That's right, CO2 does lag temperature. The current explanation is that the warming trends are kicked off by some non-CO2 source; in the case of the prominent ice age cycles, that source is thought to be Earth's orbital variations. After about 800 years of warming, a significant amount of CO2 has come out of the oceans, and that prolongs the warming via the greenhouse effect for much longer than would otherwise be the case (e.g., from considering the rate at which the Earth's orbit varies).
Sometime in the early 70's the TV show In Search Of http://en.wikipedia.org/wiki/In_Search_of... interviewed a bunch of climate scientists who were all convinced that the Earth was descending into another ice age because of the growth of glaciers and polar ice, and dropping global temp averages. And what about the much larger number of scientists who were not convinced of an impending ice age? (e.g. here and here)
I still don't think "climate scientists" know any more today than they did 20 years ago. Why? Just because they have vastly more data, much more accurate data, decades of improvement in physical modeling, and orders of magnitude more computing power, not to mention much stronger signals of anthropogenic global warming?
It's not possible to predict temperature from absolute CO2 concentrations, without knowing what all the other climate effects were at the time. In particular, there were large differences in the reflectivity of the Earth, the vegetation cover, volcanism, ocean circulation, the brightness of the Sun, the very locations of the continents, etc.
If you assume that all the other factors are roughly constant, you can at least predict that changes in CO2 concentration lead to changes in temperature, which is more visible in the paleo record.
It is certain that CO2 does cause higher temperatures; that's basic physics. What is less certain is how much other climate feedbacks may amplify the warming due to CO2.
What he (AG) didn't say was that there was a phase lag of 800 years between peaks of temp and peaks of CO2. The theory they gave behind that was that the oceans take a very long time to heat up, and as they do so they release CO2. When the oceans cool they can absorb more CO2 so the CO2 concentration drops. Um, yes, that's right, and it supports the idea of CO2 as a driver of global warming, instead of contradicting it.
Here you will learn about cloud formation by cosmic rays and how solar activity/sun spots can influence cosmic rays and therefore cloud formation. Not only is there little support for a significant influence of cosmic rays on the climate, there is some contradictory evidence; see the discussion here regarding night temperatures.
Svensmark's claims, in particular, are far stronger than what his actual study showed.
It would not be too surprising if cosmic rays had some effect on the climate, but there is little evidence that this effect is significant, let alone competitive with CO2. It also doesn't explain why the Earth shouldn't be warming even more than it is due to CO2 as well, since we know the greenhouse effect does exist.
You're absolutely correct that climate change policy needs to be viewed from a economic expected-utility perspective within a probabilistic framework. While there may be a "ridiculously low" discussion in those terms on Slashdot, there certainly is a major body of literature devoted to it — and not just worst-case perspectives. To start with, look for papers by William Nordhaus and Richard Tol and the papers that cite them. You can also look for terms like "probabilistic risk assessment" and "climate change".
Frankly, it has only been in the last 5-10 years that it has become possible to run realistic climate models fast enough to explore the whole probability space, instead of picking individual cases. That's probably why such studies have not yet begun to permeate the public consciousness.
Anyway, as far as local heating of cities, the effects you mention do contribute, but are not the main sources of the urban heat island effect. Wikipedia has a nice discussion of the main sources.
It's not cheaper than mideast oil now. Eventually it will be, but we can't rely on it, seeing how our energy needs are increasing and we're still heavily dependent on coal for power generation. One way or another, we need to lessen our usage of fossil fuels, not just oil.
But surely we only have anecdotal evidence at best with which to measure these factors. I don't think I would call proxy reconstructions "anecdotal".
Furthermore, we can measure those factors today, and the natural forcings are smaller than the anthropogenic forcings. They're not insignificant, but they're not dominant.
Incidentally, the whole 'MWP was hotter than it is now' seems dubious to me, also. I don't think that it's well supported that MWP was hotter than it is now. It was, however, roughly comparable.
I don't think 'they were making wine in Northern Britain' counts for much as good evidence Yeah, it's not great.
