As I said: When a model hindcasts historical climate, they use MEASURED solar output, which of course includes all variability. Or at least most of them do; I don't know about all of them.
When they project future climate, they usually fix solar output, or only have the 11-year cycle with fixed trend.
What's relevant to the poster you originally responded to is how models treat past solar output (in order to attribute past warming to it or to human causes).
Now, I don't know if the latest GCM runs have been updated with the last few years worth of solar data. But again, that doesn't really change the conclusion that the historical warming of the Earth cannot be explained by measured solar variability.
It's not the IR radiation which arrives from the Sun which matters. Most energy from the Sun is visible light. That gets converted to infrared when it interacts with the Earth (the Earth's blackbody radiation is in the IR region at its average temperature). Greenhouse gases absorb a little of the IR emitted from the Earth's surface, scatter some of it out to space, and scatter some of it back towards the Earth's surface. It's the last that matters; without the GHGs, most of the IR would escape to space. With GHGs, only some of it does.
I have yet to see a model that takes solar variability into account. I don't know what models you're talking about, but most if not all of the GCMs are forced by historical solar data. See, e.g., GISS ModelE for one example. They fix future solar irradiance to be constant (or cyclic about a constant mean) since, as you say, we can't predict it very well. But when comparing model output to past observations, e.g. to study the effect of the Sun on 20th century climate, they do use variable solar data.
From what I understand about global warming, as the ice melts in the artic, the gulf stream carries all this cooler water to our portion of the world, thus making it cooler as the globe warms. You're talking about a collapse of the North Atlantic thermohaline circulation.
In this scenario, fresh water in the Arctic decreases the density of the water there, reducing the rate at which northern surface waters sink when they cool, and thus reducing the rate at which warm tropical surface water reaches the North Atlantic. This cools the North Atlantic region.
Wrong. Solar radiance has fallen since the early 1990's, to the order of -0.33 watts/m-2 If you take the ACRIM data set, and if you pick the start year to be 1996, you can get a TSI trend of about -0.3 W/m^2 — with large error bars, since it's 10 years of noisy data. (If you pick PMOD, the trend is virtually non-existent.)
To convert TSI to surface-averaged radiative forcing, divide by 4, to get -0.075 W/m^2. Compare this to the CO2 forcing; with an increase from 362 to 384 ppm, and 3.7 W/m^2 for 2xCO2, and taking into account the logarithmic relation of CO2 concentration to forcing, that works out to 0.315 W/m^2, which is about 4x larger than the solar forcing trend.
or -0.1 degrees Celsius. How did you arrive at that number? Pinatubo had a peak forcing of about -3 W/m^2, and was following by a peak cooling of about -0.5 C. If you just scaled that linearly, you'd get about -0.05 C of cooling for a -0.33 C forcing. Since the forcing is actually -0.33/4 (assuming your stated trend for the sake of argument), that's -0.0125 C of cooling from solar activity over the last decade.
But consider this: Ocean heat content shows a lag response to solar input, within 10 years is typical, though the figure varies & has been hard to pin down. True; I'd put it at longer than that myself.
And now, guess what? Kevin Ternberth of NCAR is conceding that the new Argo floats can't find the expected heat, admitting that the heat may have simply bled off into space. So?
Well this disarms the entire "smoking gun" of heat hiding in a pipeline proposed by James Hansen. No it doesn't. There is plenty of heat "hiding in the pipeline", as measured by ocean heat uptake over the last 5 decades or so.
And note how it coincides with the solar dimming since the early 1990's. You mean, with the tiny solar forcing? If you want a culprit, look at clouds like Trenberth says.
The record warming rate of the 1990's also coincides with another large event: The Mt. Pinatubo eruption. The warming in the 1990s lasted far after the atmospheric effects of Pinatubo were gone.
The result was a sudden -0.6 degree Celsius decrease in stratospheric temperatures (ozone warms as it traps UV radiation) meaning that the upper troposphere warmed by at least half that much from the increased UV radiation at lower altitudes! The lower troposphere, i.e., the surface where we live (and the location at which atmospheric heat is exchanged with the ocean), cooled after Pinatubo.
The point here is this: During the 1990's the Pinatubo eruption could've caused a brief equivalent of a Little Hot Age by introducing MORE UV into the upper troposphere. Except it didn't. You might try reading publications by Drew Shindell of NASA/GISS, who has written a series of papers on the surface COOLING effects of volcanoes. (As well as some papers ruling out solar and volcanic explanations of various observed climate phenomena, and attribution of them to greenhouse gases, such as trends in the Arctic Oscillation.)
