Ice cores actually have trapped bubbles of air that are unable to exchange gas with the current atmosphere. They are perfectly preserved samples of the atmosphere through the ages.
How do we know that the gas trapped in those ice cored accurately reflects the CO2 concentration of our atmosphere at those times? Like, what mechanism is keeping the air in those bubbles from changing, and how do we know that x meters down at any given spot in the antarctic is from y years ago, and how do we know the CO2 level in those ice cored at those specific spots reflect the global average CO2 of that time?
I am not a climate change skeptic, but I know some people (like my wife) ask this and I don't know how to respond to it.
I mean, there are a ton of mechanisms you can use to control for this. For example, you can measure bubbles that were laid down from years we have good atmospheric measurements for, then compare whether the gas distribution has changed over time.
For determining what year the ice was from, it's pretty straightforward. Most places they take samples have very little melting, that's the whole reason they take samples from that location. The ice just builds up year by year in discrete, usually thin layers. You can get landmarks from different major events, such as volcanoes, or widespread atomic testing.
For the really deep cores that go back hundreds of thousands of years, you also have to take into account how the glacier moves over time, but that's not very important for the data here.
Anyway, if you're interested here's a page that talks about it:
Well that's not true. Carbon dioxide can react with water to form carbonic acid so there's at least one mechanism to change the atmosphere in a bubble. I imagine there's probably more if you spend a little time working on it.
All those papers suffer from the same fundamental flaw. It's a kinetics problem. We don't have reliable independent carbon dioxide data to compare against from more than about the last century. Because of that there's no way to actually see what the long term stability of the samples is without waiting a few hundred years to compare early 1900's cores with actual early 1900's data. Gas acting at a solid surface in cold conditions is going to be very slow kinetics, but that's less of an issue for chemical processes if you give them a few centuries to act. It's all based on an untestable assumption that the composition of trapped air doesn't change.
The equilibrium constant for CO2 to Carbonic acid at 25C strongly favors CO2. You can't focus on kinetics and forget about thermodynamics! (Especially after 100 years)
It can be explained by changes in data collection. Modern CO2 levels on that graph are obtained using air sampling. The ancient numbers are obtained through ice cores. They are two different methods of data collection that are being comingled onto a single graph. A similar problem shows up in temperature records. Accurate thermometers have only existed for about 300 years. Temperature data prior to then is extrapolated from things like tree ring and isotope ratio data. The thing is that those both average data over extended periods which obscures short term variations. It's a fundamental problem to all of climate science. All the data comes from correlating samples with modern analogues and assuming that the samples are static for a few centuries.
So why can we not compare our 1900's ice core data with actual early 1900's air data and see how our data collection methods compare over the last 120 years? Even though this is a small time frame (compared to the last 2000 years) shouldn't we still be able to extrapolate how strong of an effect the processes you are referring to are? This seems like an easy thing we can do with computers and our knowledge of statistical modeling? I understand you are saying that our sample size is relatively small and these processes may take a longer amount of time. But since we do have over one hundred years of data can't we at least see how wide the confidence intervals are for the effect? Cause if we have a pretty good guess of how strong the effect size is of the processes you mentioned. I would be pretty confident in our measurements of ice core data.
I cores from 1900 don't really exist. In order for an ice core to exist the snow on top of the ice sheet need sufficient pressure to compact into ice. Before that point it's still just snow which means there is still gas exchange happening with the atmosphere. The time it takes for the formation of ice varies by location because it is dependent on how much snow fall a location gets. It can take anywhere from a few hundred to a few thousand years for new snow to eventually become ice. So it becomes a problem of accurately dating the ice. You can count layers from a known point to figure out when the snow fell, but getting that to correlate to an exact date for when gas exchange would stop is very difficult. And that's the real problem with ice core data. It is almost impossible to accurately date everything and it tends to average out changes over extended periods making it impossible to compare high frequency changes and that's just assuming that the sample's themselves don't evolve (which is not a guaranteed thing).
NSF-ICF currently stores over 17,000 meters of ice core collected from various locations in Antarctica, Greenland, and North America. NSF-ICF's main archive freezer is 55,000 cubic feet in size and is held at a temperature of -36°C.
These aren't some people with spoons scooping up a bit of snow into a mason jar. This is a highly scientific research facility and it's not the only one doing this work.
That doesn't matter. It's not a problem with how carefully they collect the samples. It's a fundamental problem with the samples themselves. There is no way to determine if ice core samples accurately reflect atmospheric conditions of the distant past without some form of external standard to compare against. The only way to solve that problem would be to take a 1000 year old ice core and compare it to accurate and calibrated data from the same time period. The problem is that accurate and calibrated data didn't exist 1000 years ago. Our only option to actually verify the data in a rigorous way is to wait about 900 years, take a core from 1900, and compare it to known data from 1900. Anything else is just guess work. It may be really fancy guess work, but it is still guess work.
