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Temperature chart for the last 11,000 years (kottke.org)
220 points by deusclovis on Sept 21, 2013 | hide | past | web | favorite | 173 comments

For a little while I was interested in paleoclimatology and I started studying how researchers developed these historical temperature reconstruction curves. Basically you take “proxies” for temperature, things like tree rings, coral growth, sediment layer thickness, etc. and you posit a relationship between the proxy measurements and temperature. Measurements that better fit the hypothesized model get more weight in the temperature reconstruction.

The main problem is that no one knows if the hypothesized models (temperature vs. tree ring thickness, sediment layer thickness, etc.) have any validity. Why should tree rings grow linearly with temperature- what about a huge number of other variables? The temperature “signal” is at best very weak. Decoupling the temperature signal from other variables (humidity, elevation, tree species, CO2 concentration, etc.) is a hugely difficult multivariate statistics problem and most of the researchers I've corresponded with do not seem to appreciate this fact.

Another major problem is that proxies get weighted in the temperature reconstruction based on how well they fit the hypothesized temperature model. The weighting is where things get really shaky. Right away, you have biased your results in such a way that that nonconforming data is discarded / de-weighted. Note that there is not anything wrong with these nonconforming samples that invalidates them; they just don't fit the proposed models very well. Typically researchers develop their own methods for weighting samples in the temperature reconstructions and many of these methods would make a statistician cringe. Often during the weighting phase you find that a handful of proxy samples (out of a sample size of hundreds) get the vast majority of the weight in the temperature reconstructions. Sometimes the weight of a temperature reconstruction in a location is almost completely computed from a few proxy samples taken halfway around the world at a completely different elevation.

If you try to discuss these fundamental problems with climate scientists you'll typically get told that you're not a scientist (not true) or that you're a "denialist" being paid by big oil (not true). I am convinced that these temperature reconstructions are useless at best.

It's definitely not the case that climate scientists are uninterested in discussing methodological problems with paleoclimate proxies. A considerable amount of the literature is taken up with doing precisely that, and it takes up a good portion of the Paleoclimatology section of the IPCC report: http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-cha...

I know that some folks in paleoclimatology are interested in these core methodology problems. But these concerns are not conveyed to a wider audience. When a temperature reconstruction graph is released to the public there is no mention at all of these problems and one can easily get the impression that these reconstructed temperatures can be known almost as accurately as going outside and taking a reading from a thermometer.

Can the public understand that?

Excluding math, we use proxies for just about all science. With different assumptions and different criteria. I don't deny that there are politics, assumptions and margins of error but they do put effort in to minimizing them and doing real science. Take a look at pharmaceuticals, they don't even know why a lot of medicine works, in fact there is debate on if it even does... But people still buy it and take it.

The public can't understand that, but it certainly forms opinions based on it. It votes, too...

The public is, honestly, incapable of understanding, or even caring, about underlying issues in proxy temperature modeling. A large amount of the public is incapable of distinguishing between weather and climate.

Proxy temperatures, statistical methods, atmospheric modeling, etc, are all scientific areas whose knowledge can be gleamed at sufficiently well for a person with some form of higher education in science or math education (but only barely; remember that this stuff is being researched by people who have devoted their entire lives to the scientific specialty). But that is an astoundingly low proportion of the population. And even then it is clear that, as methodological errors have diminished and methods for more accurate models have appeared, that they all tend towards the same conclusion.

We should be worrying significantly more about the small but non-trivial (and ever-increasing) probability of an extinction event within the next decades rather than pretend that methodological errors, at this point, are a significant issue in identifying the climate trends we have spotted in the last decades.

You know, nearly everything is a "proxy". Kitchen thermometers use bending metal as a "proxy" for temperature. All that matters is accuracy and precision. This is how science works, at its base. There's no such thing as "sense data".

True, the signals from tree rings (etc.) are noisier than those from kitchen thermometers. Let's consider, for a moment, how you could verify the precision and come to a conclusion as to the accuracy of those signals: well, when you get the same information coming from multiple seemingly independent sources, it greatly increases your confidence in that information. Hence, if you're doing your modeling right, if you get tree ring data from all over the world, and soil samples from all over the world, and find that, sure enough, there is a common signal visible across all of them, then you say "well, the only thing that can explain this global correlation is the modulation of some global parameters". And you present your data and conclusions to a bunch of people whose job it is to poke holes in it and prove you wrong, and after a bunch of time eventually people whose job it is to prove each other wrong end up roughly agreeing on a small sliver of information that lies at the intersection of all their understandings of the world.

Signals in physics can be noisy too (fortunately, in physics you can take millions of samples). But to say "well, these error bars are too big, so therefore we shouldn't pay any attention to the trend at all -- we can decide to do something when we have much higher confidence in the precise figures. In the meantime, I'm going to oppose tighter fuel economy standards for vehicles, and revenue-neutral carbon taxation, and aggressive subsidization of alternative energy R+D, ... " because god forbid we should all drive around in smaller cars, or that we should stop subsidizing air travel, or that we should too quickly improve solar cell efficiency.

Okay. What do you say of purely geological phenomena, like glacier coverage. You can look at hydrostatic rebound, erosion patterns, etc to see where glaciers usually are. And you just have to look at pictures within the last 50 years to see where they're not. Much harder data. Same for ecological ones like flora and fauna existing in and being habituated in environments that are no longer very compatible climatologically. And for anyone in their forties or older, there's always your own damn lying eyes.

There's a billion pieces of supporting evidences for global warming. As far as I have ever heard, there's not a single piece of evidence against it, just piles and piles of FUD thrown at each model that tries to explain it.

Noone is arguing that there WAS a warming trend. The onous to prove its due to humans lies on the chicken littles. It has not yet been accomplished.

Actually, the parent was arguing that we can't trust the one figure that is in TFA. It's a picture of a warming trend.

Surprisingly enough, the fear, uncertainty, and doubt about anthropogenic warming claims have come from people who receive money from carbon-intensive industry groups. It's these people who keep on claiming that it "hasn't been accomplished". And since FUD is easy to do, the FUD-purveyors are winning in the public sphere.

What kind of evidence would convince you, exactly?

No one needs to prove it's due to humans; it doesn't matter what it's due to, it only matters that it's bad for us and we can do something about it. Natural is not equal to good, claiming it matters if humans caused it is as stupid as refusing to stop an asteroid from hitting us because it's not a man made disaster.

Heh. I've been using the same asteroid example for years.

Actually, everyone but you acknowledges the warming trend, even groups that oppose AGW theories. The fashion du jour is to blame it on volcanoes or solar output cycles. Catch up!

How accurately can we track CO2 concentration over long timespans? I get that climate science is hard and produces nebulous answers based on arguably nebulous data, but when I read about about ocean acidification and see the long-term graphs from respected organizations [1] as a layman it's really quite alarming.

I.e. maybe the climate won't spiral out of control, but it seems reasonable to be concerned about the alarming levels of CO2. As a new parent I'd love to have my dire fears of catastrophe awaiting future generations assuaged by rational hard science, but (as a layman) everywhere you look the picture is pretty bleak.

1: http://www.esrl.noaa.gov/gmd/ccgg/trends/history.html

AFAIK one of the main ways to reconstruct CO2 concentration is to study samples of air trapped inside old ice. This looks like a pretty direct and reliable method to me.

I worked in a dendrochronology/dendroclimatology lab[1] for several years and can assure you that the researchers involved are well aware of the issue of multiple influences on tree ring growth. There are a couple of ways that they go about dealing with it. NB I was more involved in precipitation reconstructions than temperature reconstructions, but I know enough about the process to discuss it here.

The first is experimental design, much like is necessary in any aspect of science: Annual tree growth is definitely a response to a variety of regional, site-specific, and tree-specific factors for any given species in a location. So in order to increase the 'signal to noise' ratio for a given signal (temperature, precip, fire, disease or whatever reconstructions), you look for combinations of species and sites for which the factor you want to study is the limiting growth factor; in other words, other things the tree needs to grow are present in abundance and one is in shortage. If you want to make a precipitation reconstruction, you find a site that has very little soil moisture storage, such as trees basically growing out of fractures in steep bedrock. If you want to study temperature, you pick species like Bristlecone Pine that grow at high elevations (which are typically relatively wet), so that the temperature/length of growing season is the annual limiting growth factor. That sort of thing.

