes down, where ever that turns out to be, it can come down heavy. Meanwhile that hotter air picks up more water and does it faster, worsening drought conditions in those areas that it does not happen to drop.

Does that help?

4

Global warming, with some local superheating, and some local cooling. The system as a whole is warming, though.

5

I would say it’s most likely a case of vaticinium ex eventu.

i.e. looking at events in hindsight and spinning them to support whatever theory one has.

6

I’m skeptical of that claim

7

One possible explanation is that heat elsewhere leads to the evaporation of water which then proceeds to head up to the NorthEast where it falls down in the form of (record breaking) snow.

Actually, that is exactly what I meant to say: there are certainly instances in which it is too cold to snow; snowfall and temperature are not linearly related. I am not certain, but I would say that snow tends to fall when it is around the freezing point and less so when the temperature drops lower. I’m not sure whether that corresponds to your experience (by subzero, what exactly do you mean) but I guess that, in principle, temperatures too cold for snow could be an explanation.

8

First off, you probably are hijacking this attempt at avoiding a hijack. The op seems to be looking for the explanation; the debate of its basis in reality is best in the thread that spawned it.

Secondly, while of course an individual year is weather and the prediction is only regarding climate (overall trends), the prediction of more snow wasn’t made after the fact of this particular year. In 2005:

9

I think it’s relevant to the OP’s question, but if he or she asks me to go to the other thread, I will.

Do you see the part about Australia? Here’s a map of Australian rainfall for the past 2 years

The southwest looks pretty dry to me.

So that’s evidence against CAGW, right? Wrong.

Australia’s drought (including in the Southwest) is being blamed on global warming

Now, you can probably find people who predicted droughts in Australia as a result of CAGW. But philisophically, it’s still the same problem if people predict lots of different things.

10

“Global warming” doesn’t necessarily mean the same result in each location at the same time – the globe is a large place, after all. A simple example: suppose that a slight temperature rise causes ice to melt in Antarctica (this is happening: remember the big news about the huge ice shelf breaking off a few weeks ago?) So, large amounts of ice break off from the glaciers in Antarctica and fall into the sea, where the currents take them northerly (natch)… and so you have a helluva lot more ice and icebergs coming into the northern waters, which chills those waters. Thus, colder waters around Tierra del Fuego is a result of global warming.

Yeah, it can sound paradoxical, but the fact is that weather patterns are complex. Hence, it perfectly possible that the same overall phenomenon can cause drought in one place and excess rain in another.

11

I offer the same caveat that I did against using this year’s weather in the NE US as “proof” of global climate change models’ accuracy to this two year pattern in SW Australia: weather over a year or two is not climate. In fact if one even looks at just the past three years instead of your cherry picked two, then SW Australia has if anything more than average rainfall than usual. While the rest of the country is, as predicted, much drier. Also my understanding is that for SW Australia the prediction was that the rainfall would more intense not necessarily more often. But even three years does not climate make. All we can say is that having more of these years with higher snowfall in NE US and more intense weather events more often is consistent with predictions. (One roll of double sixes doesn’t prove the dice are loaded and one roll of seven doesn’t prove they are fair. But rolling double sixes six out of ten times after the charge was made would make the hypothesis of loaded dice more likely true.)

12

That’s absolutely correct. Here’s a selection from the article I linked to about prophecy after the fact:

See, there’s a bit of a double-standard at work. If there is a snowy winter in New Hampshire, certain people are quick to say “Aha! Global warming!!” But if there is a drought in Southwest Australia, the same people might say “That’s weather not climate!” (Or they might say “Aha! global warming!”)

Philisophically, that’s a big problem.

13

And yet I offered the caution regarding interpretation of the one years snowy season in the NE as “proof” of climate change right off. Go figure. :rolleyes:

“More snow” in the climate of the NE US is not a postdiction, “i.e. looking at events in hindsight” - it was a prediction. Agreed that one year of it … or two … or three … do not qualify as meeting the standard of fulfilling the prediction any more than one year or three of less snow would falsify it. It is merely c.w. model expectations. Nothing more.

