A truly impressive paper was published this week with a new reconstruction of global temperatures over the last ~500 million years.
There is something tremendously satisfying about seeing a project start, and then many years later see the results actually emerge and done better than you could have imagined. Especially one as challenging as accurately tracking half a billion years of Earth’s climate.
Think about what is involved – biological proxies from extinct species, plate tectonic movement, disappearance in subduction zones of vast amounts of ocean sediment, interpolating sparse data in space and time, degradation of samples over such vast amounts of time. All of which adds to the uncertainty.
It is not as though people have not tried – we discussed this here in 2014, where we made a plea for better graphs of the global temperature. Now, 10 years later, we finally have something.
This work was first instigated as part of the pre-development of the Smithsonian’s Deep Time exhibit (which opened in 2019). The curators wanted a credible timeline of temperatures (including glaciations, hot house periods, extinctions, etc.) and, like many of us, had found the then-current literature somewhat unsatisfactory. There was a workshop in 2018 (that I attended) to discuss how one might go about doing something better – updating the data, improving quality control, and using models to better connect local or regional signals to the global means. Interestingly, the resulting PhanTASTIC (“Phanerozoic Time-evolving Averaged Surface Temperature Illustrative Curve”) effort was mostly privately funded. That brought in a postdoc, Emily Judd, who has been working on this ever since! The resulting paper Judd et al., (2024) (direct link) has just appeared in Science.
It’s worth talking about how this reconstruction was made. Prior efforts had been purely data based (with varying levels of corrections for non-climatic effects) and perhaps some effort to estimate global means differently depending on whether the data was from the paleo-tropics or higher latitudes. In this case however, a local temperature anomaly (inferred mostly from carbonate oxygen isotope ratios) was tied to the global mean using a set of climate model simulations for each 5 million year period (run with varying CO2 levels and with the best estimate of the paleogeography). This allowed even data sparse periods to be used to estimate the global mean temperatures (but with greater uncertainty). This kind of data assimilation is effectively a much lower dimensional process than the data assimilation that you might be more familiar with in weather forecasting, but can be quite skillful.
The resulting history back to 480 million years ago has the same broad sweep as has been seen before:
Warm temperatures prior to the Ordovician glaciation, rises of temperature through the Devonian, a dip through the Carboniferous, peaking again at the beginning of the Triassic, slightly cooler in the Jurassic, peaking again mid-Cretaceous and then (roughly speaking) cooling into the Neogene (and the last 3 million years of ice age cycles). However, the relative peaks of the warm and cold periods vary across the reconstructions, as does the scale of changes. Many of the previous reconstructions were however only for the ocean, and one would expect the global mean surface air temperature (as in this effort) to amplify that. For example, the mid-Cretaceous warming (~20ºC warmer than pre-industrial) is notably larger than in prior work.
What’s next?
As in another recent paleo paper, the authors make a partial attempt to estimate what they call an ‘apparent’ Earth System Sensitivity (ESS), this is just based on a regression of the reconstructed temperatures with reconstructed CO2. They get an ESS around 7.7±0.6ºC (95% CI). This isn’t however quite the right calculation (as we discussed in the previous post). The radiative forcing over such a long time period needs to take into account the increase in solar irradiance (about 4%) and the impacts of paleo-geography on temperature that aren’t linked to greenhouse gas changes. The first factor increases the apparent sensitivity, and the second decreases it. Additionally, the ESS is not the same as the ‘standard’ Charney sensitivity (which assumes static ice sheets) and so an ECS estimate would need to take into account the varying levels of land ice over this period and would be smaller. [It might be possible to do a better estimate with just this data… so watch this space].
What could go wrong?
This was a new and ambitious approach to a challenging problem, and there are still a lot of unaccounted for uncertainties. The prior estimate for the temperatures (based on a single, somewhat vintage, climate model) might be biased, the uncertainties in paleo geography might be important, the deep time corrections for diagenetic effects on the oxygen isotopes might be incorrect, etc. One would like to see this explored further in follow-on work – but this may take a while – the 100’s of climate model simulations took years to complete, and would take even longer with a more state of the art model.
This approach was designed for this specific long term reconstruction – not short term variability, but one could envisage an analogous effort more focused on the PETM, or the Permian-Triassic that could give more insight into geologically rapid changes.
