Guest Post by Bill Illis
This post is the first of what will likely be a series on the PaleoClimate.
In this part, we are just going to go through the various estimates for Temperature, CO2 and Sea Levels in the PaleoClimate. This post is also about making the data available to everyone so that others can use it. All of the data presented in this post is available for download at the end in easy to use Excel spreadsheets which also incorporates direct links to the actual data sources used.
PaleoClimate Temperature Estimates Over the Past 570 Million Years
There are various sources we can use for estimates of Temperatures in the PaleoClimate.
We have the ice core dO18 isotope data going back 800,000 years. James Zachos has a high resolution database of dO18 isotopes going back 67.0 million years. Jan Veizer has accumulated an isotope database that goes back 526.5 million years. Dana Royer and Robert Berner applied a ph-correction factor to Veizer’s database and Christopher Scotese has developed Temperature estimates that extend back into the pre-Cambrian.
For the most part, the Temperature estimates are based on dO18 isotopes and these have proven to be reasonably reliable, or more accurately, to be the most reliable temperature estimation method that is available.
The isotope data does require a number of different transformations and smoothing to make it useful as a Temperature proxy. Nobody is really sure what the proper way to carry this out is.
For one, it must be detrended as the data becomes older. The dO18 declines over time due to the radioactivity of the Earth. The above estimates are based on a simple linear detrending formula. The rationale is that the radioactive conditions would have remained reasonably constant over the last 530 million years. Others have used a second order polynomial but this does not result in much difference.
It has been noted that the dO18 isotope data should also be corrected for ice volume, sea level, the concentrations of CaCO3 in the oceans and -ph conditions of the oceans. Royer and Berner applied a ph-correction factor based on Berner’s GeoCarb III CO2 estimates. Again, this doesn’t make much difference except that Royer and Berner’s numbers are now lower than Veizer’s original database would point to.
Effectively, any transformation carried out has still got to match the record that we know about. It is still going to have to show a Carboniferous ice age, an Ordovician ice age, a hot Permian Pangea climate, a hot Cretaceous period, an Antarctic glaciation and the recent ice ages.
In other words, no matter what corrections are applied, one should just end up with something very similar to the above chart.
Detailed Temperature Estimates Over the Past 530 Million Years
Veizer’s database contains over 16,600 individual dO18 isotope data points extending back 526.5 million years. There is sufficient resolution throughout the database that we can be reasonably certain about any specific period.
The above chart has been constructed using Veizer’s data with two different smoothing parameters; a shorter one which preserves more detail and then one that emulates the Phanerozoic Climate Change chart by Robert Rohdes of Global Warming Art. It is likely that both are reasonably accurate and sometimes less smoothing is preferred to more smoothing so that more information can be extracted.
In this case, there really is more information available from the shorter Gaussian smooth. Immediately evident is that certain large temperature changes coincide with some of the large Mass Extinction events in the planet’s history.
The really unusual one is the Permian Extinction event in which 96% of marine species and 70% of large land animals died out in a very short period of time about 251.4 million years ago. Previously this was thought to be due to exceptionally hot conditions or even ocean chemistry changes.
But now one can see that temperatures actually declined by about 5.0C in a very short period of time (something that is that well-known). This temperature drop exactly coincides with the dating of the Siberian Traps volcanic events at 251 to 250 million years ago which is the largest series of volcanic events known in history. An area nearly the size of Australia may have been covered by volcanic magma flows hundreds of metres deep (some places have been measured at 4 kms deep). The volcanoes lasted for about 1 million years and, not surprisingly, temperatures fell.
The other event is the Ordovician extinction event of 443 million years ago in which 50% of the new Cambrian genera of life disappeared. This was always known to be caused by a cooling climate. But now, one can see that there is a very significant drop in the smoothed temperature estimates exactly at 443 million years ago.
The Devonian Extinction seems to be caused by a rapid increase in temperatures, as much as 10.0C in just a few million years.
