Now that Global Warming is an accepted fact, the deniers have switched their argument saying that natural variance in the Sun’s output could be the cause, not greenhouse gas trapping of heat.
I was thinking about this, and need clarification about the following:
1 - Scientists have evidence of geologically recent cool-downs and warm-ups (Greenland was indeed green around the time of Vikings, there was a mini ice-age recorded in Europe 1500-1750). Is there direct evidence that the Sun was the cause?
2 - The Sun goes through 11 & 22 & 44 year cycles of sunspot activity. Do these cycles include corresponding changes in radiation?
3 - If global warming is indeed a result of an increase in solar output, then have we detected that increase? I’m thinking that since the warming trend is, geologically speaking, instantaneous there should have been a clear and measurable change in the Sun.
As I pointed out in a post a few weeks ago, if you compare the suns irradiance over the last few centuries to the temperature of the Earth, there’s no obvious relationship. Point in fact, when the Sun was last hot was during the middle of a cold phase on the Earth.
On the other hand if you compare CO2 to the temperature of the Earth, it’s an almost picture perfect match going back thousands of years. And the tail end of the CO2 chart suddenly goes in a straight line up past anything it’s ever been in the last 400,000 years–and at the same time as the temperature of the Earth seems to be beginning to increase at an unnatural rate.
True, just knowing that CO2 and the average global temperature are linked doesn’t prove causality. But the Greenhouse Effect seems a viable explanation to show why increased CO2 would increase the temperature of the Earth, while as I haven’t heard any hypotheses to show how the reverse would be true and how an increase in the temperature of the Earth is supposed to create more CO2.
So going by the first image, if there’s supposed to be a cycle to the sun, it doesn’t appear to be showing up. It peaks in 1600 and again in 1800, but not in 2000. And as said, comparing that to the temperature, 1600 and 1800 were both low points compared with the global temperature around 2000.
Now admittedly, there does seem to be a 120,000 year cycle of some sort to the temperature of the earth, which I’m not sure what is, but fairly obviously the sudden burst in CO2 at the end isn’t related to that cycle. That seems to be something else–which humans are a pretty good bet as to being the source of.
Greenland was not “green” when the Vikings got there, Erik the Red was just a very, very good salesman. There was a relatively thin strip of fertile, forested & arable land on a few of the fjords, which the Greenlanders promptly set about deforesting & eroding away. The inland ice sheet, however, were already there, and had been for some hundred thousand years.
The rather spurious quoted figures are that human activity accounts for 10% of the CO2 released each year.
Now in simple terms, I down ten pints of beer, and blame my inebriation on the tenth.
Of course my body can handle nine pints, I have a natural ability to metabolize 9 pints - but that tenth pint is the killer.
Since Nature is force feeding me nine pints, and there is nothing anyone can do about that, my only logical course of action is to run around in circles like a headless chicken - in a vague attempt to avoid the tenth pint.
Of course all the alcohol consumption models indicate that inebriation is down to that final pint - and 2000 alcohol scientists signed a bit of paper saying so.
As far as I am concerned Global Warming is a lot nicer than the Ice Age we used to get alarmed about.
Unless you live in Africa, in which case farmland goes from minimal to nothing.
For the US itself, probably the only effect will be on agriculture. For instance, whether the California Basin will continue being profitable to farm, or if farming will move North.
(Europe may temporarily end up going cold though due to global warming, so don’t entirely rule out that Ice Age.)
To be fair, I think there is generally seen to be some correlation…For example, some of the warming in the first half of the 20th century is believed to be due to the upkick in solar irradiance during that time. And, it is generally believed that the Mauder Minimum in sunspot activitiy was correlated with the Little Ice Age.
However, solar variability is becoming a much less significant factor in the face of the growing effects from greenhouse gases. And, in particular, cannot explain the sharp rise in temperatures we have been seeing since about 1970.
Again, things are a bit more complicated. It is in fact understood that there is a 2-way relationship between temperature and CO2. I.e., there are mechanisms (not entirely understood but likely having to do in large part with the lower solubility of CO2 in water as it warms) by which rising temperatures leads to an increase in CO2…although the ice core data seems to show that these act rather gradually over close to 1000 years.
In fact, as you note there is a periodicity in the ice age - interglacial cycles…and this periodicity is explained by the so-called Milankovitch cycles. These are orbital oscillations in the earth’s orbit that have various frequencies…one involves precession of the earth’s axis so that the relationship between the seasons and when the earth is closest to the sun changes over time. (Right now, we are closest to the sun during the Northern Hemisphere winter.) A second involves oscillations in the degree of tilt of the axis (by a small amount…like 1 or 2 degrees as I recall). A third involves small oscillations in the eccentricity of the earth’s orbit around the sun. None of these oscillations results in big changes in the total amount of solar radiation that the earth receives. However, they do change the distribution of that radiation which, because of the distribution of land mass and ice on the earth, does serve to create an important triggering effect regarding the buildup or decay of ice sheets.
