" Carbon dioxide levels are the lowest they have been in 500 million years"
" Carbon dioxide has never been a driver of global temperature over 500 million years"
" When the carbon dioxide levels were 10 times higher than today the Earth was in the depths of an iceage"
Glen, that graph is meaningless. It's only for the last 800Ka. A blip in time. For most of Earth's history, the CO2 levels have been appreciably higher (much higher in most cases) than what they've been for the last 2.5 million years. How do you account for a CO2 level of 600-800ppm for most of the Tertiary/Quaternary Periods, and a high of 1200-1250ppm for the Palaeocene/Eocene epochs. Or an average of 1800ppm for the entire Mesozoic. Or an average of 2500-3000ppm for the Palaeozoic, apart from the mid to late Carboniferous, where temps were nearly as low now and so were the CO2 levels. During the Cambrian they were around 7000-8000ppm. The Earth at present is the coldest it's been for 500Ma, even during the Carboniferous period the average global temp was about a degree warmer than now.
Those Vostock ice core measurements are being taken during an ice age. The temps and the CO2 levels are going to go up and down like a yoyo!!!.
What is ultimately in dispute here is human input into the causes for climate change. Whether you believe it or not will depend on your own PoV and how much you actually know about the subject.
Wow, that is a serious pile of untruths, misconceptions and misdirection. I hope that isn't what school kids are being taught or they'll be in for a shock when they go to university to study any of the subjects those comments touch upon. Anyone who compares the climate today with that of several hundred million years ago in the context of climate change is trying to pull a fast one. It is basically irrelevent as both the geology and biology of our planet is very different now (not to mention our data on the climate then has very high error bars on it compared with more recent times). I think you are a lot better off looking at the climate over the last few hundred thousand years (5 ice ages or so) and then asking those questions of how we compare now. You would get some very different answers. Lets not forget that Homo sapiens sapiens has been here for less than 200,000 years.
I'm afraid it's you who is misinformed. If they go to uni to study those subjects, that's exactly what they will be taught. The geology of this planet has been the same as it is now, in so far as the processes we have presently are involved, for the past 1800-2500Ma. The biology, in so far as the overall biological process that occur are involved, have been pretty much the same for the past 350Ma (on land) and for 550Ma (in the oceans). The past climates have a very relevant bearing on what is happening now because we can study how the processes that occurred then mirror (or are different to) what they do today. It might come as a surprise to you that there were ice ages way back then. There were tropical zones, temperate zones, deserts, rainforests etc etc, just the same as now. The players on the stage may have been different but the stage was the same.
Now...I'm going to throw this whole debate open and put it on the line...
How many of you actually have studied as part of, or have a degree in Climatology, Geology, Atmospheric Physics/Meteorology/Chemistry etc??
It's all well and good being able to posts graphs and such supporting a position, but do you actually understand the science behind what you've posted, the context in which the graphs were produced, or are you just paraphrasing what's being said in those studies and what's being promulgated by the media??
Do you know why the results are the way they are??
Hi AstralTraveller
You are a believer in climate change by human activity and you are fully entitled to do so right or wrong. But your arguments are based on partial truths and statistcs. CO2 does block IR both ways so its effect will tend to cancel but only if it is significant in the constitution of the atmosphere.
Barry,
My position on AGW is not as cut and dried as you believe, see my previous posts. Also the thing I value most is an honest argument - something there is just too little of.
If I used partial truths it was not to decieve, just that I'm not about to write an essay. If you think I have misrepresentated the situation with respect to the IR trapping properities of CO2 or the cause of the increase in atm CO2 conc (the topics of my last post) please state specifically where my fault lies. BTW I didn't use statistics.
Your last sentence implies you didn't understand my post - there is 100% absorbance at the centre of the CO2 band even though there is only 380ppm of CO2. It also reveals that you don't know how the natural greenhouse effect works. By your mechanism there could be no natural greenhouse effect. Please look up how the natural greenhouse works, I don't have time to write it up.
Hi AstralTraveller
You are a believer in climate change by human activity and you are fully entitled to do so right or wrong. But your arguments are based on partial truths and statistcs. CO2 does block IR both ways so its effect will tend to cancel but only if it is significant in the constitution of the atmosphere.
Don't forget the amount of carbon and other elements that constitute our earth hasn't changed since the earth's creation and the cycle of combining O2 with C and the converse (carbon cycle) has been going for a long time. If the CO2 gets too high animal life will die out and vegetation will prevail thus reversing the cycle as it has done before.
