How cold was the ice age? Researchers now know

Short answer? At the very depth of the last ice age (about 20,000 years ago), average global temperature was 6 degrees Celsius (11 F) colder than today. But remember, they’re talking about average GLOBAL temperature, which includes all of those areas covered by one to two miles of ice. Average temperatures in many parts of the world were sometimes not all that much colder than today.

The following is from a release written by the University of Arizona.
______________

How cold was the ice age? Researchers now know


Image credit: Jessica Tierney, University of Arizona

A team of scientists has nailed down the temperature at the peak of the last ice age, a time known as the Last Glacial Maximum, to about 46 degrees Fahrenheit.

Their findings allow climate scientists to better understand the relationship between today’s rising levels of atmospheric carbon dioxide—a major greenhouse gas—and average global temperature.

(Just for clarity, I disagree that atmospheric carbon dioxide is ‘a major greenhouse gas.’)

The Last Glacial Maximum, or LGM, occurred about 20,000 years ago and was a frigid period when glaciers covered about half of North America, Europe and South America and many parts of Asia, while flora and fauna that were adapted to the cold thrived.

“We have a lot of data about this time period because it has been studied for so long. But one question science has long wanted answers to is simple: How cold was the ice age?” said Jessica Tierney of the University of Arizona, who led the team that also includes scientists from the University of Michigan, the National Center for Atmospheric Research and the University of Washington.

Tierney is lead author of a paper published today in Nature that found that the average global temperature of the ice age was 6 degrees Celsius (11 F) cooler than today. For context, the average global temperature of the 20th century was 14 C (57 F).

(Remember, they’re talking about average GLOBAL temperature, which includes all of those areas covered by kilometers of ice. Average temperatures in many parts of the world were sometimes not all that much colder than today.)

Co-authors of the Nature paper include Christopher Poulsen, a professor in the U-M Department of Earth and Environmental Sciences, and former U-M postdoctoral researcher Jiang Zhu, who is now at the National Center for Atmospheric Research.

For the project, the researchers used a technique that combines fossil data of past temperatures with climate model output to create maps that show how temperature differences varied in specific regions around the globe. Zhu and Poulsen were responsible for developing the climate model simulations of the LGM.

“Six degrees of global average cooling is enormous. The world would have looked much different during the last glacial maximum,” said Poulsen, who is also the associate dean for natural sciences at the U-M College of Literature, Science, and the Arts.

“The northern portions of North America, including here in Ann Arbor, Michigan, were covered by kilometers of ice,” he said. “The biggest cooling was in the high latitudes.”

The researchers said their findings fit with scientific understanding of how Earth’s poles react to temperature changes.

“Climate models predict that the high latitudes will get warmer faster than low latitudes,” Tierney said. “When you look at future projections, it gets really warm over the Arctic. That’s referred to as polar amplification. Similarly, during the LGM, we find the reverse pattern. Higher latitudes are just more sensitive to climate change and will remain so going forward.”

(The press release now veers off to talk about atmospheric carbon, I suppose to justify the researcher’s funding sources.)

Knowing the temperature of the ice age matters because it is used to calculate climate sensitivity, meaning how much the global temperature shifts in response to atmospheric carbon. The researchers determined that for every doubling of atmospheric carbon, global temperature should increase by 3.4 C (6.1 F), which is in the middle of the range predicted by the latest generation of climate models (1.8 to 5.6 C).

“Without having an accurate estimate of the LGM temperature, we couldn’t be confident in how temperature responded to changes in atmospheric carbon,” Zhu said. “Our results provide that confidence.”

Atmospheric carbon dioxide levels during the ice age were about 180 parts per million, which is very low. Before the Industrial Revolution, levels rose to about 280 parts per million, and today they’ve reached 415 parts per million.

“The Paris Agreement wanted to keep global warming to no larger than 2.7 F (1.5 C) over pre-industrial levels, but with carbon dioxide levels increasing the way they are, it would be extremely difficult to avoid more than 3.6 F (2 C) of warming,” Tierney said. “We already have about 2 F (1.1 C) under our belt, but the less warm we get the better, because the Earth system really does respond to changes in carbon dioxide.”

(Now the release gets back on track.) 

Since there were no thermometers in the ice age, the researchers developed models to translate data collected from ocean plankton fossils into sea-surface temperatures. They then combined the fossil data with climate model simulations of the LGM using a technique called data assimilation, which is used in weather forecasting.

In the future, the researchers plan to use the same technique to recreate warm periods in Earth’s past.