As is the solar trend. The sun had been as brilliant in the 50 years prior to the 1990's as it had been in thousands of years! The brilliance of the Sun is not the key point, the key point is how much has it changed in the last 50 years. And the answer is, "not much". But that's precisely the period in which we observed the strongest warming. We can probably explain some of the early 20th century warming by solar trends, but not too much of the later warming.
Then should I understand that there is a significant delay between absorption and re-emission as far as infrared radiation and CO2 are concerned, which allows for a buildup of heat in the atmosphere ? No, in scattering there is hardly any delay.
Heat builds up in two ways: Sometimes the radiation is truly absorbed. This can't happen too often or else the molecules would build up too much energy. Sometimes the radiation is absorbed and re-emitted, but the radiation which is emitted has a little less energy than the radiation that was absorbed, and some energy is left behind in the molecule.
Also, when infrared radiation is re-emitted, does it have the same wavelength as when it was absorbed ? Not necessarily, no. If the re-emitted radiation has less energy, it will have a longer wavelength.
As percentage of total gases in the atmosphere, the CO2 curve would be also look "pretty much flat". But it's not "percentage of total gases in the atmosphere" which matters here, it's "percentage of outgoing longwave radiation reduced". If you are comparing solar output to the greenhouse effect, you need to compare apples to apples. Climatologists try to do this by converting everything into "radiative forcing" (change in the net radiation flux at the top of the atmosphere, incoming or outgoing, in watts per square meter), although this doesn't quite make everything directly comparable. (A 1 W/m^2 increase in incoming shortwave radiation doesn't have exactly the same effect as a 1 W/m^2 decrease in outgoing longwave radiation, for instance.)
And (not directly related to your post) since you read "Nature" and are probably better informed than me, isn't it "scattering" rather than "absorption", when it comes to gases and EM radiation ? You can think of the general process as "adsorption and re-emission", or you can call it "scattering".
First of all, yes, duh, the absorption spectrum of CO2 is the same in vivo and in vitro. Didn't I say that? It's easy to show that adding CO2 to a gas mixture in a flask in the lab increases the greenhouse effect. But that's not the point. The question is what happens out in the real world?
As I said, the uncertainties are not in our ability to calculate the greenhouse effect in the real world: radiative transfer codes do that quite well. The uncertainty is in feedback effects. I agree that there are real-world uncertainties in climate prediction; I disagree that they lie in our understanding of the greenhouse effect in the real atmosphere.
Second of all, it's illogical to argue that (1) people are reluctant to make the changes necessary to curb CO2 emissions enough to matter, but (2) it would be easy and cheap. Only one of these things can be true.
No. People can be misinformed and irrational. Look at the way some people's minds turn off any time they hear the word "tax", no matter how much it is or what it's for. Hell, you can design a revenue-neutral carbon tax where you turn around and give 100% of the proceeds back to the public to help offset the carbon costs. ("Tax and dividend" it's been recently called, although you want to make sure it's graded to not be regressive.) The important thing is not for the government to collect income, but for the economy to be aware of the true costs of carbon and eliminate the externality in the market. More likely the U.S. Congress will ultimately vote for a cap-and-trade scheme, even though most economists think it will be less effective and no cheaper than a tax, just because the public is afraid of the word "tax".
Besides, I didn't say it would be "easy and cheap". I just said that it's not going to destroy the world economy and eliminate our ability to respond to threats for a thousand years, or any of the rest of your ridiculous hyperbole.
Just take a look at your own life, and imagine cutting your energy usage in half across the board. Drive half as many miles, use half as much electricity, spend half as much money on food that must be transported from elsewhere. You know that would be a big and painful challenge.
Half the problem would be solved if people stopped building new coal plants that don't capture carbon. And California's per-capita CO2 emissions are already half the national average, largely due to business/industrial/residential energy efficiency standards and decoupling energy production from profits. The carbon cost of food due to transportation is actually a rather small fraction of its total cost, by the way; this is an example of being misinformed. You also discount all future technological improvements in energy production and energy use efficiency.
Getting to zero emissions would be painful if we tried to do it in the next 50 years, or probably even 100. But we can go a long way towards that goal with far less pain than people presuppose.
And that leaves out the inevitable fact that economic growth -- on which our future prosperity depends -- inevitable increases energy usage.
1. Fossil energy is going to run out and we need to confront that problem anyway. 2. Energy efficiency can also accompany energy demand. The U.S., for example, is not particularly efficient in its use of energy.
