SuzanneKneeling
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Joined: 8/31/2005
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quote:
What in the world makes people think that the earth's temperature is supposed to be constant? I mean we are debating about half a degree increase. Are you saying that there has not ever been a temperature change of 0.6 degrees in the history of this planet?
Since you sound sincere in your question, I'll bite (there are plenty of denial trolls on the web who know full well what the scientific community thinks, but because of an agenda relating to anything from an unnatural attachment to their Suburban to a heavy investment in Chevron, love to float these red herrings to keep confusion alive and delay action).
In the beginning...
The earth has gone through massive, drastic changes in temperature over its history. There was a time when it was a molten mess for heaven's sake. Throughout most of human history, we wouldn't have had a prayer of living here. But then this dynamic system - through happenstance or some supernatural creator, depending on your need to believe in that - entered into a relatively long term equilibrium within a temperature range that was conducive to all the biological processes that make life as we know it possible. On top of that, there have been many temperature fluctuations of moderate length owing to natural processes (ice ages, etc.). There are also a few relatively short term natural cycles due to things like solar radiation cycles, our orbit around the sun and even the precession (wobble) around our rotational axis. In addition, through history there have been a number of random "shocks" to this equilibrium system, like asteroid strikes, volcanic eruptions, etc. All of the above have contributed to temperature changes. But aside from the cyclic ones - which are easy to model almost perfectly (e.g. we have a pretty good handle on our trip through space relative to the sun) and the random events (harder obviously to model), most of these changes have been extremely slow, long term phenomena.
What scientists are talking about when (most of them) address climate change is the extremely rapid (compared to geologic time scales) spike in both CO2 (highest it has ever been) and temperature (5 of the hottest 10 years on record happening in the last 8). The alarming thing is not so much that 1 degree F change that's occurred - see note below - but the high degree of certainty we now have in the model that connects GH gas concentrations and temperature (after modelling OUT all of the effects noted above due to natural processes). Given that, and knowing where GHG rates are going if we don't change our actions, we have a pretty good idea where temperatures would be in a few decades (and it's not pretty).
But even that 1 degree change that's happened is underappreciated by many people - and I don't blame them, as it doesn't sound like much on its face. But it isn't just a 1 degree change uniformly over the earth. It seems to be concentrated mostly at the poles and in tropical regions so far. The former is because of the nonlinear (think runaway, or "snowballing") interaction between ground reflectivity and warming. Basically as the atmosphere warms a little, it melts a little ice. Then where you used to have white (good reflector) you now have dark water (good absorber). So the area starts absorbing energy faster, which speeds up the rate of melting, which in turn lowers the reflectivity in the area, which in turn, you get the point I hope.
But why care? Well, there are lots of reasons to be concerned with warming at the poles beyond just caring about those cute polar bears (which really are threatened now, and even the administration is now acknowledging it). One is that if we melt landed ice sheets at the south pole enough that they collapse into the ocean, they really do raise the ocean level. Rush Limbaugh likes to mislead his poor abused flock with his floating ice cube fallacy (ie, melt an ice cube in the water and it doesn't raise the water level because the water is denser than ice), but he never mentions that scientists are more concerned with the landed ice shelves.
The other main concern is that as ice melts near the north pole, the fresh water freed up then pours into the northern ocean and decreases the salinity (saltiness) of the water. It's a little complicated to explain quickly, but ocean salinity is responsible for the existence of something called the Global Conveyor Belt (of which the Gulf Stream is part). [Basically salt water and fresh water have different densities, and that gradient causes vertical movements in the water and creates a return loop back to the Indian Ocean for water that is coming in on the surface from there.] This Conveyor Belt (which brings warm water up from down south) is what makes Europe inhabitable (if you look at a map you may be amazed to see that even balmy southern Europe is at the lattitude of what we consider chilly Canada). If the northern oceans lose enough of their salinity, this conveyor belt can (and has in the past, this is well documented) shut down. If it does, we get the scenario depicted in the Day After Tomorrow - though it won't happen nearly that sudden (more like a ten year span, which would still cause somewhat apocolyptic upheaval but wouldn't have made for as exciting a movie). Now, I realize some conservatives are still sore at France for being smarter than we were about Iraq, but consider the role that industrialized Europe has in the world economy and you'll want to stick with simply pouring your wine in the sewer rather than wishing this scenario upon us all.
The mechanisms for the tropics warming disproportionately escape me at the moment, but it's definitely happening in concert with all of this. What makes a small temperature change there important (beyond exacerbating drought conditions that are a major root cause of much of the civil strife you hear about) is that even a small one means a large amount of new energy in the ocean. The connection between tropical warming and increased hurricane severity is not quite as solid as the general one between GHG and warming, but it is leaning strongly that way already (caveat being the recent study finding that increased wind sheer due to warming may actually destory nascent storms and effectively cancel out the engine revving effect - though this is the first study I've seen on that so its still in the "grain of salt" file).
I haven't even gotten into the other part of the equation. Whereever you pick along the future projected temperature increase curve, the increased mean earth temperature bears another nasty traveller on its back. The variance of the temperature will also increase. What this means is not only wilder swings in weather (heat waves AND odd freezing spells like possibly the one that caused the California fruit crisis a few months ago), but other unpredictable events owing to the chaos of the system. Without getting into nonlinear dynamics and chaos theory, suffice it to say that "it's not wise to fool with Mother Nature". Not when she spent millions of years getting things precisely squared in this delicate space in time in which we've been evolving. Just not a good idea. I hear people saying "hey maybe warm will be better" and I just think, "if you had any idea what you are saying..."
Sorry for the book. I hope it's of some help.
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RE: NASA confirms global warming on Mars - 
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