Notice how the Cretaceous Period, 95 million years ago, is 2.0C to 3.0C higher than the Paleocene Eocene Thermal Maximum. The climate scientists are always talking about how unusual the PETM was but just a few million years earlier, temperatures were quite a bit higher. Dinosaurs even lived in Alaska at the time, and it was a little farther north in the period than it is now. The PETM event does not even look unusual enough in the record to spend much time on.
Notice that the timelines surrounding the Carboniferous Ice Age and the Ordovician-Silurian Ice Age are now clearly defined. These timelines match up very closely with the estimated alignment of the Continents during the periods. Even the short mid-Jurassic Ice Ages are now evident at a point in time when parts of EuroAsia were transiting the North Pole.
Detailed Temperature Estimates Over the Past 67 million Years
Zachos has developed another database of 14,800 individual estimates of dO18 isotopes that covers the past 67 million years with a resolution of less than 100,000 years in most cases.
The time period when Antarctica glaciated over (for the fourth time that is known about) is clearly evident. Temperatures reached as high as 6.0C during the PETM and the periods when Antarctica reglaciated and when Greenland’s glaciers started building occurred at 14 million years ago.
About 2.5 million years, the most recent cycle of ice ages began. In part II of the series, we may take a closer look at the ice ages in more detail.
PaleoCO2 Estimates
There are quite a few different estimates for CO2 in the PaleoClimate. We have the ice cores, we have Mark Pagani 2005 with high resolution estimates between 5.4 million years to 44.5 million years ago and we have Berner’s GeoCarb III estimates which go back to 570 million years ago.
There are others (and they have been included in the CO2 spreadsheet) but they are not as well-accepted as these. The other estimates come mainly from Stomata size (the cells that plants to use to absorb CO2), Paleosols (ancient soil deposits) and Phytoplankton among others.
Using the estimates that are most accepted and given the resolution is higher with the ice cores than with Pagani and then Pagani’s resolution is higher than Berner’s, they have been incorporated back-to-back-to-back as one series as follows.
As most of you are aware, CO2 goes as high as 7,069 ppm 520 million years ago and as low as 180 ppm during the height of the ice ages.
On the same timeline as the PaleoTemperatures Over 67 Million Years chart above, CO2 looks like this over the past 70 million years.
Paleo Sea Level Estimates
Sea level has also been included in the databases since it is not well-known that these high resolution estimates exist. In addition, sea level can certainly have an impact on the climate as well be an indicator for the climate.
There are many different sea level estimates and the most recent one covering the whole period, produced by the world-leading expert on sea level, Bilal Haq, is the most accepted version (Haq, Schutter, 2008).
Sea Level has varied by a large amount throughout history. Sea levels were as much as 265 metres higher than today 100 million years ago and have been as low as 120 metres lower than today during the Last Glacial Maximum.
Sea level seems to vary through three different mechanisms.
- Sea level falls when glaciers build up on land. Obvious enough.
- Sea level falls when continental land masses are concentrated together. Collisions and mountain building tend to squeeze the Earth’s landmasses together and there is less continental shelf area that can affect the average depth of the overall oceans. Related to the last reason, the ocean basins tend to be more mature and deeper in these situations. and,
- Sea level rises when new young ocean basins are opening. New ocean basins generally form at only 2,500 metres depth while mature ocean basins tend to deepen and reach a depth of about 6,000 metres after 100 million years. That means the overall average depth of the ocean is lower when new oceans are forming. This is particularly the case during the Cretaceous when the Atlantic Ocean was just opening up.
Sea levels rose so high during the Cretaceous as the Atlantic was just opening, that the ocean flooded North America from Texas to Inuvik, to Hudson Bay. Europe, the Middle East, North Africa and the central parts of Eurasia were also flooded by shallow oceans.
During the Carboniferous and the Jurassic, the land masses were collected together into the Supercontinent of Pangea. Sea levels fell in the earlier part as glaciers covered large parts of Gondwana, but then they stayed low as the glaciers melted and the continents moved together to form Pangea.
There are periods when there are rapid changes in sea level and these have been used by researchers to date the periods of glaciations. It appears Scotese has used earlier versions of the sea level data to date the glaciations used in his temperature reconstruction.