If you want to not only stop that growth but reverse it, that's tough. And you don't need a fancy degree to understand that.
You know, if you spent half the time reading what economists have to say on the issue as you do making hand-waving pronouncements, you might say something insightful here. There is a difference between tough and "destroying economic growth". That difference can even be quantified, albeit with substantial uncertainties that must be factored in. Nobody wants to destroy economic growth. That's why they design abatement schedules that reduce emissions by what we can afford, and adapt to
Where is your proof that it was man that has caused this. Science doesn't deal in proof. But the available evidence strongly supports that theory.
Just coming out and saying "we can measure X degrees increase in Y years" is not proof that man had anything to do with it. It is indeed evidence that man had something to do with it, when (a) the changes in atmospheric constituents introduced by man are of the right timing, rate, and magnitude to account for that increase, and (b) natural sources of climate variation are not. Long term natural changes in climate are primarily linked to changes in solar output or volcanic activity. However, neither one of those has changed in the 20th century in a way that agrees with the observed climate: there is another factor contributing. As I said, greenhouse gases provide just the right factor. Note that this greenhouse gas effect is not simply inferred as being "the unknown factor": its magnitude is predicted from first principles using atomic physics.
If you think you know of a new source of natural warming that nobody has thought of, and which agrees in timing, rate, and magnitude with the observed warming, feel free to share. Note: you also need to simultaneously explain why the greenhouse effect of CO2 is negligible, given the quantum theory of atomic spectra and the fact that greenhouse gases are what prevent the Earth from being a frozen iceball.
History is full of temperature changes, quite a few of them while man existed and walked on the Earth. Yes, we know climate has changed in the past, for natural reasons. That doesn't alter the evidence that the current climate change can be explained by man, and cannot be explained by any postulated natural source of warming.
And if you want to argue that climate is more sensitive to natural sources of warming than is currently thought, then you need to explain why the climate is not similarly sensitive to anthropogenic sources of warming. After all, the feedbacks which amplify climate forcings are largely agnostic to the source of warming.
There was once a time that it was warm enough that grapes could be grown in England. I hate to break it to you, but grapes are still grown in England.
Someone must be conceited to think that the temperature that exists now can be the only one that can exist on the planet and that if it is not that temperature then it must be man's fault. That's your strawman argument, not mine.
He said very small, then backtracked and said they're actually flat, implicating a distinct difference. No, I said originally said flat, then when you took me literally, I clarified that I meant "flat for all practical purposes", i.e. a trend which is negligibly small as far as its climatic effect is concerned. IOW, not a distinct difference.
According to all links I can read, IPCC 1990 temperature predictions were overforcasted. That isn't the kind of math that any sane person budgets billions$$ around. You have no understanding of uncertainty, or of decision making under uncertainty.
In general, all forecasts will either over- or under-forecast. The question is how big is the misforecast, and how big is it with respect to the stated uncertainties. We know that forecasts have uncertainties. That's why you're buying INSURANCE, not guarantees. The amount of uncertainty tells how much you have to hedge your bets. It only becomes a problem when your decisions are based around a given range of uncertainty, and the true outcome is outside the range that you planned for. That is, your predictions were overconfident. So far, they have not been: the observed outcome has been within the range of possibilities that were forecast.
Furthermore, you keep missing the fundamental point, which is an elementary result from decision analysis: more uncertainty means you should buy more insurance. Suppose climate models are so terrible that they can't predict anything. That would argue for even stronger reductions in CO2 emissions, to keep us closer to known territory.
You should be praising climate models, not dismissing them. Their predictions are what will save us billions of dollars, not cost us billions of dollars. If we didn't have them, we'd have to be even more averse to climate risks than we are. They aren't perfect, but being able to limit predicted warming to, say, 1-5 degrees is useful from a policy perspective.
Wait a second. You say there's no data for the past 150 years (which is BS by the way, perhaps you meant no data from 150 years ago). No, I said NASA doesn't have that data. NASA only has recent satellite data.
In addition, in terms of the timescale of the sun and earth, 150 years is also not enough time to count as a 'long term' or even 'short term' trend, it's barely a blip on the proverbial radar. That's not the point. If I was trying to predict the climate 4 billion years ago, that might be relevant. But if I'm trying to explain the climate over the last century, 150 years is an appropriate timescale.
You can't be SURE that an asteroid won't hit your home tomorrow night. Wrong analogy. My point is that the MORE unsure I am, the MORE insurance I want to buy.
I'm not sure that an asteroid won't hit my home tomorrow night, but I'm rather certain that the probability is less than 10^-6 (and probably much less than that).
