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The Puzzling Pleistocene

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The mystery of why the last million or so years of glacial variability are so different to what came before just got more mysterious…

It’s easy to understand why the ice ages have such a hold on our imaginations. Putting aside the cavemen, woolly mammoths, and sabre-toothed tigers of popular culture, the scientific questions around the pacing of the glacial cycles, their magnitude, variability, and impacts are truly profound.

Despite huge strides in understanding the ice ages – from the ground-breaking work of Hayes, Imbrie and Shackleton (1974) that demonstrated the skill of the Milankovitch model in the 1970s, the paradigm-busting results from the Greenland Ice Cores in the 1990s, the discovery of the Heinrich events, etc., there remain plenty of real and abiding mysteries including:

  • Why are the 100kyr cycles so strong?
  • What are the details of the carbon feedbacks on glacial-interglacial cycles?
  • What triggered the ice ages in the first place? (i.e. why did the impact of Milankovitch cycles get much larger over the last 2.5 million years?)
  • Why didn’t humans develop agriculture in the last interglacial?
  • What triggers the Dansgaard-Oeschgar oscillations?
  • and… what caused the change from lower magnitude 40kyr cycles to 100kyr cycles across the Mid-Pleistocene Transition (MPT)?

We have good evidence from the deep Antarctic ice cores of the coupling between CO2 and temperature over the last 800kyrs and from ocean sediment proxies, we have reasonable estimates of the coupling between CO2 and temperature over the long cooling during the Cenozoic (the last 65 million years). But, until now, we haven’t been able to really examine that intervening period – the early Pleistocene.

Theories, of course, abound. The obvious one is that the long term declines in CO2 crossed a threshold that allowed for larger ice volumes that had more resonance with the 100kyr cycles. Another is that the early ice advances (which were more spread out but less voluminous) scraped all the soils off the rocks and that subsequent ice sheets were less mobile. I think most folks expected the data (when it arrived) to basically confirm what people expected.

But sometimes the observations don’t confirm your preconceived notions. The nice thing about science is that scientists (ideally) tend to get excited at this point (instead of, say, trying to deny the new information). So what has just happened?

Two new papers, Marks-Peterson et al. (2025) (direct link) and Shackleton et al. (2025) (direct link) in Nature this week report on analyses of very old Antarctic ice. These samples come from the “blue ice” in the Allan Hills in Antarctica where multi-million year old ice surfaces after having been deposited and transported over large distances. This is quite distinct from deep drilling in places where you hope the ice has not moved much, and while it doesn’t have the nice stratigraphy of the cores, you can sample snapshots of the atmosphere over a much longer time – in this case, almost 3 million years – albeit with coarser dating.

There are two main measurements presented. The first are the GHG concentrations in the air bubbles trapped in the ice (Fig. 1), and the second is a record of mean ocean temperature inferred from the ratio of noble gases in the air bubbles (Fig. 2).

Figure 1. Records of CO2 and CH4 over the last 3 million years.
Figure 2. Inferred ocean temperatures showing a cooling of about 2ºC from the beginning of the NH glaciation to the Mid-Pleistocene Transition (MPT) (filled circles).

The first and most dramatic (or rather, non-dramatic) result, is that CO2 levels appear to have barely changed (on average) over this key period – dropping only 20-30ppm over the onset period. That isn’t nothing, but it’s only about 0.45-0.7 W/m2 in forcing, and would lead to around 1ºC in global surface cooling. The CH4 levels might have been expected to fall too, but they seem to be static. [Note that this method is not sampling the glacial/interglacial variations which are apparent in the more recent records]. The second, and somewhat confounding, result is that the global ocean seems to have cooled by about 2ºC over the same time period (with the global surface temperature change would have been larger).

So we have a conundrum. The onset of NH glaciation did happen as the planet cooled (as might be expected), but the first guess for what caused that cooling (long term trends in CO2 and/or CH4) does not appear to work.

How might this be resolved?