So, the basic story is understood to be: Changes in the earth’s orbit act as a trigger. The initial warming that occurs then releases CO2, which causes further warming. Thus, it is a symbiotic relationship.
Just to make one thing clear now, however: The current rise in CO2 is definitely due to man and not a feedback from some natural warming. We know this for a variety of reasons. First of all, there is the very strong circumstantial evidence that over the past 750,000 years (which takes us back through several ice age – interglacial cycles), ice core data shows that the level of CO2 has never been above about 300ppm, whereas it has risen from 280ppm to 380ppm since the industrial revolution. The record also never shows as fast a rise in CO2. [The level of CO2 is believed to be higher than it has been for about 20 million years although this is known with less certainty because the ways of determining CO2 once you get beyond ice core data are less accurate and time-resolved.] Second of all, we can compare the rise in the amount of CO2 in the atmosphere to the amount we know we are emitting by burning fossil fuels and they align well…Or, more precisely, they show that about half of what we release into the atmosphere each year stays there and half gets absorbed by the various sinks (the oceans, plants, …). Thirdly, we can actually like at the isotopic fractions of the various carbon isotopes in the atmospheric CO2 and see it changing in response to the carbon from fossil fuels (which has a different isotopic distribution).
And, finally, note that in this regard, the symbiotic relationship between temperature and CO2 is not comforting in the sense that it suggests that the warming we are causing through the buildup of CO2 will likely lead to the release of additional CO2 and methane through the same mechanisms as have occurred previously (for exmaple, due to the oceans warming and due to permafrost in the northern climates melting). So, this is a potential positive feedback that can accelerate the warming.
As usual, you are a font of misinformation on the subject! Yes, it is true that there are large natural exchanges of CO2 between the atmosphere and the hydrosphere, biosphere, etc. However, the point is that these exchanges were basically in equilibrium before the industrial revolution. Now, we are adding an additional source of CO2 from carbon that has long been locked away from access to the atmosphere.
If you want to go with your analogy, a better description would be that it is as if the bartender is serving up drinks but you are at the end of the bar so while they are being passed along the bar, they never actually make it down to you. Now, I walk in surreptitiously with a bottle of Scotch, come up to you and start directly feeding you glasses of it. The question would then be who is responsible for your inebriation, the bartender or me? [A better analogy I have seen used is a bathtub filled to the brim where you are running the faucet at exactly the rate that the drain is draining. Now, I come and turn the rate of the faucet up. Who is responsible for all the water that ends up on the floor?]
Unfortunately, it seems to never occur to you that this is because perhaps those scientists actually understand the science of which you speak and you do not.
@JShore
I have learnt to take your integrity as given, I reckon that you truly believe what you are saying, also that you’ve researched deeply and feel justified.
However, if I were standing on a railtrack with a possibly approaching train, I really don’t think that I would trade ‘huffing and puffing credits’ with my compadres in the hope of not getting minced.
You see, you are nomocratic, you live within very confined rules. I am teleocratic, and if I don’t like the box, well I recommend evacuation.
I live in the UK, apparently according to ‘guestimate’ figures that I don’t want to dispute, we contribute 1.6% of global anthropogenic ( like 0.16% ) of CO2 output. What we do matters less than a fart in a thunderstorm - and if you think we can stop China, India or the odd volcano (let alone decaying matter) then … well, highly optimistic is all I can say.
I am all in favour of clean air, polluted rivers and seas are revolting, but I’m not prepared to support a Canute type theory that we can stop something we don’t understand.
PS: Ever thought how broken energy saving light bulbs will produce a generation of mad hatters - that they contain mercury spooks me.
As the op notes, most of the “no action is indicated” folk have given up on the tactics practiced by FRDE. Misleading simplistic analogies and trying to belittle the solid science behind the current predictions have mainly gone by the wayside now.
But here is what continues to confuse me: why does anyone even care about the continued attempt by a few to deny Global Climate Change’s sizable anthropogenic character? To indulge FRDE in his simplistic analogies: why should I even care whether a human pulled the switch to set that train down the track or if it was a some freak natural event that caused the switch to pull? Either way I know that my continuing to just stand there is a real bad idea. Likewise on Global Climate Change: either way it is time to move on this thing now.
