You show some ignorance on the subject. Most importantly, scientifically it is hard to prove something without putting the numbers in. If you want to prove a correlation, you use your best theory, and compare the expected results with the measured results, and determine the accuracy of your estimate.
In this case, science has concluded that there can be only one explanation for global warming, which is the rapid accumulation of greenhouse gases in the past century. It fits the data, and there are simply no other explanations that fit the numbers.
To clarify this for you: suppose you see this climate change as part of the geological shifting of climate, for example the ice-age cycle (I hear this argument a lot). Then you must consider that timescales are important. Consider that the ice-ages occurs every 100,000 years or so, while the global warming we now see has mostly occurred in the last 50 years. That's a totally different timescale, which explains why the two are not related.
Climate change has always occurred, which has been properly recorded. This is on a geological timescale. Timescales are important. To give you an idea: if one ice-age cylce would take one day, such that the ice-age occurs at night, and the warm intermediate period would occur during the day, then the global warming we are seeing now would take only 45 seconds. Different timescale.
Your statement that CO2 levels are slightly higher is bull. They have risen over 30% and doubling of the CO2-level with respect to pre-industrial levels will likely take place early this century.
You seem to assume that the earth was in some sort of equilibrium, which we are now returning to. This is not true. The earth does not have stable atmospheric and climatic conditions, meta-stable would be a more accurate way of describing it.
The variations of the climate on a geological timescale are enormous events, that have caused large-scale extinctions, up to 98% of all species. Of course the earth is likely to be repopulated every time, but that doesn't mean that climate change is a good thing. Right now we are doubling the amount of CO2 in the air in a few centuries, and it is a scientific certainty that this will have a significant effect on our climate. What's your point? That some other species will become dominant after us, and it's all part of the "natural process"?
Your post is reasonably well informed, but in my opinion you make some mistakes which are crucial in estimating the effect of man-made climate change.
First, of course, you assert that water vapor creates 95% of the greenhouse effect. I do not know why you mention this number (except that it is given at several skeptic's sites), but most people seem to think that 70% is a better estimate. However, it should not be forgotten that the water vapor content of the atmosphere balances itself - as such it cannot have a direct effect on global warming and abrupt climate change. This is well explained here.
Some of your imformation is out of date. For example, the data of the temperature record for the last 18,000 years is ten years old, and is superseded by several studies. You're right that these temperature changes cannot be attributed to man, the strongest change is due to the fact that we have left an ice-age.
Because carbon dioxide gives a significant contribution to the greenhouse effect, and it has significantly risen, one can expect an abrupt change in temperatures around the globe. Lo and behold, this is what we observe! There is no, I stress, NO natural effect known that could have caused this. Also, the 0.6 C change is NOT within natural climate variation on this timescale, if you know of any events, please tell me when this has happened.
Most importantly, you already claim defeat, because CO2 has a long lifetime. But the most important effects, such as sea-level rise an large-scale shift in weather patterns occur at high CO2 concentration. It is of the utmost importance to avoid the doubling of CO2 concentrations with respect to their pre-industrial age levels. We should reduce our emissions immediately and by at least 50%.
Hand-picking two years, and doing a linear fit between them is not science. It is better to fit the entire curve and then see if you see any trends. The result still depends on the amount of smoothing you do, but at least you're not aiming for a certain trend to come out.
Maybe you don't like the "noise", but you also seem to dislike facts. If anything, there was no trend in temperatures from the 30's to the 70's if you believe NASA (http://data.giss.nasa.gov/gistemp/graphs/). According to the Third Assessment Report of the IPCC, the effect of solar cycles is considerably smaller than the effect of increased greenhouse gases.
Your solution? Let's wait until 2020, and then we can safely conclude whether we should have acted on global warming or not.
It's called fluctuations. Fluctuations are superimposed on any climate trend, and so, if you cherry-pick your years, you can draw any conclusion you want. Take a look at the NASA temperature record (http://data.giss.nasa.gov/gistemp/graphs/) and then tell me what you think the trend is.
The opinion they express is that global warming is a threat, humans are causing it, and something needs to be done about it. That is their opinion, and I think they should have every right, like you and me, to express this. I call this their sceintific opinion, because I think this is based on the research they have done. If you want to call this a policy opinion, fine. You say many scientists feel that the data do not provide evidence that humans are causing global warming. I disagree, but I think also these people should be allowed to express that viewpoint, and politicis should not try to muzzle them either. The evidence is so overwhelming that I trust the right answer will come up in the end, by having an open discussion about it.