I know we as humans are abusing our ecosystem to our own demise but CO2 is not the problem.
Barry
That doesn't make any sense. The effect doesn't cancel because CO2 doesn't block IR it absorbs the energy. The whole point is that it prevents IR radiation leaving the earth, thus increasing the energy within the atmosphere. The IR that comes from the sun is absorbed anyway so is irrelevant (kind of).
Also the atmosphere hasn't really cycled between O2 and CO2. The CO2 has been absorbed over time and O2 released. Until the O2 hit a certain level complex animal life could not exist. Whilst there is continual changes in the exact proportions, the O2 has remained fairly stable and will only be greatly affected if we removed enough plant life.
Undeniable fact: CO2 is currently increasing in the atmosphere.
Undeniable fact: the majority of the CO2 increase is due to anthropogenic emissions*.
Undeniable fact: CO2 acts as a greenhouse gas.
The argument is whether or not warming of the earth's atmosphere is happening and whether or not CO2 is a significant driver of that.
* Note I say increase, not the majority of absolute annual terrestrial emissions.
Glen, that graph is meaningless. It's only for the last 800Ka. A blip in time. For most of Earth's history, the CO2 levels have been appreciably higher (much higher in most cases) than what they've been for the last 2.5 million years. How do you account for a CO2 level of 600-800ppm for most of the Tertiary/Quaternary Periods, and a high of 1200-1250ppm for the Palaeocene/Eocene epochs. Or an average of 1800ppm for the entire Mesozoic. Or an average of 2500-3000ppm for the Palaeozoic, apart from the mid to late Carboniferous, where temps were nearly as low now and so were the CO2 levels. During the Cambrian they were around 7000-8000ppm. The Earth at present is the coldest it's been for 500Ma, even during the Carboniferous period the average global temp was about a degree warmer than now.
Those Vostock ice core measurements are being taken during an ice age. The temps and the CO2 levels are going to go up and down like a yoyo!!!.
What is ultimately in dispute here is human input into the causes for climate change. Whether you believe it or not will depend on your own PoV and how much you actually know about the subject.
Carl,
Do we know the following.
Let's reference it to the Carboniferous period.
(1) Was there a supercontinent during this period?
(2) What was the "mean" angle of Earth's rotational axis to the orbital plane during this period?
(3) If this supercontinent existed where was it's position relative to the surface of the Earth?
I'm trying to stay out of this but I will correct the above two paragraphs.
Yes water vapour is the major greenhouse gas but suggesting that CO2 has no effect just because it is in low concentration is wrong. First, it is easy to see that CO2 should trap heat by blocking outgoing IR. Since the CO2 absorption band does not fully overlap with the H2O absorption band the absorption due to CO2 is added to that of H2O. In an ideal gas these 'bands' are discrete lines but in a real gas the lines are broadened into bands. The CO2 band is, despite the low concentration, already fully blocked at its centre and the increase in absorbance is due to band broadening as the partial pressure of CO2 increases. That is why the increase in CO2 absorbance does not scale directly with the increase in CO2 cancentration. Trying to write off CO2 because of its low concentration is a bit like trying to claim that once light has travelled all those billions of km from that galaxy a mere piece of paper can't stop it reaching your telescope.
I'm surprised anyone would attempt to deny that human activity is the cause of the increase in atmospheric CO2 concentration. Records of CO2 conc go back much further than 30 years and the temporal correlation between the increase in atm CO2 and the increase in fossil fuel use is plain to see. But there is more! Consider the carbon 13: carbon 12 ratio of atmospheric CO2. These ratios are normally expressed as a 'delta value' which reports the difference in the ratio (in permille, ie. parts per thousand) of the sample from that of an internationally accepted reference material. So for carbon we talk about the d13C on the PDB scale (the 'd' should be a Greek delta but I don't have that font available). Prior to the industrial revolution the d13C of atm CO2 was about -6 permille. The carbon in fossil fuels has a value of about -27 and that of CO2 outgassed from oceans is about 0. So if the extra CO2 comes from the ocean the value will move towards 0 and if it comes from fossil fuel it will move towards -27. What do we see? The value has moved from about -6 to about -7. (The situation is a little more complicated than this but I'll stop now - I have to calibrate some d13C results so I can tell a grad student whether or not she is happy.)
Finally, someone who understands atmospheric chemistry!!!. However, there are other factors just as important as the rising CO2 concentrations which are contributing to global temp rise, which I've mentioned earlier on in this thread. The cause isn't entirely CO2 (even though it is a strong factor) and it's about time that is made clear.