Kudos
Nothing is ever the last word in paleoclimate, but this is a tremendous effort that really sets the methodological standard going forward. Well done to Dr. Judd and the rest of the team (and the many folks who’ve been pushing for a better reconstruction along the way).
References
- E.J. Judd, J.E. Tierney, D.J. Lunt, I.P. Montañez, B.T. Huber, S.L. Wing, and P.J. Valdes, "A 485-million-year history of Earth’s surface temperature", Science, vol. 385, 2024. http://dx.doi.org/10.1126/science.adk3705
- D.G. van der Meer, C.R. Scotese, B.J. Mills, A. Sluijs, A. van den Berg van Saparoea, and R.M. van de Weg, "Long-term Phanerozoic global mean sea level: Insights from strontium isotope variations and estimates of continental glaciation", Gondwana Research, vol. 111, pp. 103-121, 2022. http://dx.doi.org/10.1016/j.gr.2022.07.014
Chris McGrath says
Wow, what an impressive research effort.
But it is downright scary to think Earth’s mean temperature has in the past been 15c higher than at present given the path we’re on.
Ken Towe says
But it’s encouraging to know that life back then was not seriously affected and even flourished when atmospheric CO2 was double what it now is.
Radge Havers says
Snark?
Or have you seriously never heard of mass extinctions and this thing called ‘evolution’ (perhaps they mistakenly call it ‘evilution’ where you come from)?
Piotr says
There is life “flourishing” in the near-boiling geysers. Does not mean that that other life that tried to lived there “was not seriously affected“. Particularly that adapting to the new environment takes a long time, the time that we don’t give to the currently living life.
And certainly humans would not thrive in the rapidly warming climate, nor will our civilization which would collapse without food production by agriculture, which in turn requires moderate, stable and predictable climate.
As a species we may have been ready for agriculture for many 10,000s of years – but we actually succeeded ONLY about 12,000 yrs ago i.e. only AFTER the great climatic upheavals of the last ice maximum and most of the subsequent deglaciation period were over. And most of our staple foods originate from moderate, not scorching hot climates.
So your being “encouraged” is either unwarranted, or disingenuous – the latter if it is a part of an old denier trope – that if some organisms thrived in the past, then so will we – and therefore we can use as much oil and gas as oil multinationals, Russia, Saudi Arabia and Iran would like us to.
CJ says
— “and therefore we can use as much oil and gas as oil multinationals, Russia, Saudi Arabia and Iran would like us to.”
Another denier trope. The US is the #1 largest producer of oil and gas in the entire world bar none.
Obama did that. Trump and Biden have continued that great Oil & Gas Tradition of the Democrat Party
Barton Paul Levenson says
CJ: Trump and Biden have continued that great Oil & Gas Tradition of the Democrat Party
BPL: Democratic Party. “Democrat Party” is a pejorative term coined by GOP politicians.
Nigelj says
Ken Towe. Indeed there was plenty of life way back then when it was much hotter than today, but also several mass extinctions along the way, caused by rapid temperature changes. You missed that bit.
Susan Anderson says
Ken T:
Back when, pray tell. Look again! Typical fake skeptic response, but the numbers don’t lie. Check the years involved.
Rory Allen says
Indeed, and when the last great city disappears under the waves of an Ocean 50 metres higher than today, life on Earth will get back to normal: without the intrusive interference of human civilization. Evidence of Homo sapiens will remain as a puzzling layer of excessively radioactive ash.
Ray Ladbury says
And plastic and polyhalides, don’t forget the plastic and polyhalides!
Susan Anderson says
Thank you! I saw this in the news earlier and wasn’t sure of its provenance. I don’t want to use the word ‘believe’ as it implies magical thinking, but where I cannot evaluate for myself, I trust RealClimate.
Barton Paul Levenson says
We believe things we think are true. The dichotomy between “believe” and “know” came from religion-versus-atheism disputes. There is no reason to disparage belief unless you’re using it as a club against theists. I believe E = Mc^2 because I think it is true. I can’t “know” it because I’ve never visibly converted matter into energy
Susan Anderson says
Thanks. It’s hard to find the right words, but I often speak out about belief/faith because so often people are eager to condemn the scientific enterprise as a belief system in order to discredit it. Of course, to be human is to be incomplete and vulnerable to semantic issues, as language is an imperfect vehicle. [And, chortle, language itself is a belief system!]