So, I just think it's a little disingenuous to state that those factors were meaningful then, but meaningless now. For the second time, I didn't say that they were meaningless now. I said that their effects now are smaller than in the past, and definitely smaller than the anthropogenic effects now.
You are stating as fact that which is to be proved. Why don't you try reading the scientific literature? On this subject, it is vast, and you can find a treatment of any particular natural forcing you care to consider. In particular, try the 2007 IPCC SPM report for a summary of the relative contributions of these forcings. (The chapters to be published later this year contain more detailed references to the literature from which these estimates were drawn.) They have some nice graphs of how well you can account for temperature increases if you leave out anthropogenic forcings and consider only natural forcings.
What are "natural climate forcings" Solar irradiance, natural greenhouse gases, surface albedo, volcanic aerosols, etc.
and what does it mean to say they are "smaller than the natural variation at those earlier events"? It means that they haven't changed as much as they did during the MWP or LIA, and so can be responsible for only smaller amounts of climate change — too small to account for all of the climate change which has taken place in industrial times.
Where are these people who scream about "dirty hippie globaloney-worshipping libtard Gorebots the instant the word 'warming' leaves one's mouth?" I see several of them regularly on any Fark thread on global warming; I can name a few of the individuals. It is not really that hard to find, especially on conservative-dominated boards. You can actually Google for some of those epithets in the context of global warming if you like.
Maybe it's because, in the current political climate, the mere suggestion that global warming is not caused by humans is already considered extremist? In the current political climate under the Bush administration? Yeah, right.
But it is true that an anti-AGW position is pretty extreme within the scientific community.
Are you talking about the Fischer-Tropsch process? Note that (a) this costs money, (b) coal supplies are not unlimited, and (c) coal is already used heavily in electricity generation. Yes, we can do without crude oil for a while, but it's not going to be pretty.
Do we need a model for the forcers in order to theorize their existence? There has to be some kind of physically plausible mechanism, yes.
It seems to me that we didn't have a model for global warming when we started theorizing its existence Actually, greenhouse-gas induced global warming was theorized before the existence of global warming was even measured.
Furthermore, there are many plausible factors which can conceivably influence the climate on Earth, regardless of whether we know what the correct factors are or not. There is really only one factor which can influence the climates both the Earth and Mars at the same time, and that is the Sun.
Could be increased magnetic field strength. If you're referring to the two planetary magnetic fields, they are not related. If you mean the Sun's magnetic field, it is negligible compared to the Earth's magnetic field at the location of the Earth.
Could be changes in the solar wind. Yes. But solar wind mechanisms for climate change have been studied and found lacking, the same as solar irradiance mechanisms.
whole institutions have seen their funding dry up over that sort of thing Really? Which institutions?
I didn't say that they are not "relevant", they are just not presently the major drivers of climate change. The variation in the natural climate forcings over the last 150 years is smaller than the natural variation at those earlier events, and is smaller (and slower) than the current anthropogenic forcings.
I remember the morning shows claiming "global cooling". That's nice. Do you also remember what the actual scientific literature was claiming at that time? Of course not. Try here and here.
Ted Danson said, on the Johnny Carson show, that we won't be here in 15 years. He was wrong and so is Algore Brilliant logic there.
You alarmist blindly listen to scientist that claim they can tell us what the climate was 1000 years ago and what it will be if we don't change our wicked ways. Did you ever stop to think that these are the same people that can't tell us what the weather will be like next week. Alarmist? What, is anyone who thinks global warming is happening and will continue to happen an "alarmist" to you?
And no, they are not "the same people". One group is climatologists, and the other meteorologists. It is far easier to predict a global annual average climate than it is to predict a local weather event at a particular city on a particular day.
I am not ready to endorse a global economic "adjustment" based on a theory. It is not "just" a theory, but one supported by an enormous amount of evidence.
Man-made CO2 represents 4% of the annual output of CO2 on the planet. 96% of all CO2 is generated by natural causes. That's not the relevant figure. What's relevant is (a) what fraction of the annual CO2 accumulation is due to man-made CO2, and (b) how large is that accumulation relative to pre-industrial values.