What I would be more worried about is if the methane clathrate deposits in the oceans decide to sublimate. These are very sensitive to temperature fluctuations. If they all decide to go, we're in a lot of trouble. Think rising CO2 levels are bad, if the clathrate deposits sublimate, the rise in temp over time will make CO2 look like a comfortable spring picnic. Only good thing about methane is it doesn't last long in the atmosphere...5-10 years...before it's scrubbed out by biological and hydro-geological processes.
I'm afraid it's you who is misinformed. If they go to uni to study those subjects, that's exactly what they will be taught. The geology of this planet has been the same as it is now, in so far as the processes we have presently are involved, for the past 1800-2500Ma. The biology, in so far as the overall biological process that occur are involved, have been pretty much the same for the past 350Ma (on land) and for 550Ma (in the oceans). The past climates have a very relevant bearing on what is happening now because we can study how the processes that occurred then mirror (or are different to) what they do today. It might come as a surprise to you that there were ice ages way back then. There were tropical zones, temperate zones, deserts, rainforests etc etc, just the same as now. The players on the stage may have been different but the stage was the same.
Now...I'm going to throw this whole debate open and put it on the line...
How many of you actually have studied as part of, or have a degree in Climatology, Geology, Atmospheric Physics/Meteorology/Chemistry etc??
It's all well and good being able to posts graphs and such supporting a position, but do you actually understand the science behind what you've posted, the context in which the graphs were produced, or are you just paraphrasing what's being said in those studies and what's being promulgated by the media??
Do you know why the results are the way they are??
I studied geology at university (though in a limited way and it was a fair time ago), I studied chemistry at university (again limited) and I am a plant biologist by profession. One thing I can tell you is that the vegetation has most certainly changed significantly in the time you claim it hasn't. One of the largest impacts has been the evolution of grasses, which is much more recent and has totally changed the vegetation in large parts of the world.
Of course the paleoclimate informs us in how the climate works, who would deny that. But it is disingenuous to talk about 500 million years ago and how we are colder now. The point is that for the last several hundred thousand years the climate has been relatively stable (glacial/interglacial cycles), and all the measurements we have indicate that we are now going off that stable range. Why?
The best guess we have is that it is due to anthropogenic CO2 emissions. So do you consider that we are currently warming or not? If you consider that we are, then what do you think the cause is?
Finally, someone who understands atmospheric chemistry!!!. However, there are other factors just as important as the rising CO2 concentrations which are contributing to global temp rise, which I've mentioned earlier on in this thread. The cause isn't entirely CO2 (even though it is a strong factor) and it's about time that is made clear.
What I would be more worried about is if the methane clathrate deposits in the oceans decide to sublimate. These are very sensitive to temperature fluctuations. If they all decide to go, we're in a lot of trouble. Think rising CO2 levels are bad, if the clathrate deposits sublimate, the rise in temp over time will make CO2 look like a comfortable spring picnic. Only good thing about methane is it doesn't last long in the atmosphere...5-10 years...before it's scrubbed out by biological and hydro-geological processes.
Then Carl I don't understand your position. I am familiar with what Astral Traveler posted as well (I've worked with people studying stable isotopes in the atmosphere - and I can assure all the ones I have come across are fairly convinced that climate change is occurring and that humans are the major players). No one is seriously claiming that CO2 is the only component, and you yourself point out some of the big problems that could happen if the earth warms.
Undeniable fact: CO2 is currently increasing in the atmosphere.
Undeniable fact: the majority of the CO2 increase is due to anthropogenic emissions*.
Undeniable fact: CO2 acts as a greenhouse gas.
1. yes CO2 is increasing but is still at levels around 0.03% of the atmosphere. The way everyone is going on one would think that it was something like 10% and rising rapidly. There is a huge level of hysteria involved in the notion of CO2 rising.
2. this statement is well; not entirely correct. Deforestation, release of CO2 from the oceans due to acidification (which could be Sol's doing via high solar minimum outputs) are equally attributable to CO2 increases. This blanket statement really is that.
3. yes CO2 is a green house gas, but not the major constituent amount and certainly a lot more insignificant than the "climate change debater" make it out to be.
What is being said for the drop in temperatures in the last 3 years? The most recent studies are showing that temperatures have levelled off and are now reducing. Mean while CO2 keeps rising. This is incongrous with the premise of the climate change debaters. What do the climatologists have to say about that? Shall we just ignore that fact?
