{"id":92495,"date":"2020-10-23T11:27:46","date_gmt":"2020-10-23T16:27:46","guid":{"rendered":"https:\/\/news.medill.northwestern.edu\/chicago\/?p=92495"},"modified":"2020-10-23T14:35:35","modified_gmt":"2020-10-23T19:35:35","slug":"milankovitch-theory-flaw-climate-change-new-study","status":"publish","type":"post","link":"https:\/\/news.medill.northwestern.edu\/chicago\/milankovitch-theory-flaw-climate-change-new-study\/","title":{"rendered":"Even most scientists don\u2019t know that this famous climate theory is flawed, researchers say"},"content":{"rendered":"

By Caroline Catherman<\/strong>
\nMedill Reports<\/em><\/p>\n

New research has found a big flaw in one of the most widely accepted theories about earth\u2019s climate, Milutin Milankovitch\u2019s century-old theory of ice ages. This evidence, which echoes past findings, means that some long-term climate predictions could be more inaccurate than scientists realize, the researchers said. But they worry that this vital information won\u2019t become general knowledge for years.<\/span><\/p>\n

\u201cIt takes about a generation of new scientists to remove older ideas and bring newer ideas in,\u201d said Thomas Lowell, professor of geology at the University of Cincinnati, during the recent Comer Climate Conference, an annual national conference held over Zoom this year.<\/span><\/p>\n

\"\"
Milankovitch proposed that cyclical changes in earth\u2019s wobble, orbit shape and tilt relative to the sun cause ice ages. Figures are not to scale. (Animations and facts from nasa.climate.gov.)<\/figcaption><\/figure>\n

The theory in question proposes that gradual changes in our planet\u2019s movements and position add up over time to vary how much solar radiation reaches Earth. This variation in solar radiation affects whether each hemisphere experiences periods of cooler or warmer summers. Milankovitch predicted that thousands of years of colder summers cause ice ages.<\/span><\/p>\n

\u201cIf you surveyed 100,000 geologists, 99,099 would say that\u2019s correct, in terms of causing ice ages. But it has one big problem,\u201d said Brenda Hall, a professor of glacial & quaternary studies at the University of Maine’s Climate Change Institute.\u00a0<\/span>
\n<\/span><\/p>\n

The theory’s hidden undoing<\/h2>\n

Milankovitch predicts that ice ages would occur at opposite times in the Northern and Southern Hemispheres. When one hemisphere was having cold summers, and heading towards an ice age, the other would be having warm summers, heading away from an ice age.<\/span><\/p>\n

But Hall and Lowell\u2019s new research from the Falkland Islands corroborates recent research<\/a> in New Zealand by suggesting that the two hemispheres experienced the last major ice age, which peaked about 20,000 years ago, at nearly the same time.\u00a0<\/span><\/p>\n

These findings, currently undergoing peer review for publication, mean that scientists may not fully understand why the planet goes in and out of ice ages, said Hall.<\/span><\/p>\n

This, Hall said, is crucial to understanding climate change.<\/p>\n

\u201cIf we want to have any hope of making climate predictions, we need to know how the different pieces of the system work,\u201d she said.<\/span><\/p>\n

Hall added that researchers should begin considering other theories. One older theory is the idea that, rather than gradually shifting in and out of ice ages, earth’s climate rapidly changes due to sudden triggers. If true, this would have troubling implications for Earth’s future climate.<\/p>\n

“If we can have ice age cycles, these massive changes in climate, because of very small changes … that tells us that a very small change could produce a big reaction. And we’re in the process of initiating one of those changes,” Hall said, referring to human-caused increases in greenhouse gas emissions.<\/p>\n

But before many climate researchers will reconsider whether this theory is accurate, they must be convinced that the issue is up for debate.<\/p>\n

Scientists are battling to replace a broken theory<\/h2>\n

Convincing scientists to consider alternative theories is a long process that some people have been attempting since as far back as <\/span>1984<\/span><\/a>, when John Mercer published a paper with evidence of simultaneous ice ages.
\n<\/span><\/p>\n