Conclusion
Putting all the best estimates together, here is a view of the Temperatures, CO2 and Sea Level throughout the past 526 to 570 million years.
In subsequent posts, we may look at the Milankovitch Cycles and the recent ice ages, Continental Drift through time and how that may have affected the climate and then the empirical evidence surrounding the CO2 doubling sensitivity in the PaleoClimate.
The main purpose of this post was to just make the data available to everyone. Others are free to use to use this data in any manner they see fit.
The data is available in three different easy-to-use Excel spreadsheets and can be downloaded at this link. The Paleo Temp Database is a very large file and may be a slow download.
[Paleo Temp CO2 Sea Level Data]
PaleoClimate Temperature, CO2 and Sea Level Estimates
Guest Post by Bill Illis
This post is the first of what will likely be a series on the PaleoClimate.
In this part, we are just going to go through the various estimates for Temperature, CO2 and Sea Levels in the PaleoClimate. This post is also about making the data available to everyone so that others can use it. All of the data presented in this post is available for download at the end in easy to use Excel spreadsheets which also incorporates direct links to the actual data sources used.
PaleoClimate Temperature Estimates Over the Past 570 Million Years
There are various sources we can use for estimates of Temperatures in the PaleoClimate.
We have the ice core dO18 
isotope data going back 800,000 years. James Zachos has a high resolution database of dO18 isotopes going back 67.0 million years. Jan Veizer has accumulated an isotope database that goes back 526.5 million years. Dana Royer and Robert Berner applied a ph-correction factor to Veizer’s database and Christopher Scotese has developed Temperature estimates that extend back into the pre-Cambrian.
For the most part, the Temperature estimates are based on dO18 isotopes and these have proven to be reasonably reliable, or more accurately, to be the most reliable temperature estimation method that is available.
The isotope data does require a number of different transformations and smoothing to make it useful as a Temperature proxy. Nobody is really sure what the proper way to carry this out is.
For one, it must be detrended as the data becomes older. The dO18 declines over time due to the radioactivity of the Earth. The above estimates are based on a simple linear detrending formula. The rationale is that the radioactive conditions would have remained reasonably constant over the last 530 million years. Others have used a second order polynomial but this does not result in much difference.
It has been noted that the dO18 isotope data should also be corrected for ice volume, sea level, the concentrations of CaCO3 in the oceans and -ph conditions of the oceans. Royer and Berner applied a ph-correction factor based on Berner’s GeoCarb III CO2 estimates. Again, this doesn’t make much difference except that Royer and Berner’s numbers are now lower than Veizer’s original database would point to.
Effectively, any transformation carried out has still got to match the record that we know about. It is still going to have to show a Carboniferous ice age, an Ordovician ice age, a hot Permian Pangea climate, a hot Cretaceous period, an Antarctic glaciation and the recent ice ages.
In other words, no matter what corrections are applied, one should just end up with something very similar to the above chart.
Detailed Temperature Estimates Over the Past 530 Million Years
Veizer’s database contains over 16,600 individual dO18 isotope data points extending back 526.5 million years. There is sufficient resolution throughout the database that we can be reasonably certain about any specific period.
The above chart has been constructed using Veizer’s data with two different smoothing parameters; a shorter one which preserves more detail and then one that emulates the Phanerozoic Climate Change chart by Robert Rohdes of Global Warming Art. It is likely that both are reasonably accurate and sometimes less smoothing is preferred to more smoothing so that more information can be extracted.
In this case, there really is more information available from the shorter Gaussian smooth. Immediately evident is that certain large temperature changes coincide with some of the large Mass Extinction events in the planet’s history.
The really unusual one is the Permian Extinction event in which 96% of marine species and 70% of large land animals died out in a very short period of time about 251.4 million years ago. Previously this was thought to be due to exceptionally hot conditions or even ocean chemistry changes.
But now one can see that temperatures actually declined by about 5.0C in a very short period of time (something that is that well-known). This temperature drop exactly coincides with the dating of the Siberian Traps volcanic events at 251 to 250 million years ago which is the largest series of volcanic events known in history. An area nearly the size of Australia may have been covered by volcanic magma flows hundreds of metres deep (some places have been measured at 4 kms deep). The volcanoes lasted for about 1 million years and, not surprisingly, temperatures fell.