This system which we live is so complex that I doubt that humans have the slightest grasp as to what is really going on.
1. yes CO2 is increasing but is still at levels around 0.03% of the atmosphere. The way everyone is going on one would think that it was something like 10% and rising rapidly. There is a huge level of hysteria involved in the notion of CO2 rising.
2. this statement is well; not entirely correct. Deforestation, release of CO2 from the oceans due to acidification (which could be Sol's doing via high solar minimum outputs) are equally attributable to CO2 increases. This blanket statement really is that.
3. yes CO2 is a green house gas, but not the major constituent amount and certainly a lot more insignificant than the "climate change debater" make it out to be.
What is being said for the drop in temperatures in the last 3 years? The most recent studies are showing that temperatures have levelled off and are now reducing. Mean while CO2 keeps rising. This is incongrous with the premise of the climate change debaters. What do the climatologists have to say about that? Shall we just ignore that fact?
This system which we live is so complex that I doubt that humans have the slightest grasp as to what is really going on.
1. The absolute amount is not the issue, the issue is the effect. If the atmosphere was 0.03% cyanide the world would be a very different place.
2. Deforestation is part of anthropogenic emissions and a big part of the problem, I don't understand your point.
3. This is the same point as 1. Saying it is only 0.03% tells us nothing about the impact. How would you like 0.03% of alpha-radiation emitters in your diet? The big question is over what that impact is. The consensus in climate scientists is that the impact is significant. I'm not a climate scientist, though I have attended lectures by those that are, so I will go for the consensus. As nicely stated earlier, if 97% of doctors recommend one treatment and 3% another, who would you go with?
(1) Was there a supercontinent during this period?
(2) What was the "mean" angle of Earth's rotational axis to the orbital plane during this period?
(3) If this supercontinent existed where was it's position relative to the surface of the Earth?
Regards
Steven
Yes we do know about the state of the planet at the time. Without hunting for the particular references (as I don't have them on me and it'll take time to get them), I can tell you that the continents were assembling into Pangaea...Laurasia (that's Nth America and much of Eurasia) was moving towards the equator, whilst Gondwanaland was situated mostly over the Sth Pole and was covered in a large ice sheet.
I've got some maps (see below) for you to give you an idea of what the situation was in so far as the positions of the continents are concerned, as well as a climatological map. The situation is very similar as it is today, climatologically. You may have to download the graph and climatological map...they don't look so great when you click on them to display!!! (just tested them).
The Earth's average axial tilt in the Carboniferous was pretty much the same as it is now. They've been able to deduce this from the varve deposits from lake sediments of the period. What a varve is...is the annual deposits of fine clay and other particle sediments that build up as layers in the bottom of lakes in cold climates. The size of each layer, the types of minerals and such present and their internal physical characteristics can be used to determine many things...lengths of the year and hence orbital motion, length of the day at the time of deposition, how long the seasons lasted etc. From these, they've been able to determine the length of the day (from memory about 23 hours) and an orbit about the same as now.
I'm afraid it's you who is misinformed. If they go to uni to study those subjects, that's exactly what they will be taught. The geology of this planet has been the same as it is now, in so far as the processes we have presently are involved, for the past 1800-2500Ma. The biology, in so far as the overall biological process that occur are involved, have been pretty much the same for the past 350Ma (on land) and for 550Ma (in the oceans). The past climates have a very relevant bearing on what is happening now because we can study how the processes that occurred then mirror (or are different to) what they do today. It might come as a surprise to you that there were ice ages way back then. There were tropical zones, temperate zones, deserts, rainforests etc etc, just the same as now. The players on the stage may have been different but the stage was the same.
Now...I'm going to throw this whole debate open and put it on the line...
How many of you actually have studied as part of, or have a degree in Climatology, Geology, Atmospheric Physics/Meteorology/Chemistry etc??
It's all well and good being able to posts graphs and such supporting a position, but do you actually understand the science behind what you've posted, the context in which the graphs were produced, or are you just paraphrasing what's being said in those studies and what's being promulgated by the media??
Do you know why the results are the way they are??
And one more before, I get on with some work. As you well know the land masses were in a very different position to now during those hot periods you talk about, which resulted in big differences in ocean currents and big differences in climate. That's what I meant about the geology (though I would be surprised if outgassing has remained the same over the last 500 million years - but I have no idea). As I already said, the biology has change a lot since land plants first appeared on earth.
So the bottom line is, how can data on climate 500 million years ago be more relevant than the last one million years?
