An Inconvenient Truth

[Cap'n Refsmmat]

Pangloss, this is the Ecology and the Environment forum. Unless you have some sort of scientific argument against climate science (and I have seen none beyond the "post hoc" claim, which has been refuted), I suggest this discussion should stop.

[Mr Skeptic]

Besides, I believe I've earned some acknowledgement for the points I've raised AND given evidence for in this discussion.

 

Absolutely. Everyone deserves acknowledgment for the points they've raised AND given evidence for. That's why we acknowledge the IPCC's report, for example. However, most people are disappointed with the number of points that you've given evidence for.

 

[...]

You said that the community shuts down dissention when it has no scientific merit (in this post). I disagreed with that in this post, saying that dissent is shut down here for political reasons, not scientific ones. I've gone on to show examples of that in this thread.

 

Come to think of it, you did try to support this point that you made:

The reason the community around here generally shuts down dissention is that it has no scientific merit.

(to bascule) I don't buy this, by the way. Nobody tries to shut down experimental attemps to measure the speed of light or a myriad of other commonly accepted scientific theories. They try to shut down global warming "denialists" because they feel harmed by the dissent. That's a political position, not a scientific one.

 

However, that is a strawman. No one here is saying we should shut down experiments to measure global temperature changes. The proper analogy would be if people were claiming that light moved at, say, 100 miles per hour, and everyone else saying something like, You're wrong, silly. Basically, you are comparing people trying to stop people from saying things that have been shown to be false by experiments, with people trying to stop people from doing experiments.

 

If you feel we have ignored another of your points that you raised AND provided evidence for, please remind us of it, and we can have a scientific discussion about that, rather than just trading insults and rhetoric about unsupported statements.

[Realitycheck]

I think that potentially the single most significant argument supporting the idea that current global warming is man-made is that, if you look back over time, the major causes of global warming in the past were most likely caused by events that were irregular from the norm, not just sudden unexplainable shifts in the gas content of the atmosphere and subsequent temperatures. Everything happens for a reason and there has not been any other reasons promoted as to why or how global warming has been initiated other than what we keep discussing.

[SkepticLance]

The data relating to the basics for global warming is clear cut. Since about 1976, the world has been warming at a very steady rate, and alongside it, CO2 has been also increasing at the same steady rate. Over this time period, there is no alternative cause for the warming that matches the need for a steady change to cause a steady change.

 

In other words, for the past 30 odd years, global warming is anthropogenic. I see no other credible interpretation of the data.

 

The strange thing is when we get down to predictions. The range of alternatives is staggering. We get Prof. de Freitas saying that the warming has peaked and we are now about to go into a cooling phase. We get Prof. Hansen saying that the warming is going to accelerate, and the sea level will rise five metres in the next 100 years, flooding all coastal cities, sea ports, and all low lying coral atolls, plus destroying Bangla Desh. We even get Prof. Lovelock saying that it is now too late, and most of the human species will die, along with a big chunk of all other species on this planet, and all we can do is try to save a few humans.

 

All these predictions come from the same data. My own view is that we should avoid extremists at either end of the prediction spectrum. Warming is currently 0.18 C per decade and sea level rise is 3 mm per year. My own prediction is that these will continue (plus or minus a moderate amount) until humanity achieves a balance in greenhouse gases.

[iNow]

Speaking of citing sources for our numbers... The below can be used to supplement the post above, and possibly correct any misunderstandings it has spawned:

 

 

http://www.epa.gov/climatechange/science/recenttc.html

 

Records from land stations and ships indicate that the global mean surface temperature warmed by between 1.0 and 1.7°F since 1850 (see Figure 1). These records indicate a near level trend in temperatures from 1880 to about 1910, a rise to 1945, a slight decline to about 1975, and a rise to present (NRC, 2006). The Intergovernmental Panel on Climate Change (IPCC) concluded in 2007 that warming of the climate system is now “unequivocal,” based on observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level (IPCC, 2007).

 

According to the National Oceanic and Atmospheric Administration's (NOAA) 2007 State of the Climate Report and the National Aeronautics and Space Administration's (NASA) 2007 Surface Temperature Analysis:

 

• Since the mid 1970s, the average surface temperature has warmed about 1°F.
  