The vast majority of the increase in CO2 accumulated in the atmosphere since pre-industrial times (about 100 ppm) is due to man-made CO2.
The Earth has gone through more massive changes in it's history than you seem to be capable of conceiving. That's nice. It is, however, irrelevant to the question of whether we want the changes that are coming over the next century or two.
CO2 levels have been as high as 7000ppm in the past. So? Do you want to live in the Cambrian period?
Sea levels are "noticeably rising"? [...] Even the IPCC only claims a maximum of 15 millimeters over the 6000 year average. I can't find that figure, and I don't know why you think that's relevant to global warming.
They claim about 200 mm (8 inches) over just the time since 1870 or so (see Figure SPM-3b), with a maximum rise of 22 cm (also ~8 inches) for the 20th century.
The 2007 IPCC report is claiming a maximum rise of about 18 inches, or about the same as during the Medieval Climate Optimum. Again, I don't know where that figure came from, or whether it's supposed to refer to a historical rise or a future projection.
In fact, were anthropogenic global warming a reality, we'd find that storm severity would decrease because storms are driven by the heat engine effect, namely the flow of heat from the equator towards the poles. That is far from accepted. Most climate science predicts increased storm severity.
In fact, this was the prediction published in several papers up until about 1999, when they suddenly reversed themselves. Oh, a conspiracy theory. Well, let's see what those papers are, and what the later papers citing them had to say.
Of course, in 2006, those same scientists predicted a "killer" Atlantic hurricane season, and not one single hurricane touched North American soil. You will note that hurricane intensity for any given year depends strongly on El Nino/La Nina, which was not predicted for 2006.
Suddenly we were back to the climate scientists, and they actually said, "The reason we had so few hurricanes was because of global warming." Who said that? And was it the same climate scientists as those who said that hurricances will increase due to global warming?
So, now we have global warming if there's more hurricanes, global warming if there's less hurricanes, and, we must assume, global warming if there's no hurricanes. That's called non-falsifiable, and there's a name for its practice, but it's not science. The word is religion. Yeah yeah, "science = religion", the last refuge of the intellectually lazy Slashdotter.
The fact is that there is disagreement within the scientific community on this matter. Most of them are leaning towards "global warming has a small to medium increase in hurricane intensity', but you can still find people on different sides of the spectrum. For that matter, you can always find at least a few people on any side of the spectrum in pretty much any field.
Is the Earth warming up? Satellite measurements continue to show, at most, a mild and limited warming, mostly in the Northern Hemisphere, and mostly in the middle latitudes. Observations show global warming of 0.5-0.7 degrees C over the last hundred years, with an accelerated rate of warming in the last 40, and different amounts of warming in different locations (more at higher latitudes).
Will it also cause problems? Probably. But we have no way of knowing for certain. It will have some benefits, and some problems, and right now the problems appear to outweigh the benefits, which is why pretty much all major governments are paying attention to the issue.
I do think that people who are trying to come up with alternate theories are likely having funding turned off (regardless of the subject at hand). That is the nature of 'unbiased scientific research'. Really? Then how is it that people like Lindzen, Svensmark, etc. get funded and publish their work?
It has been the documented case for decades. Every theory that exists today was once an "alternate theory". What is this "documented evidence" that anybody in any field is "likely" to have their funding cut for any alternative theory?
Contrast that sort of "fish bowl" science research with those in the astrophysics/solar weather fields that say our sun has/is going "berzerk" in the past 30 years. That's nice, but this "out of whack" Sun still isn't producing anything like the kind of irradiance fluctuations necessary to explain global warming.
Every major planet in the solars system is ALSO experiencing a warming trend Sigh. Not that again. Try here.
There is plenty of evidence for alternative explanations to climate change. Really? You haven't presented any so far.
So why are we not hearing them? Are you kidding? You can't read a discussion of global warming without running into "solar warming" advocates, repeating the same old claims.
HOW MUCH do you think a project like that would cost and WHO DO you think is going to get the money for it? Climatologists sure aren't going to get the money for it, so I'm at a loss to figure out what this has to do with climate science.
