If you haven’t seen the xkcd on climate change, you ought to — putting it on a 40,000 year time scale makes it clear how exceptional the changes in global temperature are right now. Oceanoxia has another of Munroe’s climate change illustrations which is very good.
Pharyngula
Evolution, development, and random biological ejaculations from a godless liberal
4,000 year time scale? What are you, some kind of Young Earth Creationist?
The full chart covers 22,000 years, more or less.
Unfortunately it’s difficult to compare what we’re supposed to compare in the graphic, because the dotted line seems to need fairly wide error bars (by the graphic’s own admission), and doesn’t have them.
Actually, where the graphic does mention small errors/deviations, it labels the more extreme one “unlikely”, which is important. So odds are the current trend is about as significant as it looks. More or less.
odds are we will not do shit until a bunch of major port cities around the fucking world are underwater and then not without a lot of finger pointing and blame assigning thrown in for good measure
uncle frogy
Brian Pansky: we’re supposed to compare the global temperature anomaly, and the dotted line is the central estimate as per Marcott et al. You can also view it here, with error bars and fewer cartoons:
https://www2.bc.edu/jeremy-shakun/Marcott%20et%20al.,%202013,%20Science.pdf
The temperature when Marcott et al did their research was already above the 1-sigma error for the top temperature in the Holocene. Also, as mentioned in the comic, it’s extremely unlikely that there were any short excursions out above the 1-sigma band.
Not explained in the comic: to have a warm excursion (more than 1-sigma), the only mechanism we really know of is a large emission of CO2, which lasts a long time — long enough it would show up in the proxies. To go below, a volcano can pull you down for a couple years and clear up completely within the decade, which the proxies might miss.
My link is busted, you’ll need to copy-paste it.
@unclefrogy, nah, when Wall Street is under water, we’ll then invade whoever has higher ground – even if it’s our own country.
@numerobis, what I don’t see in the graphs is, is there any accounting for methane release from both permafrost and methane hydrate formations?
One of the problems with greenhouse gases is, they’re non-linear in relationship of quantity released vs their greenhouse effects.
I went to a lecture by one of the climatologists advising the IPCC. He said that the ice ages had a 6-7C temperature difference, not the 4.5 in that diagram. . The last time we had this much CO2 in the atmosphere was before plants colonised the land..Ouch…
@davem #9
Time frame correction: The last time we had this much CO2 in the atmosphere was more like 15 million years ago. CO2 levels have been much higher on Earth in the past – over 1,000 ppm, if I recall, with terrestrial plants and animals all over the place.
https://www.sciencedaily.com/releases/2009/10/091008152242.htm
By my interpretation the central message of this graphic is that the rate and scale of modern warming is unprecedented – but this can’t be proven from the data available.
We simply don’t have ancient temperature records with the same precision and resolution as our modern records. Shakun et al’s reconstructed temperatures are averaging “high-resolution temperature records” which have a median resolution of 200 years – this means these high resolution records typically have 1 data point, every 200 years. Add to this they have substantial dating uncertainty (hundreds of years in most cases), and they are not true measurements of temperature, but approximations with inherent uncertainty. Then all these records get averaged – and there will be no way to reconstruct rapid global temperature changes on decadal time scales. It simpler terms, the graph compares apples (reconstructed temperatures, averaged on 100+ yr time scales) to oranges (modern, measured surface temperatures).
……
There are regional records, of high resolution that show very rapid temperature changes – greater than anything we experienced over the last 100 years. We should be concerned about the rate and magnitude of the current warming, but it’s unlikely to be unprecedented (at least at present). In fact, an argument has been made that rapid and extreme climate change is a feature of the earth system, and we should therefore be wary about disrupting the status quo in case we inadvertently trigger a rapid change in state.
Knowing the US, we’ll probably have a set of serious climate calamities in the 2020s that will finally get the US to start hastily trying to curb emissions belatedly. Underpinning that, of course, will be years of activism finally getting their moment to make a change.
@andyb #11
I’m sure you can cite those regional records, right? I mean, I’m sure you wouldn’t make an unevidenced assertion, would you?
And what about the fact that the recent massive spike in global average temperature just happens to coincide with a massive spike in atmospheric CO2 levels? Is that just one of those funny coincidences? How about the fact that the ratio between the temperature rise and the rise in atmospheric CO2 levels just happen to follow almost exactly the ratio predicted in the mid 19th century based on the chemistry of CO2? Just another of those darn coincidences?
FFS, that’s the most frustrating part of climate change denial. The science behind the greenhouse effect is absurdly simple. It was deduced from basic chemical properties long before we had the means to actually verify that it was correct, and in all the time since then every bit of evidence we’ve found has just confirmed and reconfirmed the theory. For AGW to be wrong, we would have to be MASSIVELY wrong about not just climate science but about basic, simple fucking chemistry.