The other event is the Ordovician extinction event of 443 million years ago in which 50% of the new Cambrian genera of life disappeared. This was always known to be caused by a cooling climate. But now, one can see that there is a very significant drop in the smoothed temperature estimates exactly at 443 million years ago.
The Devonian Extinction seems to be caused by a rapid increase in temperatures, as much as 10.0C in just a few million years.
Notice how the Cretaceous Period, 95 million years ago, is 2.0C to 3.0C higher than the Paleocene Eocene Thermal Maximum. The climate scientists are always talking about how unusual the PETM was but just a few million years earlier, temperatures were quite a bit higher. Dinosaurs even lived in Alaska at the time, and it was a little farther north in the period than it is now. The PETM event does not even look unusual enough in the record to spend much time on.
Notice that the timelines surrounding the Carboniferous Ice Age and the Ordovician-Silurian Ice Age are now clearly defined. These timelines match up very closely with the estimated alignment of the Continents during the periods. Even the short mid-Jurassic Ice Ages are now evident at a point in time when parts of EuroAsia were transiting the North Pole.
Detailed Temperature Estimates Over the Past 67 million Years
Zachos has developed another database of 14,800 individual estimates of dO18 isotopes that covers the past 67 million years with a resolution of less than 100,000 years in most cases.
The time period when Antarctica glaciated over (for the fourth time that is known about) is clearly evident. Temperatures reached as high as 6.0C during the PETM and the periods when Antarctica reglaciated and when Greenland’s glaciers started building occurred at 14 million years ago.
About 2.5 million years, the most recent cycle of ice ages began. In part II of the series, we may take a closer look at the ice ages in more detail.
PaleoCO2 Estimates
There are quite a few different estimates for CO2 in the PaleoClimate. We have the ice cores, we have Mark Pagani 2005 with high resolution estimates between 5.4 million years to 44.5 million years ago and we have Berner’s GeoCarb III estimates which go back to 570 million years ago.
There are others (and they have been included in the CO2 spreadsheet) but they are not as well-accepted as these. The other estimates come mainly from Stomata size (the cells that plants to use to absorb CO2), Paleosols (ancient soil deposits) and Phytoplankton among others.
Using the estimates that are most accepted and given the resolution is higher with the ice cores than with Pagani and then Pagani’s resolution is higher than Berner’s, they have been incorporated back-to-back-to-back as one series as follows.
As most of you are aware, CO2 goes as high as 7,069 ppm 520 million years ago and as low as 180 ppm during the height of the ice ages.
On the same timeline as the PaleoTemperatures Over 67 Million Years chart above, CO2 looks like this over the past 70 million years.
Paleo Sea Level Estimates
Sea level has also been included in the databases since it is not well-known that these high resolution estimates exist. In addition, sea level can certainly have an impact on the climate as well be an indicator for the climate.
There are many different sea level estimates and the most recent one covering the whole period, produced by the world-leading expert on sea level, Bilal Haq, is the most accepted version (Haq, Schutter, 2008).
Sea Level has varied by a large amount throughout history. Sea levels were as much as 265 metres higher than today 100 million years ago and have been as low as 120 metres lower than today during the Last Glacial Maximum.
Sea level seems to vary through three different mechanisms.
· Sea level falls when glaciers build up on land. Obvious enough.
· Sea level falls when continental land masses are concentrated together. Collisions and mountain building tend to squeeze the Earth’s landmasses together and there is less continental shelf area that can affect the average depth of the overall oceans. Related to the last reason, the ocean basins tend to be more mature and deeper in these situations. and,
· Sea level rises when new young ocean basins are opening. New ocean basins generally form at only 2,500 metres depth while mature ocean basins tend to deepen and reach a depth of about 6,000 metres after 100 million years. That means the overall average depth of the ocean is lower when new oceans are forming. This is particularly the case during the Cretaceous when the Atlantic Ocean was just opening up.