• The Earth’s surface is currently warming at a rate of about 0.32ºF/decade or 3.2°F/century.
  
• The eight warmest years on record (since 1850) have all occurred since 1998, with the warmest year being 2005.
  
• Additionally (from IPCC, 2007):
   
  
• The warming trend is seen in both daily maximum and minimum temperatures, with minimum temperatures increasing at a faster rate than maximum temperatures.
  
• Land areas have tended to warm faster than ocean areas and the winter months have warmed faster than summer months.
  
• Widespread reductions in the number of days below freezing occurred during the latter half of the 20th century in the United States as well as most land areas of the Northern Hemisphere and areas of the Southern Hemisphere.
  
• Average temperatures in the Arctic have increased at almost twice the global rate in the past 100 years.
  

 

 

According to NOAA's National Climatic Data Center:

 

• For the period 1958-2006, temperatures measured by weather balloons warmed at a rate of 0.22°F per decade near the surface and 0.27°F per decade in the mid-troposphere. The 2006 global mid-troposphere temperatures were 1.01°F above the 1971-2000 average, the third warmest on record.
  
• For the period beginning in 1979, when satellite measurements of troposphere temperatures began, various satellite data sets for the mid-troposphere showed similar rates of warming — ranging from 0.09°F per decade to 0.34°F per decade, depending on the method of analysis.

[SkepticLance]

To iNow

 

I hate those kinds of references. Why cannot they use Celsius like all civilised people?

[iNow]

To iNow

 

I hate those kinds of references. Why cannot they use Celsius like all civilised people?

 

Haha. I don't "hate" any references. They tend to be nice to have, which is why I share them so frequently in my posts.

 

I do though agree that the American system is outdated, malaligned with the rest of the planet, and desperately needs to be updated.

 

Alas, I'm not as powerful as you might imagine and have thus far failed in my attempts to catalyse such an across the board change myself, but I'll keep trying.

 

 

With all of that said, though, there is a benefit in sharing one's source, even when the data is consistent across several sources. It allows other readers to make the conversions themselves, to put the numbers which have been shared into the proper context, and also research on their own any questions they may have. Transparency in science is rather more important than some who claim to understand science appear willing to acknowledge.

 

 

Whoa... sorry. I do feel better, but apologize for trying to make a bigger point that extends beyond this thread.

[CarolAlynn]

Gore had it backwards. His entire movie (and it was a movie produced to make him money) relys on the fact that as co2 rises so does temperature. The truth is when the sun heats the earth, the ocean (which is the biggest contributer of co2 on earth) slowly heats up and then releases more co2 into the atmosphere. There is an 800 period gap between when the earth starts to heat up and when the ocean starts to release more co2.

 

The earth is normally much colder than this. We call the period we are living in right now an interglacial period, and they tend to be much shorter warming periods between long ice ages. I would be more worried about an ice age than runaway global warming. Although i try not to worry to much about that either as it will happen no matter what we think about it or try to do. The earth is more powerful than us!!!

[bascule]

Gore had it backwards. His entire movie (and it was a movie produced to make him money) relys on the fact that as co2 rises so does temperature.

 

Increasing CO₂ concentrations have had an increasingly positive forcing effect for the past half century.

 

The truth is when the sun heats the earth, the ocean (which is the biggest contributer of co2 on earth) slowly heats up and then releases more co2 into the atmosphere.

 

While it's true that temperature affects the solubility of CO₂ in ocean water, this in no way comes close to explaining the massive increases in CO₂ concentrations we're seeing now, nor do all other natural sources of CO₂ in combination.

[SkepticLance]

bascule

 

You and Carol are both right.

Al Gore, however, is not. He tried to say that the previous interglacial warmings were caused by CO2 build up, when the warming came first and the CO2 build up did not happen till 800 years later.

 

The current CO2 build up is a different situation, but that does not change the inherent dishonesty of Al Gore's film.

[antimatter]

Are we really going to start this all over again?

[MrSandman]

Bam! here's a thought (I haven't read all the previous threads but please forgive me). Maybe it's just a cycle the earth will go through I'm not sure about you guys, but here is washington we've just had one of the coldest winters in a long time. Not to mention it's suppose to snow tonight in the passes.