The Greenland ice core records for one, although there are other land-based, annually or decadally resolvable records that document abrupt climate shifts (at least regional in nature) – the Bølling-Allerød/Younger Dryas transition, terminal Younger Dryas, and 8.2 kya event are all good examples (all have Wikipedia articles if these are unfamiliar terms).
I had to look up FFS. If my post above drives you to swearing about global warming denialists, you should read it more carefully.
@Abe Drayton, #10, when one hits between 1000 – 2000 ppm CO2 in ambient air, drowsiness and “poor air” complaints begin. Hit around 2000 – 5000 ppm, headaches, sleepiness, stagnant, stale and stuffy air complains are made. Poor concentration, loss of attention, increased heart rate and even minor nausea may be present.
Something well studied after problems were noted in buildings after the last energy crisis convinced companies to build structures super tight, to conserve energy. Since mitigated by literally drilling holes in those tight buildings, to let fresh air back in.
Not the best reference, but collates a lot of sources in a readable format:
https://www.kane.co.uk/knowledge-centre/what-are-safe-levels-of-co-and-co2-in-rooms
@Andyb #11, you ignore proxy data, the Greenland ice cores are only one proxy point, tree rings are another, other areas where atmospheric gases are captured are also considered. It turns an approximation of a century and change into a century approximation, but warming an environment by a degree takes a hell of a lot of energy, that can be absorbed energy, reflected back or forced. Regardless, one has to explain where that energy came from. The effect is observed, what was the cause. As our solar measurements have been ongoing, as for insolation levels have been approximately measured for several centuries and directly measured for decades, I imagine that comparing surface radiometer measurements to orbital measurements are also apples and oranges, yes?
If yes, perhaps we can agree that things are warming up once Wall Street is fully under two meters of water?
Abe D
Yep. That’s down to plate tectonics.
Our current atmosphere is the way it is due to the various collisions of significant plates. The Himalayas being the principal reason why rocks crack and absorb CO2 at the rate they do. But the African plate pushing north is also forcing up the Alps – it’s just that it’s not as fast (anyone who’s seen an animation of India positively scooting across the globe to crash into Asia while the rest of plate movements are quite leisurely gets the idea) so the Alps are in virtual equilibrium, losing as much height each year from erosion as they’re gaining from being pushed upwards.
The current layout of continents with several very large, very high mountain ranges is extremely unusual when looked at from a geological perspective. This bloke does a very nice explanation of all climate-related things geologically. https://www.youtube.com/watch?v=Yze1YAz_LYM
I’ll I can suggest is that you read the papers from which the temperature reconstructions are from in this cartoon (I really like xkcd infographics, and am a big fan of Tufte – but I don’t like this one). This cartoon gives the false impression that the rate of warming we’ve experienced is unprecedented over the last 22000 years – in this cartoon, (natural) abrupt climate change does not exist – and we know this is not true. The reason, as I tried to explain, is that these paleo-temperature reconstructions are a much coarser resolution than modern temp records (Shakun – the older record is 200-yr averages, and Marcott is 120-yr average) – then they get stacked.
Here’s a quote form Marcott Here’s the beginning of the last paragraph
So if the stacked paleo records don’t resolve variability over decades or a century, we shouldn’t be comparing this averaged record to recent warming to determine how anomalous the rate of recent warming has been relative to the last 22000 years. We know that some regional records, of high resolution, document very rapid climate change (over a span of years). The infographic makes a note of this if you look closely (they have an inset figure – but it would be better if they just plotted one data point every 200 or 120 yrs, and added error bars, rather than the dashed line with no errors.
None of my statements should be interpreted as a denial of global warming – clearly the warming we are experiencing is fast, and its mostly from CO2, but with the paleo-temperature data-sets we currently have available, we may have to wait a few hundred years to see how our warming really compares with abrupt climate events of the past.
I don’t expect any major “climate calamities” within the next decade or two decades. We’ve all lived through some very rapid climate change already – and most people can’t tell at all (which is part of the problem). We’re frogs being boiled. I expect most of our resources to be spent on adaption, not prevention (and if we just made major reductions in population, we could manage a range of environmental problems.)
RE #16, the rate of volcanic degassing and the removal of carbon by burial (from plants and calcite shells), are the other key factors on long time scales. The Cretaceous had high rates of volcanic degassing, and seafloor spreading – but there werre also high rates of carbon burial because sea levels were high. I’m burning Cretaceous coal right now to type away at my computer.
Weathering rates are also affected by the concentration of CO2 in the atmosphere – if CO2 goes up, more CO2 is removed by weathering.