Currently the Western World produces most of the greenhouse gases in question. No doubt China is in line to catch up. No doubt that any effective plan needs to have enough of the rest of the world involved that China will adopt measures as well in order to be able to participate (?dominate?) in the world economy. Those plans need to have options that such an emerging economy can adopt. China has lots of coal and is developing a huge appetite for oil. They will only implement carbon sequestration technologies on coal plants if we make such a normative expectation for members of the world’s economies. They may adopt alternatives to increased oil consumption once available just out of an informed awareness that dependency of oil from the ME or Russia is politically undesirable and will be over a modest long term unable to keep up with their thirst anyway.
You may change your tune if GW disrupts the Gulf Stream. (The Gulf Stream, in case you’ve forgotten, is what allows the UK and Western Europe to have a warmer climate than Russia or Greenland.)
Well, one can always use this sort of logical fallacy in dealing with problems that involve a large number of people, i.e., “my emissions or my country’s emissions are small compared to the total so we don’t have to do anything.” Ideally, everyone wants to be a “free rider”.
As for China and India: Yes, their emissions are going to have to be controlled too. However, we are stuck with the world in which we live where there are political and economic realities in addition to scientific realities. And, the reality is that because we [the industrialized nations] have greater technological capacity, because we are responsible for the bulk of the current elevated CO2 levels [i.e., the cumulative amount of emissions], and because we have a way larger emissions rate per capita, they are going to expect us to take the first steps.
As this EPA fact sheet explains, the amount of mercury in a CFL is less than the amount one saves from going into the air because of their greater efficiency if you get your electricity from a coal-fired plant. And, of course, if you dispose of the bulb properly, there is no reason why the mercury should ever get into the environment.
The amount is also very small compared, e.g., to the amount in a mercury thermometer or an old thermostat. So, even if it breaks, the risks are small.
jshore, your posts are always welcome. Sorry I haven’t been on the Board for a while, I’ve been working in the Solomon Islands, where internet connections are … well, let me call them “dubious” …
You say:
This explanation, which is repeated at the RealClimate web site, has always mystified me, for several reasons.
Why should there be a ~ 1000 year delay between the onset (and end) of the warming at the start of an interglacial, and the associated change in CO2 level? The oceans and the biosphere have responded much more quickly than this to the current rise in CO2.
According to the Vostok data, temperatures rose from ~ 17,000 to 14,000 years BP, then dropped for about 2,000 years, then started rising again. If rising CO2 were driving the glacial-interglacial transition as you say, why should the temperature drop?
Why did the CO2 level continue to rise for ~ 1,000 years after the temperature stopped rising?
The numbers don’t match up. If CO2 is the cause of the glacial-interglacial temperature rise (after the first thousand years), it implies a change of 13°C for a doubling of CO2 … which seems very unlikely. If that were actually the case, the recent CO2 increase should have increased global temperatures by about 6°C, which obviously hasn’t happened.
The Vostok temperature data is available here, and the CO2 data is available here.
Let me know your thoughts on this question, as that explanation has always seemed like hand-waving to me.
Jshore: Hey, I just wanted to tell you that your even-handed, ‘stick to the science’ approach to the issue is very much appreciated. And by the way, you have done more than anyone else on this board to pull me over to ‘your’ side, because of the way you debate it. We don’t agree on all points regarding what to do about warming, but you’ve convinced me on the science some time ago. So thanks for the effort.
Going with what Sam said, I’d also like to extend my own thanks to Jshore, who has done a bang up job in these myriad debates. Also, I think I’ll extend the same thing to intention, who’s posts I’ve been also following in these debates, and who has also done an outstanding job IMHO.
Though I consider myself reasonably intelligent, I have to admit that I haven’t been able to figure much of this stuff out. I think a lot of folks who ‘debate’ this are almost taking a ‘faith based’ approach…they don’t really understand either, and are just jumping on the bandwagon (or being contrary depending on which position they are taking), without really understanding what they are saying. I know for my part thats how it is…my main contribution, such as it has been, has been to try and look realistically at the economic impacts being proposed or generated, and try and see what ROI we could expect for our money (I’ve been disappointed thus far in the waffling answers to this :)).
At any rate, keep up the good work guys…the peanut gallery is avidly watching how this thing goes.
Well, first of all, there are apparently some issues in resolving the data down to this scale…I.e., it is not trivial to see exactly how the CO2 and temperature scales align because of the different ways in which CO2 and the isotope temperature record are recording in the ice. See here.