Sea levels rose so high during the Cretaceous as the Atlantic was just opening, that the ocean flooded North America from Texas to Inuvik, to Hudson Bay. Europe, the Middle East, North Africa and the central parts of Eurasia were also flooded by shallow oceans.
During the Carboniferous and the Jurassic, the land masses were collected together into the Supercontinent of Pangea. Sea levels fell in the earlier part as glaciers covered large parts of Gondwana, but then they stayed low as the glaciers melted and the continents moved together to form Pangea.
There are periods when there are rapid changes in sea level and these have been used by researchers to date the periods of glaciations. It appears Scotese has used earlier versions of the sea level data to date the glaciations used in his temperature reconstruction.
Conclusion
Putting all the best estimates together, here is a view of the Temperatures, CO2 and Sea Level throughout the past 526 to 570 million years.
In subsequent posts, we may look at the Milankovitch Cycles and the recent ice ages, Continental Drift through time and how that may have affected the climate and then the empirical evidence surrounding the CO2 doubling sensitivity in the PaleoClimate.
The main purpose of this post was to just make the data available to everyone. Others are free to use to use this data in any manner they see fit.
The data is available in three different easy-to-use Excel spreadsheets and can be downloaded at this link. The Paleo Temp Database is a very large file and may be a slow download.
[Paleo Temp CO2 Sea Level Data]
Bill Illis (05:31:11) :
“…In the post, I noted there is nothing particularly special about the PETM in comparison to the overall record. It just provides a convienent target for global warming exageration. There was a different continental alignment at the time and, in subsequent posts, we may cover how that has affected the climate including the PETM.”
Reply: I think the fact that the continents have move around so much over the millennia is often not considered sufficiently when trying to understand major swings in climate. If the pattern of ocean currents caused by tectonic movement stops the transport of warm water to the poles then greater cooling and freezing will occur making conditions more extreme.
Thank you very much Bill for an interesting post, it’s very useful to have all the data together in one place. I look forward to learning more as this series unfolds.
Bill,
I support strongly Paul Dennis’ second posting about radioactivity and the explanation for shifting d18O fractionations over time. This is an interesting problem – the likes of Veizer have noted that shell fractionation temperatures show an increasingly hotter Cambrian ocean with values way above their typical values. As Paul suggests alteration/diagenesis can explain the shift. Alternatively some have suggested the isotopic ratios of the ocean was different in the early Phanerozoic compared to modern (SMOW) values, but whatever you do remove the radioactivity explanation from your stable isotope discussion.
Regarding Paul Dennis’ and nvw’s comments, it is clear that I got that part wrong. The data does have to be detrended however.
There are a lot of experts at this site about individual specific aspects of this. I guess I was also hoping that others would chime in as well and say this part should be done this way.
Somebody has to put all this together.
The issues surrounding global warming have been mostly theoritical to date; climate models and theory. We should go back to ground and look at what the actual empirical evidence says. What is the actual CO2 doubling in the PaleoClimate. The modelers always report that 3.0C per doubling is consistent with X simulation of Y geologic period. Then one looks at the actual Temperature and CO2 data (even the data they supplied) and 3.0C per doubling does not work at all. But to do that, you need to have reliable CO2 and Temperature estimates and it should hold together over the whole record.
gtrip (10:16:34) :
“As if what happened millions of years ago really matters????”
So please tell us where to draw the line between what really matters and what doesn’t matter.
Causation means that everything is built on what happened previously.
[BTW, excellent link you posted upthread. Thanks for that.]
gtrip (10:16:34) says:
“As if what happened millions of years ago really matters???? This blog seems to losing it’s purpose. We don’t and will never live in a world that existed millions of years ago. Wake up and drink some coffee already.”
LOL, and we wonder why it is so hard to explain this all to some folks.
“The past is prologue” -Shakespeare
Mark Hugoson,
re your comment concerning d18O and tropical storms. When talking about oxygen isotope data it is important to separate out whether one is writing about water oxygen isotope composition, or one is writing about the isotope composition of carbonates.