Steven Emmerson says
How about “The difference between religion and science is that religion believes things whereas science temporarily accepts things while the evidence lasts.”
Keith Woollard says
I’m sorry, I have to step in here because this is getting far too religious for a scientific blog!
Belief has no real meaning in scientific debate and people try and use it to bring religion closer to real knowledge. You believe something iff it cannot be proved. By definition a god that is outside our 4d physical universe can never be proved, and so you have to have faith. There is no choice in the matter.
I don’t believe E=Mc^2, I know it to be true otherwise fusion and fission bombs and fusion reactors would not exist, and granite would not create heat and a thousand other things.
What you call belief in the scientific sense is the temporary acceptance of a working hypothesis until a better one comes along.
And Susan, it isn’t that we are incomplete or vulnerable, nothing is complete. Go and read Godel Escher and Bach if you haven’t already
Barton Paul Levenson says
KW: You believe something iff it cannot be proved . . . I don’t believe E=Mc^2, I know it to be true
BPL: You are drawing a false dichotomy. If you “know” something you also believe it.
All arguments whatsoever depend on premises at some point, and if you go far enough, those premises must be accepted on faith. This applies to the scientific method as well. We must assume empirical evidence is valid; you can’t prove empiricism empirically without arguing in a circle. Drawing a distinction between “scientists know” and “theists believe” may make you feel superior to the other, but it doesn’t accurately describe the other’s thought processes, or yours,
If something you believe is true in objective reality, it is a true belief. If you believe something which is not true in objective reality, it is a false belief. That’s the only distinction that matters.
Susan Anderson says
I prefer Johann Sebastian, if you speak of Bach.
Susan Anderson says
I would also beg people not to be so eager to condemn those of faith. The misuse of said faith is a travesty, but many scientists are well able to hold faith and work objectively in science. Attacking people puts their backs up; better to attack the ideas by providing context from the central tenets of their religion, which often contain ideas of humility, compassion, and inclusion.
Ken Towe says
It’s nice to realize that these past high temperatures, regardless of the cause, did not create the “catastrophes” to the biota that current models predict. Even with atmospheric CO2 more than double what it now is in the late Eocene oceans the carbonate plankton diversified with a lower pH.. Plant life on land was lush. This is evidence that it’s not the rate of increase in temperature that counts. It’s the amount at the end. Today’s global temperatures are very low by comparison. That’s not scary, it’s encouraging.
mev says
I didn’t realize that the biota that exist today were the same biota from millions of years ago that survived and flourished during those past high temperatures. Thanks, I must have fallen asleep in that class.
Piotr says
Ken “”All is for the best in the best of all possible worlds” Towe says: This is evidence that it’s not the rate of increase in temperature that counts. It’s the amount at the end
In what logical system the observation that given LONG ENOUGH time (millions of years) some life can adapt to warmer climates – proves that the RAPID warming over decades or few centuries, i.e. not leaving life enough time to evolve – is OK, i.e. “ it’s NOT the rate of increase in temperature that counts” ?
Barton Paul Levenson says
KT: It’s nice to realize that these past high temperatures, regardless of the cause, did not create the “catastrophes” to the biota that current models predict.
BPL: Those temperatures were reached very slowly, giving life time to adapt. When temperatures changed rapidly, for instance at the End Permian event, much of the biota were wiped out,
In any case, the Mesozoic didn’t have 800 million people and trillions of dollars worth of infrastructure along coastlines.
Tomáš Kalisz says
Amazing!
Such achievements strengthen my hope that in coming years, a team or a collaboration of several teams perhaps provides also a reconstruction of past global precipitation and of the partition thereof between land and sea. As a very start, last 300 years would already represent a significant progress, as it appears that so far, only regional precipitation reconstructions are available, providing no clue yet if the precipitation partition between land and sea remains stable, fluctuates, or changes with a certain trend.
Such a global precipitation reconstruction could also provide a useful test bed for existing climate models (and a constraint for newly developed climate models), and – hopefully – help improving them.
T
Piotr says
Tomas Kalisz: “,i>Amazing!