The "97% of doctors" is a poor analogy in this debate. You might as well throw in that 97% plus of financial analysts failed to predict the GFC, yet you still trust them to manage your smaller super fund even today and now 97% of them can't agree on whether the world is recovering or not.
I'd say more than 97% of doctors were at odds and challenged Warren and Marshall yet their "tenacity and prepared mind challenged the prevailing dogma". They were awarded the Nobel prize in Physiology or Medicine 2005 with their "remarkable and unexpected discovery" re peptic ulcer disease. Until then people were told it was lifestyle and stress related.
Someone once said Science progresses one funeral at a time.
The "97% of doctors" is a poor analogy in this debate.
PeterM.
No worries Pete...if you got cancer, I'd take it that you'd ignore all the specialists & MRI scans and go with the guy who says "eat mung beans and maybe take a couple of asprin"
I studied geology at university (though in a limited way and it was a fair time ago), I studied chemistry at university (again limited) and I am a plant biologist by profession. One thing I can tell you is that the vegetation has most certainly changed significantly in the time you claim it hasn't. One of the largest impacts has been the evolution of grasses, which is much more recent and has totally changed the vegetation in large parts of the world.
Of course the paleoclimate informs us in how the climate works, who would deny that. But it is disingenuous to talk about 500 million years ago and how we are colder now. The point is that for the last several hundred thousand years the climate has been relatively stable (glacial/interglacial cycles), and all the measurements we have indicate that we are now going off that stable range. Why?
The best guess we have is that it is due to anthropogenic CO2 emissions. So do you consider that we are currently warming or not? If you consider that we are, then what do you think the cause is?
I didn't say that the vegetation hasn't changed. I said that even though the "players" have changed, the "stage" and the processes involved are much the same as they are now. There are differences (most notably atmospheric oxygen content), but the physics of the processes driving the climate is the same.
The climate for the past 2.5Ma hasn't been stable at all and claiming it has been is not correct. If it was stable, there'd either be continuous ice or none at all. The climate has fluctuated wildly over the last 2.5Ma, with much of the time being colder than at present (or what is "normal" for interglacials). Even during the interglacials, the climates have gone up and down like a yoyo...the present interglacial being a very good example (even more so than the last two examples).
I never denied that the earth is warming...all I am saying is that there are other factors, just as important as a rise in CO2 which have contributed to the warming and most are man made. Instead of blaming it all on the CO2 why don't they look at some of these other factors...like the increasing spread of plant monocultures in agriculture over the last 100-200 years, the great increase in the size and spread of urban areas and the materials they're constructed out of, the cutting down of the forests, the huge increase in the numbers of cows on the planet (there's 1.5 billion of them...1/5th of them in India alone...remember methane) etc. You're a plant biologist...what happens when you replace a complex ecosystem (like the grasslands) with a monoculture of, say, wheat, over vast areas of your landmass. What you get, apart from all the usual problems in diversity, nutrient fluctuations etc etc, is a raising of the average temperature in the atmosphere surrounding the wheat. The IR flux off the wheat is higher than off the original ecosystem. Take temp measurements before and after the wheat is planted and you'll see the difference. You also get bare soils at some stage...bare soils get hot and re-radiate the heat, the also have higher CO2 output than a normal grassland or forest because of the exposed bacteria load in the soil. So there's a double whammy. Cut down the forest (forest cover on the planet has dramatically decreased over the last 100-150 years) and the same thing happens...temps rise. Not only that but you also get changes in climate patterns which spread worldwide. It's happening with the Amazon and the SE Asian forests and climate right now.
Look at where most of the temp measurements have been taken in the last 150 or so years...in and around towns and cities. As you'd be aware of, towns and cities are usual quite a bit hotter than their surroundings and have their own peculiar microclimates, which also effect the surroundings. Increase the size and extent of those towns and cities over time. Change the materials out of which they're constructed, and what happens?? The urban heat islands grow larger and hotter and affect their surroundings even more so. What does that do to the measurements you take??
You cannot divorce local or regional changes in climate from the overall global system. They're intimately interconnected. For example, the temperatures in much of China have gone up ever since they deforested and de-grassed much of the country, especially the northern half. Now they're having greater problems with desertification and rising temps than they've ever had beforehand. The same is happening in the Amazon. if they keep cutting it down at the rate they are, in 50 or so years you're going to have desertification and rising temps there. Not only that, it's one of the two major heat engines of the planet...and it's lungs as well. What happens when it disappears is going to make the rising CO2 levels look quaint.