Most of Bill’s data base and discussion is about marine carbonate isotope composition. Your comment relates to the isotope composition of precipitation. In tropical areas there is little, or no correlation between temperature and the precipitation isotope composition. There is, however, a strong ‘amount’ correlation where the oxygen isotope composition of the rainfall is correlated with the amount of rainfall. At mid to high latitudes the isotopic composition of precipitation is strongly correlated with temperature. This is best understood in terms of fractional distillation and the temperature dependence that is measured can also be calculated closely using a Rayleigh distillation model and adiabatic cooling of an air mass.
When discussing carbonates (as in Bill’s data collection) the temperature signal is caused by the temperature dependence of isotope partitioning between sea water and the precipitating carbonate. This fractionation has been both calculated ab initio, experimentally calibrated and checked against field samples. If one knows the sea water composition then it is possible to use the isotope composition to calculate temperature.
Of course sea water composition is not constant over geologic time. On short time scales the composition is largely regulated by the volume of continental ice sheets. Large volumes of ice during glacial periods results in positive shifts in the sea water oxygen isotope composition (ice volume effect). This is because isotopically light water, depleted in 18O, evaporates from the oceans and is ultimately locked up in ice sheets.
On longer time scales the isotopic composition of the ocean is buffered by hydrothermal circulation of ocean water at mid-ocean ridges. The question that remains to be answered is how this has varied over time. i.e. has enahnced rates of sea floor spreading at some periods resulted in a changed oxygen isotope composition. There has been some work based on ophiolite isotoep composition to try and answer this but the results are not especially convincing.
nvw’s comments about Veizer’s observation of apparent high Cambrian ocean temperatures are correct. This is due to the fact that high temperature recipitation from sea water has an isotopic signature similar to that of diagenetically altered sediments. To resolve the issue one tries to isolate samples that have not been altered. Hence my comment about using micrsocopy, xrd, cathodoluminesence etc. to identify signs of alteration. These might include evidence of aragonite to calcite phase changes, the dissolution of high Mg calcite etc.
I have agreed to write a 101 primer on isotopes and palaetemperatures for WUWT but it will be a week or so before I can finish it.
Bill Illis (10:56:13) :
There are a lot of experts at this site about individual specific aspects of this. I guess I was also hoping that others would chime in as well and say this part should be done this way.
Paleo-Sciences have long been a love if mine. You have presented before us a summery of what we think we know.
By compiling the data of real researchers we can extract ourselves from the pseudo science of the current crop of spin merchants and study the things that confound us. We should drag ourselves away from the politics.
You have made a step in the right direction. Thank you.
About the possibility of measuring sea levels in the geologic past. What is measured is really the amount of continental onlap, which can be converted to sea level under the assumption that the continents on average have remained at approximately the same level. This is probably true as a first approximation since the data from different areas and continents agree fairly well, but does not apply everywhere and always. For example everybody agrees that sea level was very high almost everywhere in the late Cretaceous. However in Australia sea levels went down during the same period. The only reasonable explanation is that the whole Australian continent rose at this time, for reasons that are not well understood.
The relative sea levels, i e that sea levels went up or down x meters during a specific interval are fairly easily derived from sequence stratigraphy as has already been pointed out, and these data are more reliable than the absolute levels which are only approximate. Exact values are not possible because of tectonic movement. Even the almost invariably quoted 4-6 meters higher sea level during the previous interglacial only 120,000 years ago is very shaky when you dig into the details, it is just as likely to have been only 2-3 meters.
Bill,
Perhaps as a geologist I have an inflated opinion as to the importance of geology 🙂 but the dataset you have collected and the arguments it contains is one of the most important constraints over the role of CO2 and global warming.
To me the data you have collected from published sources shows:
CO2 has been much higher in the past
These levels have not caused “run away” temperatures.
These levels have not caused permanent ocean acidification and the complete extinction of marine invertebrates.
So yes, I agree with your concerns about the validity of the 3 deg C per doubling. I don’t care what some climate modeler says about 450 ppm CO2 tipping point – just look at the geologic record and you know the modeled predictions are wrong. You do not need to spend $79 billion on climate change research when the data is right in front of you (unless of course your academic career is dependent on believing your research needs a flitch of that funding.)