The op was however asking why it such an event was felt to be c.w. global climate change models when it seemed counter-intuitive to him/her. My purpose was merely to clarify why the models have predicted that result.

14

I recall an explanation for the phenomenon from several years ago. The basic sequence of events goes like this. Because of global warming, warm air masses form in the northern Pacific. On some occasions those warm air masses are pushed northward towards the arctic. When that happens, they drive the arctic air masses southward. In particular the jet streams (large ‘rivers of air’ in the upper atmosphere) are deflected southward across North America. So the arctic region heats up while parts of North America get a taste of arctic weather. (It’s somewhat tough to understand with a 2-D map, but if you look at a 3-D globe you can see how warm air pushing north across the Pacific would push arctic air over the ‘top of the world’ and southward into North America.)

15

If you can actually lay the blame on anything except a statistical fluke, you can probably make a pretty good argument that warmer temperatures mean more water in the air. More water == more snow up north where it’s cold enough to fall as frozen precipitation. Note that while you folks up in NH have been having a good old-fashioned Currier and Ives winter, it was a fairly local phenomenon. Down here near Boston and even further west in Mass, it’s been maybe unusually wet but nothing special in terms of snowfall. While we did have snow cover most of the winter, we didn’t have any real blizzards or righteous dumpings of snow.

If anything, our winter was fairly normal and just slightly warmer than usual with fewer arctic intrusions than usual.

So you folks in NH are probably just victims of storm tracks that travelled a bit further north than usual while carrying more moisture than usual.

16

elfkin477, you ask a good question:

Yes. It means that they don’t understand the concept. The problem that we face here is that the “forecasts” involving global warming are generally very vague and often not falsifiable. For example, somebody above cited this forecast:

Well, since about half the years have “heavier” rain or snow than average, that forecast is absolutely meaningless in terms of any given year. So for someone to say that global warming is responsible for this years snow doesn’t mean a thing, despite the AGW forecast of “heavier snow”.

However, there is absolutely nothing in the global warming scenarios to explain the current leveling off of global temperatures this century. Not one model, not one AGW supporter, no one forecast that. The temperature trend from 1970 to the present (Feb '08) is 0.17°C ± 0.03°/decade (HadCRUT3 data), which statistically is significantly (p<0.05) below any modeled trend that I am aware of.

w.

17

If you apply the “weather is not climate” principle evenhandedly, then you are not one of the people I was referring to.

Only in the strictest sense. I would include, under the rubric of postdiction, situations involving “counting the hits and not the misses.” Which applies here, since the prediction you cited missed on Southwet Australia.

And speaking of Southwest Australia, I noticed that the time period you cherry-picked goes back to April 1, 2005. Meanwhile, the prediction you cite was made around October 15, 2005 – 6 months LATER. Thus you managed to include the winter of 2005, i.e. you engaged in postdiction even in the strictest sense.

18

brazil we seem to be talking past each other. If you look at my posts I am quite clear that this year’s snow cannot, in and of itself, be considered evidence. It is weather. As years of data accumulate you can begin to say something about climate.

You had characterized the model prediction that particular regions’ climates will show greater precipitation (including snow) as a post-diction. I pointed out that such was not the case. It is a prediction and one that a single year or several years of data cannot verify or falsify.

You then used a two year period to try to falsify the model. I again pointed out that weather is not climate and pointed out further that 3 years of data gives an entirely different result. That also does not verify or falsify the model. Climate requires more data than that. It was not meant as a test of the model but as an illustration of how short term data is too noisy to answer questions regarding climate.

I have counted no hits or misses. I have explained why the model predicts increased precipitation and greater drought both and that greater volatility is part of the model predictions. I have also strongly stated that one year or several is not meaningful data even if it is consistent with model predictions.

19

Apparently so, as you seem to have missed my point.

No. But, anyway, I’m not going to repeat what’s in my posts. They speak for themselves.

Have a nice day.

20

Subzero = below 0F. If it didn’t snow at considerably below freezing, it would rarely snow in NH where we most often have temperature in the teens and twenties through January and February.