There is no suggestion of planting more trees either as you can't make money off of planting trees. It costs too much. Yeah, well, duh. There are plenty of things that you don't hear about because they're economically infeasible. What is your point?
we have fossil fuel for centuries. Upon which facts is this claim based?
Even large oil companies like BP think we're going to hit peak oil production sometime this century. Exxon thinks that we're going to hit peak oil at least pragmatically (due to economics and politics, not just raw supply).
Considering that it is still the case that solar intensity decreased slightly for most of the time that this warming took place, exactly what process do you think is at work on Mars that has any relevance at all to the Earth's climate?
we are blessed with a natural CO2 scrubbing system that can adapt to the output and expand as needed. We need only allow it to do it's job. Given the rate at which the carbon cycle works and the residence time of CO2 in the atmosphere, it will be a number of centuries before our natural CO2 scrubbing system can get rid of what we've put into the air. In the meantime, we still have global warming to deal with.
There ability to handle heat goes up proportionally to the amount of CO2 so plants that exist at 75F @ 380ppm can thrive at 90F to 100F @ 1500 ppm. So?
You may also note that there ability to process CO2 to O2 becomes more efficient at higher CO2 levels as well. There are many contributions to the carbon cycle, including the respiration sensitivity, carbon fertilization factor, thermocline diffusivity, etc. It is far from a foregone conclusion that the carbon cycle will improve its overall efficiency at higher temperatures; some models even have the soil becoming a net carbon source. It is definitely not the case that efficiency increases will outpace CO2 increases.
There's people who say that global warming is just a result of the fact that temperatures are taken in the cities, and that cities are much hotter than they used to be. The "global warming = urban heat island effect" hypothesis has been completely discredited. See, e.g., Wikipedia. Urban heat islands do exist, but demonstrably do not bias temperature records anywhere close to enough to approach the amount of global warming which has taken place. The IPCC estimates that their net contribution to global temperature means is less than 0.05 degrees, and may actually be zero.
"Scientists who dissent from the alarmism have seen their funds disappear, their work derided, and themselves labelled as industry stooges.."
Yeah....welcome to MODERN 'Science'. Even if those claims were true, you should've seen non-modern science. It was much easier to have your scientific career destroyed a few centuries back, if you made enemies within your field. Science was small enough, and the cultures hierarchical enough, that it was far more a tight-knit old boys club. And I won't even get into what disagreeing with the royal or religious authorities could do to you. Believe me, modern science is heaven for skeptics.
Despite anyone's particular leanings as to cause (anthropogenic, cyclic, or otherwise) I wonder if increased water vapor levels are contributing. It may also be noted that as temperature rises, water vapor levels would increase, perhaps enhancing any warming trend. Yes, that's correct: temperature increases lead to higher concentrations of water vapor, which in turn enhances the warming. With respect to CO2-induced global warming, the measure of this effect is known as "climate sensitivity", although water vapor will enhance warming from any source. In fact, such feedbacks significantly amplify the amount of warming that CO2 can produce; climate sensitivity is the key parameter to nail down when it comes to modeling climate change.
However, increases in water vapor cannot themselves lead to a warming trend; they can only amplify an existing trend. That's because if you try to ramp up water vapor concentration while keeping temperature constant, the excess water vapor immediately precipitates back out of the atmosphere (which can't hold any more at that temperature). That's why water vapor is known as a "feedback" and is not a "forcing", as is CO2. See here for more.
Slashdot Mirror
That's right, CO2 does lag temperature. The current explanation is that the warming trends are kicked off by some non-CO2 source; in the case of the prominent ice age cycles, that source is thought to be Earth's orbital variations. After about 800 years of warming, a significant amount of CO2 has come out of the oceans, and that prolongs the warming via the greenhouse effect for much longer than would otherwise be the case (e.g., from considering the rate at which the Earth's orbit varies).
In other words, climate feedbacks are important.