If I were more unsure, say, probability possibly as high as 10^-2, then you bet I'd be considering asteroid insurance.
Bad science is when you start accepting the accuracy of predictions as greater than what the data warrants. That's amusing, considering that Pielke Jr. conveniently refuses to state the accuracy of the predictions (the error bars), and only plots the linear predictive means. I already cited a reference which does this comparison correctly, namely, to see whether the observations lie within the error bars of the predictions (they do).
Cutting CO2 emissions is not a sensible decision if you don't have a lot of certainty about future climate: namely, that it's going to get much warmer. No, that's exactly the opposite of my point. My point is that the more uncertainty you have, the less willing you should be to perturb the system away from what you know. Therefore, the more uncertainty you have about future warming, the more insurance you ought to buy. It's only if you're SURE that there WON'T be a big change that you continue with "business as usual".
Do I really need to drag out temperature predictions from just 10 years ago? Like these? Please do.
Forward good math and science, not predictions that are suspect. Just because predictions have uncertainty does not mean that they are bad math and science. If you're going to make a claim that bold, please be prepared to back it up.
Since another poster was confused on this point: solar output isn't literally "flat", it has just changed very little, when averaged over the 11-year solar cycle. (The solar cycle itself introduces noticeable changes in irradiance, but the underlying trend, upon which that cycle is superimposed, has been quite small over the last 50 years.)
Irradiance is the energy that gets to ground level. No, that's insolation. Total solar irradiance, which is what I've been discussing, is defined at the top of the atmosphere, over all wavelengths.
Just because most UV doesn't get to ground level (or life would be well and truly fucked), it doesn't mean that the atmosphere doesn't get warmed by it anyway. I don't disagree with you, but I also don't know what that has to do with the comment you're replying to.
What part of "universities and environmental research groups" did you not understand? What part of "cite your sources" did you not understand?
The IPCC is run by *shocker!* governments. 1. The IPCC WG1 report is written by, and cites, scientists. 2. Who cares? The fact that something is run by governments (such as that noted champion of global warming, the Bush Administration) has nothing to do with the fact that it cites the scientific literature. Who wrote a report which cites that literature has nothing to do with the existence or content of that literature.
You claim that since I don't remember every source I've used when doing research out of the dozens of topics I've researched that I'm obviously making it up. No, I claim that you don't understand the subject, your sources, or where your sources came from. I also claim that your research skills are PATHETIC, if you never even read an IPCC report and "all the literature" you found claims that the Medieval Warm Period was 5 degrees warmer than today. The report I cited refers to at least a dozen studies coming to opposite conclusions. How is it that your "unbiased" research somehow managed to miss all those papers, and only find ones which support skeptic claims?
And I can see from your continued responses that you are totally uninterested in discussing any of the science, preferring to engage in political conspiracy theories. And you call ME a troll.
wrong, there has been 5 degrees raise in the past 30 years I repeat: Over the last 30 years, there has been less than 1 degree F of warming, globally. That is, averaged over the surface of the globe. Locally, there have been places which have warmed more, warmed less, or cooled. See here.
But at the poles, the change has been a whopping 14 degrees. No, not over the last 30 years; see the map I linked earlier (the West Antarctic ice shelf area is the only place that comes close to that). But you're right that the Arctic warms much faster than the rest of the world. (The Antarctic not so much, except for WAIS.)
Try to use some small amount of intelligence here. Solar irradiance (not "temperature variations") has been flat in the sense that the 50-year trend is close to zero. It is not literally unchanging. The point is that the overall irradiance trend is much smaller than what is needed to explain a surface warming trend.
I should note that the last link above concentrates on the degree to which solar effects have been responsible for the recent warming, i.e., during the post-1970 period the poster above was discussing. Solar irradiance changed more rapidly earlier in the 20th century, and CO2 concentrations were lower, so solar effects contributed relatively much more to the warming of that period than they do today.
Even NASA's data seems to disagree with you. NASA doesn't have any data for the last 150 years.
We had twice your number since 1970 alone. If that were a long term trend, you might have a point. But you're not looking at the trend, you're looking at the difference in minima, and you're only looking at two full solar cycles at that. i.e., you're basically looking at noise.
If you look at the trend over the last 150 years or so, as I said, you find about 1 to 3 W/m^2 increase in irradiance, e.g. here or here.
A 0.05% increase per decade, over a century, is 0.5%. Solar irradiance has not been increasing at a constant rate, either.