There are always multiple potential ways out of a conundrum: subsequent analyses might find an issue with the observations, there might be a hyper-sensitivity to the small CO2 changes at this time (but why?), there might be something else driving the change (volcanism? dust aerosols?), or… what? None of these possibilities are obvious winners, and of course, they are not mutually exclusive. Eric Wolff (direct link) in his commentary seems to think that the ocean is doing the driving, but I think that might be backwards.

The funny thing is that paleo-climatologists have been wanting these old ice analyses for a long time – with the anticipation that they would help answer these questions. But they seem to be posing many more questions than they have answered.

Broader issues

One thing this shows is that scientists can’t be complacent. As we’ve seen with surprising climate events even over the last few years (2023, Antarctic sea ice, the increases in the Earth’s Energy Imbalance), the more you look at the planet (or even the universe) the more surprising things you find. Science is an active search for deeper understanding – and we are not done yet.

Final thought

At face value, these results seem to suggest that CO2 declines were not the dominant/only cause of the cooling at the onset of the ice ages, despite expectations. Some of the usual suspects are certainly going to claim (fallaciously) that this means that CO2 can’t be the cause of anything. This is obviously a stupid argument so feel free to judge anyone that makes it.

Nonetheless,…

There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy.

References

  1. J.D. Hays, J. Imbrie, and N.J. Shackleton, "Variations in the Earth's Orbit: Pacemaker of the Ice Ages", Science, vol. 194, pp. 1121-1132, 1976. http://dx.doi.org/10.1126/science.194.4270.1121
  2. H. Heinrich, "Origin and Consequences of Cyclic Ice Rafting in the Northeast Atlantic Ocean During the Past 130,000 Years", Quaternary Research, vol. 29, pp. 142-152, 1988. http://dx.doi.org/10.1016/0033-5894(88)90057-9

The post The Puzzling Pleistocene first appeared on RealClimate.

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sarcozona
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Trump health care fraud crackdown alarms disability advocates | STAT

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The Trump administration has zeroed in on its next target: ending health care fraud.

President Trump announced Monday the creation of a task force devoted to ending fraud, waste, and abuse in all federal benefits. On Tuesday, the administration expanded its Medicare and Medicaid fraud probe to Republican-led Florida.

The Centers for Medicare and Medicaid Services head Mehmet Oz — a former television star — has become the administration’s face, publishing numerous videos, social media posts and regulations that tout the agency’s commitment to crushing fraud in hospice, home health, durable medical equipment, and other industries. In January, CMS threatened to withhold roughly $2 billion in funding for 14 Medicaid services in Minnesota for the next year.

To the disability community, the crackdown feels less like the administration is rooting out crime and more like it is using fraud as an excuse to cut critical services — especially after the administration’s tax bill last year that slashed Medicaid funding by $1 trillion over 10 years, forcing state health officials to consider ending critical services like home care for millions of people.

Advocates worry that broadly targeting state Medicaid funding, like in Minnesota, will risk people’s lives. More than a quarter of Americans have a disability, and many of them require the home care, wheelchairs, autism therapy, and nonemergency transportation that have been targeted by CMS. 

“Access to Medicaid [home and community-based services] is a matter of life, death, and independence for millions of Americans with disabilities, older adults, and their families and loved ones. We strongly oppose the overly broad actions CMS is taking to freeze funding for Medicaid HCBS services in Minnesota and the threats to freeze funding for services across the country,” wrote representatives from the Disability and Aging Collaborative and the Consortium for Constituents with Disabilities. The groups represent nearly 200 organizations that advocate for people with disabilities and aging populations.

Disability

The timing of the recent, targeted efforts by federal authorities is especially problematic and threatens gains won over many years of activism, advocates told STAT.

“We’ve been fighting to expand access to these services over decades and decades. It hasn’t been easy, but there has been bipartisan support for expanding these programs and services,” said Natalie Kean, federal health advocacy director at Justice in Aging. “To be constantly trying to defend what we have is exhausting.”