Beware of Tomases bearing praise – they must have a ulterior motive. Here we didn’t have to wait long to see it – it started from the 2nd word:
TK: Amazing! Such achievements strengthen my hope that in coming years, a team or a collaboration of several teams perhaps provides also a reconstruction of past global precipitation and of the partition thereof between land and sea
WHAT FOR? “Global precipitation” is the EFFECT, NOT THE DRIVER of the climate – both today AND in the geological past. And knowing that – because we have told in reply to your 100s? of posts – you STILL want many researchers spending many years of their research life and using a lot of computing time that could have been used for more productive goals – so you and the other “anything but GHGs” deniers can misrepresent their work as supporting the claims you, JCM and Shurly weren’t able to defend using the existing scientific knowledge?
Tomáš Kalisz says
in Re to Piotr, 23 Sep 2024 at 5:53 AM,
https://www.realclimate.org/index.php/archives/2024/09/phantastic-job/#comment-824791
Dear Piotr,
I fully agree that precipitation is rather a climate effect than a climate driver. Although the same applies for temperature, nobody seems to question the importance of temperature reconstructions.
You will perhaps agree that precipitation cannot be unequivocally derived from temperature and that precipitation projections may be equally important as temperature projections.
That is why I think that global precipitation reconstructions, especially with respect to land/sea precipitation partition, may represent an independent and equally important benchmark for climate theory and for development of the respective modelling tools as already do global temperature reconstructions. For this reason, I do not think that investing time and effort in a global precipitation reconstruction would have been a useless enterprise.
Best regards
Tomáš Kalisz
Herb says
Thank you for this great explainer. I was reviewing this press release (https://news.arizona.edu/news/study-over-nearly-half-billion-years-earths-global-temperature-has-changed-drastically-driven) from the Unviersity of Arizona and encountered this quote by Dr.Jessica Tierney: “We found that carbon dioxide and temperature are not only really closely related, but related in the same way across 485 million years. We don’t see that the climate is more sensitive when it’s hot or cold,”
I guess I am a little confused as to how this relates to estimating the levels of global warming we are expected to experience over the next ~100-300 years, even after reviewing your previous “Miocene” blog post.
I reviewed this other paper that Dr.Tierney was a part of, Last Glacial Maximum pattern effects reduce climate sensitivity estimates” (https://www.science.org/doi/10.1126/sciadv.adk9461). It found a modern ECS of ~3C, as expected by the IPCC consensus. I remember this paper featured heavily in discussion of global warming “acceleration” from a couple months ago. That is an entirely different topic and I look forward to following your commentary on that issue as global temps develop over the next few months. Does this new paper contradict that previous finding? Or is it really too apples-to-oranges to compare?
I hope my questions make sense. I am a complete novice regarding this topic. Thanks so much.
Julian says
I’d also like to see someone more knowledgeable to speak his mind about this to be honest. One important thing to remember is that ECS is not ESS – different feedbacks, different timescales, but I’m curious how these two papers are related.
zebra says
Herb (and Julian)
“I guess I am a little confused as to how this relates to estimating the levels of global warming we are expected to experience over the next ~100-300 years,”
Very little.
I’m wondering if either of you or both could answer a question… I’m not being critical at all, but I am truly curious, because you seem like the kind of people who are serious about learning: Why would you think that it does??
In my experience, it is very difficult to help people build understanding without some idea of “where they are at” in the first place. And it would be nice if there could be even a brief dialogue with people like yourselves (rather than the usual suspects here).
MA Rodger says
I think the question being asked was what we can learn about ECS from these two papers – Judd et al (2024) (with Tierney a co-author) calculating AESS [=“apparent” Earth System Sensitivity] and Cooper et al (2024) (with Tierney a co-author) which calculates S [= 150-year effective sensitivity – see the 2nd paragraph of Sherwood (2020) section 2.1 for the full description]. And ECS is relevant to how reactive the planet’s climate will be to our poking it with a sharp dose of AGW.
My take on it is that S should be considered as equivalent to ECS with Sherwood et al telling us ” This quantity therefore approximates the long‐term Charney ECS, though how well it does so is a matter of active investigation.” (I say “should be” because ECS assessments are inexact so S will be useful to nail dlwn the true value.( Thus Cooper et al present a value for “modern-day ECS” saying “the best estimate becomes 2.9°C, 66% range 2.4° to 3.5°C (2.1° to 4.1°C, 5 to 95%), substantially narrowing uncertainty compared to recent assessments.”
The AESS of Judd et al is more difficult being not immediately a true ESS and introducing the need to understand the relationship between ESS & ECS.