The second is that researchers use many other forms of measurements than simply ring width to tease these problems out. For example, many people use oxygen isotopic ratios[2], latewood (the dark outer part of the tree ring) density measurements[3], and other measurements in tree rings, both because of the unique and accessible response of the tree, and because (unlike, say, sediment cores) the tree rings are much more quickly, accurately and reliably dated at the single-year precision.

Third, there is a lot of statistical analysis thrown at the problem. I didn't work a lot with this, or see people in my lab do it, but I am aware of researchers doing multivariate statistics techniques such as principal component analysis[4]. I'm sure there is a lot more, but you can do a Scholar search as easily as I can.

Fourth, one of the strengths of the multiproxy technique is that many of them are independent, and they all show a lot of correlation to the temperature records during the instrumental calibration period. There is some divergence before this period, but not as much as would be expected otherwise. There is also the problem of weighting, like you mention, and I don't think anyone is comfortable with it but I don't think it's as ad-hoc as you make it out to be. A review (by a statistician) that discusses this is here[5]; I didn't read it in depth.

[1] http://www.uark.edu/misc/dendro/

[2] http://link.springer.com/article/10.1007/s00382-013-1674-3

[3] http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-11-00139....

[4] http://onlinelibrary.wiley.com/doi/10.1111/j.1600-0706.2010.... [5] http://www.stat.unc.edu/postscript/rs/Sensitivities-Submitte...

Some more discussion of the problem here: http://www.skepticalscience.com/Tree-ring-proxies-divergence...


The Science paper: http://www.usu.edu/geo/physical/MarcottEtal_Science_2013.pdf

Online supplemental material: http://www.sciencemag.org/content/suppl/2013/03/07/339.6124....

The figure itself is a new plot by Potsdam University researchers for realclimate.org, though, using the same dataset, but not a graphic taken directly from the paper (the paper's Fig. 1 has some alternate versions).

I think this stinks. The Science paper says their reconstruction is smoothed and has low time resolution. They say it preserves no variability at all on timescales <300 years, and attenuates even 1,000 year variations. Superimposing this with the 30-year Hadley data seems misleading, because it is on a very short timescale which is suppressed from the paleologic data.


"Because the relatively low resolution and time uncertainty of our data sets should generally suppress higher-frequency temperature variability, an important question is whether the Holocene stack adequately represents centennial- or millennial scale variability. [...] The results suggest that at longer periods, more variability is preserved, with essentially no variability preserved at periods shorter than 300 years, ~50% preserved at 1000-year periods, and nearly all of the variability preserved for periods longer than 2000 years (figs. S17 and S18)."

The realclimate.org post discusses that as a potential issue, yes. See the section following the sentence: Because the proxy data have only a coarse time resolution – would they have shown it if there had been a similarly rapid warming earlier in the Holocene?

I read this as "no, it wouldn't show up".

"Had there been such a global warming before, it would very likely have registered clearly in some of these data series, even if it didn’t show up in the averaged Marcott curve."

I'm not arguing their conclusions. I'm criticizing the way they present this data. This composite reconstruction is so weak, that if you shifted 20th century AGW back 5,000 years, it would completely erase it. That's how powerful the smoothing is.

I can buy that view, yeah. It presents conclusions that are probably true, but the plot is a bit in the pop-science direction in doing so, in the sense that the plot itself is not really a rigorous way of establishing those conclusions. The paper doesn't include this kind of plot, probably for those reasons.

Throwing my hat into the ring here:

1) I think that we, as the human population, should actively move toward more efficient, less destructive industry on principle, not just because of the threat of climate change. I think making it about climate change gives too many opportunities for argument derailment. Think about when "tree hugger" was a pejorative term; i mean, who DOESN'T want to hug a tree? I think it's a lot harder for people to argue against the idea of "leave a place as you found it" than to find flaws a data set. It also allows for much broader regulation. For example, we could then start focusing on legislation against pharm manufacturers allowing meds to seep into the water supply rather than just the air pollution they're producing.

2) I'm starting to wonder why we're not focusing more on adaptation to than prevention of climate change. I've been watching a lot of TED talks lately (thanks, Netflix!) about the impact of climate change, and the one that I'm thinking of was a researcher who spent time in the arctic studying the wildlife there, and made the case that we should prevent climate change so that we can save arctic wildlife. But I wonder, if we were alive in the age of dinosaurs, would we be saying that we need to clean up the atmosphere to prevent the impact winter that would inevitably kill them? While I love wildlife, I almost feel like it's not our responsibility as humans to tamper with natural processes like extinction. In our prevention efforts, we may also be preventing natural selection and, by extension, adaptation. It could be a reality that we'll face an extinction event that wipes out all other non-domesticated mammalian life. While we can all agree that an Earth like that would suck, we know that, 600 million years from now, EVERYTHING will be wiped out. People speculate that, at this time, humans themselves will either become extinct or will have migrated off the planet. So, my question is, are we prepared to jump ship if Earth becomes uninhabitable? Is it realistic to try to change all 5,000,000,000,000,000,000 kilograms of atmosphere, or should we starting thinking about building habitats for space living?

While I love wildlife, I almost feel like it's not our responsibility as humans to tamper with natural processes like extinction.

The fundamental premise is not that extinction is bad, but that extinction we cause is bad. If a fox tramples your neighbor's garden, that's too bad. If you trample your neighbor's garden, you should fix it.

Loss of diversity is bad. Everything else is all right, as long as in the long term there is no loss of diversity.

The trouble is, that at the current state of science and technology we can not engineer and control ecosystems. We can not even model ecosystems. As a result we are breaking things and we even have no idea how badly we are breaking things when we are extracting resources. Like when we are turning diverse ecologies into monocultures, when forests are being turned into these 'beautiful' fields of golden wheat.

It does NOT have to be that way. There is no natural law that says that it is necessary to destroy diversity if one wants to grow food or extract resources. It is just that our technology is very primitive and that's the only way we've been able to do it so far. With right technology one can have it both ways. But we don't have it. Not yet.

And meanwhile, well. Conservation, common sense and minimizing our damage to the ecology is probably a best that we can do...

Humans are either fully part of the natural process, or everything we do interferes with it.

There's a very real choice about how we want to change the environment of the earth, but lets not couch it in meaningless terms like natural vs. unnatural.

Hunter gatherer societies are no more natural/unnatural than cities.

In literal terms, humans are "natural" actors. When we have an effect on nature, it is a "natural" process. I don't disagree with that. But just because what we do is "natural", doesn't mean it is "good". "Good" and "natural" are not the same.

As for the line between human actors vs. non-human actors... when it comes to players in the ecosystem, humans are simply overpowered. That is the root of the problem. Nature has struck a balance in most places, and the ecosystem shifts slowly because everything is close to balance. This gives the other players in the system time to react. Humans are very, very good at destroying balance, so we often warrant special consideration.

Think about your history. The only other actors that brought about the destruction of habitats, ecosystems, and species in as short a time and as great of numbers as humans are natural disasters.

> Humans are either fully part of the natural process, or everything we do interferes with it.

Thank you for describing what I was trying to say much more elegantly. :)

I used to agree completely with you, but now I realize that, given the second law of thermodynamics, it's impossible to restore an entire ecosystem back to a previous state. From what I hear, one goal of ending climate change is to allow icecaps to re-form and to last longer throughout the year, which ostensibly will end the suffering of polar bears "stranded" at sea. However, even if we did remove all excess amounts of greenhouse gases from the atmosphere (which, as of today, is something that's barely discussed seriously), it's not going to suddenly reverse the adapted behavior of polar bears. This is a totally hypothetical and unscientific story, but let's pretend that the ice caps melted such that polar bears were forced inland and began foraging for food in human-populated areas. In response, the government of Canada single-handedly puts up the money to remove all excess greenhouse gases from the atmosphere. Over a period of decades, the ice grows back, but: do we really expect the polar bear population, which has now adapted to foraging for garbage, to suddenly move back to their initial habitat? Chances are, food will be more plentiful for them in a human-populated area. Now let's assume that polar bears play a significant role in seal population control. Well, now that the polar bears have adapted and are now living further inland, the seal population booms in the arctic region. In fact, it gets so big, that now penguin populations are in rapid decline! So, at this point, we've spent probably trillions of dollars, haven't really helped the polar bears at all, and have directly contributed to the endangerment of penguins. And this is all assuming that our plan even works! Not to mention the fact that there may be other species that died off that played a huge impact on balancing the ice-filled arctic ecosystem.