Now it doesn't go the full 1.2% we'd need to explain the Global Warming (unless it went up as a different rate before), but it almost halves the effect we can blame ourselves for. This analysis has already been performed, far more carefully than your analysis, and does not support your conclusion. See, for instance, here, which I cited elsewhere in this thread.
It's known to increase the warming effect in the laboratory. That's easy physics. But in real life? That's harder. The spectral bands of CO2 don't go away if the CO2 is in the free atmosphere instead of a lab.
We don't know enough about the atmosphere to calculate the effect with enough certainty Says you. The strength of the CO2 greenhouse effect is not the real uncertainty here; that's known pretty well from line-by-line radiative transfer codes. The uncertainties are mostly in the atmospheric feedbacks that you mentioned before (e.g., clouds).
[Reducing CO2 emissions] would have enormous dislocating economic effects. That means it will greatly reduce the size and health of the future world economy, slow down scientific and technological progress (which both depend on a healthy economy to pay for them), and greatly strain social and political agreements that keep world peace. Again, says you. Have you read any of the economics? Try here or here.
Besides, whether it's expensive is not the question. The question is whether cutting CO2 is more expensive than the alternative (not cutting it and letting global warming happen).
Pretty much every economic cost-benefit analysis indicates that some mitigation of CO2 emissions is more cost effective than none. See my links above for details.
That's all fine if it's necessary to prevent an Ice Age or runaway warming that will leave Earth like Venus. Runaway warming isn't going to happen, and reducing the warming that will happen does not require the destruction of the world economy.
problem is, we can only make such a staggeringly huge change in our habits perhaps once in a thousand years. Another conclusion backed up by extensive socioeconomic analysis, no doubt. But perhaps you could deign to provide some citations to this analysis.
By making that change now, in the direction of reducing CO2 emissions, we give up the ability to make any similarly massive change for a long time. Because we'll be in a post-apocalyptic world living in caves and cannibalizing each other? Give me a break. We will cut back on whatever CO2 we can afford, and adapt to whatever climate change remains. Note that we're going to have to wean ourselves off of fossil fuels ANYWAY, albeit at a slower rate than if GHGs weren't a concern.
Or might there be some other climate effect, driven by the Sun, say, to which we will in the future really wish we had preserved our ability to respond? An unforseen climate effect could produce unforseen warming, or unforseen cooling. If it produces warming, then we needed to cut back on CO2 anyway, even more so than with the current global warming. If it produces cooling, we can start burning the fossil fuels that we stopped burning earlier to fight global warming.
If you're really concerned about future climate change, you should be arguing that we should save our fossil fuels in case we need them later to influence the climate, instead of burning them all when we don't. The more uncertainty we have about future climate, the less willing we should be today to do things which perturb that climate, and the more insurance we should buy. "Not cutting CO2 emissions" is only a sensible decision if you have a lot of certainty about future climate: namely, that it's not going to get much warmer.
The question of the influence of solar output on the Earth's energy budget is not as settled as you imply. In the first place, he's right, only very subtle changes in the huge amounts of energy flowing in and out of the Earth's ecosystem are required, and these are inherently difficult to measure accurately. Generally speaking, you're subtracting large and nearly equal numbers from each other, which is always tricky. You're confusing two issues: measuring solar input, and measuring the Earth's energy balance. The latter is hard. The former can be done with precision. We do know how large the changes in the Sun's output have been, and they're not really very large. In fact, they've been flat for about 50 years.
Secondly, the Sun does more than simply heat the Earth through radiation. [...] These things may have subtle effects on, for example, cloud formation -- and therefore on the Earth's albedo. That's true, but you're still going to run into the problem that it's hard to explain a changing climate using solar output which isn't changing.
It's only by averaging over a long time that you can even see any temperature change. You have to average over about 20-30 years to get a smooth signal, but the trend over the last 150 years is very visible above the noise.
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As I said: When a model hindcasts historical climate, they use MEASURED solar output, which of course includes all variability. Or at least most of them do; I don't know about all of them.
When they project future climate, they usually fix solar output, or only have the 11-year cycle with fixed trend.
What's relevant to the poster you originally responded to is how models treat past solar output (in order to attribute past warming to it or to human causes).
Now, I don't know if the latest GCM runs have been updated with the last few years worth of solar data. But again, that doesn't really change the conclusion that the historical warming of the Earth cannot be explained by measured solar variability.