[swansont]

So? It's been close to 37 ºC (~100 ºF) along the mid-Atlantic east coast the past several days. Global is a key word here.

 

Looking at anything less than several years and you run the risk of measuring the noise rather than the signal. ~11 years is a good span to use, since it averages out any single-cycle solar variability.

[jryan]

Increasing CO₂ concentrations have had an increasingly positive forcing effect for the past half century.

 

This isn't exactly true as CO2 has a logarithmic effect on warming. So the actually contribution of heating by CO2 is lessening over time regardless of it's source.

 

This is the big conundrum in climatology right now. If the real effect of CO2 on global warming is to jump start runaway warming (which is necessary for the gloomier models to be true) then the bulk of the damage of anthropogenic CO2 has already been done. If we were to remove all of the anthropogenic CO2 from the atmosphere right now the natural warming, and the corresponding ocean release of CO2, would still be sufficient to take up our slack and continue the runaway warming.

 

Which then begs the question of why this hasn't already happened in much warmer times in the past.

 

Hmmm.. maybe it's because our predictions have been based on bad data and therefor can't properly model the intricate mechanisms of global climate....

 

While it's true that temperature affects the solubility of CO₂ in ocean water, this in no way comes close to explaining the massive increases in CO₂ concentrations we're seeing now, nor do all other natural sources of CO₂ in combination.

 

Of the increase seen in the last 100 years (280 ppm to 380 ppm) only a protion of that is anthropogentic... unless you assume that the ocean released no CO2 following the little ice age. But we both know that that isn't the case. So of the increase, what portion is anthropogenic, and what is attributed to the expected warming?

[swansont]

This isn't exactly true as CO2 has a logarithmic effect on warming. So the actually contribution of heating by CO2 is lessening over time regardless of it's source.

 

It isn't generally true, but then, that's not what was claimed. An exponential increase in CO2 will have a linear effect on temperature. An increasing exponential value will have an increasing effect. That's basic math.

 

Now, if you want to claim or refute what has actually happened, cite some frikkin' data.

 

This is the big conundrum in climatology right now. If the real effect of CO2 on global warming is to jump start runaway warming (which is necessary for the gloomier models to be true) then the bulk of the damage of anthropogenic CO2 has already been done. If we were to remove all of the anthropogenic CO2 from the atmosphere right now the natural warming, and the corresponding ocean release of CO2, would still be sufficient to take up our slack and continue the runaway warming.

 

Which then begs the question of why this hasn't already happened in much warmer times in the past.

 

Hmmm.. maybe it's because our predictions have been based on bad data and therefor can't properly model the intricate mechanisms of global climate....

 

 

Or, maybe that's what actually happened. You're comparing what happened over the course of thousands of years and dismissing it, without any support, by comparing it to what has happened here over several decades and under somewhat different conditions.

 

 

Of the increase seen in the last 100 years (280 ppm to 380 ppm) only a protion of that is anthropogentic... unless you assume that the ocean released no CO2 following the little ice age. But we both know that that isn't the case. So of the increase, what portion is anthropogenic, and what is attributed to the expected warming?

 

How much C02 should be released for that amount of temperature change? The Vostok core data graphs show 80 ppm change for a temperature change of 8 ºC. Is it linear? 1 ppm per tenth of a degree?

 

http://en.wikipedia.org/wiki/Image:Vostok-ice-core-petit.png

[doG]

Maybe it's just a cycle the earth will go through....

 

Speaking of climate cycles here's a historic view of the Earth's cycles:

 

 

We're still coming out of the last ice age and still way below the historic average temperature for Earth. A recent discovery of mammal burrows in Antarctica suggests that it was ice free in the past.

 

The Earth is certainly warming up and to some extent that looks normal, but to what extent? I haven't really seen much effort in anyone's analysis that tries to address the difference between normal warming and any accelerating effects above that curve. Looking at the past it seems obvious that the planet will get considerably warmer as it approaches the historical average so the big question is how fast will it get there and how much will it effect us.

[SkepticLance]

Just to add fuel to the flames ......

 

I was looking at a graph of global temperatures over the past million odd years. There have been ten glacial periods and ten interglacials. There is an interesting trend in maximum interglacial temperatures. They seem to be rising.