Hopefully you can see what I'm trying to get at...the problem is far more than just CO2. By rights, if it was just CO2 rise, then during the Ordivician Period, there shouldn't have been a major ice age. The CO2 levels were around 4200ppm. even though Gondwana was over the Sth Pole, it shouldn't have had ice...but it did, lots of it. The average global temps at the time were only 2 degrees higher than now. So what was keeping the planet that cool, given the high CO2??. It wasn't a different orbit or whatever...they were pretty much the same as now. The Sun was only 3-4% dimmer than now...we get greater differences now, between summer and winter solar insolation than that. You have to look at the rates of erosion and the chemical/hydrological processes involved, the physical positioning of the continents and how they affect global sea and air circulation patterns and host of other things. You also have to remember there were bugger all land plants at the time...maybe some "pond scum" if you were lucky. That would greatly affect the amount of CO2 present in the atmosphere.
See what I mean...CO2 can be important over large times scales, but there's more to short and medium term climate change than just an increase in CO2. Other factors come into play...and at present much of the other things we're doing is only making things worse.
I didn't say that the vegetation hasn't changed. I said that even though the "players" have changed, the "stage" and the processes involved are much the same as they are now. There are differences (most notably atmospheric oxygen content), but the physics of the processes driving the climate is the same.
The climate for the past 2.5Ma hasn't been stable at all and claiming it has been is not correct. If it was stable, there'd either be continuous ice or none at all. The climate has fluctuated wildly over the last 2.5Ma, with much of the time being colder than at present (or what is "normal" for interglacials). Even during the interglacials, the climates have gone up and down like a yoyo...the present interglacial being a very good example (even more so than the last two examples).
I never denied that the earth is warming...all I am saying is that there are other factors, just as important as a rise in CO2 which have contributed to the warming and most are man made. Instead of blaming it all on the CO2 why don't they look at some of these other factors...like the increasing spread of plant monocultures in agriculture over the last 100-200 years, the great increase in the size and spread of urban areas and the materials they're constructed out of, the cutting down of the forests, the huge increase in the numbers of cows on the planet (there's 1.5 billion of them...1/5th of them in India alone...remember methane) etc. You're a plant biologist...what happens when you replace a complex ecosystem (like the grasslands) with a monoculture of, say, wheat, over vast areas of your landmass. What you get, apart from all the usual problems in diversity, nutrient fluctuations etc etc, is a raising of the average temperature in the atmosphere surrounding the wheat. The IR flux off the wheat is higher than off the original ecosystem. Take temp measurements before and after the wheat is planted and you'll see the difference. You also get bare soils at some stage...bare soils get hot and re-radiate the heat, the also have higher CO2 output than a normal grassland or forest because of the exposed bacteria load in the soil. So there's a double whammy. Cut down the forest (forest cover on the planet has dramatically decreased over the last 100-150 years) and the same thing happens...temps rise. Not only that but you also get changes in climate patterns which spread worldwide. It's happening with the Amazon and the SE Asian forests and climate right now.
Look at where most of the temp measurements have been taken in the last 150 or so years...in and around towns and cities. As you'd be aware of, towns and cities are usual quite a bit hotter than their surroundings and have their own peculiar microclimates, which also effect the surroundings. Increase the size and extent of those towns and cities over time. Change the materials out of which they're constructed, and what happens?? The urban heat islands grow larger and hotter and affect their surroundings even more so. What does that do to the measurements you take??
You cannot divorce local or regional changes in climate from the overall global system. They're intimately interconnected. For example, the temperatures in much of China have gone up ever since they deforested and de-grassed much of the country, especially the northern half. Now they're having greater problems with desertification and rising temps than they've ever had beforehand. The same is happening in the Amazon. if they keep cutting it down at the rate they are, in 50 or so years you're going to have desertification and rising temps there. Not only that, it's one of the two major heat engines of the planet...and it's lungs as well. What happens when it disappears is going to make the rising CO2 levels look quaint.
Hopefully you can see what I'm trying to get at...the problem is far more than just CO2. By rights, if it was just CO2 rise, then during the Ordivician Period, there shouldn't have been a major ice age. The CO2 levels were around 4200ppm. even though Gondwana was over the Sth Pole, it shouldn't have had ice...but it did, lots of it. The average global temps at the time were only 2 degrees higher than now. So what was keeping the planet that cool, given the high CO2??. It wasn't a different orbit or whatever...they were pretty much the same as now. The Sun was only 3-4% dimmer than now...we get greater differences now, between summer and winter solar insolation than that. You have to look at the rates of erosion and the chemical/hydrological processes involved, the physical positioning of the continents and how they affect global sea and air circulation patterns and host of other things. You also have to remember there were bugger all land plants at the time...maybe some "pond scum" if you were lucky. That would greatly affect the amount of CO2 present in the atmosphere.