So, given that scenario, I think the better question to ask is, what benefit would we, as humans, get from a return to a cooler Earth? IMO wildlife will take care of itself: adapt, die off, etc. the same way it always has. BUT, I think that too often the focus is put on sad-looking animals and melted snowcaps, which makes it seem like global warming is just an "environmentalist" issue rather than a serious threat to human life.

Oh, come on, are you trying to say that all endangered species will just adapt to live amongst humans if their habitat is destroyed? Your idea about polar bears foraging for human garbage is laughable: These creatures are (1) purely carnivorous, and (2) incapable of living in warm climates. Polar bear population has plummeted as their natural habitat has dwindled. Further, the reason for wanting to save the polar bear is not just to save one species, but that this animal's decline is a bellwether for the decline of the entire arctic ecosystem. We can't say for sure what will happen if the arctic ecosystem disappears.

The ongoing massive extinction event driven by human activity is a real thing. Do you want to live in a world where the only animals alive are ones that humans raise as livestock, or that thrive amongst humans? Nothing but pigs, chickens, pigeons, sparrows, cockroaches, bass and such. Sounds awfully grim to me, but without serious efforts towards preserving wildlife, this is precisely what the future holds.

It is purely a question of having the right technology. There is no law that says that you can not engineer a polar bear that is not purely carnivorous, is capable of living in warm climate and very useful to humans in some way. Same goes about every other species.

And it is not that sad. Well designed ecologies can be diverse and beautiful. Even more diverse and beautiful than naturally evolved once.

[citation needed]

Well, I can't source precisely that phrasing. But imagine an engineered ecology that is: less cruel than a naturally evolved one; as diverse; also includes some 'dinosaur-killer-sized' asteroid impact aversion system that prevents global scale mass extinctions. Wouldn't you find that ecology more beautiful than a naturally evolved one (that we have now)?

Given humanity's track record, my imagined idea of an engineered ecology is not so rosy as yours. Who would do it, and what would their motivations be?

> Well, now that the polar bears have adapted and are now living further inland, the seal population booms in the arctic region. In fact, it gets so big, that now penguin populations are in rapid decline

No penguins in the Arctic, no polar bears in the Antarctic; they have little-to-no bearing on each others population (even indirectly via seal populations). You could've chosen a better example.

This mistake caused me to laugh outright. It illustrates the lack of actual information or expertise within the parent comment.

You are misapplying the second law of thermodynamics and calling it wisdom. The second law specifically applies to a closed system. Earth is not a closed system. There is no fundamental reason local entropy cannot be maintained.

You're mistaken; the Earth is a closed system in the case I describe.

The Earth is not a closed system.

I'd like mosquitoes to go extinct. Why would that be bad?

This is where we delve into questions of whether we can understand the impact of our actions. Mosquitoes actually underpin a great number of relationships in nature. Most people have largely cast aside the question of whether it is ethical because of how much harm mosquitoes cause to humans, but there remains that sticky question of what happens to the ecosystems when they are gone.

Also, before someone posts a link to "that" article, let me say in advance it was written by an intern based on interviews that (in my opinion) suggest exactly the opposite of what the writer concludes.

It would be very bad. Birds and small fish hugely depend on mosquitoes for their diets.

Ticks are another matter. While birds will eat them, no species that I know of depends on them for its diet. We probably can safely eradicate ticks.

Mosquitoes help pollinate blueberries. Without blueberries we have nothing to anti the oxidants.

We have unfortunately already occupied much of our neighbor's garden, should we destroy our farms and cities and return all these land to animals?

While I love wildlife, I almost feel like it's not our responsibility

Two points:

1. The conditions on Earth which support other megafauna also, largely, are beneficial to humans. Change those conditions and it's likely that the extinctions aren't so much bad for humans as indicators of changing conditions which are bad for humans.

2. Conservation biologists have recognized that the Earth and its biosphere isn't a static system, and that conservation efforts shouldn't be aimed at "holding back the tides" so to speak. But noting when changes are happening at scales which are likely to have strongly negative impacts for humans, civilization, and the almighty economy, and deciding to take preemptive action, could be a very good thing.

There's a huge difference between wiping out all life (or much of it) within the next 200 years, and the next 800 million.

Assuming you've got an 85 year lifespan, that's the difference between living for your full life, or just 25 minutes.

My own definition of "sustainability" is "so long as the extrinsic conditions are conducive to human survival". Even with genetic drift, that's likely a few millions to tens of millions of years.

> why we're not focusing more on adaptation to than prevention of climate change

The reality is that prevention is cheaper (there is also an issue of distribution of the cost, though). Prevention of climate change effectively means not using energy from fossil fuels, while adaptation means paying extra energy cost for each unit of energy you get from fossil fuels.

This extra cost is actually greater than extra cost that would be incurred if you used non-fossil fuel source. So if you decide to continue to use fossil fuel sources at all, the total cost (savings due to cheap fuel + mitigation costs) will always be higher than the non-fossil energy sources (higher cost to get the energy but savings on mitigation).

There are enough gigatons of carbon (oil, coal, methanhydrates) available and ready to burn to render this planet uninhabitable in a time frame of centuries. That's nothing someone can adapt to. We can adapt to +2°C, likely to +4°C and perhaps even to +6°C, but there has to be an upper limit, otherwise you simply keep adapting until you run out of money.

Why is it so hard to imagine changing our lifestyle might be the easiest thing to do?

The tropics right now are cool enough to live in, right? I have hard time believing even +50°C would render the planet uninhabitable.

At a wet-bulb temperature of 95F (35C), thermal stress is lethal to humans in a few hours in most cases.

While air temperatures routinely exceed 95F (which is already hot), that's generally at much lower humidities. A wet-bulb 95F means that relative humdity is 100%, and the body effectively cannot cool itself.

You're also going to have trouble cooling yourself from your surroundings, as everything will be that warm -- water, ground, etc. http://www.tgdaily.com/sustainability-features/49635-future-...

Even swimmers have been known (or suspected) to succumb to thermal stress when swimming through warm waters. The international body governing open-water competitions has set an upper bound for competitions of 31C (87.8F): http://www.swimmingworldmagazine.com/lane9/news/Commentary/3...

Most swimming pools are heated to between 78 and 82F. The difference between the lower and upper ends of that range are pronounced: slightly cool to slightly warm if you're not very active. Many swimmers will find anything over 80F unpleasantly warm, and may prefer cooler temperatures, though lower than about 72F generally feels chilly regardless.

There are a lot of other problems with release of carbon on a massive scale, starting with gross acidification of the oceans and a significant reduction of oxygen in the atmosphere.

A +50 change means the hottest regions, that already reach up to 50 degrees, would hit boiling point for extended periods of the year. Some if those are by the sea, which would continuously boil, filling the atmosphere with steam and cause a new greenhouse effect boost and a wave of heating that would push temperatures even higher.

The problem is there are certain thresholds that cause new greenhouse effects to kick in and push temperatures even higher. For example, if temperatures rise enough to melt the Methane frost layers, they'll melt and probably kick global temperatures up another 5 or 6 degrees all by themselves. If we trigger enough of these knock on effects in a chain, well end up with an unlivable atmosphere. That's the extreme scenario, but it is not impossible.

An atmosphere filled with clouds would cause more greenhouse than the amount of sun it reflects away? Do you have a source on that?

You're right Bill Gates and Warren Buffet will survive.

How about the entirety of Russia? I don't see why it takes being rich to live in a formerly-cold now-hot area.

And even people in poverty can migrate. I really don't understand your point.

Look, it is not like adding 6°C on all temperatures and that's it. Weather is getting extreme and the environment changes then. There is a book called 6 degrees by Mark Lynas. It is a good read. He spend some time in the archives and collected what might change by comparing to past times. Rainforests will probably die or at least move, sea level will raise by ~70 meters.

On top millions or billions of people start moving around because their homes and their jobs no longer exist. Food will get a problem because the oceans go acid. Did you ever chose jellyfish as a diet? Social friction will increase. After Sandy NY run short on gas supply, remember the guarded gas stations? The western economy relies on weather behaving within a reasonable range, imagine cities without food, because the just in time transport system stucks in 2m snow for weeks. I can continue the list even more, but the point is basically everything will change: culture, economy, cities, agriculture, food, friends, borders, countries, and so on.