 

The last interglacial temperature actually reached a peak about 2 Celsius more than the present (or more). Perhaps, if the long term trend is real, the current interglacial was destined by 'natural' processes to get even warmer.

 

http://www.geo.umass.edu/climate/papers2/francisetal2006a.pdf

 

Actually, that does not explain current CO2 levels, but it may still be a good stick to stir certain people with.

[jryan]

It isn't generally true, but then, that's not what was claimed. An exponential increase in CO2 will have a linear effect on temperature. An increasing exponential value will have an increasing effect. That's basic math

 

Now, if you want to claim or refute what has actually happened, cite some frikkin' data..

 

I assumed you knew what the increase of CO2 have been over the last 150 years. I didn't think you would need a study quote for such a basic bit of data.

 

The CO2 has increased by roughly 35% in the last 150 years. The funny thing is that you agree with my statement of the logarithmic characteristics of CO2 as a GHG... you are just pissed because I didn't post a study that predicts the CO2 increase will be less than enough to counter that basic bit of physics.

 

So what is your proof that the CO2 will grow geometrically?

 

Or, maybe that's what actually happened. You're comparing what happened over the course of thousands of years and dismissing it, without any support, by comparing it to what has happened here over several decades and under somewhat different conditions.

 

Sorry, I forgot that the AGW folks are the only ones allowed to compare now to the last 1000 years. Yeesh.

 

 

How much C02 should be released for that amount of temperature change? The Vostok core data graphs show 80 ppm change for a temperature change of 8 ºC. Is it linear? 1 ppm per tenth of a degree?

 

http://en.wikipedia.org/wiki/Image:Vostok-ice-core-petit.png

 

What happened to "different times, different conditions"?

 

Well, actually I will consider your point because.... we can then say that the human contribution of CO2 is in the neighborhood of 20ppm in the last 150 years, or about 5%.

 

Even eliminating 130 of the industrial years from the contribution (a decision in YOUR favor) we could say we contributed 20ppm in the last 30 years.... So, what is the effect of a 5% increase in CO2 on the log scale?

[JohnB]

An exponential increase in CO2 will have a linear effect on temperature. An increasing exponential value will have an increasing effect. That's basic math.

Swansont, there must be a limit to the effect mustn't there? At some point in the curve the atmosphere would become opaque to IR and after that point it wouldn't matter how much CO2 you added.

 

That seems basic to me, so am I missing something?

[swansont]

Swansont, there must be a limit to the effect mustn't there? At some point in the curve the atmosphere would become opaque to IR and after that point it wouldn't matter how much CO2 you added.

 

That seems basic to me, so am I missing something?

 

It depends on what opaque means. Is it where an IR photon can't on average, make it out of the atmosphere without scattering? (That's called "optically thick" in atomic physics jargon) Because you will still get an effect if that scattered photon gets absorbed further out in the atmosphere. I suspect, but don't know for sure, that this is the source of the logarithmic behavior.

 

It seems to me that if you had a really small concentration, so that a photon had, say, a 0.1% chance of being absorbed, and then you doubled the concentration, you'd have a 0.2% chance of being absorbed. At some point, though, a second absorption becomes likely, and that's where the linear behavior ends (this is related to saturation of absorption in atomic spectroscopy, though I'm used to thinking of this in terms of changes in light intensity). So there would seem to be a difference in response between an opaque and a transparent atmosphere at he wavelengths in question.

 

At the far extreme, I can see that if a photon would take a million scatters to leave that adding more CO2 to make that a million and one has a small overall effect, but I don't see how that's inconsistent with it being a logarithmic dependence.

 

I assumed you knew what the increase of CO2 have been over the last 150 years. I didn't think you would need a study quote for such a basic bit of data.

 

The CO2 has increased by roughly 35% in the last 150 years. The funny thing is that you agree with my statement of the logarithmic characteristics of CO2 as a GHG... you are just pissed because I didn't post a study that predicts the CO2 increase will be less than enough to counter that basic bit of physics.

 

So what is your proof that the CO2 will grow geometrically?

 

I think you have no clue what pissed me off, even though I mentioned it in the previous exchange: You rarely cite data to support your claims. In this case, the claim was

"So the actually contribution of heating by CO2 is lessening over time regardless of it's source."