It's not the IR radiation which arrives from the Sun which matters. Most energy from the Sun is visible light. That gets converted to infrared when it interacts with the Earth (the Earth's blackbody radiation is in the IR region at its average temperature). Greenhouse gases absorb a little of the IR emitted from the Earth's surface, scatter some of it out to space, and scatter some of it back towards the Earth's surface. It's the last that matters; without the GHGs, most of the IR would escape to space. With GHGs, only some of it does.
In this scenario, fresh water in the Arctic decreases the density of the water there, reducing the rate at which northern surface waters sink when they cool, and thus reducing the rate at which warm tropical surface water reaches the North Atlantic. This cools the North Atlantic region.
To convert TSI to surface-averaged radiative forcing, divide by 4, to get -0.075 W/m^2. Compare this to the CO2 forcing; with an increase from 362 to 384 ppm, and 3.7 W/m^2 for 2xCO2, and taking into account the logarithmic relation of CO2 concentration to forcing, that works out to 0.315 W/m^2, which is about 4x larger than the solar forcing trend. or -0.1 degrees Celsius. How did you arrive at that number? Pinatubo had a peak forcing of about -3 W/m^2, and was following by a peak cooling of about -0.5 C. If you just scaled that linearly, you'd get about -0.05 C of cooling for a -0.33 C forcing. Since the forcing is actually -0.33/4 (assuming your stated trend for the sake of argument), that's -0.0125 C of cooling from solar activity over the last decade. But consider this: Ocean heat content shows a lag response to solar input, within 10 years is typical, though the figure varies & has been hard to pin down. True; I'd put it at longer than that myself. And now, guess what? Kevin Ternberth of NCAR is conceding that the new Argo floats can't find the expected heat, admitting that the heat may have simply bled off into space. So? Well this disarms the entire "smoking gun" of heat hiding in a pipeline proposed by James Hansen. No it doesn't. There is plenty of heat "hiding in the pipeline", as measured by ocean heat uptake over the last 5 decades or so. And note how it coincides with the solar dimming since the early 1990's. You mean, with the tiny solar forcing? If you want a culprit, look at clouds like Trenberth says. The record warming rate of the 1990's also coincides with another large event: The Mt. Pinatubo eruption. The warming in the 1990s lasted far after the atmospheric effects of Pinatubo were gone. The result was a sudden -0.6 degree Celsius decrease in stratospheric temperatures (ozone warms as it traps UV radiation) meaning that the upper troposphere warmed by at least half that much from the increased UV radiation at lower altitudes! The lower troposphere, i.e., the surface where we live (and the location at which atmospheric heat is exchanged with the ocean), cooled after Pinatubo. The point here is this: During the 1990's the Pinatubo eruption could've caused a brief equivalent of a Little Hot Age by introducing MORE UV into the upper troposphere. Except it didn't. You might try reading publications by Drew Shindell of NASA/GISS, who has written a series of papers on the surface COOLING effects of volcanoes. (As well as some papers ruling out solar and volcanic explanations of various observed climate phenomena, and attribution of them to greenhouse gases, such as trends in the Arctic Oscillation.) As is the solar trend. The sun had been as brilliant in the 50 years prior to the 1990's as it had been in thousands of years! The brilliance of the Sun is not the key point, the key point is how much has it changed in the last 50 years. And the answer is, "not much". But that's precisely the period in which we observed the strongest warming. We can probably explain some of the early 20th century warming by solar trends, but not too much of the later warming.
Heat builds up in two ways: Sometimes the radiation is truly absorbed. This can't happen too often or else the molecules would build up too much energy. Sometimes the radiation is absorbed and re-emitted, but the radiation which is emitted has a little less energy than the radiation that was absorbed, and some energy is left behind in the molecule. Also, when infrared radiation is re-emitted, does it have the same wavelength as when it was absorbed ? Not necessarily, no. If the re-emitted radiation has less energy, it will have a longer wavelength.
First of all, yes, duh, the absorption spectrum of CO2 is the same in vivo and in vitro. Didn't I say that? It's easy to show that adding CO2 to a gas mixture in a flask in the lab increases the greenhouse effect. But that's not the point. The question is what happens out in the real world?
As I said, the uncertainties are not in our ability to calculate the greenhouse effect in the real world: radiative transfer codes do that quite well. The uncertainty is in feedback effects. I agree that there are real-world uncertainties in climate prediction; I disagree that they lie in our understanding of the greenhouse effect in the real atmosphere.
Second of all, it's illogical to argue that (1) people are reluctant to make the changes necessary to curb CO2 emissions enough to matter, but (2) it would be easy and cheap. Only one of these things can be true.