It worries me that you think it's a scientist job to not get in the way when politicians say something, just because those are the ones that pay them. We all know where this can lead to. Just replace "global warming" by "WMD" and scientists by "CIA".
Look, I would be very concerned if my government funded research, and then discarded the results because it doesn't agree with its policy. We are not talking about scientist's *policy* opinions here, these people need permissions to express their *scientific* viewpoints. You and other Americans are being denied the result of science that you yourselved paid for. Public funding is for the greater good, not to support whatever administration is currently ruling!
The government doesn't need to tamper with the results or directly influence the scientific discussion. They just need to suppress the outcome of that discussion. I think the New York Times article I linked to is quite a good example of that. If on top of this, Bush is calling out for the need of more research, that's just hogwash.
Actually, Bush has behaved entirely responsibly with regard to global warming.
Have you even RTFA? If scientists need clearance from government officials to talk to media, wouldn't you agree that somehow, Bush is not completely candid about it?
It's just hard to grasp how wrong your statement is. When Bush just came into office, the US had already signed the Kyoto protocol. Bush used the classic political manoeuvre of parking the whole issue in the "we need more research" department, meanwhile pulling out of Kyoto, the only framework we had of reducing greenhouse emissions worldwide. Of course it was only a first step, but Bush is argueing from both sides: it's insufficient, India is not participating etc. and also it is too much, too costly etc.
After that, he continued the political game by rallying countries for an alternative emissions agreement, which is based on voluntary cutdowns (and we know how well that works, voluntary reductions was also the basis for his environmental policies in Texas when he was the governer there). Then the administration tried to prevent the people from realizing that global warming is, indeed, a threat, altering climate reports, putting pressure with funding and now deciding who can and cannot talk to the press.
Good observation, about the evolution of the global-warming sceptics. There are four steps here:
1. Global warming does not exist. 2. Global warming exists but it is not a threat. 3. Global warming exists and it is a threat but there's nothing we can do about it. 4. Global warming exists and it is a threat and we could have prevented it but it's too late now.
The point is that it is not relevant whether things are "natural". If you define "natural" as "the way it used to be", than it would be natural that there are no icecaps on the poles, which was the case for most of the history of the earth. It would be natural that sea levels are much higher than they are now, about 70 metres more. It would also be natural that homo sapiens would not be present.
I think it is clear that this is not the situation we want to be in. Bu please, tell me, did the comparison of current CO2-levels with the Vostok-core surprise you?
I am not sure what a worrywart is, but thanks for making an argument. In the graphs you link to you see there is a strong correlation between CO2-levels and temperatures. This can also be seen if you go back even further in time. When dinosaurs walked the earth, temperatures were much higher due to an enhanced greenhouse effect. This arguments is sometimes used as a proof that climate change is somehow "natural".
To get back to your graph, unfortunately the current levels are not plotted on the left side. This wouldn't be possible, because they are way off this scale. The current level is 380 ppm. Do you see the urgency of the situation now?
China signed AND ratified the Kyoto protocol.
The US signed the Kyoto protocol, but did not ratify it.
Australia signed nor ratified the Kyoto protocol.
Global warming is happening right now. Purely from an economic point of view, it would be both wiser and less costly if we apprehend the problem in the present and not postpone.
I'm sorry, but you haven't got a clue on the quantitative effects of global warming. Estimates are that global tempertures will rise 2-6 degrees C within the next century. And you know what? It doesn't stop there! You can call that "jumpy" or "rediculous", but sooner or later, we're gonna have to act. And the later we do it, the more costly it's going to get. Global warming sceptics don't like this conclusion, and I always hear the same arguments. First they said "there is no global warming!". Then it became clear that temperatures were rising, and they said "it's not anthropogenic, it's the sun!". Then it became clear that the effects of the sun-cycles were too small to explain the heating, and now they say "okay, there is global warming and we're causing it, but it's too late to do anything about it, and would cost too much money anyway".
Since the normal levels of CO2 in the atmosphere are high, it still contributes an important part of the Earth's heat retention despite its relatively weak per-mole power.
I am glad you agree with me that CO2 is a significant greenhouse gas. It is unfortunate that you have mixed up this last statement, CO2 levels are, in absolute terms, very low, only 0.03%, much lower that concentrations of water vapor. Due to its STRONG absorption it contributes signifcantly. Methane is an even stronger greenhouse gas, but is vary scarce (0.00017%) and thus has a smaller contribution.