 

Which is only true of a certain behavior of CO2 increase. An behavior that is NOT being observed, since we are seeing an exponential (or faster) increase. If you have a source that shows CO2 increases are slower than an exponential, CITE THEM.

 

Proof that CO2 will grow geometrically is a strawman. I never claimed that, and it is irrelevant to the point bascule made and to which I added, which refers to recent CO2 changes. Future growth is a separate issue.

 

Sorry, I forgot that the AGW folks are the only ones allowed to compare now to the last 1000 years. Yeesh.

 

You should apologize, but it should be for failing to cite data and making strawman arguments.

 

What happened to "different times, different conditions"?

 

Well, actually I will consider your point because.... we can then say that the human contribution of CO2 is in the neighborhood of 20ppm in the last 150 years, or about 5%.

 

Even eliminating 130 of the industrial years from the contribution (a decision in YOUR favor) we could say we contributed 20ppm in the last 30 years.... So, what is the effect of a 5% increase in CO2 on the log scale?

 

I'm just trying to fill in some quantification to your argument, since you refuse to do so.

 

If the release of CO2 from ocean warming is your concern, and it's 0.1 ppm per tenth of a degree (as the historical data might imply), how does this account for 80 ppm of CO2? Has the temperature risen 8 ºC? That's news to me.

Edited June 13, 2008 by swansont
multiple post merged

[jryan]

It depends on what opaque means. Is it where an IR photon can't on average, make it out of the atmosphere without scattering? (That's called "optically thick" in atomic physics jargon) Because you will still get an effect if that scattered photon gets absorbed further out in the atmosphere. I suspect, but don't know for sure, that this is the source of the logarithmic behavior.

 

It seems to me that if you had a really small concentration, so that a photon had, say, a 0.1% chance of being absorbed, and then you doubled the concentration, you'd have a 0.2% chance of being absorbed. At some point, though, a second absorption becomes likely, and that's where the linear behavior ends (this is related to saturation of absorption in atomic spectroscopy, though I'm used to thinking of this in terms of changes in light intensity). So there would seem to be a difference in response between an opaque and a transparent atmosphere at he wavelengths in question.

 

At the far extreme, I can see that if a photon would take a million scatters to leave that adding more CO2 to make that a million and one has a small overall effect, but I don't see how that's inconsistent with it being a logarithmic dependence.

 

Your explanation makes the false assumption that the second half of the CO2 increase has the same amount of thermal IR to potentially absorb as the first. But since the available thermal IR decreases for each doubling, the next X amount of CO2 absorbs less than the previous because there is less to absorb. Eventually all the thermal IR (which is the wavelength in question) is absorbed and increases in CO2 have little effect.

 

 

I think you have no clue what pissed me off, even though I mentioned it in the previous exchange: You rarely cite data to support your claims. In this case, the claim was

 

I post citations when I think it is waranted, but since you have been interested in this topic for a while now I assume you know the basics. The most complex basic statement has been the logrithmic effect of CO2 absorbtion, you accept that. What you do not accept is my assertion that the CO2 increase will not be sufficient to impose a linearity on the GHG effect of CO2.

 

Now to the disection of where we stand in this little debate:

 

My original statement was in response to Bascules's assertion (uncited) concerning the increased forcing effect of CO2... I did not discount this entirely, but rather qualified it with the unstated logrithmic effect.

 

YOU then jumped in and asserted that the "exponential increase" in CO2 will force linearity into the CO2 forcing observed.... so it is up to YOU to cite where such an exponential increase in CO2 is probable. If it isn't, then your assertiuon if just baseless hyperbole.

 

Your latter sources don't support your assertion of an exponential increase... all you have, I woiuld guess, is the IPCC "scenarios" where they make predictions of the forcing effects of CO2 based on arbitrary "if it doubles then..." statements. So show me the real world studies that show that the increase in CO2 will continue to accelerate exponentially.

 

The citation requirements are in your court.

 

"So the actually contribution of heating by CO2 is lessening over time regardless of it's source."