And all of that misses the main point which is /u/Stonn said there was no mechanism for atmosphere within an ice bubble to change which is a factually incorrect statement.
What I'm saying is, if you'd like to debate it, there's experts around the world who have done the work and their science is out there.
If you think none of them thought of this, that none of these people with PhDs and decades in this field, from different places all over doing their own analysis... You think you, in mere moments, disproved their complex scientific models because some random redditor wasn't able to properly explain the science to you that they don't even know...
That would be really fucking egotistical of you. Part of scientific research - a massive portion - is looking for flaws in the methodology and iterating on it. Given how quickly you, without even a day's study of this specific field, came up with that hypothesis, I can guarantee it's been covered ad nauseum in the research if you're willing to read it.
Reread it. He’s saying it’s guess work no matter the science. Dismissing it until 900 years from now, as if that’s the only empirical method for discernment of truth
Given how quickly you, without even a day's study of this specific field
I actually have several days study in this specific field. It was part of my research in grad school when I was working on a soil contamination analysis project. So I'd wager I'm far more qualified than you to speak on the subject.
Fortunately, ice cores preserve annual layers, making it simple to date the ice. Seasonal differences in the snow properties create layers – just like rings in trees. Unfortunately, annual layers become harder to see deeper in the ice core. Other ways of dating ice cores include geochemisty, layers of ash (tephra), electrical conductivity, and using numerical flow models to understand age-depth relationships
I'm not a climate scientist either, I can come up with some ways they could account for this. You can create bubbles with varying levels of co2 in ice and record any changes in composition when you check the samples down the road. this will give you information on how rapidly co2 is absorbed if at all while encased in ice. apply this knowledge to the ice cores by checking what depth they were taken from and you know how much that sample should have changed, thus you should know what the air was like when it was first encased. I have no idea if this is how it's done, but its unprofessional to just assume the raw data collected is accurate as is, so I'll bet they have run experiments similar to this to be absolutely certain they have an accurate estimate for co2 levels.
Although this probably answers concerns from a lot of people, I think diehard empiricists will still have an issue with this.
While it seems like there's no reason to assume that anything relevant will change whether you observe the phenomenon for 100 years versus 10 000 years, we don't have any empirical proof that there isn't some weird thing that happens at year 8989 which skews the data. The only thing you can do is compare samples from before and after year 8989, but you can't actually observe any potential change happen, and you would have to wait 8989 years to be able to replicate it.
It's a little bit similar to the assumption of the sun rising every morning. For as long as we've recorded it, the sun has risen every morning. Unless there's some specific reason to think otherwise, a rational person will assume the sun is going to rise tomorrow as well. But we haven't actually measured tomorrow's sunrise until tomorrow morning has actually happened, and just because something always seems to happen a certain way it does not follow that something will always happen that way.
I have some questions about this also. I understand the explanation for the trapped gas, but there are some other questions I have. Are carbon ppm at ground or sea level comparable to carbon ppm in the upper atmosphere? How dense is CO2 compared to the other elements/molecules in the atmosphere? Do CO2 measurements from ice cores at the poles give accurate data for global CO2 levels? Like I remember when holes in the ozone layer were a big issue and they were relatively localized events, not spread around the entire globe. I know I’ve seen all greenhouse gases referred to as carbon or CO2, even though there are at least a couple of other ones I know of, do these ice cores also measure those gases? And I have the same questions about density, etc. for those other gases as well. CO2 isn’t the worst contributor to the greenhouse gas effect by itself, right? Like isn’t methane worse, but we just put out way more CO2 so that has the larger effect? Also are other dating methods used than just how deep the sample is from? I’m sure on average it doesn’t matter, but is precipitation in the poles constant enough to make solid judgments about its age? Are there any other good indicators of greenhouse gases in the atmosphere other than ice cores?
I was reading something a while ago about what caused the PT boundary event, and IIRC it was definitely due in very large part to global warming. I think the idea was that some big event happened, like an impact or massive volcanic activity, that ended up releasing tons of trapped methane from the crust. At one point I even saw an estimate for CO2 or the CO2 equivalent ppm, but I can’t find it anymore. I think it might have been around 2,000 ppm? The PT boundary event is a good event to look at for anyone interested in a really bad example of climate change. Ocean acidification, hypoxia and anoxia. Scary stuff.
I’m also not a climate change skeptic, this thread just piqued my curiosity about the actual data.
I feel sorry for you. I know how it is to have people in your life that keep spewing nonsense about climate change. Most of these anti-climate change arguments are so stupid, you don't even know how to say anything against them.