The last thing I can imagine is 7 billion people moving orderly to Russia or Canada to begin a new live in peace.

Many areas already deal with extreme temperature variance, the only change will be which areas need to do so.

And exactly how fast do you think the overall temperature is going to change? All the predictions I've seen have been single digit degrees per century.

he only change will be which areas

That's not even wrong.

What's changing is the total energy within the biosphere. That's going to have profound effects throughout the ecosystem. Modeling just what those will be is very difficult.

One trend that's already emerged has been an increasing variability and range to the jet stream, especially in how it increasingly "wanders" north to south. This means that regions might see very rapid and wide temperature swings from summer to winter or back over the course of a few hours to a day. For crops and ecosystems which rely on more predictable and stable conditions, this could prove deadly.

Glacial melting and rising seawaters don't just mean floods, but salt-water intrusion, disturbances of ocean current systems (themselves responsible for transporting vast quantities of heat around the globe, etc.

Some breakdowns in systems seem to have been very rapid. During and toward the end of the last glaciation period, vast ice dams and lakes would form, some over what's now Utah (historic Lake Bonneville, of which the Great Salt Lake is among the last remnants), as well as in eastern Canada. The formation and bursting of ice dams in the pacific northwest lead to the formation of what are now known as the Washington Badlands by way of the Missoula Floods -- as many as 25 major inundation events which created waterfalls, gravel banks, sandbars, and other features, over what's now dry land. Flow speeds exceeded 80 MPH and consisted of cubic _miles_ of water. https://en.wikipedia.org/wiki/Missoula_Floods

In what's now Eastern Canada, bursting of an ice dam shut is thought to have shut down the Gulf Stream at least once, in a period of one year or less: http://news.nationalgeographic.com/news/2009/09/090914-north...

Both circumstances involved warming, though from lower temperatures than today's baseline. The point is that secondary and tertiary climate change effects can be difficult to predict, but also exhibit very great nonlinearity. That is: we don't know what might happen, and it could happen very quickly, even in hours, or days. Certainly massive changes in less than a year's time are possible.

+50°C ? The areas of Earth where today the temperature never grows beyond, say, -10°C (40°C sounds like close to an upper limit, to me) are quite small.

But most importantly... +50°C is survivable ? OK. Then when the temperature reaches +75°C, what do we do ? +100°C ?

I'm surprised at how many people seem to think we can simply patch problems from day to day and only do anything short term. It seems extraordinarily short-sighted to me.

Building dikes? Sure, building dams for sealevel three meters higher sounds reasonable, right? Oh well, that's what the Netherlands already have? Let's just build a new six-meter dam then, where's the problem? Well, six meters might be doable, but what do we do when 12 meters are needed? 50? 100?

Fair points in general on short-term solutions, but citation seriously needed on where you get 12 meters higher sea levels and 100 degrees C from.

In fact those two would essentially climax hilariously, because at 100 degrees the sea will be in the atmosphere, thousands of metres high.

I got them in the same place the GP got their 50°C from, I presume - my ass.

The point is: there is no predictable upper limit, period.

I wasn't trying to give a real number, I was saying that 'too hot, planetwide' is rather unrealistic. The initial ass-number was '6', why does your argument rely on numbers an order of magnitude larger?

Because there is no predictable upper limit, and any quick fix is at immediate risk of not being enough shortly later.

I think it's perfectly reasonable to postpone worrying about 50+ degrees until it's already shifted at least 5. If it turns out 5 is terrible, we'll have hundreds of years to implement plans to stop 50.

If you think 5 degrees is catastrophic, then sure worry about that in 2013. But it won't make the planet uninhabitable.

The icy tundra areas mostly don't have good soil. Even if they get the temperatures of the American midwest they will not produce nearly the same calories/year/acre. So even if populations could all start migrating north (without somehow triggering world-spanning conflicts as millions of people get forced across national borders) their food source won't be coming with them.

How on earth is this ludicrous wall of text the top comment? "We should look into moving into outer space once we've destroyed the planet" -- are you for real?

I'm with you on #2. One way to look at this chart is that if we 'correct' all of our input into the system then the system will revert to its previous norm, i.e. we'll plunge into an ice age and glaciers will begin to move south over North America and Europe. On the other hand our ability to 'fine tune' our control is all but impossible on these large scales so "control" of the climate is still beyond our reach.

So perhaps investing in keeping old people alive during hot and cold snaps might be a good investment and infrastructure that is impervious to same.

A couple points:

1) CO2 concentration has a long half-life in the atmosphere, so even if we immediately stopped emitting every molecule of fossil fuel-derived CO2 into it, we'd still see the effects of what we've done for the past century for at least another couple centuries.

2) People mostly hope to lower the rate at which our CO2 emissions rate increases, and maybe in certain countries make it negative. Both of those, however, are derivatives of the relevant value for purposes of the greenhouse effect and ocean acidification: the absolute level in the atmosphere. Which has zero chance of decrease even under the most aggressive conceivable prevention efforts.

3) The graph doesn't even cover the last major glaciation event: the last glacial maximum was around 20k years ago.

4) Biggest issue: the people who will be most adversely effected by climate change are people who don't have the resources to adapt. I don't dismiss the idea out of hand that it might be cheaper to put efforts into mitigation than prevention: we're definitely going to have to do some mitigation work. But you are not going to convince Western countries to spend trillions of dollars building levees in Bangladesh.

What's with thanking Netflix for TED talks??? They are available anyway at TED.com anyway or other places, given their Creative Commons license…

I think he's thanking netflix for making them easily available and discoverable to him.

Your #2 reminds me of something Bjorn Lomborg (yeah yeah, I'm not a fan either - nor a hater, in fact, I just don't know enough about the nuances of the issues involved to have an opinion that's well thought out enough to defend) said in an interview on Dutch television years ago.

He said the money spent on implementing Kyoto was much better spent combating the direct effects of global warming, for example by building dikes in areas that were too poor to build them themselves and that were likely to be affected by rising sea levels, like Bangladesh.

To my layman's ears, that sounded quite reasonable.

It still does, in fact.

How do you fairly raise those revenues that'd fund the trillions of dollars worth of mitigation efforts? People who disproportionately generate CO2 emissions are disproportionately responsible for the need for mitigation efforts.

So Lomborg's argument isn't so much against putting a Pigouvian tax on carbon emissions, as it is earmarking the revenues derived from those emissions for mitigation efforts instead of using it to pay down deficits or pay for other services. Which is certainly something I can agree with, but it seems politically implausible. First lets get a carbon tax.

Learned something today. Thanks. Didn't know what a "Pigouvian tax" was.

Somewhat more on topic: in the interview I saw Lomborg didn't talk about earmarking or anything like that, he merely said the money would be better spent elsewhere.

Maybe a carbon tax would indeed be the best way to go about collecting the money, come to think of it. "Want to pollute? Fine. Just pay up for the 'Dikes for Bangladesh' fund first."

I think that we, as the human population, should actively move toward more efficient, less destructive industry on principle

That's definitely a must. But I'm not sure if it's doable, seeing the global population just keeps on growing: as long as industry is destructive and always more of it is needed, the net result still is destructive. Might sound bold, but a lot of problems would be solved by combining clean industry with a _lot_ less people to serve.

Notice how abused land is mostly not privately owned by its abusers.

Clear cutters are given lumber rights temporarily, but since they don't own the lot, they gain nothing from replanting and controlled burning.

Another great asset of private ownership is the inherent drive toward efficiency, which has been great as far as environmental impact reduction goes.

"Thanks, Netflix"? www.ted.com

Temperature chart for the last 425,000 years: http://ctdonath.blogspot.com/2012/02/global-climate-change-i...

Right, lets just "cope" with climate change the same way we did 425,000 years ago. By dying, I guess?

What's wierd is that despite that fact that's you've done your best to make AGW look like a non-issue, the chart for the 100 last years looks extremely worrying.

Fact is there's a 125,000 year cycle. We're at the high of one, due for a long drop. When I bring out this long term data, funny how many people shriek at it - but there it is, and the "warmers" won't produce any graphs covering the same (or longer) periods.