No. People can be misinformed and irrational. Look at the way some people's minds turn off any time they hear the word "tax", no matter how much it is or what it's for. Hell, you can design a revenue-neutral carbon tax where you turn around and give 100% of the proceeds back to the public to help offset the carbon costs. ("Tax and dividend" it's been recently called, although you want to make sure it's graded to not be regressive.) The important thing is not for the government to collect income, but for the economy to be aware of the true costs of carbon and eliminate the externality in the market. More likely the U.S. Congress will ultimately vote for a cap-and-trade scheme, even though most economists think it will be less effective and no cheaper than a tax, just because the public is afraid of the word "tax".
Besides, I didn't say it would be "easy and cheap". I just said that it's not going to destroy the world economy and eliminate our ability to respond to threats for a thousand years, or any of the rest of your ridiculous hyperbole.
Just take a look at your own life, and imagine cutting your energy usage in half across the board. Drive half as many miles, use half as much electricity, spend half as much money on food that must be transported from elsewhere. You know that would be a big and painful challenge.
Half the problem would be solved if people stopped building new coal plants that don't capture carbon. And California's per-capita CO2 emissions are already half the national average, largely due to business/industrial/residential energy efficiency standards and decoupling energy production from profits. The carbon cost of food due to transportation is actually a rather small fraction of its total cost, by the way; this is an example of being misinformed. You also discount all future technological improvements in energy production and energy use efficiency.
Getting to zero emissions would be painful if we tried to do it in the next 50 years, or probably even 100. But we can go a long way towards that goal with far less pain than people presuppose.
And that leaves out the inevitable fact that economic growth -- on which our future prosperity depends -- inevitable increases energy usage.
1. Fossil energy is going to run out and we need to confront that problem anyway.
2. Energy efficiency can also accompany energy demand. The U.S., for example, is not particularly efficient in its use of energy.
If you want to not only stop that growth but reverse it, that's tough. And you don't need a fancy degree to understand that.
You know, if you spent half the time reading what economists have to say on the issue as you do making hand-waving pronouncements, you might say something insightful here. There is a difference between tough and "destroying economic growth". That difference can even be quantified, albeit with substantial uncertainties that must be factored in. Nobody wants to destroy economic growth. That's why they design abatement schedules that reduce emissions by what we can afford, and adapt to
If you think you know of a new source of natural warming that nobody has thought of, and which agrees in timing, rate, and magnitude with the observed warming, feel free to share. Note: you also need to simultaneously explain why the greenhouse effect of CO2 is negligible, given the quantum theory of atomic spectra and the fact that greenhouse gases are what prevent the Earth from being a frozen iceball. History is full of temperature changes, quite a few of them while man existed and walked on the Earth. Yes, we know climate has changed in the past, for natural reasons. That doesn't alter the evidence that the current climate change can be explained by man, and cannot be explained by any postulated natural source of warming.
And if you want to argue that climate is more sensitive to natural sources of warming than is currently thought, then you need to explain why the climate is not similarly sensitive to anthropogenic sources of warming. After all, the feedbacks which amplify climate forcings are largely agnostic to the source of warming. There was once a time that it was warm enough that grapes could be grown in England. I hate to break it to you, but grapes are still grown in England. Someone must be conceited to think that the temperature that exists now can be the only one that can exist on the planet and that if it is not that temperature then it must be man's fault. That's your strawman argument, not mine.
In general, all forecasts will either over- or under-forecast. The question is how big is the misforecast, and how big is it with respect to the stated uncertainties. We know that forecasts have uncertainties. That's why you're buying INSURANCE, not guarantees. The amount of uncertainty tells how much you have to hedge your bets. It only becomes a problem when your decisions are based around a given range of uncertainty, and the true outcome is outside the range that you planned for. That is, your predictions were overconfident. So far, they have not been: the observed outcome has been within the range of possibilities that were forecast.
Furthermore, you keep missing the fundamental point, which is an elementary result from decision analysis: more uncertainty means you should buy more insurance. Suppose climate models are so terrible that they can't predict anything. That would argue for even stronger reductions in CO2 emissions, to keep us closer to known territory.
You should be praising climate models, not dismissing them. Their predictions are what will save us billions of dollars, not cost us billions of dollars. If we didn't have them, we'd have to be even more averse to climate risks than we are. They aren't perfect, but being able to limit predicted warming to, say, 1-5 degrees is useful from a policy perspective.
You're right, 5 degrees is around the central estimate for future warming by 2100.
I'm not sure that an asteroid won't hit my home tomorrow night, but I'm rather certain that the probability is less than 10^-6 (and probably much less than that).
