Cold Waves and Climate Change: A Bleg

I seem to be coming across this a lot recently, so this is a bleg: can anyone reading this tell me how the rather indisputable  “cold wave” that we seem to be in can be attributed to, or even reconciled with, global warming? I’ve heard that it actually follows from the prevailing theories of climate change that there would be a few extremely cold months and an increased, more intense season of high temperatures, but I can’t see how the simplistic theory that we learn about in 6th standard( greenhouse gases accumulate, prevent the earth from radiating all the heat it receives, which over a period of time leads to an increase in the earth’s temperatures) fits in with this, and I’ve forgotten nearly everything I learned in the Ecology and Environment course that the Supreme Court made all of us take in second year.

Theories, theories...

Theories, theories...

This query is most recently motivated by the post on The Reference Frame that Matthew shared, where Lumo concludes that it doesn’t, and takes this as further proof of his theory that global warming is just bunk. science Another acquaintance had written another post-satire, as it turns out- with essentially the same question, and at that time I’d mentioned the global warming=extremes theory(with the caveat that a) I wasn’t sure and b) climate change can’t possibly have progressed so far as to cause this in any case), which was promptly seconded.  On further thought, however, nothing I know about the theory(and admittedly I’m not an expert, but even so) really fits.

The movie The Day After Tomorrow had a situation where climate change caused extreme cooling, but that premise was based on the idea that the melting ice caps had disrupted the North Atlantic current. Aside from the obvious problem with taking science lessons from Hollywood, I’m pretty sure that if either of those 2 causes were to blame, we’d have heard about it already. The NY Times-hosted blog Dot Earth, which I found after a quick google, has an article that seems to be on topic (the title reads Cold Weather in a Warming Climate) but turns out to be a sociological/political argument about how the skeptics are essentially attention seekers. Unfortunately, most of the posts on this and various other blogs with the same viewpoint on climate change seem to be focused on the political rather than the scientific questions. Maybe this is justifiable, given what an outsider can reasonably assume to be the consensus on climate change by the scientific establishment, but it leaves a lot of questions unanswered.

Someone asked nearly the same question on Yahoo Answers as well, and the responses there came from both points of view. Some were almost scientific, but not exactly convincing or detailed. The most helpful thing there was “singular events cannot prove or disprove a trend.”

Another post over at Newshoggers.com had  some more scientific explanations:

Researchers have found the first real evidence that eight thousand years ago the earth warmed up and much of the Northern Hemisphere got really cold really fast. The idea of rapid climate change is not new. The Department of Defense’s Office of Net Assessment has issued a report on the geo-political dangers of rapid climate change and The Woods Hole Oceanographic Institute has a good explanation of the mechanism responsible for Abrupt Climate Change

The equatorial sun warms the ocean surface and enhances evaporation in the tropics. This leaves the tropical ocean saltier. The Gulf Stream, a limb of the Ocean Conveyor, carries an enormous volume of heat-laden, salty water up the East Coast of the United States, and then northeast toward Europe.

This oceanic heat pump is an important mechanism for reducing equator-to-pole temperature differences. It moderates Earth’s climate, particularly in the North Atlantic region. Conveyor circulation increases the northward transport of warmer waters in the Gulf Stream by about 50 percent. At colder northern latitudes, the ocean releases this heat to the atmosphere-especially in winter when the atmosphere is colder than the ocean and ocean-atmosphere temperature gradients increase. The Conveyor warms North Atlantic regions by as much as 5° Celsius and significantly tempers average winter temperatures.

But records of past climates’ from a variety of sources such as deep-sea sediments and ice-sheet cores’ show that the Conveyor has slowed and shut down several times in the past. This shutdown curtailed heat delivery to the North Atlantic and caused substantial cooling throughout the region.

The diminishing or shut down of this global heat pump happens rapidly and although it’s effects can be seen in just a few years they can last over a century.

Reasonable enough, although I’m definitely in the tropical zone, and it shouldn’t apply to me. Can anyone explain why and how the “heat pump” has been diminished/ shut down? And more specifically, how climate change/the greenhouse effect causes it to shut down? Obviously, I’m not looking for a definite theory: reasonable, preferably (but not necessarily easily or immediately) falsifiable hypotheses are good.

PS: This is a sincere bleg. I actually read through the “Inconvenient Truth” transcript to see if Al Gore had anything to say. Any explanation, assuming it lays some claims to being scientific or at least logical, is welcomed. (He starts off on the scientific theory by saying “That brings up the basic science of global warming. I’m not going to spend a lot of time on this because you know it well.” Like I said, that sums up pretty much the entire environmentalist position.)

PPS: My views on global warming, for those who think it matters: I “believe”, as far as scientific truth can be said to be a matter of belief, in the “simplistic” greenhouse effect theory which I mentioned above, and common sense suggests that if that were the only effect we should at some point see “Global Warming”.  This is definitely not the only effect, even if it’s the initial one: there’s things like feedback and forcing and various dynamic equilibria and what-not, that can both support and detract from the theory. I’m willing to concede that it mostly supports, however. Evidence is another matter.  The fact that the average global temperature is supposedly increasing is not necessarily because of global warming(ok, strictly speaking it is: I mean that it’s not because of the greenhouse effect), because the far better tested-not to mention obvious- link between urbanization/industrialization and temperature predicts that should happen anyway with the amount of growth the world has been going through. When it will “matter” is more contentious, partly because what matters is a value judgement, and partly because there’s reasonable sounding science on both sides, as far as I can tell without any formal study.

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4 thoughts on “Cold Waves and Climate Change: A Bleg

  1. I have no idea… My knowledge is pretty much what you mention here already…
    But I can add this (taken from here: http://www.intuitor.com/moviephysics/dayAft.htm ) about “The Day After Tomorrow”:

    Current theories indicate that melting ice caused by global warming could dilute northern seawater enough to reduce its density to that of southern seawater, thereby shutting down the ocean’s Gulf Stream. With no Gulf Stream to carry heat northward, northern temperatures would fall. According to the movie, when the Gulf Stream shuts down, the weather almost instantly changes from a global warming crisis into a major ice age.

  2. Read the entire page… I knew the movie sucked, but I had no idea it had THAT many issues. 🙂

    Anyway, I was hardly wondering if something like that was going to happen. I was wondering whether the gulf stream was in the process of slowing down, gradually, so that winters became more extreme. That seems to be the surviving candidate theory. However, clearly there’s a negative feedback loop associated with it( gets hotter–>ice melts–>current stops–>gets colder–>ice stops melting/freezes again), which should take care of it automatically. Although, they say the delay for the loop is pretty large, which could account for some of it.

  3. However, this is hardly the general global warming=extremes theory that a lot of people are bandying about. So even if that holds, the question’s still open.

  4. Oh yeah… gotta love Movie Physics, they can take everything apart. [I promise, if I ever write something remotely scientific, I’ll have like 30 persons from different fields check it… :)]

    Anyway, unfortunately I can’t really add anymore science to answer your question… 😦 It sucks, not knowing.

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