See what I mean...CO2 can be important over large times scales, but there's more to short and medium term climate change than just an increase in CO2. Other factors come into play...and at present much of the other things we're doing is only making things worse.
Phew, a big post! Well on the whole I don't disagree. I have a few points:
1) By stable, I mean that for the last 600,000+ years or so we have seen cycles, where the max and min temperatures are similar (compared with the range over the 2.5 billion years before that). All the evidence I have seen points to us now tracking out of those cycles, thus we have the problem.
2) The ecosystem arable stuff is quite a bit more complex than you point out and those same changes occurred when the world went from being primarily covered in forest to having large areas of grassland (also the grassland can't hold as much C, so if it had always been there we wouldn't have all the coal we are burning), changing agriculture techniques (no till etc.) means that bare soil is increasingly less common. But I don't disagree with your point.
3) Temperature measurements are made at various levels in the atmosphere (and with various results), plus urban heat islands etc. are adjusted for in the models and the data interpretation, so I don't think that those factors negate the predictions for future climate.
4) I'll freely admit I know little if anything about the major controls on global temperature over the billion year timescales you are talking about (though I am fascinated). You appear to be suggesting that those controls are not well understood? Considering the differences that you have pointed out between then and now, and the relative recent stability (see my definition above!!!!), I would still say that making comparisons with the last million years or so was a much better option than looking at pre-cambrian times....
5) I agree totally with your paragraph on deforestation, I also agree absolutely that CO2 is not the only player in climate change. I don't think anyone would disagree, certainly not the modellers, who do include a whole raft of things.
So in summary, the difference between you and me is that you consider CO2 increases to be a smaller impact than most models predict and that possibly the degree of warming is overestimated due to biased data?
My opinion is basically that all areas of biology are already seeing the effects of climate change (whatever the cause). Not being a climate scientist (but also not being totally ill informed) I have seen no convincing arguments that the basic assumptions of the "97%" are incorrect and I don't have the background to judge whether any of the "3" have some wacked out idea that might just be correct. I'll exclude from that 3% all the jokers who are peddling disinformation for some end I don't understand.
In general we understand the cause and pathogenesis of cancer, at least on a biological level. There are biomarkers for cancer that can be detected at very low levels. A doctor relies on the pathology tests before making a definitive diagnosis.
Climatology is really in its infancy by comparison, in general we don't know the causes of temperature change, though we think we have identified some of the factors. The mechanism by which these factors effect our planet are the subject of much discussion.
My own personal philosophy is that the risk of inaction is far greater than the risk of action. If, in the end the CO2 problem isn't a problem we may have reforested a good deal of land, reduced our dependency on oil and other fossil fuels (have to declare a vested interest in this as it frees more up for me to use motor racing), reduced the world's political dependency on the Middle-East and cleaned up some of the particulates in the air. All this is going to cost money, but all are benefits, to quote an old conservative politician, "there's no such thing as a free lunch". I welcome paying more tax to clean up the mess, so my children don't have to. Kinda like I welcomed paying more Medicare levy until the Government forced me to take out private health insurance (yet another rant of mine), as long as they put the money into public hospitals (which I don't think they did).
And one more before, I get on with some work. As you well know the land masses were in a very different position to now during those hot periods you talk about, which resulted in big differences in ocean currents and big differences in climate. That's what I meant about the geology (though I would be surprised if outgassing has remained the same over the last 500 million years - but I have no idea). As I already said, the biology has change a lot since land plants first appeared on earth.
So the bottom line is, how can data on climate 500 million years ago be more relevant than the last one million years?
Yes, they were, but you have to look at the positions in which they were in the overall context of the climates that occurred when they did. Climates have changed and fluctuated over millions of years but much of the overall basic patterns have remained the same. During the Carboniferous, for example, the climate overall was much the same as now. The climate zones and weather patterns were quite similar, but the CO2 level was 800ppm. That should mean, according to the those that believe it's the CO2 causing the climate change, it should've been much hotter, but it wasn't. What does that tell you??.