Now, either you have some secret source, that is not know to the general audience of scientists, or you just make up this claim that "water vapor is the only strong greenhouse gas significantly contributing to Earth's heat retention". Let's stick with the standard numbers, or as an 1990 IPCC report says "If H2O were the only GHG present, then the GHE of a clear-sky midlatitude atmosphere... would be about 60-70% of the value with all gases included; by contrast, if CO2 alone was present, the corresponding value would be about 25%".
Which is exactly why I responded to your post, and not to all the sceptics. You see ignorance where there is none. We can keep writing more elaborate weather models and use bigger computers, but the simple fact is that CO2-concentration has gone rampant, and this will cause a major shift in our climate. We know that! In addition we have the power to do something about it, right know. It will be costly, but it is a decision we have to make right know!
I call BS. You're taking the facts out of context.
As water vapor, H2O has a positive feedback causing further "warming" but when it forms clouds it has a negative "cooling" affect. So there's a least one model than suggests CO2 will cool the Earth. Also, more clouds means more rain which means more plants which means less CO2. So it's quite possible for the Earth to self regulate itself.
It is well known that water vapor is a strong greenhouse gas. As you mention it is also a coolant, by cloud formation. The water cycle is self-regulating and humans cannot effect it directly. Disturbing the CO2-concentration could however change the balance of the natural greenhouse-effect, and a new balance at a higher temperature could be the result. So, factually speaking, your argument about H2O is not relevant.
I'm not saying CO2 isn't a problem but what the IPCC has done is to take the worse possible senario out of a whole bunch of other options.
You obviously have not looked at the reports, because, as always, they take several scenario's into account, including "business as usual", which is also the worst case scenario (i.e. take no action whatsoever).
Don't forget, CO2 makes up only 0.04% of the atmosphere and over 90% of CO2 came from natural, non anthropogenic sources.
That it makes up only 0.04% of the atmosphere is not a relevant fact. What is a relevant fact is how much it contributes to global warming. ALL of the CO2 came from natural sources, it has just been sitting in the ground for a very long time. ALL of the increase of CO2 (about 30%) since the start of the industrial age comes from antropogenic sources, as can be concluded from isotope measurements. I have the feeling that you just made up the 90%, but if you have a source for that number I'd be happy to hear it.
There's also some evidence that about 30% of the 8 gigatons of annual CO2 can be accounted for by forest fires
Again, this is an irrelevant fact. Even more CO2 is produced by bacteria each year, but this is part of the natural cycle. What is important is, how much humans exhaust in addition to the natural balance of CO2.
It boggles my mind how absolutely wrong this discussion is. Please, take about 10 minutes to study global warming. You'll find these facts:
Carbon dioxide is one of the most important greenhouse gases.
Carbon dioxide has risen by about 30% it the last 100 years. This is caused by humans. 30% is substantial. The rise is accelerating (look up: Keeling curve).
Global temperatures are rising dramatically, in the order of 0.5 C in the last 20 years.
The northern icecap is melting and is expected to be gone this century. Glaciers are retreating.
Now, all of these things are FACTS which are not being disputed by anybody. Now there is a theory, called global warming, which connects all these facts in a quantitative way. The first calculation on this was done already in 1896 by Svante Arrhenius, and the predicted temperature rise has not changed significantly since then. WHY DO PEOPLE THINK WE NEED MORE INFORMATION BEFORE WE ACT?
We should keep in mind that the earth sees huge temperature swings without the aid of man's actions.
You should understand that you're giving an argument in support of the theory of antropogenic (man-made) global warming. At the times you talk about, the concentration of carbondioxide was much greater than it is today. This show how a strong increase in this greenhouse gas (30% at present time) due to human behavior is likely to have a strong effect on our climate.
You can compare temperature changes in the past here. The present temperature rise is quite significant and certainly not at a slower rate compared with previous ice ages (if you calculate the rise in deg/decade)
Slashdot Mirror
You show some ignorance on the subject. Most importantly, scientifically it is hard to prove something without putting the numbers in. If you want to prove a correlation, you use your best theory, and compare the expected results with the measured results, and determine the accuracy of your estimate.
In this case, science has concluded that there can be only one explanation for global warming, which is the rapid accumulation of greenhouse gases in the past century. It fits the data, and there are simply no other explanations that fit the numbers.