See, also, Cuffey and Vimeux, “Covariation of carbon dioxide and temperature from the Vostok ice core after deuterium-excess correction,” Nature 412, 523-527 (2001), which discusses a correction that needs to be made to the isotope temperature record. (I don’t think the correction affects the onset of deglaciation very much although it does affect the onset of glacial.)
That said, the speculation has been that if the 800 year time lag is accurate, this would correspond to some sort of time scale for overturning of the oceans.
Is this the so-called Younger-Dryas event? I’m not really up on that…and I am not even sure if that was a global temperature change…Was it? I also don’t know if the Cuffey and Vimeux correction improves the agreement at all. I guess the answer is that I don’t know.
Well, your number of 13°C per doubling of CO2 isn’t quite as bad as on another messageboard where someone had extended the line from the Vostok record to predict what turned out to be something like 28°C per doubling! Here are the mistakes that I thought that person had made:
Nobody is (or should be) claiming that all the temperature rise…or even all after the first 1000 years…was caused by a rise in CO2 levels. In fact, the accepted explanation is that the effect goes both ways. I.e., the initial rise (or fall) in temperature is triggered by the earth’s orbital oscillations. These then cause a change in CO2 levels, which then amplifies the change in temperature. The best estimate is apparently that about 1/2, or a little less, of the change in temperature is due to changes in CO2 and methane concentrations.
(2) The plots from the Vostok ice core show the estimates of the temperature change in that region, which is likely about a factor of 2 or so larger than the global temperature change because of polar amplification.
(3) As you know, the response of temperature to rising CO2 levels is expected to be roughly logarithmic. So…one can’t just extend a straight line to predict the temperature rise from a given increment of CO2. (I doubt you made this mistake, but the guy on this other messageboard had.)
(4) Because CO2 levels are changing so rapidly, the earth is out of radiative balance and thus the change in temperature has not caught up to the current CO2 levels. Furthermore, we likely have cancelled out some of the warming that would have occurred due to greenhouse gases with our emissions of sulfate aerosols.
Here is Hansen’s calculation of climate sensitivity implied by the ice age vs interglacial temperatures and atmospheric compositions.
The one thing that I always used to wonder is how they could be so confident that the greenhouse gases are contributing about 40% or so to the temperature rise. I.e., it seems like if they are underestimating the ice albedo effects by almost a factor of two, you could do away with the contribution from greenhouse gases almost altogether.
However, the problem with that logic is that it isn’t internally-consistent. I.e., even if the ice albedo forcing was ~6 or 7 W/m2 by itself and it alone produced all of the effects, you still have an implied sensitivity of about 3/4°C per W/m2, which (since we know the radiative forcing due to changes in greenhouse gases), then implies that they play a significant role in contradiction to our initial assumption. So, what you really need is to find some mechanism that resulted in a way-bigger radiative forcing difference between ice age and interglacial than anything that is understood, so that the climate sensitivity is low and thus the effect of the radiative forcing due to CO2 is small. I.e., you need to overthrow pretty much our entire current understanding of paleoclimate. This seems rather unlikely. (I think there are other issues in that it is rather hard in climate models to get the ice ages to be synchronous in both hemispheres when the only forcing is the “trigger” due to orbital oscillations, which vary the distribution of sunlight hitting the earth without causing much change in the total amount. The radiative forcing due to the greenhouse gases is necessary to get things to work.)
Sam Stone and xtisme: Thanks very much for the kind words. I really appreciate it and, Sam, I am very glad to hear that I have influenced your thoughts on the issue!
The thread was about whether global warming is being caused by solar irradiance, not whether it is worth fighting global warming.
As to whether it’s worth it, well think of it like this: Saying that the UK causes 1% of the pollution to create abnormal temperature, and that for every percentage point that you cut means that the duration of the “heat age” will last one year less, then if the UK can cut 25% of it’s emissions, then that’s three months of normal temperature created.
And now if we assume that for every year that we are in the heat age, 2000 people die of famine in Africa, then 3 months cut off would be saving 500 lives.
500 lives in the long run of things I suppose doesn’t matter all that much, but I think it’s hard to argue that you shouldn’t try and save those lives if you have the power to. Pollution should be lowered, just the same as you shouldn’t toss your candy bar wrapper out the window of your car. It’s hard to make any argument not to lower pollution in your own country.
The one argument is that it will just move to China–but hey, just don’t buy products from China. It will cost more, but it costs more to wait until you get to a trash can to throw away your candy wrapper than to toss it now, just the same.
Credit where credit is due my friend. You’ve been carrying the majority of the water on this debate IMHO…sort of the Darwins Finch of Global Warming, or the Tamerlane of anything dealing with history. FWIW you’ve been instrumental in making me less ignorant on this subject as well.