Will the climate be warmer with higher CO2 – probably. Will that be the end of the world – unlikely.
Here is another example of where one could go with this.
This is a chart of the temperature estimates of the last 3 ice ages, together with what 1.5C per CO2 doubling and 3.0C per doubling results in. Also included is the global solar irradiance estimates from Berger and Loutre 1991.
CO2 can only explain a small part of the temperature changes. The Milankovitch Cycles vary the amount of solar energy received at high latitudes but the global solar irradiance does not predict that ice ages should occur. There is another critical component to the climate equations that is not taken into account enough and that is the Albedo of the Earth.
http://img261.imageshack.us/img261/2127/last3iceages.png
That is because CO2 is usually not the only forcing acting on the system. For the glacial – interglacial cycles, as you point out, the change in albedo due to ice sheet and vegetation changes is important. (The Milankovitch Cycles are the “trigger” in the sense that they are what cause the ice sheets to start growing or melting, but they don’t contribute significantly to any global annual mean forcing.) The correct way to do the calculation is to add up all of the forcings and divide the temperature change by those total forcings. That gives you a climate sensitivity in C / [W/m^2]. Then to convert that to a climate sensitivity for a doubling of CO2, you multiply by the radiative forcing due to a doubling, which everyone agrees is around 3.5-4.0 W/m^2.
Well, as your plot suggests, the albedo part is the largest contributor to the forcings. What is your evidence that it “is not taken into account enough”?
Nicely presented work. However in the current GW debate the time scales that we are looking at here make all this work basically irrelevant.
Our human endeavor started a mere 100.000 years or so ago and what matters for our survival are not comparisons with times tens of millions of years ago. We will not have the time to ‘evolve’ or wait for the ecosystem that supports us to ‘evolve’ to conditions much different to the current if the change is fast. What matters is what will happen in the next few human generations.
The consensus at current that average temps will increase by as much as 4 Deg this century alone is the problem. It is the speed of the change that is the issue. Such change will rapidly change the ability of the ecosystem to support our current requirements for agricultural output while sea level rises would make massive disruptions of the living arrangements of large parts of our civilization inevitable. The resulting misery for billions of people is the issue.
It is irrelevant in this discussion that Earth would eventually evolve an ecosystem that considers a much warmer world ‘normal’ again – give or take few million years…!
Bill
This is excellent. May I suggest if you take this forward, and I hope you do, that the geological chronostatigraphic ages are added to the x axis, as well as the millions of years BP. It would be very helpful for many of us more familiar with the standard geological convention.
Valid queries have been posted about sea level reference base. There is a considerable published literature on interpreted sea levels through geological time built by iterative observations of transgressions and regressions but in my view, at the end of the day, relative sea level has to be treated as a best estimate qualitative, rather than precise, figure.
Joel (13;21),
What is the Albedo estimate during the PETM? What is the Albedo estimate at the last glacial maximum? It is 0.298 today.
Ready, set, go … Makes a really good start point — Great post. Look forward to the follow on postings.
Smokey (11:12:14)
Gacooke (11:21:07) :
The point is that nobody knows what the weather was 75 million years ago. We may calculate what the “climate” was at that time. If that is the case then we should also just look at our current “climate” in those terms and a generation or two is not even a blip on that screen!
Bill: Not sure if an estimate has been made for the PETM. For the Last Glacial Maximum, the estimate of the change in forcing due to ice sheet and vegetation changes from Hansen is -3.5 +-1.0 W/m^2 ( http://naturalscience.com/ns/articles/01-16/ns_jeh2.html ), which I guess would correspond roughly to a change in albedo by 0.01, e.g., it would be 0.288 rather than 0.298.
Samoht , you state:
“The consensus at current that average temps will increase by as much as 4 Deg this century alone is the problem. It is the speed of the change that is the issue.”