To clarify this for you: suppose you see this climate change as part of the geological shifting of climate, for example the ice-age cycle (I hear this argument a lot). Then you must consider that timescales are important. Consider that the ice-ages occurs every 100,000 years or so, while the global warming we now see has mostly occurred in the last 50 years. That's a totally different timescale, which explains why the two are not related.
I shouldn't respond to a troll, but here goes...
Climate change has always occurred, which has been properly recorded. This is on a geological timescale. Timescales are important. To give you an idea: if one ice-age cylce would take one day, such that the ice-age occurs at night, and the warm intermediate period would occur during the day, then the global warming we are seeing now would take only 45 seconds. Different timescale.
Your statement that CO2 levels are slightly higher is bull. They have risen over 30% and doubling of the CO2-level with respect to pre-industrial levels will likely take place early this century.
You seem to assume that the earth was in some sort of equilibrium, which we are now returning to. This is not true. The earth does not have stable atmospheric and climatic conditions, meta-stable would be a more accurate way of describing it.
The variations of the climate on a geological timescale are enormous events, that have caused large-scale extinctions, up to 98% of all species. Of course the earth is likely to be repopulated every time, but that doesn't mean that climate change is a good thing. Right now we are doubling the amount of CO2 in the air in a few centuries, and it is a scientific certainty that this will have a significant effect on our climate. What's your point? That some other species will become dominant after us, and it's all part of the "natural process"?
Actually, carbon dioxide is a small player. Water is responsible for at least 90% of the Earth's greenhouse effect.
This number shows up quite often, but I've never found a credible source for it. Can you point me to the reference where you got this number? Thanks.
Your post is reasonably well informed, but in my opinion you make some mistakes which are crucial in estimating the effect of man-made climate change.
First, of course, you assert that water vapor creates 95% of the greenhouse effect. I do not know why you mention this number (except that it is given at several skeptic's sites), but most people seem to think that 70% is a better estimate. However, it should not be forgotten that the water vapor content of the atmosphere balances itself - as such it cannot have a direct effect on global warming and abrupt climate change. This is well explained here.
Some of your imformation is out of date. For example, the data of the temperature record for the last 18,000 years is ten years old, and is superseded by several studies. You're right that these temperature changes cannot be attributed to man, the strongest change is due to the fact that we have left an ice-age.
Because carbon dioxide gives a significant contribution to the greenhouse effect, and it has significantly risen, one can expect an abrupt change in temperatures around the globe. Lo and behold, this is what we observe! There is no, I stress, NO natural effect known that could have caused this. Also, the 0.6 C change is NOT within natural climate variation on this timescale, if you know of any events, please tell me when this has happened.
Most importantly, you already claim defeat, because CO2 has a long lifetime. But the most important effects, such as sea-level rise an large-scale shift in weather patterns occur at high CO2 concentration. It is of the utmost importance to avoid the doubling of CO2 concentrations with respect to their pre-industrial age levels. We should reduce our emissions immediately and by at least 50%.
Hand-picking two years, and doing a linear fit between them is not science. It is better to fit the entire curve and then see if you see any trends. The result still depends on the amount of smoothing you do, but at least you're not aiming for a certain trend to come out.
Using a fitting segments of cubic polynomials, the result that comes out is this: http://www.phys.uu.nl/~romans/temp.png
Maybe you don't like the "noise", but you also seem to dislike facts. If anything, there was no trend in temperatures from the 30's to the 70's if you believe NASA (http://data.giss.nasa.gov/gistemp/graphs/). According to the Third Assessment Report of the IPCC, the effect of solar cycles is considerably smaller than the effect of increased greenhouse gases.
Your solution? Let's wait until 2020, and then we can safely conclude whether we should have acted on global warming or not.
It's called fluctuations. Fluctuations are superimposed on any climate trend, and so, if you cherry-pick your years, you can draw any conclusion you want. Take a look at the NASA temperature record (http://data.giss.nasa.gov/gistemp/graphs/) and then tell me what you think the trend is.
The opinion they express is that global warming is a threat, humans are causing it, and something needs to be done about it. That is their opinion, and I think they should have every right, like you and me, to express this. I call this their sceintific opinion, because I think this is based on the research they have done. If you want to call this a policy opinion, fine. You say many scientists feel that the data do not provide evidence that humans are causing global warming. I disagree, but I think also these people should be allowed to express that viewpoint, and politicis should not try to muzzle them either. The evidence is so overwhelming that I trust the right answer will come up in the end, by having an open discussion about it.