Disability rights organizations packed a House Committee on Energy and Commerce hearing on Tuesday to protest the broad brush health officials are painting in their hunt for fraud. Two people wearing black shirts that said, “Medicaid cuts will kill,” flanked Kim Brandt, CMS deputy administrator and chief operating officer, as she answered questions about the agency’s tactics for tackling fraud and explained how it has used new artificially intelligent algorithms to stop over $2.1 billion in purportedly fraudulent payments.

“Crushing fraud is not simply about recovering funds after the fact,” said Brandt. “It’s about preventing harm, preserving trust, ensuring that these programs remain strong for current and future generations.”

Committee chairman Rep. John Joyce (R-Pa.) suggested fraud is “running rampant,” while Rep. Randy Weber (R-Texas) said that “thieves are making way with the taxpayer dollars.” But experts say there are no reliable measures of fraud in Medicaid or Medicare. Some of the eye-popping numbers cited by the Trump administration — the Department of Health and Human Services Office of Inspector General recently reported $285.2 million in overpayments for autism therapy in Colorado — are not necessarily fraud, but improper or potentially improper payments, which can be the result of missing documentation and not necessarily the work of “thieves.”

State and federal officials also have long-standing programs to look at the existence of health care fraud. The Department of Health and Human Services Office of Inspector General reported more than 1,100 convictions and $1.4 billion in recoveries in fiscal year 2024. 

“Any dollar that’s lost fraudulently for [Home and Community Based Services] is a dollar that doesn’t make its way to someone in need,” said Kendra Davenport, CEO and president of Easterseals, a nonprofit that provides services like home care around the nation. “So we certainly want there to be less fraud, and we recognize there probably is some fraud, but we really take umbrage with broad accusations of fraud, waste, and abuse, you know, because we think they undermine programs that so many millions of Americans rely on.”

Brandt spent much of the hearing talking about why the best way to prevent fraud was to move away from the “pay and chase” approach to a more aggressive “stop and cop” approach, in which fraudulent payments are canceled before they go out the door. She touted a “really cool series of algorithms” that, “much like Netflix tells you what movie to watch, it tells us these are high-risk people you want to keep an eye on.” 

Brandt didn’t explain how these algorithms work, or what factors are taken into account by the algorithm to flag something as high risk.” Minnesota, California, New York, and now Florida have received notice that they are or could be investigated for fraud abuse. Brandt said other states will receive similar inquiries from CMS.

“It feels very much like a 180 from decades of bipartisan agreement across administrations … where there has been an intentional investment in helping people stay in their own communities and their own homes instead of being forced into institutional settings, “ said Alison Barkoff, the former head of the federal Administration for Community Living.

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Critics urge Ottawa to help Inuit resist Chinese surveillance and economic dependence

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The Carney government is leaving Inuit communities at risk of Chinese surveillance and economic dependence and isn't facing up to the threat China poses to the North, critics say.
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Vancouver closes out first no-snow winter in 43 years with more of them on the way

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Vancouver is poised to close out its first official snow-free winter in 43 years, in what environmental researchers say may become a new norm for southwestern British Columbia rather than an anomaly.
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Iran sets its price to end the war

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sarcozona
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So many problems could have been avoided by not giving Israel weapons
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Dickhead With Ute Taller Than Himself Not So Fucking Smug About It Now — The Shovel

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March 18, 2026

An Australian man who bought an American pick-up truck the size of a two-storey townhouse because he thought it would make him look tough, has pulled his head in a little after realising he may be spending $500 a week on petrol by the end of the year.

Ben Tanner, who bought the oversized vehicle so he could sit two metres above traffic and feel briefly important, was seen at a local servo staring in mounting horror as the pump ticked past a figure normally associated with emergency plumbing.

Friends say Tanner, who believed his car made other cars look “like little bitch hatchbacks”, was quietly wishing he had a little bitch hatchback right now.

“He used to rev the engine whenever he left the driveway. Now he just sort of rolls down the hill in neutral,” one neighbour said.

But Tanner said getting rid of the ute was not an option. “My RAM 2500 ute is now my entire personality, so I don’t really have an option. I’ll just have to take out a second mortgage I guess,” he said.

The ute, which has a tray the size of a regional airport, has never transported anything heavier than a bag of potting mix.

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