 

Which is only true of a certain behavior of CO2 increase. An behavior that is NOT being observed, since we are seeing an exponential (or faster) increase. If you have a source that shows CO2 increases are slower than an exponential, CITE THEM

 

Proof that CO2 will grow geometrically is a strawman. I never claimed that, and it is irrelevant to the point bascule made and to which I added, which refers to recent CO2 changes. Future growth is a separate issue..

 

Well, that's a lie... here is your first statement in this debate:

 

"It isn't generally true, but then, that's not what was claimed. An exponential increase in CO2 will have a linear effect on temperature. An increasing exponential value will have an increasing effect. That's basic math."

 

Exponential and geometric growth are the same thing.

 

 

You should apologize, but it should be for failing to cite data and making strawman arguments.

 

Again, I am making basic statements that YOU agree with. Where we disagreed was in the growth of CO2 and it's effect on warming.

 

And I am not making a strawman argument... your claim is well documented.

 

I'm just trying to fill in some quantification to your argument, since you refuse to do so.

 

You need to focus on filling your own holes.

 

 

If the release of CO2 from ocean warming is your concern, and it's 0.1 ppm per tenth of a degree (as the historical data might imply), how does this account for 80 ppm of CO2? Has the temperature risen 8 ºC? That's news to me.

 

Your thumbnail numbers are actually, wrong (you misplaced a decimal)... but I will let that slide. The chart, assuming CO2 as the driver, shows 80ppm increase equals 8 ºC increase.... so 100ppm increase should equal a 10 ºC... assumingg linearity. But even going back to the logrithmic argument, 80ppm equals 8ºC... but 100ppm equals 0.63ºC.

 

Care to explain?

Edited June 13, 2008 by jryan

[swansont]

Your explanation makes the false assumption that the second half of the CO2 increase has the same amount of thermal IR to potentially absorb as the first. But since the available thermal IR decreases for each doubling, the next X amount of CO2 absorbs less than the previous because there is less to absorb. Eventually all the thermal IR (which is the wavelength in question) is absorbed and increases in CO2 have little effect.

 

Thermal IR gets absorbed and then re-emitted, some of which gets sent back to earth. You're only addressing half of the issue. But I think that's why it's a logarithmic function — because the probability of any new molecule "seeing" any IR keeps going down. If I get a moment, I'll work it through.

 

I post citations when I think it is waranted, but since you have been interested in this topic for a while now I assume you know the basics. The most complex basic statement has been the logrithmic effect of CO2 absorbtion, you accept that. What you do not accept is my assertion that the CO2 increase will not be sufficient to impose a linearity on the GHG effect of CO2.

 

bascule claimed that the CO2 forcings had increased, and has posted many links and graphs to support various claims. Your counter-claim was that no, the contribution had decreased. You have not backed up that claim.

 

Now to the disection of where we stand in this little debate:

 

My original statement was in response to Bascules's assertion (uncited) concerning the increased forcing effect of CO2... I did not discount this entirely, but rather qualified it with the unstated logrithmic effect.

 

YOU then jumped in and asserted that the "exponential increase" in CO2 will force linearity into the CO2 forcing observed.... so it is up to YOU to cite where such an exponential increase in CO2 is probable. If it isn't, then your assertiuon if just baseless hyperbole.

 

Since we are dealing with history here, the probability of whatever happened to CO2 is identically 1. The increase in CO2 has been exponential in recent years. I provided a link.

 

 

 

 

Your latter sources don't support your assertion of an exponential increase... all you have, I woiuld guess, is the IPCC "scenarios" where they make predictions of the forcing effects of CO2 based on arbitrary "if it doubles then..." statements. So show me the real world studies that show that the increase in CO2 will continue to accelerate exponentially.

 

The citation requirements are in your court.

 

Again, this discussion has centered on what has happened in the past. To cite future projections is moving the goalposts.

 

 

Well, that's a lie... here is your first statement in this debate:

 

"It isn't generally true, but then, that's not what was claimed. An exponential increase in CO2 will have a linear effect on temperature. An increasing exponential value will have an increasing effect. That's basic math."

 

Exponential and geometric growth are the same thing.

 

I have no idea what your point is here. Earlier you agreed that the the dependence of temperature on CO2 is logarithmic, thus an exponential increase in CO2 will cause a linear increase in temperature. If the exponential speeds up (e^ax and a increases) then the temperature increase will speed up as well. This is, as I said, basic math.