My understanding of the latter is that, relative to ECS, ESS accounts for changes in albedo due to melting ice caps and shifting eco-systems, processes which are normally seen as take a long time, eco-wise stuff like the northward move of the African Sahel or Siberian Taiga in a warming climate. (Mind, I’d reckon the die-off of Amazonia isn’t probably such a long-winded process.)
The relationship between ESS & ECS will vary, not least with the amount of ‘glacial feedback’ as shown in fig 2 of Passenier (2021) which suggests ESS/ECS in a range of 1.0 to 2.4 with Passenier pointing to 2.0 fitting today’s ‘glacial feedback’ which probably fits with Burton et al (2023) who calculate ESS/ECS for the Pliocene (5.4 – 2.4 My bp when the world was a little less icy than today ) at ESS/ECS = 1.7.
I’m not sure this AESS should be considered as an approximation to ESS for the full Phanerozoic. But let’s run with the idea that it is.
Judd et al are plotting their 485My global temperature reconstruction alongside a 460My log-CO2 reconstructions (as in their fig4a) and pointing out CO2 is shown (yet again) as the primary climate ‘control knob’, and quite convincingly. They then consider the sensitivity of this ‘control knob’ and use OLS thro the Paleozoic (650My-250My) data finding per doubling of CO2, +7.8°C (± 0.3°C 1sd) and thro’ the Cenozoic (66My-present) +8.2°C ± 0.4°C.
(The Mesozoic is not so useful in support of radical ‘control knob’ theory as CO2 remains relatively flat while the planet warms perhaps +10°C.)
Judd et al do make plain they are “somewhat surprised” by this “consistent relationship between CO2 and GMST across the record.” As they point out, these lengthy periods will be subject to at least solar forcing and the Land:Ocean ratio (impacting presumably surface albedo) which they attempt to quantify & plot out in their fig S.11a. The solar forcing is substantial over the full period (+9.8Wm^-2) but their assessed LandOcean effect helpfully acts in the opposite direction pretty-much the same amount thro’ the Paleozoic. For the Cenozoic (which is helpfully shorter) the solar and their LandOcean do not cancel, adding a +1Wm^-2 over the last 40My. And that adds a third on top of the CO2 forcing, a significant amount. Does that mean Cenozoic AESS should be reduced by a quarter to [0.75 x +8.2°C =] +6.15°C? And thus would suggest modern ECS = 0.5 x ESS = +3.1°C?
I’m not sure.
John Hearps says
Hi great work. How did this data relate to Milanokovic (?) cycles of warming and cooling?
Piotr says
John Hearps: How did this data relate to Milanokovic (?) cycles of warming and cooling?
Probably doesn’t. The long time scale (500 M yrs) comes at the price of time resolution – which is nowhere near to what would be needed to resolve the Milankovic cycles (periods 100kyrs or less)
And the climate is sensitive to Milankovic cycles only under very specific conditions – the right paleogeographic conditions and in very low CO2 concentration.
And we already know a lot about the Milankovic cycles from studies having the right time resolution – particularly in the last 800,000 yrs – as these have high-resolution and high quality data from ice cores.
Mal Adapted says
Piotr: And the climate is sensitive to Milankovic cycles only under very specific conditions – the right paleogeographic conditions and in very low CO2 concentration.
Thanks. I was trying to explain this to my sister, who is intelligent but educated in the humanities. I forgot about the very low CO2 concentrations required for astronomical cycles to initiate ice ages. Amazing how Milankovitch got it right for the Pleistocene with only the science of his time. He did get support from Wegener regarding the role of continental drift, but Google’s search A.I. says:
“No, Milutin Milanković, the scientist who developed the Milankovitch cycles theory, did not have a comprehensive understanding of carbon dioxide’s role in climate change as it was not widely recognized during his time; his theory focused solely on the Earth’s orbital variations as the primary driver of ice ages, without considering the significant impact of CO2 levels.”
Sounds authoritative. Is it true?
Piotr says
Mal: “Sounds authoritative. Is it true?”
Probably true – given that in his time we didn’t know that much about the feedbacks resulting in the glaciation cycles.