It's not possible to predict temperature from absolute CO2 concentrations, without knowing what all the other climate effects were at the time. In particular, there were large differences in the reflectivity of the Earth, the vegetation cover, volcanism, ocean circulation, the brightness of the Sun, the very locations of the continents, etc.
If you assume that all the other factors are roughly constant, you can at least predict that changes in CO2 concentration lead to changes in temperature, which is more visible in the paleo record.
It is certain that CO2 does cause higher temperatures; that's basic physics. What is less certain is how much other climate feedbacks may amplify the warming due to CO2.
Svensmark's claims, in particular, are far stronger than what his actual study showed.
It would not be too surprising if cosmic rays had some effect on the climate, but there is little evidence that this effect is significant, let alone competitive with CO2. It also doesn't explain why the Earth shouldn't be warming even more than it is due to CO2 as well, since we know the greenhouse effect does exist.
You're absolutely correct that climate change policy needs to be viewed from a economic expected-utility perspective within a probabilistic framework. While there may be a "ridiculously low" discussion in those terms on Slashdot, there certainly is a major body of literature devoted to it — and not just worst-case perspectives. To start with, look for papers by William Nordhaus and Richard Tol and the papers that cite them. You can also look for terms like "probabilistic risk assessment" and "climate change".
Frankly, it has only been in the last 5-10 years that it has become possible to run realistic climate models fast enough to explore the whole probability space, instead of picking individual cases. That's probably why such studies have not yet begun to permeate the public consciousness.
I didn't say that; that was CastrTroy.
Anyway, as far as local heating of cities, the effects you mention do contribute, but are not the main sources of the urban heat island effect. Wikipedia has a nice discussion of the main sources.
It's not cheaper than mideast oil now. Eventually it will be, but we can't rely on it, seeing how our energy needs are increasing and we're still heavily dependent on coal for power generation. One way or another, we need to lessen our usage of fossil fuels, not just oil.
Furthermore, we can measure those factors today, and the natural forcings are smaller than the anthropogenic forcings. They're not insignificant, but they're not dominant. Incidentally, the whole 'MWP was hotter than it is now' seems dubious to me, also. I don't think that it's well supported that MWP was hotter than it is now. It was, however, roughly comparable. I don't think 'they were making wine in Northern Britain' counts for much as good evidence Yeah, it's not great. So, I just think it's a little disingenuous to state that those factors were meaningful then, but meaningless now. For the second time, I didn't say that they were meaningless now. I said that their effects now are smaller than in the past, and definitely smaller than the anthropogenic effects now.
Climate change on those bodies is not attributable to anything relevant to the Earth's climate. See here.
But it is true that an anti-AGW position is pretty extreme within the scientific community.
Are you talking about the Fischer-Tropsch process? Note that (a) this costs money, (b) coal supplies are not unlimited, and (c) coal is already used heavily in electricity generation. Yes, we can do without crude oil for a while, but it's not going to be pretty.
Furthermore, there are many plausible factors which can conceivably influence the climate on Earth, regardless of whether we know what the correct factors are or not. There is really only one factor which can influence the climates both the Earth and Mars at the same time, and that is the Sun. Could be increased magnetic field strength. If you're referring to the two planetary magnetic fields, they are not related. If you mean the Sun's magnetic field, it is negligible compared to the Earth's magnetic field at the location of the Earth. Could be changes in the solar wind. Yes. But solar wind mechanisms for climate change have been studied and found lacking, the same as solar irradiance mechanisms. whole institutions have seen their funding dry up over that sort of thing Really? Which institutions?
I didn't say that they are not "relevant", they are just not presently the major drivers of climate change. The variation in the natural climate forcings over the last 150 years is smaller than the natural variation at those earlier events, and is smaller (and slower) than the current anthropogenic forcings.
And no, they are not "the same people". One group is climatologists, and the other meteorologists. It is far easier to predict a global annual average climate than it is to predict a local weather event at a particular city on a particular day. I am not ready to endorse a global economic "adjustment" based on a theory. It is not "just" a theory, but one supported by an enormous amount of evidence.