1. Exactly what “consensus” ? Where is your evidence ?
2. Fossil fuel burning increased about 1200% after 1945. Compare the rate of temperature rise between 1910 to 1940 with subsequent rates of temperature rise (and fall). Exactly where is the increased rate of warming caused by fossil fuel burning supposed to be ?
Bill’s excellent article shows that mammals have lived successfully with CO2 levels of 2500ppm and temperatures 8 degrees higher than currently.
So we’re all gonna die if we don’t get to 350 ppm CO2?
http://heliogenic.blogspot.com/2009/10/so-were-all-gonna-die-if-we-dont-get-to.html
The following publication may also be useful on this topic:
Bintanja, R. Wal, R.S.W. van de & Oerlemans, J., Modelled atmospheric temperatures and global sea levels over the past million years
Nature 437, 125-128 (1 September 2005) | doi:10.1038/nature03975
Abstract
Marine records of sediment oxygen isotope compositions show that the Earth’s climate has gone through a succession of glacial and interglacial periods during the past million years. But the interpretation of the oxygen isotope records is complicated because both isotope storage in ice sheets and deep-water temperature affect the recorded isotopic composition. Separating these two effects would require long records of either sea level or deep-ocean temperature, which are currently not available. Here we use a coupled model of the Northern Hemisphere ice sheets and ocean temperatures, forced to match an oxygen isotope record for the past million years compiled from 57 globally distributed sediment cores, to quantify both contributions simultaneously. We find that the ice-sheet contribution to the variability in oxygen isotope composition varied from ten per cent in the beginning of glacial periods to sixty per cent at glacial maxima, suggesting that strong ocean cooling preceded slow ice-sheet build-up. The model yields mutually consistent time series of continental mean surface temperatures between 40 and 80° N, ice volume and global sea level. We find that during extreme glacial stages, air temperatures were 17 ± 1.8 °C lower than present, with a 120 ± 10m sea level equivalent of continental ice present.
Fabulous post. I constantly look for this type of graphical correlation function and this one is the best I have seen so far. I would like to see a few more additions to the plot:
1. Eccentricity of the Earth’s orbit. It has roughly the same period as the recent ice ages.
2. Absolute irradiance of the sun for the last 500M yrs. It has gone up 5% (linearly, I think) while CO2 has gone done in very rough proportion to total solar output. And yet, the Earth’s temperature has varied up and down independent of the solar output but always within roughly the same limits. Clearly, a strong negative feedback mechanism is at work which can discard or absorb solar energy as needed to maintain the system within is historical temperature range. Carbon dioxide is only a part of this feedback system if it is not a response instead.
3. A wild one: One paper I read plotted “number of species vs time” and found a rough 64Myr cycle. That in itself is interesting. How does it compare the other parameters shown in your graph?
Re: Bill Illis comment to me. Reread what I said. I did not compare temperature to CO2 — which apparently you thought I said. I said look at the relative stability of the CO2 record since Antarctica parked on the South Pole. For approximately the past 25 million years the CO2 level has not (from the graph) changed much.
Samoht (13:23:02) says:
“The consensus at current that average temps will increase by as much as 4 Deg this century alone is the problem.”
Where is that consensus? And how does it account for the non-temperature rise for the first decade?
gtrip: The point should be that you can’t accurately predict what the climate will be like unless you understand how it got the way it is.
Gacooke (15:07:48) :
gtrip: The point should be that you can’t accurately predict what the climate will be like unless you understand how it got the way it is.
And the point is that there is no way that you, I, or anyone, can know how our current climate came to be, especially by studying the climate of 70 million years ago. To think so is folly.
gtrip says: “And the point is that there is no way that you, I, or anyone, can know how our current climate came to be, especially by studying the climate of 70 million years ago. To think so is folly.”
If you mean to “know” in the complete extent, perhaps not. But you can learn important information even when your understanding is not complete.
Of course, information from the last few decades may be more relevant to understanding today’s climate than information from 70 or 700 million years ago. That doesn’t make the information irrelevant though.
The OP seems to be taking the tack of providing information on what we “think” the global data set is telling us and plans to move to more human time scales in the future. Is it you point that it isn’t worth describing and discussing? Or are you only interested in the last 6000 years?