 

 

 

Your thumbnail numbers are actually, wrong (you misplaced a decimal)... but I will let that slide. The chart, assuming CO2 as the driver, shows 80ppm increase equals 8 ºC increase.... so 100ppm increase should equal a 10 ºC... assumingg linearity. But even going back to the logrithmic argument, 80ppm equals 8ºC... but 100ppm equals 0.63ºC.

 

Care to explain?

Yes, I had a typo. 8 degrees causes 80 ppm, means 1 ppm increase is caused by a 0.1 degree increase.

 

You were worried about the warming causing CO2 release, and the historical data show that we should expect 1 ppm per 0.1ºC increase in temperature, on average. But you've got the cause and effect reversed now. the 100 ppm increase is not from ocean release — that only accounts for something of order 10 ppm. So the other 90 ppm would be anthropogenic.

 

If a doubling of CO2 should cause a 3º increase in T, a 5% increase should cause a 0.2º rise in temperature. Is that about what we've seen?

[jryan]

Thermal IR gets absorbed and then re-emitted, some of which gets sent back to earth. You're only addressing half of the issue. But I think that's why it's a logarithmic function — because the probability of any new molecule "seeing" any IR keeps going down. If I get a moment, I'll work it through.

 

Actually, my understanding is that the IR retention is reflected IR, which comes from both the warmth of the Earth, reflection of IR that is caught on the way out, and the conversion of the higher wave lengths to IR from heating of the Earth's surface.

 

I know it goes both ways, but it is not a viscious cycle.. ie. a set amount of CO2 can only retain so much heat.

 

 

bascule claimed that the CO2 forcings had increased, and has posted many links and graphs to support various claims. Your counter-claim was that no, the contribution had decreased. You have not backed up that claim.

 

Since we are dealing with history here, the probability of whatever happened to CO2 is identically 1. The increase in CO2 has been exponential in recent years. I provided a link.

 

Well, the communication problem we are having revolving around what the exponential growth actually is. That is to say, this growth takes the form a, ar, ar^2, ar^3... ar^n (where "a" is the starting value, and "r" is the common ratio) . We are arguing about exponential/geometrical growth and haven't established what "r" we are talking about. When we are talking about "doubling the CO2" that would indicate we are talking about an r of 2 (a, 2a, 4a, 8a, 16a... etc.). Geometric growth is also the common term for growth with a common ratio of 2.

 

So the exponential growth can be any growth that can be attributed a common ratio.

 

Linearity would only happen if the growth was inverse of the logrithmic curve. But it's not.

 

Again, this discussion has centered on what has happened in the past. To cite future projections is moving the goalposts.

 

Since this is a thread about a movie that talks completely about predicting the future, I would say that keeping the discussion from talking about the furture would be off topic.

 

 

I have no idea what your point is here. Earlier you agreed that the the dependence of temperature on CO2 is logarithmic, thus an exponential increase in CO2 will cause a linear increase in temperature. If the exponential speeds up (e^ax and a increases) then the temperature increase will speed up as well. This is, as I said, basic math.

 

As I stated earlier, the linearity depends on the exponetial growth being roughly the same as the decreasing logaritmic effect of the CO2.

 

You were worried about the warming causing CO2 release, and the historical data show that we should expect 1 ppm per 0.1ºC increase in temperature, on average. But you've got the cause and effect reversed now. the 100 ppm increase is not from ocean release — that only accounts for something of order 10 ppm. So the other 90 ppm would be anthropogenic.

 

If a doubling of CO2 should cause a 3º increase in T, a 5% increase should cause a 0.2º rise in temperature. Is that about what we've seen?

 

I haven't gotten the cause and effect reversed, the ocean does release more CO2 when it warms. The exact amount of that release per degree I couldn't tell you. Is it linear? I would guess not, as almost nothing in nature is linear.

[swansont]

Actually, my understanding is that the IR retention is reflected IR, which comes from both the warmth of the Earth, reflection of IR that is caught on the way out, and the conversion of the higher wave lengths to IR from heating of the Earth's surface.

 

I know it goes both ways, but it is not a viscious cycle.. ie. a set amount of CO2 can only retain so much heat.

