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I just discovered this book and web site that covers the history of the science behind Global Climate Change. It does an excellent job of summarizing the real science involved, the controversies that have been resolved and the current scientific uncertainties.
It is widely regarded as a relatively unbiased scholarly work. I highly recommend it for anyone interested in Climate Change.
A while back, I asked the question here "What would be required to change your mind about Climate Change?" If you gave that question serious thought, I suggest you read this history that explains how the scientific community has changed its mind about climate change.
posted
Interesting, Rabbit. Thanks for the link. I think my mind just changed itself, when I wasn't paying attention. The question now becomes what should we do about it.
Did you see the article about pumping CO2 underground in last month's Scientific American? That combined with much greater use of fission power plants might do the trick. I'm told that the new pebble bed reactors are inherently safe, and the description of why that's true makes a lot of sense.
It seems to me that we are coming to a time when the human species will exercise fine control over the earth's climante and ecosystems. We are going to have to learn how to do this in order to survive much longer on this planet, I believe. My understanding is that there are still large uncertainties. For instance, the new idea that even as long as 15,000 years ago, humans because of agriculture started changing the global climate. If true this would mean (for reasons explained in the article which I won't describe here) that the global average temperature is even more sensitive to CO2 levels in the atmosphere than we previously thought, moreso than most of today's climate models assume. So that (again if that particular theory is true) we are even more sitting on a hair trigger than we previously thought.
Anyway, there do still seem to be large uncertainties, from what I read, though I am no expert on the field, as you are. So it's unclear exactly what's needed to bring this under control. We're carrying out a large real-life experiment in global climate change on our only liveable planet, which seems inadvisable in the extreme, but on the other hand, we'll get really good data this way.
Shutting down technological civilization to eliminate CO2 release seems seriously inadvisable, so the main thing we need to keep in mind is that it's going to be expensive, whatever means we must take to fix the problem, and that a certain amount of damage will certainly be done that's irreperable. We need to forsee that and prepare for it, I think.
Global climate change is on my list of potential worldwide disasters that we need to address, but it's only fourth or fifth on the list. Do you think it should move into first place?
Posts: 6246 | Registered: Aug 2004
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quote: is is mounted on the Web site of the Center for History of Physics of the American Institute of Physics. Discovery of Global Warming site created by Spencer Weart with support from the American Institute of Physics, the National Science Foundation and the Alfred P. Sloan Foundation.
Certainly, there's no lack of credentials at this site.
Assuming that global warming is happening, and that it was at least partly humankind who was responsible...
How will any of this affect the next ice age? I'm not up to speed on geology as much as some other sciences, but am I correct in assuming that ice ages just haven't decided to stop happening have they?
I was taught in school that ice ages tend to happen every 10,000 years or so, and that the last ice age was about 10,000 years ago.
How do you think civilization's impact has affected the cycle? Are there large enough gaps in my knowledge that this is no longer an issue, but nobody has told me why its not?
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But wouldn't it have happened pretty soon (within a couple hundred to a thousand years) without our help?
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We have a pretty good idea of the processes that might cause such changes. The biggest factor influencing climate today is Man. It might have happened.
But things that crop up in x amount of years, don't follow a schedule. Look at earthquakes for example, or previous climate modeling. The SF Bay Area is due for a good sized shake, but the last one we had was Loma Prieta, and that wasn't as large as the big one we might refer to as "El Grande". It could happen today, or it might happen in fifty years. It's a measure of odds, not certainties.
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The article I read about the impact of agriculture on climate claimed that we've already delayed the onset of the next ice age through human activities in prehistory. This theory is by no means universally accepted, however. It was interesting, though.
Ice Ages have been pretty darned regular for the last few dozen cycles, I think, up until this one, which is delayed already by several thousand years. It has to do with the slight eccentricity of the earth's orbit, they think, and the precession of the perihelion point with respect to the summer/winter tilt of the earth's axis of rotation. During times that summer in the Northern Hemisphere coincides with the earth's closest approach to the sun, I think, the earth warms up, maybe? It's something like that, though I forget the exact details. But that is why it's so very regular, the period. I can't find the issue of SciAm with that article to look it up again to make these statement more exact and accurate. Geologists or Climatologists, can you fill us in?
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quote:Ice Ages have been pretty darned regular for the last few dozen cycles, I think, up until this one, which is delayed already by several thousand years.
I've heard similar things Anne Kate.
I gotta say, the idea of an ice age coming scares me way more than global warming. Of course if global warming can cause the next ice age, then that sucks too. But its sort of a darned if you don't, darned if you do sort of thing, it seems to me.
We need to be able to have control over the climate in some way or another at some point, or "global warming" will become an ironic legend told in caves and in equatorial communities.
But I still think I must be wrong about something here, or else it would be a bigger issue in the global warming debates. I would love to have some sort of intellectual closure on this.
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Right now, as hot as it is here in the midwest, I'm all for an ice age. A short, mild one, though.
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What causes an ice age? The orbit of the earth oscillating between carrying the planet closer and further from the sun? If that is so, is there a gradual yet somewhat constant temperature change that happens throughout that oscillation? And wouldn't global warming soften the effects of an ice age? Why would it bring an ice age on sooner or make it more severe?
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quote:Why would it bring an ice age on sooner or make it more severe?
If I remember correctly, there is some debate over whether the polar ice melts can mess with the salt/fresh water balance in the north atlantic, theoretically messing with the north atlantic current.
That current is what keeps europe warm, even though its altitude is comparable to that of siberia. So a problem with that current could trigger the sort of glacial growth associated with an ice age.