Let's look at a time less remote from us than this...the Cretaceous. CO2 concentration was 1700ppm, average global temp was 18 degrees, 6 higher than now. The continents were pretty much recognisable though somewhat out of position, but their distribution relative to one another was similar to today. CO2 levels fell to around 1000ppm by the end of the period and it cooled to around an av' of 16 degrees worldwide. The plant biology of the time was remarkably similar to now. You had conifer forests and flowering plants had actually supplanted most non flowering plants in variety and numbers of species by the mid to late Cretaceous. Apart from the fact you had large munchy biteys running around, the world was remarkably like now, except there was 50% more oxygen around than now. The temperature profile for the Cretaceous is remarkably constant for the much of the period, CO2 levels were not. They dropped 700ppm. What is that telling you about the correlation between CO2 and temperature??. Actually, when the CO2 levels were at their highest during the period, the temps were at their lowest...doesn't quite ring true, does it?? This is despite the fact that warm seas covered much of the continents at the time and carbonate deposition was high.
Yes, they were, but you have to look at the positions in which they were in the overall context of the climates that occurred when they did. Climates have changed and fluctuated over millions of years but much of the overall basic patterns have remained the same. During the Carboniferous, for example, the climate overall was much the same as now. The climate zones and weather patterns were quite similar, but the CO2 level was 800ppm. That should mean, according to the those that believe it's the CO2 causing the climate change, it should've been much hotter, but it wasn't. What does that tell you??.
Let's look at a time less remote from us than this...the Cretaceous. CO2 concentration was 1700ppm, average global temp was 18 degrees, 6 higher than now. The continents were pretty much recognisable though somewhat out of position, but their distribution relative to one another was similar to today. CO2 levels fell to around 1000ppm by the end of the period and it cooled to around an av' of 16 degrees worldwide. The plant biology of the time was remarkably similar to now. You had conifer forests and flowering plants had actually supplanted most non flowering plants in variety and numbers of species by the mid to late Cretaceous. Apart from the fact you had large munchy biteys running around, the world was remarkably like now, except there was 50% more oxygen around than now. The temperature profile for the Cretaceous is remarkably constant for the much of the period, CO2 levels were not. They dropped 700ppm. What is that telling you about the correlation between CO2 and temperature??. Actually, when the CO2 levels were at their highest during the period, the temps were at their lowest...doesn't quite ring true, does it?? This is despite the fact that warm seas covered much of the continents at the time and carbonate deposition was high.
Ah, but we're not talking about correlations really are we? The models are much more sophisticated than that and based on the physics involved. I would have thought that an equation of: proportion of radiation not intercepted by other gases x fraction of radiation potentially absorbed by CO2 x CO2 concentration would give bounds on the CO2 effect both then and now (I realise that is a silly simplification, but you get my drift). I find it very hard to believe that those sort of calculations have not been done for the carboniferous and for the current climate. No doubt there are many factors that can be tweaked to give differing results, but it should give a range and it should allow sensitivity analysis to be done, giving probabilities. So I'm genuinely interested to know the likely explanations for the differences you point out.
The bottom line is though, that we're now talking about correlations rather than known physics and that is a risky basis in my opinion....
It's all about risk, and as I see it cutting CO2 emissions is the one thing most likely to help....
Yes we do know about the state of the planet at the time. Without hunting for the particular references (as I don't have them on me and it'll take time to get them), I can tell you that the continents were assembling into Pangaea...Laurasia (that's Nth America and much of Eurasia) was moving towards the equator, whilst Gondwanaland was situated mostly over the Sth Pole and was covered in a large ice sheet.
I've got some maps (see below) for you to give you an idea of what the situation was in so far as the positions of the continents are concerned, as well as a climatological map. The situation is very similar as it is today, climatologically. You may have to download the graph and climatological map...they don't look so great when you click on them to display!!! (just tested them).
The Earth's average axial tilt in the Carboniferous was pretty much the same as it is now. They've been able to deduce this from the varve deposits from lake sediments of the period. What a varve is...is the annual deposits of fine clay and other particle sediments that build up as layers in the bottom of lakes in cold climates. The size of each layer, the types of minerals and such present and their internal physical characteristics can be used to determine many things...lengths of the year and hence orbital motion, length of the day at the time of deposition, how long the seasons lasted etc. From these, they've been able to determine the length of the day (from memory about 23 hours) and an orbit about the same as now.
are incorrect and I don't have the background to judge whether any of the "3" have some wacked out idea that might just be correct. I'll exclude from that 3% all the jokers who are peddling disinformation for some end I don't understand.