If I were more unsure, say, probability possibly as high as 10^-2, then you bet I'd be considering asteroid insurance. Bad science is when you start accepting the accuracy of predictions as greater than what the data warrants. That's amusing, considering that Pielke Jr. conveniently refuses to state the accuracy of the predictions (the error bars), and only plots the linear predictive means. I already cited a reference which does this comparison correctly, namely, to see whether the observations lie within the error bars of the predictions (they do).
What is the reverse of my statement?
Since another poster was confused on this point: solar output isn't literally "flat", it has just changed very little, when averaged over the 11-year solar cycle. (The solar cycle itself introduces noticeable changes in irradiance, but the underlying trend, upon which that cycle is superimposed, has been quite small over the last 50 years.)
2. Who cares? The fact that something is run by governments (such as that noted champion of global warming, the Bush Administration) has nothing to do with the fact that it cites the scientific literature. Who wrote a report which cites that literature has nothing to do with the existence or content of that literature. You claim that since I don't remember every source I've used when doing research out of the dozens of topics I've researched that I'm obviously making it up. No, I claim that you don't understand the subject, your sources, or where your sources came from. I also claim that your research skills are PATHETIC, if you never even read an IPCC report and "all the literature" you found claims that the Medieval Warm Period was 5 degrees warmer than today. The report I cited refers to at least a dozen studies coming to opposite conclusions. How is it that your "unbiased" research somehow managed to miss all those papers, and only find ones which support skeptic claims?
And I can see from your continued responses that you are totally uninterested in discussing any of the science, preferring to engage in political conspiracy theories. And you call ME a troll.
Hypocrite.
Try to use some small amount of intelligence here. Solar irradiance (not "temperature variations") has been flat in the sense that the 50-year trend is close to zero. It is not literally unchanging. The point is that the overall irradiance trend is much smaller than what is needed to explain a surface warming trend.
I should note that the last link above concentrates on the degree to which solar effects have been responsible for the recent warming, i.e., during the post-1970 period the poster above was discussing. Solar irradiance changed more rapidly earlier in the 20th century, and CO2 concentrations were lower, so solar effects contributed relatively much more to the warming of that period than they do today.
If you look at the trend over the last 150 years or so, as I said, you find about 1 to 3 W/m^2 increase in irradiance, e.g. here or here. A 0.05% increase per decade, over a century, is 0.5%. Solar irradiance has not been increasing at a constant rate, either. Now it doesn't go the full 1.2% we'd need to explain the Global Warming (unless it went up as a different rate before), but it almost halves the effect we can blame ourselves for. This analysis has already been performed, far more carefully than your analysis, and does not support your conclusion. See, for instance, here, which I cited elsewhere in this thread.
Besides, whether it's expensive is not the question. The question is whether cutting CO2 is more expensive than the alternative (not cutting it and letting global warming happen).
Pretty much every economic cost-benefit analysis indicates that some mitigation of CO2 emissions is more cost effective than none. See my links above for details. That's all fine if it's necessary to prevent an Ice Age or runaway warming that will leave Earth like Venus. Runaway warming isn't going to happen, and reducing the warming that will happen does not require the destruction of the world economy. problem is, we can only make such a staggeringly huge change in our habits perhaps once in a thousand years. Another conclusion backed up by extensive socioeconomic analysis, no doubt. But perhaps you could deign to provide some citations to this analysis. By making that change now, in the direction of reducing CO2 emissions, we give up the ability to make any similarly massive change for a long time. Because we'll be in a post-apocalyptic world living in caves and cannibalizing each other? Give me a break. We will cut back on whatever CO2 we can afford, and adapt to whatever climate change remains. Note that we're going to have to wean ourselves off of fossil fuels ANYWAY, albeit at a slower rate than if GHGs weren't a concern. Or might there be some other climate effect, driven by the Sun, say, to which we will in the future really wish we had preserved our ability to respond? An unforseen climate effect could produce unforseen warming, or unforseen cooling. If it produces warming, then we needed to cut back on CO2 anyway, even more so than with the current global warming. If it produces cooling, we can start burning the fossil fuels that we stopped burning earlier to fight global warming.
If you're really concerned about future climate change, you should be arguing that we should save our fossil fuels in case we need them later to influence the climate, instead of burning them all when we don't. The more uncertainty we have about future climate, the less willing we should be today to do things which perturb that climate, and the more insurance we should buy. "Not cutting CO2 emissions" is only a sensible decision if you have a lot of certainty about future climate: namely, that it's not going to get much warmer.