I am not so sure that ice ages are caused by the orbit/tilt of the earth though. Its been a while, I will need to do some reading.
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Any other insight would be great too. It just seems to intuitive that global warming would soften the effects of an Ice Age. But I guess it is far more complicated than that--especially if no one really knows what causes an ice age to begin with.
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My fear is that mankind will respond to the threat of global warming or the emergence of an ice age by altering some aspect of our environment. The action would seem to make sense but after a few years, an oversight will emerge, something like the currents changing in a subtle and unpredicted way as a result of our tampering. The results would start a rapid chain reaction of events that would ultimately result in earth's atmosphere resembling that of Mars.
Okay, I'm really exaggerating here, but it wouldn't shock me if mankind's solution ended up causing more problems. I'm not saying we shouldn't do something, I'm just emphasizing our current lack of understanding of our environment.
Posts: 1256 | Registered: May 2005
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In addition to Xavier's comments, the change in the currents could not only cause a temperature drop to certain areas like Europe, but it might also mean more rainfall. More rain and cooler temperatures would mean more ice and snow which would reflect more of the sunlight away from the earth. This would make it even colder while furthering the change in the currents and weather patterns. One problem compounds the other resulting in massive climate changes for the entire earth.
It's kind of like the butterfly effect. One event can initiate and amplify other events, which also explains why the weather is so hard to predict in the first place.
Posts: 1256 | Registered: May 2005
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quote: The orbit of the earth oscillating between carrying the planet closer and further from the sun?
No! Ice ages have generally started very abruptly and they are thought to be caused by changes in ocean current. The oceans store huge amounts of energy and are a major factor in determining climate. There is a major cirulation of water and energy in the oceans known as the conveyor belt. At the equator, Surface water is warmed and moves to high latitudes where it releases heat to the atmosphere. As a result, the water cools - becoming denser - and sinks to the deep ocean. The ice caps play a significant role in the process. During the northern hemisphere winter, ocean waters freeze expanding the ice caps. As the freeze, the salt is concentrated in the liquid water which causes a significant increase in density and speeds the sinking of the water.
Most of the sinking in the modern ocean happens in the North Atlantic. Warm waters are carried north by the Gulf Stream, cooling as they travel. By the time they reach the vicinities of Labrador and Iceland, these waters have grown cold and dense. During winter waters sink thousands of metres below the surface. Heat which is released as these waters sink (conservation of energy) is responsible for the relatively warm temperatures enjoyed by western Europe.
In previous ice ages, there have been major shifts in the ocean conveyor belt. It is unclear whether these are the cause of the ice ages but it is clear that they play and important role and may explain why ice ages start very abruptly. One theory is that as the earth warms, eventually enough ice melts at the north pole to shift the ocean currents leading to sudden changes in climate.
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quote:It's kind of like the butterfly effect. One event can initiate and amplify other events, which also explains why the weather is so hard to predict in the first place.
Not quite, the weather is driven by quite different force than those that drive climate.
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Wow! That is amazing. For an ice age to be triggered by such small things, then build and build until something else knocks things back into whack.
I am totally fascinated. And if global warming can indeed bring on an ice age, then it becomes even more important for us to keep it in check.
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But without (human caused) global warming, an ice age is going to happen anyway.
In fact, we are just about due for one. Right Rabbit?
Forgive me, but I still am not sure what the appropriate response is to global warming, considering the threat of an ice age in the next thousand years (or sooner).
Wouldn't the earth get one right around this time, whether humans existed or not?
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quote:It's kind of like the butterfly effect. One event can initiate and amplify other events, which also explains why the weather is so hard to predict in the first place.
Not quite, the weather is driven by quite different force than those that drive climate.
I meant it as an analogy to better understand how small events can cause a chain reaction that can have large scale consequences. That's why I stated "kind of like" and my meaning "One event can initiate and amplify other events."
I didn't mean to make things confusing.
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Understood Camus. I have heard to many people say that we can't predict next weeks weather, so we couldn't possibly predict climate change. I was responding to them rather than you.
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Rabbit, Upon re-reading my post, I can see why you might come to that conclusion based on what I said. Probably wasn't the best analogy anyway. Posts: 1256 | Registered: May 2005
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But has it been demonstrated that we can predict climate change? I didn't realize that it had at all. I thought all we did was refine our models more and more until they would duplicate past climate changes as accurately as possible.
Rabbit, I've read that about the conveyor belt several times, but I've also read in Scientific American (my source for all this stuff) that the timing of ice ages follows exactly this pattern of orbital dynamics, in which northern hemisphere summer (because the N.H. has so much more land mass, I suppose, and because of the conveyor belt) interacts with the perihelion (or perhaps aphelion) of the slight eccentricity of the earth's orbit. You spend slightly more time at aphelion, right, while you're a bit closer at perhihelion? I can't remember which it is, but clearly there are various competing theories here and all is not cut and dry.
All we can say is that we know we're changing things, and that's not safe, since it's wildly experimenting on our only liveable planet. There's no guarantee, is there, that the ideal solution is to leave the earth's atmosphere in the same state it would have been without any human changes?
You are the expert on this, not I, and it seems clear that something should be done, that we should pay attention to this and be able to make whatever changes are needed. It seems overwhelmingly convincing that we will have to do something to adjust the atmosphere, and it will likely be expensive, but isn't it true that nobody is sure yet exactly what that is? Taking all economically feasible steps to limit the release of greenhouse gases seems a safe bet, but what counts as economically feasible at this stage is subject to a wide range of interpretations.
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