The vast majority of the increase in CO2 accumulated in the atmosphere since pre-industrial times (about 100 ppm) is due to man-made CO2. The Earth has gone through more massive changes in it's history than you seem to be capable of conceiving. That's nice. It is, however, irrelevant to the question of whether we want the changes that are coming over the next century or two. CO2 levels have been as high as 7000ppm in the past. So? Do you want to live in the Cambrian period? Sea levels are "noticeably rising"? [...] Even the IPCC only claims a maximum of 15 millimeters over the 6000 year average. I can't find that figure, and I don't know why you think that's relevant to global warming.
They claim about 200 mm (8 inches) over just the time since 1870 or so (see Figure SPM-3b), with a maximum rise of 22 cm (also ~8 inches) for the 20th century. The 2007 IPCC report is claiming a maximum rise of about 18 inches, or about the same as during the Medieval Climate Optimum. Again, I don't know where that figure came from, or whether it's supposed to refer to a historical rise or a future projection. In fact, were anthropogenic global warming a reality, we'd find that storm severity would decrease because storms are driven by the heat engine effect, namely the flow of heat from the equator towards the poles. That is far from accepted. Most climate science predicts increased storm severity. In fact, this was the prediction published in several papers up until about 1999, when they suddenly reversed themselves. Oh, a conspiracy theory. Well, let's see what those papers are, and what the later papers citing them had to say. Of course, in 2006, those same scientists predicted a "killer" Atlantic hurricane season, and not one single hurricane touched North American soil. You will note that hurricane intensity for any given year depends strongly on El Nino/La Nina, which was not predicted for 2006. Suddenly we were back to the climate scientists, and they actually said, "The reason we had so few hurricanes was because of global warming." Who said that? And was it the same climate scientists as those who said that hurricances will increase due to global warming? So, now we have global warming if there's more hurricanes, global warming if there's less hurricanes, and, we must assume, global warming if there's no hurricanes. That's called non-falsifiable, and there's a name for its practice, but it's not science. The word is religion. Yeah yeah, "science = religion", the last refuge of the intellectually lazy Slashdotter.
The fact is that there is disagreement within the scientific community on this matter. Most of them are leaning towards "global warming has a small to medium increase in hurricane intensity', but you can still find people on different sides of the spectrum. For that matter, you can always find at least a few people on any side of the spectrum in pretty much any field. Is the Earth warming up? Satellite measurements continue to show, at most, a mild and limited warming, mostly in the Northern Hemisphere, and mostly in the middle latitudes. Observations show global warming of 0.5-0.7 degrees C over the last hundred years, with an accelerated rate of warming in the last 40, and different amounts of warming in different locations (more at higher latitudes). Will it also cause problems? Probably. But we have no way of knowing for certain. It will have some benefits, and some problems, and right now the problems appear to outweigh the benefits, which is why pretty much all major governments are paying attention to the issue.
You're being ridiculous.
The heat from those sources has negligible impact on the global mean temperature.
Those furnaces, air conditioners, lights, etc. do draw electrical power and produce CO2 at power plants, though.
Even large oil companies like BP think we're going to hit peak oil production sometime this century. Exxon thinks that we're going to hit peak oil at least pragmatically (due to economics and politics, not just raw supply).
Considering that it is still the case that solar intensity decreased slightly for most of the time that this warming took place, exactly what process do you think is at work on Mars that has any relevance at all to the Earth's climate?
Yeah....welcome to MODERN 'Science'. Even if those claims were true, you should've seen non-modern science. It was much easier to have your scientific career destroyed a few centuries back, if you made enemies within your field. Science was small enough, and the cultures hierarchical enough, that it was far more a tight-knit old boys club. And I won't even get into what disagreeing with the royal or religious authorities could do to you. Believe me, modern science is heaven for skeptics.
However, increases in water vapor cannot themselves lead to a warming trend; they can only amplify an existing trend. That's because if you try to ramp up water vapor concentration while keeping temperature constant, the excess water vapor immediately precipitates back out of the atmosphere (which can't hold any more at that temperature). That's why water vapor is known as a "feedback" and is not a "forcing", as is CO2. See here for more.