It worries me that you think it's a scientist job to not get in the way when politicians say something, just because those are the ones that pay them. We all know where this can lead to. Just replace "global warming" by "WMD" and scientists by "CIA".
Britain is expected to meet (http://news.bbc.co.uk/2/hi/science/nature/4849672 .stm) its Kyoto target.
Look, I would be very concerned if my government funded research, and then discarded the results because it doesn't agree with its policy. We are not talking about scientist's *policy* opinions here, these people need permissions to express their *scientific* viewpoints. You and other Americans are being denied the result of science that you yourselved paid for. Public funding is for the greater good, not to support whatever administration is currently ruling!
The government doesn't need to tamper with the results or directly influence the scientific discussion. They just need to suppress the outcome of that discussion. I think the New York Times article I linked to is quite a good example of that. If on top of this, Bush is calling out for the need of more research, that's just hogwash.
Actually, Bush has behaved entirely responsibly with regard to global warming.
Have you even RTFA? If scientists need clearance from government officials to talk to media, wouldn't you agree that somehow, Bush is not completely candid about it?
It's just hard to grasp how wrong your statement is. When Bush just came into office, the US had already signed the Kyoto protocol. Bush used the classic political manoeuvre of parking the whole issue in the "we need more research" department, meanwhile pulling out of Kyoto, the only framework we had of reducing greenhouse emissions worldwide. Of course it was only a first step, but Bush is argueing from both sides: it's insufficient, India is not participating etc. and also it is too much, too costly etc.
After that, he continued the political game by rallying countries for an alternative emissions agreement, which is based on voluntary cutdowns (and we know how well that works, voluntary reductions was also the basis for his environmental policies in Texas when he was the governer there). Then the administration tried to prevent the people from realizing that global warming is, indeed, a threat, altering climate reports, putting pressure with funding and now deciding who can and cannot talk to the press.
And this you call "responsibly".
Good observation, about the evolution of the global-warming sceptics. There are four steps here:
1. Global warming does not exist.
2. Global warming exists but it is not a threat.
3. Global warming exists and it is a threat but there's nothing we can do about it.
4. Global warming exists and it is a threat and we could have prevented it but it's too late now.
Right now, we've just passed step 2.
The point is that it is not relevant whether things are "natural". If you define "natural" as "the way it used to be", than it would be natural that there are no icecaps on the poles, which was the case for most of the history of the earth. It would be natural that sea levels are much higher than they are now, about 70 metres more. It would also be natural that homo sapiens would not be present.
I think it is clear that this is not the situation we want to be in. Bu please, tell me, did the comparison of current CO2-levels with the Vostok-core surprise you?
I am not sure what a worrywart is, but thanks for making an argument. In the graphs you link to you see there is a strong correlation between CO2-levels and temperatures. This can also be seen if you go back even further in time. When dinosaurs walked the earth, temperatures were much higher due to an enhanced greenhouse effect. This arguments is sometimes used as a proof that climate change is somehow "natural".
To get back to your graph, unfortunately the current levels are not plotted on the left side. This wouldn't be possible, because they are way off this scale. The current level is 380 ppm. Do you see the urgency of the situation now?
China signed AND ratified the Kyoto protocol.
The US signed the Kyoto protocol, but did not ratify it.
Australia signed nor ratified the Kyoto protocol.
Global warming is happening right now . Purely from an economic point of view, it would be both wiser and less costly if we apprehend the problem in the present and not postpone.
I'm sorry, but you haven't got a clue on the quantitative effects of global warming. Estimates are that global tempertures will rise 2-6 degrees C within the next century. And you know what? It doesn't stop there! You can call that "jumpy" or "rediculous", but sooner or later, we're gonna have to act. And the later we do it, the more costly it's going to get. Global warming sceptics don't like this conclusion, and I always hear the same arguments. First they said "there is no global warming!". Then it became clear that temperatures were rising, and they said "it's not anthropogenic, it's the sun!". Then it became clear that the effects of the sun-cycles were too small to explain the heating, and now they say "okay, there is global warming and we're causing it, but it's too late to do anything about it, and would cost too much money anyway".
It's plain defeatism, and you're joining it.