Yes, the data is limited. BUT - I hunted it down, put it together, gave it what I considered fair context, and there it is. Don't like it? counter with your own half-million year graph, not snide religious insults.

It's almost as if the very scientists who collected, analyzed, and are most familiar with the 125,000 year cycle are also the ones who are very worried about the current trends.

The simple point is that CO2 levels are likely higher now than in the last 20 million years[1], and the current rate of temperature change is likely faster now than any time in the last 65 million years [2]. The prehistorical cycles are large, but they are also slow- we're acting on unprecedentedly fast timescales now. How you can be so arrogant is beyond me. Do you think that climatologists, the very people who produced our complete understanding of our Earth's past, are merely unaware of prehistorical cycles? Perhaps they're "ignoring" it? (...while continuing to publish about and do research on them). Do you think you're more clever than scientists, who somehow haven't noticed that there are long term climate cycles in their published results, despite still managing to write extensively about them? It must be a bizarre mindset which leads to your arrogance.

1. http://www.grida.no/publications/other/ipcc_tar/?src=/climat...

2. http://www.sciencemag.org/content/341/6145/486

Arrogant? All I did was graph long term data and present it, observing that people freak when it shows something other than what their doctrine insists.

Sure I expect those scientists are familiar with the timeframe I present. Then why don't they present it? Why no comments on the non-warming of the last decade? If 20M years of CO2 data, then why no graphs showing correlation with temps? (BTW, CO2 lags temp.) How about that massive arctic ice sheet growing now growing well beyond normal reach? And ya gotta admit the frequency of global warming conferences getting snowed out is just funny.

How about "that massive arctic ice sheet growing now growing well beyond normal reach"? What do you mean?

Reports I have seen show that although the ice did not drop to last year's record low (instead regressing towards the mean as you would expect), it was still well below the average for the last 30 years and the trend is towards reduced ice.

Are you suggesting that this year's result means the trend has reversed?


> Arrogant? All I did was graph long term data and present it, observing that people freak when it shows something other than what their doctrine insists.

You're arrogant because you believe that a single graph disproves or even begins to question the work of hundreds of doctoral and post-doctoral theses and thousands of man-years of research by people much smarter and informed than what you may find in this thread.

And while there are certainly many fields of human endavour with questionable analysis, climate science is not one of them.

Tried to check your sources, and for the first could not find anything talking about CO2 levels going back 20 million years, and the second links to a non existent article.

When you say the "warmers won't produce any graphs covering the same periods", I think you are wrong. They do.

Here's an example.


It's really important to consider the well established cycles in climate, not because they are proof that human changes don't exist, but to put our change in context.

Anthropogenic climate change is IMHO indisputably real and startlingly fast in geological terms, BUT it is dwarfed by the natural variations in climate over the long term and may even (if we don't overdo it) have saved us from another ice age in the long term. I'm not sure anyone understands what the climate is doing enough in order to make concrete predictions or to know what the interaction of our global warming with the long term cycle's cooling will do. It's great that attention is becoming more and more focused on this topic, but we don't need dire predictions and polarisation which have taken place - it is counterproductive.

It startles me how people pick sides and start using labels like denier and apologist on this topic - surely there is room for debate on what we should do about climate change? Do we have to be either for or against AGW and therefore for or against mitigating it? Isn't it reasonable to suggest looking at AGW in context, and also to show that humanity is going to have to deal with far greater swings over the long term in climate than just a few degrees?

If anything I'd say this long-term chart indicates we have to redouble our efforts to understand climate change, and if we can't control it, work on ways to mitigate its effects, because even if we control our own short term effects, long term the earth will move from ice age to tropical and we'll have to adapt.

Do you know why the original 11,000 year chart doesn't look anything like the 10,000 year chart in your link?

His chart is based on a single data set (the vostok ice core) for the majority of that period (plus modern temp records slapped on at the end, but it's not visible in the 10,000 year graph) which is not representative of global climate. Correlating proxy records with modern instrument records of temperature is not trivial either (which becomes far more apparent once you look at more than a single proxy record).

It's just cherry picked data to make a cheap political point. The scale of the vertical axis makes it very hard to see what is happening during interglacials, which is what we are in at the moment. If we were worried about an ice age arriving in the next couple of centuries the choice of scale might have some merit, to show how much colder it could possibly get. But we are worried about rapid heating, which that scale does a good job of hiding.

Why do people worry about the possibility of entering an ice age? That seems like the sort of thing humanity is much more prepared to survive.

We are more prepared to survive a 10 degrees drop than a degree and a half increase?

Not so much that a degree warmer is hard to survive, but the associated things that either come along with or are implied by global warming seem more damaging than colder weather and more ice, which we already know humans survived no problem ages ago when they migrated through Siberia and Alaska.

Possibly because it's a three word AGW denying blog post, and includes only from ice core data from Antarctica, whereas the 11,000 year data in the original post is compiled from multiple combined sources.

I'd hate to assume bad faith on the part of a climate change denier, but I can't help but speculate that the data source was chosen specifically because it made the point s/he wanted to make.

but I can't help but speculate that the data source was chosen specifically because it made the point s/he wanted to make

You don't thing that isn't happening among those who raise the AGW alarm? As the morally "right" position to hold, it even grants leave to do so righteously.

If only we had some sort of rigorous process for evaluating the evidence impartially, and coming up with conclusions, and constantly reevaluating those conclusions when new evidence comes to light.

Actually, I've heard of something like that - I think they called it "science". Hey, maybe we should put some "scientists" on this question, and see what they come up with!

I really wish there was some possibility of making any statement having to do with global warming without the polarizing positions: There aren't camps. You don't get to wear a jersey with the team colors.

Or at least there shouldn't be.

Science is very imperfect (does this really need to be stated?). Scientists are people. People are fallible, and people are quadruple fallible in groups.

In the face of an avalanche of information, history has shown over, and over, and over again that people have a tendency to essentially select data that fits the narrative, and to grossly overestimate the confidence of one's understanding of complex systems (we're seeing this already as the model of global warming veers wildly from what is actually happening with the world. This model was used, with high confidence, to pitch massive economic restructuring world-wide, but it has become evident that we as a species know less about how to model a world climate system than we imagine).

As someone else pointed out, this very submission has the egregious mistake that it compares granular data with 350-year smoothed data (which itself is taken from derived sources) -- being in the financial industry, I've seen countless cases where such shenanigans are used for very fraudulent purposes, but this is science because it fits the accepted narrative.

I'm not a "climate change denier", as an aside, though it's unfortunate that some cannot rationally reply to anything without such absolutism. I am naturally skeptical, however.

[I should apologize for getting hot under the collar, previously. I should have been much more circumspect in composing my reply.]

Granted, science is imperfect and all too human. I'd even go so far as to argue that it's deficient, dysfunctional, and perhaps even somewhat defective. But its products are orders of magnitude more credible than some random scientific-context-free graph by someone with no scientific reputation on the line. Most scientists have decades of experience and plenty to lose if it turns out they were sloppy or selective. By contrast, those doing anti-AGW advocacy can do "drive-by" FUD: they can use dirty data tricks because they don't need to convince a scientific community, there are negligible reputational consequences if they're wrong or they deliberately mislead, and their funding is secure regardless because either they're unfunded or it comes from murky or agenda-heavy sources rather than from competitive science grants.

What can be infuriating is when people equate drive-by FUD with, e.g., the products of the IPCC. This is tantamount to rejecting the entire scientific enterprise.

Do you have any freaking clue, whatsoever, how science works? Do you?

I'm pretty sure you freaking don't. Because if you did, you'd understand that everyone is out to prove each other wrong. And these aren't clueless denier I've-got-an-engineering-degree-and-I-read-some-articles-and-so-I-know-everything-tards that are doing the proving-wrong: these are people who've spent 30 years reading papers, talking with thousands of similarly knowledgeable people, and collecting and analyzing data. This isn't to say that they know everything or that they're always right or that they aren't subject to groupthink: those problems definitely exist. But what they're good at -- what they spend ALL THEIR TIME DOING -- is making sure that cherry-picking, and other stuff like it, isn't going on.

They're not bumbling fools who work at think tanks and therefore aren't at all accountable to their peers for the arguments they make or the things they say; these are people whose job it is to be right about things that very few people are thinking about, and to make sure that other people are right when they're doing the same. That's what they spend their days doing.

Please stop.