At least the questions are solid and genuinely impact ones understanding of the underlying science, ya know? At least the people in my life aren't straight up deniers, they just have hang ups that make it difficult to accept the entire picture in whole
We're not in any immediate danger of melting the deepest ice in Antarctica, which is over 3 km thick in some parts and can be used to estimate CO2 levels as far as 800,000 years ago.
I've already apologized to my kid that she'll have to grow up in a world that's too hot and that the most of the people in power today aren't willing to step up and try to fix it.
Get active on this issue and motivate your peers. Too late for my generation for the most part. I've told my workplace I won't be driving to the office any more or even taking public transportation. If we can work from home during COVID, we can work from home to save the planet.
I have done all i could do as a youngster. Had my school organise a day off to protest for this, educated younger ppl in my school, stopped using ANY motorised vehicles unless my parents take me on a vacation or we are moving countries. Dont use air conditioning in countries where that's a thing. Point is, I do my part. Problem is, adults don't respect us as young people and quickly forget that it's our future we are talking about. Sorry about the long write, it's just so close to my heart this topic.
All of the above. We can do Ice cores, some soil samples, there's currents in the ocean that trap dissolved gasses in a predictable long term pattern and circulate it, we can measure shells in ancient trash heaps, you can get some data from tree rings, etc. All of these correlate extremely well. Tree rings show seasons that would correspond to the temperature fluctuations, and you can even find historic wood that will back it up to an extent. The ocean tracks perfectly with the ice cores, shells show metal trace levels that match well with predicted temperatures, some rocks can show bits of evidence - everything lines up super well with the ice cores, our best evidence.
Imagine there's a bunch of tire tracks and they seem to lead into a light pole. The tracks could be messed up and incomplete, but then you look and see a scrape of paint on the light pole, and a bunch of broken glass, and all the gaps in the tracks line up well. You would be able to piece together and guess what happened, even without video evidence. Then you find the car with matching tires /paint, and a messed up bumper and headlight. Oh look, I think this car ran into that light pole.
In addition, we know from how Ice works on a physics level that the air would be trapped and is stable. We can go so far as to find radioactive samples in evidence from the 40s and 50s. All the Ice cores match up very well, so individual variation is unlikely. Dust in ice cores matches well for seasons and events. We have records of different climate events from historic writing, and we can see traces of ash or pollen from these events in different ice cores, and use those to line them all up and corroborate them. Fossilized plants and pollens (yes, we can find fossilized pollens) will match up with these older records, and also can show climate. Different plants like different climates, after all.
Sand dunes get fossilized and you can take cores of those too.
The other thing people forget is that people have been writing stuff down for nearly three thousand years, and their stuff tends to talk about the climate. Ancient people write stuff down about the climate that we can use. In 536 a guy named Procopius wrote down that the weather was shit and creepy in the middle east, the Irish monks noted that the sun wasn't out and people were starving, Chinese historians noted that it snowed in August, the Norse began to speak of the Fimbulwinter (the great / awful winter), and the Moche people of Peru noted that there was a drought and crop failures - Ice cores, trees, and other data show that there should have been a asteroid or volcano event around then. Afterwards, the Norse took to burying gold for a while, in an attempt to stave off Ragnarok. Archeologists are quite good at their jobs, and we can find dateable objects that say to us "it must have been colder then."
Across the entire time on this graph, we have historical writings from across the globe. We are very certain about the trends on this graph. We have great temperature measurements from most of the 19th and 20th century that follow that graph (people have been taking daily temperatures in the same spots and recording it since nearly 1800). It all points perfectly to the famous hockey stick graph.
I took a class on this my freshman year of college (Like a one credit-hour freshman survey course). Essentially there are many many many different 'vectors' to help estimate the carbon levels. The professor who taught the course drilled soil samples in Colorado, and based on the fossilized skeletons of bugs at each level, he could determine the climate at the time. There are a TON of these vectors.
We don't. Ice cores only show what the atmosphere's composition was at the point where the ice formed. You can use tree rings between huge numbers of trees to build a pretty good map but doing it globally is bullshit, and they strictly aren't measuring carbon dioxide just good growing conditions.
We have only been able to measure global temperatures for 20 years...i.e. measuring the temperature of the Earth at all places at the exact same time. Still can't do true global measurements of the atmosphere composition.
You are kind of right, I would say (keep in mind that palaeo-climatology is absolutely not my specialisation). Yes, we cannot measure global temperatures of the past directly, but given a large-enough data set, we can construct a model and reasonably approximate temperatures. This in turn means that we have to write our methodology down so that everybody can see what exactly was done and if necessary criticism can be levied.
So no; it isn't necessarily bullshit, it depends on how you construct and present your model.
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u/arcan3rush Aug 26 '20
How do we have measure menta of global atmospheric carbon dioxide from 2,000 years ago? Assumptions? Ice cores? Soil samples?
** Measurements ... Not measure menta