Since the normal levels of CO2 in the atmosphere are high, it still contributes an important part of the Earth's heat retention despite its relatively weak per-mole power.
I am glad you agree with me that CO2 is a significant greenhouse gas. It is unfortunate that you have mixed up this last statement, CO2 levels are, in absolute terms, very low, only 0.03%, much lower that concentrations of water vapor. Due to its STRONG absorption it contributes signifcantly. Methane is an even stronger greenhouse gas, but is vary scarce (0.00017%) and thus has a smaller contribution.
Now, either you have some secret source, that is not know to the general audience of scientists, or you just make up this claim that "water vapor is the only strong greenhouse gas significantly contributing to Earth's heat retention". Let's stick with the standard numbers, or as an 1990 IPCC report says "If H2O were the only GHG present, then the GHE of a clear-sky midlatitude atmosphere... would be about 60-70% of the value with all gases included; by contrast, if CO2 alone was present, the corresponding value would be about 25%".
CO2 is a significant greenhouse gas.
Which is exactly why I responded to your post, and not to all the sceptics. You see ignorance where there is none. We can keep writing more elaborate weather models and use bigger computers, but the simple fact is that CO2-concentration has gone rampant, and this will cause a major shift in our climate. We know that! In addition we have the power to do something about it, right know. It will be costly, but it is a decision we have to make right know!
I call BS. You're taking the facts out of context.
As water vapor, H2O has a positive feedback causing further "warming" but when it forms clouds it has a negative "cooling" affect. So there's a least one model than suggests CO2 will cool the Earth. Also, more clouds means more rain which means more plants which means less CO2. So it's quite possible for the Earth to self regulate itself.
It is well known that water vapor is a strong greenhouse gas. As you mention it is also a coolant, by cloud formation. The water cycle is self-regulating and humans cannot effect it directly. Disturbing the CO2-concentration could however change the balance of the natural greenhouse-effect, and a new balance at a higher temperature could be the result. So, factually speaking, your argument about H2O is not relevant.
I'm not saying CO2 isn't a problem but what the IPCC has done is to take the worse possible senario out of a whole bunch of other options.
You obviously have not looked at the reports, because, as always, they take several scenario's into account, including "business as usual", which is also the worst case scenario (i.e. take no action whatsoever).
Don't forget, CO2 makes up only 0.04% of the atmosphere and over 90% of CO2 came from natural, non anthropogenic sources.
That it makes up only 0.04% of the atmosphere is not a relevant fact. What is a relevant fact is how much it contributes to global warming. ALL of the CO2 came from natural sources, it has just been sitting in the ground for a very long time. ALL of the increase of CO2 (about 30%) since the start of the industrial age comes from antropogenic sources, as can be concluded from isotope measurements. I have the feeling that you just made up the 90%, but if you have a source for that number I'd be happy to hear it.
There's also some evidence that about 30% of the 8 gigatons of annual CO2 can be accounted for by forest fires
Again, this is an irrelevant fact. Even more CO2 is produced by bacteria each year, but this is part of the natural cycle. What is important is, how much humans exhaust in addition to the natural balance of CO2.
It boggles my mind how absolutely wrong this discussion is. Please, take about 10 minutes to study global warming. You'll find these facts:
Carbon dioxide is one of the most important greenhouse gases.
Carbon dioxide has risen by about 30% it the last 100 years. This is caused by humans. 30% is substantial. The rise is accelerating (look up: Keeling curve).
Global temperatures are rising dramatically, in the order of 0.5 C in the last 20 years.
The northern icecap is melting and is expected to be gone this century. Glaciers are retreating.
Now, all of these things are FACTS which are not being disputed by anybody. Now there is a theory, called global warming, which connects all these facts in a quantitative way. The first calculation on this was done already in 1896 by Svante Arrhenius, and the predicted temperature rise has not changed significantly since then. WHY DO PEOPLE THINK WE NEED MORE INFORMATION BEFORE WE ACT?
We should keep in mind that the earth sees huge temperature swings without the aid of man's actions.
You should understand that you're giving an argument in support of the theory of antropogenic (man-made) global warming. At the times you talk about, the concentration of carbondioxide was much greater than it is today. This show how a strong increase in this greenhouse gas (30% at present time) due to human behavior is likely to have a strong effect on our climate.
You can compare temperature changes in the past here. The present temperature rise is quite significant and certainly not at a slower rate compared with previous ice ages (if you calculate the rise in deg/decade)