"And you are lynching Negroes". I'm not going to respond to this obvious fallacy beyond that.

There is no fallacy here, and your offensive, inappropriate retort has absolutely no place in this discussion.

You specifically decided to label one proposing an unwelcome data point as "climate change denier", which in an instant made your position clear, hence my reply.

>your offensive, inappropriate retort has absolutely no place in this discussion

I assume that means you're unaware of the historical meaning behind the quote: http://en.wikipedia.org/wiki/And_you_are_lynching_Negroes

The fallacy in question is also known as "tu quoque".

Edit: Also, it's interesting how often I point out a fallacy in someone's reasoning, only to have them say "there's no fallacy". In virtually every case, the situation was that they simply didn't see the fallacy. A better answer would be "I don't see the fallacy you're talking about."

Different data set. The 10,000 year chart is only Antarctic ice cores. The 11,000 year chart is a composite of a number of temperature records - tree rings, etc.

The 11,000 year chart is a composite. Funny how the data takes a wild change right where a completely new data source is included.

You realise that there is an entire paper in Science about how they synthesised the various temperature records? http://www.usu.edu/geo/physical/MarcottEtal_Science_2013.pdf

If you have something constructive to say about the methodology then let us know rather than making ignorant comments that tell us more about your political ideology than about the science.

Another comment notes of that paper:The Science paper says their reconstruction is smoothed and has low time resolution. They say it displays no variation at all on timescales <300 years, and attenuates even 1,000 year variations. Superimposing this with the 30-year Hadley data seems misleading, because it is on a very short timescale which is suppressed from the older data.

Let me guess, you're a Republican?

The OP made a perfectly legitimate observation. People should be skeptical of anyone trying to prove a point by showing a graph.

Thanks for posting a link to the actual science.

I suspect that "geological record" quoted is only one source - the graph in the original link is many sources combined.

Also, note the scales are totally different, and that the original link at least states sigma (uncertainty.)

Also, look at the scale of the Y-axis. One has a range of 1C and the other has a range of 15C.

Wait...are we in "summer" on that time-scale now?!

Yup. At the end of the Dog Days of August, expecting an early hard frost. We'll be wishing for "warming" soon enough.

My skepticism in climate change is based on a long history of censuses in the scientific community that later proved to be completely wrong.

I'm not saying we should not try to understand the world. I'm saying we should realize we have limits. The more complex the system we seek to understand, the more we should be skeptical. The climate of the entire planet and to the degree one particular species impacts it seems extremely complex to me. Hence, I am highly skeptical.

No one is saying that we should devote 100% of GDP to mitigating global warming. Go ahead, factor in the uncertainty. What % of GDP should we spend to avert the very real possibility catastrophic warning occurs? What % are we spending?

If it were left up to me, I would say we should have zero forced spending and an unlimited amount of voluntary spending to avert a potential global warming catastrophe.

Let me remind you, that at any time you are free to donate any amount of your own money to thwart global warming. That's not what some people really want though. They don't want to spend their own money on the problem. They want to spend other people's money on the problem. And I contend we don't know nearly enough about the issue to cross that line.

I'll be happy to agree not to force anyone else to spend their money to avert global warming. But there is one additional provision I'll require: I must be free to shoot anyone harming me by contributing to global warming.


Really what you are saying is do nothing, at least be honest about it.

Only if you and all the other folks who are convinced of a need to act on global warming choose to do nothing. The reality is that even among those who think "we" need to act, most do not even have enough conviction on the matter to volunteer to spend a dime of their own money on it.

Because the world's climate is a public good, game theory predicts that this kind of thing won't ever work.

We are semi-rational actors in a dynamic competitive system. We can all want X to happen, and be willing to spend money to make X happen, but realize that doing so would make our own lives worse because of the non-participation of others, and so we contribute to making X happen not directly, but instead by trying to put rules in place that enforce participation.

I refer you to: http://en.wikipedia.org/wiki/Public_good http://en.wikipedia.org/wiki/Tragedy_of_the_commons http://en.wikipedia.org/wiki/Game_theory

Out of idle curiosity, can anyone tell me more about what a 0.4 (0.6, 1, 2...) °C anomaly feels like, maybe with reference to cities that have climates with differing annual averages? I mean, is it like shifting every city 5 ° in latitude closer to the equator, or what?

(I know this wouldn't capture the whole story, I'm just curious.)

EDIT: I guess the state of New York has a range of annual average temperatures from 4 °C to 12 °C, so maybe this isn't useful at all. http://en.wikipedia.org/wiki/Climate_of_New_York#Temperature...

Think of it more as extra energy being imparted to the global weather system. This will have all sorts of fun and exciting effects, and as I understand the warming will be greatest at the poles. Alaska has warmed by about 1.6[0] in the last 60 years, and the interior of Alaska by 1.4° C in the last 100[1], compared to a global temperature rise of .8° C over the same period. This has resulted in the melting of thousands of cubic kilometers of glacial ice, with this study[2] suggesting that this is the largest glaciological factor in rising sea levels.

To the eyes of the native inhabitant, the glacial retreat is shocking, with the lower altitude glaciers most affected. We've built glacier overlooks in some places, where once the glacier was a stone's throw away, and now it's barely visible, and in another few decades the only thing they'll be able to show anyone there are photos. I've seen photos from the early 1900s of glacial termini which towered over the masts of a sail-rigged steamer. Today there is a fjord there, and the glacier is more than 13km away.

And you want to know what that feels like?

How about instead you imagine how it feels to watch the Arctic melting around you, while an endless circus of millions deny that it's even happening.

[0] http://climate.gi.alaska.edu/ClimTrends/Change/TempChange.ht... [1] http://oldclimate.gi.alaska.edu/papers/Arctic62-3-295.pdf [2] http://glaciers.gi.alaska.edu/material/arendt_phd.pdf

> And you want to know what that feels like? How about instead you imagine how it feels to watch the Arctic melting around you,

I said in the original comment that I was well aware this wasn't the entire story.

There are some subjects where I really wish I could ask questions like someone new to the topic and not immediately be branded as some kind of enemy.

My apologies if you read any offense in my words; none was intended. Unless you happen to have a heat ray and a hatred for H20 solids, I can't imagine that you've had much of a personal hand in making it melty up here. I hope the data I provided may serve you even if my rhetoric don't.

Ah, sorry for reading too much into your comment.

While I've got you here, and while we're pushing the civil boundaries on the topic, there's something on this subject I'm curious about, but have always been afraid to ask...

Won't a more accessible / inhabitable taiga be kind of awesome?

I mean, low lying areas without hurricane protection swallowed by the seas, algal blooms, the shutdown of the thermohaline cycle leading to a frozen Europe, midwestern desertification, all these are well down the bad side of the ledger. Harms are still outweighing the good. But isn't some of what's going on up north good for humanity?

I complain about glaciers, but they're really just the tip of the icefield. Most of the ground here is some variety of permanently frozen (permafrost)[0], so that's all going to melt at some point. Most of the population here does not live on/near permafrost, despite that map. However, if you do happen to go to Fairbanks or some more northerly hellhole, you'll find all the buildings are built on stilts, elevated a few feet off the ground. If they were not, the ground underneath would melt and sink (ice is less dense, remember), and eventually you'd be making a nice cross-stitch for "Home Sweet Bog".

So there's that. There's no soil in most of Alaska; it's either been scraped away by glaciers or the frozen layer is too close to the surface for much to develop. In some places the pine taproots can only get a meter or so down, and you'll have endless forests of man-high spindly pines. In many other places there are no trees at all. This is generally what we call taiga. When the permafrost underneath this melts, you're not going to have fertile soil left behind, at least not for a really long time.

On the plus side, Alaskans are probably not going to complain a whole lot about a warming trend, and the Northwest Passage is finally a thing. Maybe my friend will finally be able to grow avocados? It's hard to come up with a lot of other things that might be beneficial -- maybe we'll have more opportunities for strip mining now that the glaciers are gone. Maybe in a few million years the Alaskan Bog will be a good source of petrochemicals.

Really it's pretty hard to come up with good things, especially compared to "most of the ground will melt". Siberia is likely to be much the same story, as well as large parts of Canada -- you can find your own permafrost maps for there. Oh, and we have problems with coastal storms here too, and are already having to relocate whole villages (Newtok, Shishmaref, etc)[1][2]. Probably the only really good thing is that not a lot of people live here now, otherwise it'd be pretty easy to call the Arctic as the region most severely affected by AGW.