\u201cI feel like there have been some proposals as to, \u2018what else could it be?\u2019\u201d said Meredith Kelly, associate professor of earth science at Dartmouth College. \u201cUntil we figure that out, and it\u2019s really well tested, and well-explained, it\u2019s not going to show up in textbooks.\u201d\u00a0<\/span><\/p>\n

Lowell said that scientists in older generations are the biggest defenders of Milankovitch because they were taught to regard his theory as fact.<\/span><\/p>\n

\u201cIf you look at the world, and everybody tells you it\u2019s flat for 40 years \u2026 and you walk around and you discover that it\u2019s not flat \u2026 you\u2019re gonna have problems convincing people who haven\u2019t traveled out of their flat sphere that the earth is round,\u201d Lowell said.\u00a0<\/span><\/p>\n

Why Milankovitch’s theory gained acceptance<\/h2>\n

Several prominent studies have appeared to support Milankovitch\u2019s theory. A <\/span>1976 study<\/span><\/a>, for example, found evidence of a correlation between earth\u2019s cycle in and out of ice ages and the so-called Milankovitch cycles. Lowell said these findings were strong enough that many people thought the issue was resolved, even though there was no evidence that this was a cause and effect relationship.\u00a0<\/span><\/p>\n

\"southern
Hall and Lowell\u2019s research in the Falkland Islands took them to the top of Mount Osborne, where they used surface exposure dating to track ice ages by mapping the advance and retreat of glaciers over thousands of years. (Brenda Hall)<\/figcaption><\/figure>\n

It also took a long time to build evidence against Milankovitch because the Southern Hemisphere wasn\u2019t as well studied as the Northern Hemisphere. When scientists found evidence that the Southern Hemisphere came out of the ice age at the same time as the north, the evidence was initially dismissed as a fluke, said Lowell.\u00a0<\/span><\/p>\n

The new generation of scientists is key<\/h2>\n

\u201c[The Milankovitch Theory] made sense. It wasn\u2019t until you get into the details that you start pulling a thread, and it starts unraveling,\u201d Lowell said. \u201cIt\u2019s taken a long time\u2026 to get to where we are today.\u201d\u00a0<\/span><\/p>\n

Lowell hopes that scientists in the next generation will weave up a new idea with the unraveled Milankovitch thread. For her part, Meredith Kelly has done her best to correct the canonical theory during her 12 years of teaching an intro to geology class, even as she gives her students a textbook that reveres Milankovitch.<\/span><\/p>\n

\u201cOne of the students on the first day asked me if I was going to teach about Milankovitch, and I told her, \u2018Yes, but I\u2019m going to tell you that he\u2019s wrong,\u2019\u201d Kelly said with a laugh.\u00a0<\/span><\/p>\n

Professors such as Kelly give Lowell hope.\u00a0<\/span><\/p>\n

\u201cScience will march on,\u201d he concluded.<\/span><\/p>\n

Caroline Catherman covers health, environment, and science news at Medill. You can follow her on Twitter at <\/i>@CECatherman.<\/i><\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

By Caroline Catherman Medill Reports New research has found a big flaw in one of the most widely accepted theories about earth\u2019s climate, Milutin Milankovitch\u2019s century-old theory of ice ages. This evidence, which echoes past findings, means that some long-term climate predictions could be more inaccurate than scientists realize, the researchers said. But they worry […]<\/p>\n","protected":false},"author":710,"featured_media":92557,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5045,29],"tags":[],"class_list":["post-92495","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-fall-2020","category-health-and-science"],"yoast_head":"\nEven most scientists don\u2019t know that this famous climate theory is flawed, researchers say - Medill Reports Chicago<\/title>\n<meta name=\"description\" content=\"\u201cIf you surveyed 100,000 geologists, 99,099 would say that\u2019s correct, in terms of causing ice ages. 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