If the amount of solar radiation in summer in Arctic increases enough to reduce amount of snow/ice compared to the previous summer – then less icy land and especially ocean will absorb more solar radiation => warmer temps => even less ice next summer and so on and on. Also the initial increase in solar radiation amplified by ice feedback, at some point start the other three positive feedbacks of T with CO2, CH4, and water cycle heating, each increasing T, and in the next cycle the higher T cause even less ice, more CO2, more CH4 and more water cycle warming.
Of these, in Milankovic time we didn’t know anything about CO2, CH4, and water cycle – feedbacks. Whether he connected the dots with melting ice decreasing water and land’s albedo – or just left at the realization that there are 3 cycles in amount/distribution of solar radiation that I don’t know. Wikipedia note suggests the latter:
“ established the astronomical theory of climate as a generalized mathematical theory of insolation ”
The ice link may have been pointed to him later, again Wikipedia:
“ He accepted Köppen’s suggestion that cool summers were a crucial factor for glaciation and agreed to calculate the secular progress of insolation of the Earth at the outer limit of the atmosphere for the past 650,000 years for parallels of 55°, 60° and 65° northern latitude, where the most important events of the Quaternary glaciations occurred.”
I don’t think his contacts with Wegener were linking continental drift with glaciation cycles – it seems to be a separate idea that Milankovic found interesting. I think the realization that you can have glacial cycles, triggered by orbital cycles, ONLY under specific conditions * came much later.
Those specific conditions are:
– that the Earth has to be cold enough to have summer ice – without it you don’t get ice-albedo feedback going (and the orbital forcing alone does not increase T enough to start the other three feedbacks). That’s why I said that “ climate is sensitive to Milankovic cycles […] in very low CO2 concentration”
– correct paleogeography – if you have continent in high latitudes instead of the ocean – Milakovic can’t trigger the ice-albedo effect.
That’s why recent glaciation cycles are triggered by Milankovic changes in solar radiation in summer in Arctic, NOT in Antarctica – Arctic is mainly oceanic – meaning that warmer than usual summer will melt sea-ice and decrease albedo; Antarctica has a continent in the centre – meaning that the ice is thick and elevated – so warmer than usual summer – doesn’t melt enough ice to expose dark water or ground, hence ice albedo feedback in Antarctica is too weak to jumpstart the other three feedbacks.
Now, because you need to get paleogeography and CO2 right – that’s why the glaciation periods are so rare – the previous one was in late Carboniferous, caused paradoxically by the success of plants in early warm and humid climate of early Carboniferous. Forests of tree ferns and tree lycophytes, after their death fell into swamps, and in low O2 mud – plant C wasn’t decomposed to CO2, but instead was sequestered in the ground, becoming ultimately coal. With so much CO2 taken out of the air, one of the condition of an ice age was met…
So ferns and lycophytes by their spectacular success, sowed the seeds of their own demise (a bit ironic since taxonomically they are called “seedless vascular plants”… ;-) ): their explosive growth changed their climate to the one in which they could no longer thrive. And when the climate ultimately rebounded, they didn’t – outcompeted by other groups, the few who survived, live today in shadows of their conquerors.
Perhaps a lesson for us…
Or at least – for the modern day Candides who are so pleased to notice that: “ It’s nice to realize that these past high temperatures did not create the “catastrophes” to the biota that current models predict. “
Kevin McKinney says
Fascinating development. Very much worth following the link back to the published paper.
Thanks, Gavin!
Russell Seitz says
It’s so good that all the usual lobbyists and ignorami have rushed to traduce it.
The solution- brace and stick to X, the comedy of manners formerly known as Twitter, where diversity of opinion on climate and energyis at once deplored and needed.
Garth Mihalcheon says
Thanks for highlighting this important paper! In perspective, the Holocene that nurtured civilization is a rare climatic oasis indeed. This deep time perspective underscores the obscene risks humanity is taking by burning up our stores of fossil carbon in an absurdly short time frame.
J Robert Gibson says
EXCELLENT. THANK YOU.
We now need climate scientists to advise on the impacts of actions policy makers might take to save Earth’s biosphere from excessive GHGs in its atmosphere.
–
Specifically:
1) The paper concludes that the temperature response to a doubling of CO2, (including fast and slow feedbacks) of ∼8°C. Given this, what be the long-term equilibrium if Net Zero is achieved by 2050 on different plausible pathways.
2) Advising on the impacts of different geo-engineering options which could improve the post 2050 climate.