[0] http://i1109.photobucket.com/albums/h427/m4135/ps9_zps5c9b1b... [1] http://en.wikipedia.org/wiki/Shishmaref,_Alaska [2] http://www.theguardian.com/environment/2013/aug/05/alaska-ne...

Ah, thanks! I do appreciate the insight here...

Nuclear winter, Club of Rome, ozone depletion, acid rain, chicken flu, Y2K, SARS, human sacrifice, cats and dogs living together...

Great post, but I don't think the parent was attempting to make some kind of rhetorical point, merely asking an honest question.

In the maps linked below, each isotherm represents a 2 C difference. So a global rise of 2 C would be equivalent to a 100-200 km or so shift towards the equator, for a given location. Or nearly equivalent to the temperature difference in the center of a major city compared to its suburbs.



If the temperatures are be equally distributed plus 1°C feels like 1°C plus. But that's not the case neither in space nor time. I worry more about the peaks.

googling "industrial revolution averted iceage" returns a few conservative blogs, smugly pleased with the possibility

the only credible commentary i can find is in a nytimes article:

"Scientists say that if natural factors were still governing the climate, the Northern Hemisphere would probably be destined to freeze over again in several thousand years. 'We were on this downward slope, presumably going back toward another ice age,' Dr. Marcott said."


I cannot cite the exact words, but in discussions professors have indeed expressed the opinion that a next ice age won't be of concern for us.

Those charts, especially those going back further, are a good argument for why we will need to control the climate at some point in the future (but please not when we have not figured out how to without significant risk).


By "conservatives" exit means the American kind, who by and large deny the existence of AGW.

The dispute isn't about AGW, it is about CAGW.

   AGW: human activity increseas CO2
        increased CO2 => increases temperature

   CAGW: Catastrophic Anthropogenic Global Warming
         human activity increases CO2
         increased CO2 => increases temperature
         positive climate feedback mechanisms => magnified warming
It is that last item where the controversy lies. Climate models all have a parameter that represents the climate sensitivity which predicts the way the climate responds to changes to input.

If you believe that the sensitivity is high, then small changes to the input (via CO2 warming, for example) lead to large changes in the system and catastrophic results.

If you believe the sensitivity is low, then small changes to the input do not have catastrophic outcomes.

There has been considerable news of late that observations of temperature changes over the last 15-20 years do not match the predictions over the same time period of the models using a high climate sensitivity values.

Edit: fixed formatting and spelling

>The dispute isn't about AGW

For most conservatives it is. Even in this thread we have people claiming it's all just a natural cycle.

>There has been considerable news of late that observations of temperature changes over the last 15-20 years do not match the predictions over the same time period of the models using a high climate sensitivity values.

New papers that suggested slightly lower sensitivity gave figures that were still within the range put forward in the last IPCC report, and still suggested sensitivities high enough to cause serious and damaging climate change unless emissions are reduced.

Climate is a noisy system, you can't measure significant change in global surface temperature in only 15 years. You should take the time to go and look at the actual temperature data to get a feel for how noisy it is[1]. Short term cycles like ENSO -- that we currently have no real ability to predict -- have a far greater impact on surface temperatures over those time scales[2]. It just so happens that the last 15 years or so have seen a dominance of la Niña years (which correlate with cooler surface temperatures) for reasons we don't really understand; it could just be random or possibly ENSO could have been affected by climate change.

There has been no "pause" at all in other measurements: 2012 was the lowest recorded extent and volume of arctic sea ice and the trend is clear: http://psc.apl.washington.edu/wordpress/wp-content/uploads/s...

Ocean heat has continued to rise: http://www.nodc.noaa.gov/OC5/3M_HEAT_CONTENT/

The only people talking about a "pause" are conservative pundits and climate change deniers. It shows weaknesses in the models, but nobody was claiming that the models were accurate for short timescales or that we have the complete picture a at all. There are still huge gaps in our understanding, but that is hardly a cause for celebration.

[1] http://www.skepticalscience.com/pics/HadCRUT4vs3.jpg [2] https://tamino.wordpress.com/2013/09/02/el-nino-and-the-non-...

So it's like if you're not disputing smoking is bad for health, but you're saying it's not "catastrophically" bad?

It's like the sooner one stops smoking, the less chance he has for a "catastrophic" lung cancer; it's not like when you smoke 10K cigarettes you sure won't get cancer but if you smoke 20K you sure do.

Of course, different people call "catastrophe" different things, but the analogy is quite apt here. There is no "catastrophe" coming, in the sense of a sudden disaster. We can stop any time, and the sooner we stop, the better overall result (and less costly) will be.

I think you are mistaken.

You are assuming that the climate system can be modeled via linear mechanisms, that human caused changes are more significant (from a climate modeling standpoint) than natural variations, and that the costs of modifying human behavior (e.g. more expensive energy via renewables vs coal) are less than the costs of adjusting to a changing climate.

My biggest frustration with the CAGW adherents is that they don't assign any cost to their proposed mediation policies. Often their cures are worse than the disease.

CAGW is used as a justification for all sorts of increases in government power, which by itself is probably more dangerous than even the worst scenarios promulgated by CAGW supporters.

There is no innate rule that warm=bad. Your analogy is too broken to be useful.

That's due to the little ice age (http://en.wikipedia.org/wiki/Little_Ice_Age), which extended to the mid 19th century, not man-made climate change.

apologies; I thought it was mainstream to believe that the "little ice age" would have continued into a proper one if not for the industrial revolution. This part of my comment remains relevant though:

Conservatives have little to be smug about here - it shows that climate change is indeed anthropogenic, contrary to their narrative for the last 20 years - the red line, modern records, show a much faster rate of change than anything in the natural period.

I think it is mainstream to acknowledge the possiblity of that, but not have a fixed believe. After all, it's climate science and we're only at the beginning, and who knows, there might have been another few thousand years of stable climate.

This plot compares an inferred model to the instrumental record. Here is the study expressed in the words of Real Climate: http://www.realclimate.org/index.php/archives/2013/09/paleoc...

  Over the last decades, numerous researchers have 
  painstakingly collected, analyzed, dated, and calibrated 
  many data series that allow us to reconstruct climate 
  before the age of direct measurements. Such data come e.g. 
  from sediment drilling in the deep sea, from corals, ice 
  cores and other sources. Shaun Marcott and colleagues for 
  the first time assembled 73 such data sets from around the 
  world into a global temperature reconstruction for the 
  Holocene, published in Science. Or strictly speaking, many 
  such reconstructions: they have tried about twenty 
  different averaging methods and also carried out 1,000 
  Monte Carlo simulations with random errors added to the 
  dating of the individual data series to demonstrate the 
  robustness of their results.
Marcott et al.'s graphic states that their model reflects historical temperatures so accurately that it can measure the average temperature of the entire globe continuously back to 8000 years ago, to within a small fraction of 1 degree Celsius (i.e. the 1-sigma error bars). That is simply an extraordinary claim given:

1) The "divergence problem". The lack of correlation between model inputs like tree rings and the instrumental record over the last few decades is acknowledged by all; climate scientists generally state that it is due to anthropogenic factors, arguably assuming the consequent.


2) Serious climate model prediction failures over the past 10 year period, as acknowledged in Nature:


In other words, key model inputs used in climate reconstructions do not strongly correlate with the instrumental record over the last 30-40 years ("the divergence problem") and climate models have so far had a poor track record over the last 15 years, with average temperatures winding up below the envelope of model predictions. These predictive failures in the datasets we can check bode ill for the prospect of hindcasting global average temperatures to within 1 degree more than 8000 years ago.

In the same article, they explicitly mention that the study is not based on tree ring proxies. In fact, all the global reconstructions are based on many different proxies.

I also think you misrepresent the 2nd article. The question is what and on what time scale are you trying to predict. I believe they are talking about more precision more short-term models. Just like we can predict winter and not predict weather, we can predict warming due to human forcing, but not the specific details.

In the end, however, it's completely irrelevant to AGW if there was a higher temperature in the past or not. The theory of AGW doesn't stand just on that argument (nor any other single argument, for that matter).

Without trying to say too much, one big reason we can predict winter is that we've had hundreds of thousands of years of experience with it.