 

I don't think anything here contradicts what I've said. A set amount of CO2 can only retain so much heat, but more CO2 retains more heat. As the concentration goes up, the effectiveness of the new addition is less, or put another way, you have to add more CO2 to cause the same temperature increase. It's logarithmic.

 

Well, the communication problem we are having revolving around what the exponential growth actually is. That is to say, this growth takes the form a, ar, ar^2, ar^3... ar^n (where "a" is the starting value, and "r" is the common ratio) . We are arguing about exponential/geometrical growth and haven't established what "r" we are talking about. When we are talking about "doubling the CO2" that would indicate we are talking about an r of 2 (a, 2a, 4a, 8a, 16a... etc.). Geometric growth is also the common term for growth with a common ratio of 2.

 

So the exponential growth can be any growth that can be attributed a common ratio.

 

Linearity would only happen if the growth was inverse of the logrithmic curve. But it's not.

 

I don't think this is the communication problem. The communication problem is that bascule claimed that the forcings were increasing, and you claimed they were decreasing. And you still haven't presented ANY MATERIAL to support that claim.

 

Since this is a thread about a movie that talks completely about predicting the future, I would say that keeping the discussion from talking about the furture would be off topic.

 

yes, future claims are on topic for discussion about the movie. But this particular part of the discussion was based on the past. So stop changing the subject.

 

 

As I stated earlier, the linearity depends on the exponetial growth being roughly the same as the decreasing logaritmic effect of the CO2.

 

 

 

I haven't gotten the cause and effect reversed, the ocean does release more CO2 when it warms. The exact amount of that release per degree I couldn't tell you. Is it linear? I would guess not, as almost nothing in nature is linear.

 

Your question was

Of the increase seen in the last 100 years (280 ppm to 380 ppm) only a protion of that is anthropogentic... unless you assume that the ocean released no CO2 following the little ice age. But we both know that that isn't the case. So of the increase, what portion is anthropogenic, and what is attributed to the expected warming?

 

Since you presented nothing else on the matter, I gave a back-of-the-envelope estimate. Based on the historical data, where heating caused CO2 change, we see around 80 ppm change when the temperature changes 8ºC. From that, I would say just a few ppm — likely less than 10 — of the recent CO2 increase is due to to ocean heating. Over a small range like that, linear probably isn't too bad of a guess.

 

However, from this, stating "But even going back to the logrithmic argument, 80ppm equals 8ºC... but 100ppm equals 0.63ºC." is most certainly switching cause and effect. Nobody here is claiming that the 80 ppm increases caused all of the historical temperature increase. (It's fair to say a claim is that it contributed)

[SkepticLance]

Swansont

A question. When you say 8 C increase equals 80 ppm CO2 increase, are you talking about air or ocean temperature? This is significant since the ocean has warmed over the past few decades to a level that is a small fraction of the air temperature increase.

 

I affirm the exponential nature of the relationship between CO2 and warming. It does not mean warming is linear, of course, since linearity results from one specific CO2 increase curve, and it is unlikely we would get exactly this curve.

 

The last few decades have seen an exponential increase in CO2 and the average warming has been close, but not exactly, linear. Predictions are dangerous and usually wrong, but I have always dived in where angels fear, etc. I predict the next few decades will see further exponential CO2 increase, coming from the explosive growth in the economies of China and other nations. Warming should be once more close to linear.

 

Another point. The exponential growth is actually all greenhouse materials together - not just CO2. To take a hypothetical example - imagine a planet with 100 ppm of methane and 100 ppm of CO2. The methane is a very potent greenhouse gas, and CO2 much less potent. If the CO2 doubled in that case, the warming would be utterly trivial, since total greenhouse effect began at such a high level.

 

On Earth, this principle is significant since water vapour is the most potent greenhouse material, and it varies enormously from place to place. So, if we began in a place with minimal water vapour - like the high Arctic - and increase CO2, the warming will be potent. However, if we began in a place with much more water vapour, such as the Amazon basin, and increase CO2 to the same degree, the warming will be quite minimal.

 

We need to recognise that the degree of warming for a set CO2 increase depends heavily on how much water vapour is in that place.

Edited June 13, 2008 by SkepticLance
multiple post merged