Of these:
– Carbon Dioxide Removal has a role but will be too slow to save us from severe deterioration of the climate.
– What impact’ might action to re-establish the Arctic Ocean sea ice have? (*Ideas of pumping sea water iinto the air in winter near the north pole so as to thicken the ice-cap.) https://www.climaterepair.cam.ac.uk/refreeze
– What impact would a sun-shield at the L1 point between the Earth and the Sun. have?
Regarding the sun-shield at the L1 Point:
– The UK Royal Society’s 2009 paper on geo-engineering dismissed space-based sun-shields as being too expensive and taking too long to put in place. Since then the development of large re-useable rockets (Spaceship and New Glenn) promises to remove both these constraints. by bringing down the cost of transport from Earth to the L1 point and increasing capacity to launch mass into space by a couple of orders of magnitude
– NASA’s Advanced Composite Sail research provides a basis for developing the satellites needed https://www.nasa.gov/mission/acs3
– Space-based avionics have developed to a point where low-weight avionics can manage a constellation of 6,000+ satellites.
Mitch says
I’ve only had a quick look at the paper, but have some skepticism. Direct estimates from marine samples are only available for periods younger than about 150 million years. So 2/3 to 3/4 of the globe doesn’t have samples to ground truth the work. The marine samples that are available are almost all from inland seas, not the same thing as the ocean.
Nevertheless, it is a step forward.
David says
Congratulations to Dr. Judd and her entire team for producing a worthy work garnering the notice and praise it is receiving. Haven’t chewed through the entirety yet, but as Susan Anderson aptly noted: “ …but where I cannot evaluate for myself, I trust RealClimate.”
It will be interesting to see what happens when folks are able to try using this work in regards to the efforts studying the biodiversity booms and busts for this 485 million year period (beyond the Big Five.)
I can already hear the denial proclamations coming: “see, no worries!” “Drill, baby, drill!” and just generally the “Told ya! This proves [insert various inane denier conspiracy claim here]”
Paul Pukite (@whut) says
When the average paleo global temperature was above 35C (or 90F), how was that distributed latitudinally? Was it then well-above 100F at the equator, while still quite warm near the poles year-around?
Paleoclimatology may be similar to geology at getting to a fundamental understanding : “Geology is like trying to learn about barley by studying beer” — https://geoenergymath.com/2024/09/23/amo-and-the-mt-tide/
Kevin McKinney says
To your question, Paul:
https://www.sciencedaily.com/releases/2010/08/100824132417.htm
(“How giant tortoises, alligators thrived in High Arctic 50 million years ago”)
Not a complete answer, by any means, but definitely bearing on methodological and substantive aspects.
Scott says
Hey, so–it looks like were in a cold spell as of late, correct?
Ray Ladbury says
It looks like such cold spells are essential for a complex civilization of humans to thrive, also.
Kevin McKinney says
Correct, and not news, either. But “as of late” accounts for something like 3 million years, which means that current life has had time to become well-acclimated to the “cold spell.” That’s adaptation time that we are not affording the biosphere this go-round.
Susan Anderson says
It’s about the timeline; trying to exploit this is a fool’s game for the gullible. Due to compression the final uptick is almost invisible, but comprises the entirety of the recent and shocking global heating. If you are interested, a couple of recommendations, the delightful A (Very) Short History of Life on Earth by Henry Gee will flesh out the perspective.
https://royalsociety.org/medals-and-prizes/science-book-prize/books/2022/a-very-short-history/
And if you like depth the somewhat grim (and loooong) Frankopan’s The Earth Transformed: An Untold Story is massively informative. – https://www.theguardian.com/books/2023/mar/02/the-earth-transformed-by-peter-frankopan-review-history-through-a-different-lens
tl;dr synopsis: comparison with other ages of the last 450 million years will tell you human habitation on earth evolved in a relatively hospitable period of its history. You (and we) would not enjoy (or survive) those warmer periods.
Julian says
“A (Very) Short History of Life on Earth” is such a good recommendation. It was one of the books I read while I was trying to make sense of the problems we have as a species, the other being “A Darwinian Survival Guide” by Daniel Brooks and “Ishmael” by Daniel Quinn. Both are fantastic reads that really do put things in context (namely, why agricultural civilization just isn’t a solution to any problems we’re facing and never was – and what can we do about it).