The plot does seem too precise to take seriously IMO, although I am an engineer, and not a climate scientist.

Well, there are a certain number of explicit and implicit caveats that don't make it into the made-it-to-the-top-of-HN pretty graph.

One is that this is based on other people's work, as the GP mentioned. Updates to those works will affect this one; the hope is that those 73 underlying datasets aren't systematically biased and any errors will cancel out. Another is that those error bars are probably 95% confidence. So we fully expect that about 550 out of the 11,000 years in this chart will fall outside of that range. A final bit is that we're only reconstructing averages here; it's a lot easier to guess the average number of shoes owned by 1000 people than the exact number of shoes owned by 1.

These extra caveats don't invalidate the data or render it useless, they just qualify it. You shouldn't look at the graph and think, "Here is the exact temperature for the last 11,000 years", you should think, "Given our current best understanding of the available data, the average global temperature for 10,450 out of the last 11,000 years probably fell into this 0.4 degree C range."

> Well, there are a certain number of explicit and implicit caveats that don't make it into the made-it-to-the-top-of-HN pretty graph.

They're not supposed to. These are supposed to be caught by peer review. If you believe Nature, then you should believe Science, too (I am talking about journals here :-)).

BTW, they explicitly discuss the possibility of "missing" temperature peaks in the RC blogpost.

How many results published in Nature turned out to be wrong later?

(I don't know the answer, but I heard the number is quite high.)

> Another is that those error bars are probably 95% confidence

The legend claims one-sigma (68% confidence assuming normality)

It's a graph of temperature anomalies!

Am I alone in finding the graph scary? This rate of change in temperature is probably not something that would be easy to slow down, yet it feels like not many people care about this.

World population chart for the same timeframe: http://upload.wikimedia.org/wikipedia/commons/b/b7/Populatio...

It seems that the uncertainty is much higher at the end of the blue curve. I wonder why.

It also seems that the red curve has no uncertainty data.

I would not dare draw any conclusion from these curves before I have satisfying explanations for these two questions.

It's probably because all the climate scientists in the world are trying to trick you.

Yes, and it is not clear on the diagram, if the red curve is actually inside the uncertainty range. At least on my screen I really can't tell.

"Worry about global warming impacts in the next 100 years, not an ice age in over 10,000 years. "


Basically none of these memes are new. They often rely on misunderstanding of context. (For those who didn't know, skeptical science rebuts these commonly found arguments against global warming.)

Of note is that the chart's error bars fill the entire scale near the end, so the measurements could really be anywhere there. It's anyone's guess whether or not temperatures have somehow mysteriously skyrocketed or not.

My personal inkling is that the alarmist reports are wrong, and the changes aren't as drastic as reported; since the same people publish results from proprietary, rigged climate models.

Can someone please explain how we're able to know the temperature in 4,000 BC with an accuracy of +/- .2° C?

Global temperatures are basically flat for the last 17 years, and below every single computer model of climate change. This is even more stark given the fact that the most co2 has been produced in the last 17 years. I think the theory is pretty much broken and they need to figure a better model.


Please, you need to study statistics again.

Check the graph in the parent article.

Zoom into any 17 year period between -3000 and 1900 and it will "look flat", and during many 17 year periods the temperature temporarily went up, but nonetheless you can see there's a clear downward trend throughout that period.

It's impossible to deny that this trend has been sharply reversed.

A 17 year period is normally supposed to tell you nothing interesting - but the 17 year period up to 1996 clearly indicates something quite disturbing is going on.

Climate change is not negated by a temporary plateau.

That's comparing apples to oranges. All the other data used to create the original graph o calculate temperature such as tree rings, etc do not take into account the temperature of the oceans, etc. There may be perfectly good explanations as to why the temperature may be flat, but those same explanations are not being fed into the graph that the OP posted.

>All the other data used to create the original graph o calculate temperature such as tree rings, etc do not take into account the temperature of the oceans, etc


What's flat is not global temperature, that's 2m air temperature. 90% of the greenhouse effect goes into the ocean. That's the place to look for rising temperatures and hopefully all that accumulated energy of latest 2 decades gets not released at once into the atmosphere with next El Niño.

How much do we humans contribute to the heating of the world? The heat we output from our bodies and population increases must mean more heat.

I say this because a friend has a small barn and in it two horses, two pigs and some chickens. He said the barn doesn't use any heat source because the heat from the two horses is enough to warm the barn. Even a bucket of water in the barn won't freeze.

A human uses about 100W. I don't know about horses, but depending on how well-insulated the barn is, a few hundred watts would make a significant difference.

About those humans heating the Earth -- the effect of the GHG's we emit is tapping into solar insolation, which is huge, so it probably dwarfs the above figures (see next paragraph). Also, the energy that powers us (food) would be turned into heat by other processes anyway.

Order of magnitude: population of 7 billion * 100W/person = 9.7TW. Solar insolation 1361 W/m^2, over the projected area of the earth, which totals 175,000,000 TW.

I just throw that figure (100W) as a useful order of magnitude estimate.

The cyclical recurrence of interglacial and glacial periods (we're technically still in one of these) can theoretically be explained by cyclically evolving properties of the Earth's orbit around the sun such as the precession of the Earth's ratational axis (google Milankovitch cycles). This theory is consistent with the gradual cooling trend observed thus far into the Holocene epoch, and predicts it will continue for tens of thousands of years. The linked graph shows this very nicely.

A sudden, full-blown glacial period would be far more disastrous for human civilization than significant global warming. The latter would submerge densely populated coastal areas and force humans to move to the new coastlines, but the overall capacity of the Earth to support life would increase, just as it did at the start of the Holocene. The former would result in a large reduction in the Earth's carrying capacity and global famine.

Any change in the Earth's temperature is going to be disruptive to both human civilization and the existence of other species on Earth. We have reversed the effects of several thousand years of cooling in just a couple of centuries and, assuming we are able to continue extracting and burning hydrocarbons at an unabated pace indefinitely (dubious) we could significantly change the face of the world, but it will still support our civilization, just in a very changed state. Avoiding the pain of this change is ample incentive to curb the use of hydrocarbons. (Edit: It has taken centuries and a significant portion of the world's hydrocarbon reserves to produce less than a degree of warming. At this rate, even if we evaded peak-oil for another thousand years the Earth will still be in a glacial period.)

However, we should be much more aware of events that could trigger another glacial period. Megaeruptions or large meteor impacts could plunge global temperatures suddenly and catastrophically. These are far greater threats to our species, but we are both incapable of adequately predicting them or preventing them if we do predict them. The probability of this sort of event happening in a single human lifespan is remote, while global warming is a certainty, but these events will eventually occur with certainty. Managing global warming is certainly a good idea for the comfort of our civilization, but we should have more eyes on the bigger threats. (Edit: Even if we tried, we would be unable to maintain global warming indefinitely simply by burning hydrocarbons. In the ten-thousand year time-frame we will need to find other ways to combat gradual cooling.)

> Managing global warming is certainly a good idea for the comfort of our civilization, but we should have more eyes on the bigger threats

Orrrr we could do more than one thing at once?

In any case, a "sudden, full-blown glacial period" has never happened according to any geological record we have. The most "sudden" have happened over centuries. The actual, demonstrated suddenness of current warming trends is a major part of the problem.

There are a bunch of problems in your post (I have no idea where you get the idea that we're in a glacial period, these are just labels, but no one calls the Holocene anything but an interglacial; it is well established that Milankovitch cycles do not explain current trends; current atmospheric carbon will be there for centuries to come and will not stop warming us even if we were to stop all emissions today; you neglect ocean acidification, sea level rise, etc), but the fact remains that its ridiculous to assert that "we should have our eyes" on one threat instead of another, when we could have much more scientists and funding for asteroid detection if someone would exert some political will. That is what's necessary, not trying to minimize other threats with specious (at best) arguments.

thanks for adding "the bigger picture" into the mix.

I don't think this chart comes close to proving that Obama was born in the United States.

Sorry but I hear a lot of speculation, not real reports of hard actual life threatening changes.

Maybe soft ones like the sea temperature and acidity, but most people can still go out and food still grows.

Until you were there to measure the temperature, all you have is just the output of a model. The model is not the world.

Start burning tires folks. We need to save ourselves from an ice age.

Well, the upside is, we fixed the ice age that was trying to happen.

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