Chris Colose says
Although there are many aspects of. the temperature curve similar to previous studies, it does have more warm-end variability and hotter temperatures, especially near 90 Ma (see their supplemental figure https://postimg.cc/68vcjth2) which is interesting. I’m interested in playing around with a GCM soon to see how you can get global temps up to 35-40 C with reasonable boundary conditions during this interval (in the Fast-Atmosphere Ocean Model that Gary Russell has run at GISS it happens between 8-16x CO2, but with modern continents and solar flux https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2013GL056755). There’s also interesting implications for habitability and heat stress, especially in the tropics (even in the age of mammals this is some fruitful territory to explore).
There are also a few (likely minor) things not modeled in the prior, including a slightly evolving length of day from ~22 to 24 hours, and atmospheric O2 levels. For example, an atmosphere with 30% oxygen and present-day N2 mass would have a surface pressure of over 1150 mb and broaden the absorption features of GHGs. But these can also affect their sensitivity estimate, which isn’t quite right for the other reasons too. They do try to calculate the other forcings (their supplemental S11 but I don’t think that carried over to the ESS regression)
@Paul they do show results for the pole-to-equator temperature gradient (their Fig. 3) which does indeed flatten in hothouse climates as we expect.
Hairy Butler says
Take a good look at this image from the article: https://www.realclimate.org/images/graph-from-scott-wing-620px.png
In roughly a century, we’ve gone about halfway towards the “no ice caps” tipping point.
That’s horrific.
Jonathan David says
The impulse-response-like “spike” at the Ordovician glaciation appears anomalous somehow. The presence of ice caps seems to create a quasi-stable climate state for approximately 10^8 years. I would guess that this is primarily driven by continental drift in which the poles are over land. The absence of oceanic currents would allow the formation of ice caps and other “short time scale” phenomena such as ice ages. The cause of the Ordovician glaciation seems inconsistent with this idea. It would be very interesting to see a more detailed comparison of polar land configurations especially at the ~260 million and ~360 million crossing points as well as the 445–444 Ma.
It’s also very striking how well periods of mass extinction coincide with these crossings. This is perhaps obvious but not something I can recall hearing. The extinctions at 445–444, 372–359, 252 and 201.3 Ma. align well with these transitions. The anomaly here is the Cretaceous extinction at 66 Ma which doesn’t seem to fit into this picture. One could conclude that extinctions arise from “extreme’ temperature changes (on a geological time scale) and not on temperature levels per se.
William says
There may be a cure for too many humans on the planet and emitting too much gas.
The coming microbial crisis: Our antibiotic bubble is about to burst
Andreas J. Bäumler https://orcid.org/0000-0001-9152-7809Authors Info & Affiliations
Science
19 Sep 2024
Vol 385, Issue 6715
DOI: 10.1126/science.ads3473
Nigelj says
Scott, yes we are in a cold spell relative to the extended hot spell millions of years ago. However it looks like we wont be in a cold spell for very long. Anthopogenic warming has already increased approximately one degee C above pre industrial, and it is projected to increase to 3 – 5 degrees by 2100 and about 6 – 8 degrees after three centuries , (all at BAU scenario). It could be more than 8 degrees after thousands of years based on the long term ESS (earth system sensitivity) response..This means SLR would be 1 – 2 meters by 2100, maybe 3 – 6 metres after three centuries and in the tens of metres over millenia time frames..This all has profound implications.
We have probably already done enough mitigation work already to reduce all this slightly, but we are not doing nearly enough mitigation to adequately resolve the problem or to keep warming below 2 degrees. We need more strenouus efforts to develop renewable energy and electricy the transport system and develop viable carbon sequstration and reduce our levels of energy use (within reason)..
Of course its not really the prevailing temperature that is the main issue. Its the rate of change, and anthropogenic warming is causing rapid change, and past history suggests this is when you get the mass extinction events, because species dont have enough time to adapt ( to rapid warming or cooling). This affects not just human lives, but our farming productivity, all our trillions of dollars of infrastructure. especially coastal infrastructure, and a variety of other species.
Climate change is already costing humanity money and resources, insurance premiums are going up, people lives have been damaged, and this is just a taste of what could be coming. The climate is non linear, so things may get worse at an accelerating pace, and we could pass various tipping points making it even harder to fix the problem.. This is what worries me.