(I would love to see their planned recreation of earlier warm periods, because those earlier warm periods took place long before the Industrial Revolution.)

“If we can reconstruct past warm climates,” Tierney said, “then we can start to answer important questions about how the Earth reacts to really high carbon dioxide levels, and improve our understanding of what future climate change might hold.”

The research was supported by the Heising-Simons Foundation and the National Science Foundation.

Release written by the University of Arizona

August 26, 2020
Contact: Jim Erickson ericksn@umich.edu,
Mikayla Mace mikaylamace@arizona.edu

More information:


16 thoughts on “How cold was the ice age? Researchers now know”

  1. “Their findings allow climate scientists to better understand the relationship between today’s rising levels of atmospheric carbon dioxide—a major greenhouse gas—and average global temperature.” CO2 IS NOT a ‘major greenhouse gas’. Poor reporting.

  2. “but the less warm we get the better, because the Earth system really does respond to changes in carbon dioxide.”

    CO2 lags global temperatures as evidenced by the Vostok ice core temperature reconstruction. The ONLY place on the EM spectrum that is not overwhelmed by water vapor’s emissivity is at the 11-15 μm band.

    In other words, if the planet is doomed, it’s because of just 4 μm of LWIR bandwidth. How irresponsible of the universe to make life so sensitive to such a minor function!

  3. But was the North Pole in the same place as it is now? It seems strange that so much of North America was under that amount of ice.

    Could the Earth have tipped? Could the North Pole have been in Hudson’s Bay at one time?

    • Cliffhild – the cold doesn’t follow the drifting magnetic poles…
      the poles are cold because of a lack of sunlight, not due to magnetism.

    • What would happen temperature and weather-wise if planet Earth lost the tip/angle it has right now and was basically standing upright towards the Sun?
      What is making it tip now? and has it always been that way?

  4. 6 degrees C colder is what is needed to get the average temperature in the southern, land locked parts of Scandinavia below 0C. People are really surprised when they realize how cold it is here.

    And when they start talking about how the gulf stream will heat us. Realize that is was less than 50000 years ago that you could walk from France to England. Nature changes.

  5. I don’t get the logic of this paper. Do they regard the last glacial maximum (LGM) as something desirable, that they want us to go back to? It was a mini extinction event, megafauna such as the sabre toothed tiger and woolly rhinos died out. 180 ppm CO2 is low enough to stress plants. This makes no sense.

  6. CliffHild

    Look at the recent jet-stream patterns, which are guided seasonally by the interaction between the solar magnetic field and the earth’s magnetic field. Then look at the shape and locations of the glacial ice during the last ice age. A very close match. Persistant dragging down of polar air over extended periods of time by a meandering jet-stream, caused the massive build up of ice, due to almost constant snowfall. Robert explains this in his books.

  7. “A team of scientists has nailed down the temperature at the peak of the last ice age, a time known as the Last Glacial Maximum, to about 46 degrees Fahrenheit.
    Their findings allow climate scientists to better understand the relationship between today’s rising levels of atmospheric carbon dioxide—a major greenhouse gas—and average global temperature.’ … glurge, glurge, and more of the very same thick syrupy CO2/climate propaganda glurge

    CO2 at only one in twenty-five hundredths (400 ppm) of the atmosphere is “a major greenhouse gas”… looks like they’re still jumping the same shark pen, like ‘groundhog day’ over and over but now with the third or forth wave of globalist clown scientist replacing and/or recycling previous “teams of IPCC ‘scientist stooges’ including Phil Jones, Michael Mann and Jessica Tierney from The University of East Anglia, Brown University and now University of Arizona.

    Why is this micro proportion, of an essential trace gas, close to negative nothing of a percent the of the atmosphere even a ‘hydro-fracking’ thing anymore? I propose that the trillions of nano-sized viruses floating in the atmosphere are really the major ‘Fun Green House Particles’ driving this clown car climate universe. I’d round file this whole propaganda release written by the IPCC ‘ladies baseball team’ from the University of Arizona including their “nailed down temperature to 46 degrees Fahrenheit at the peak of the last ice age” findings, lockdown the whole university, reduce the population of all the IPCC CO2 farting clowns and mask up the rest of these multi-lettered scientists with impermeable rainbow print fashion fabric. Praying for paradise at the ‘end of time’ and the dashboard lights finally start to dim on these recycled banal ‘CO2/Conjob-1984 Clown Shows’.
    https://youtu.be/C11MzbEcHlw
    https://en.wikipedia.org/wiki/Funhouse

    https://en.wikipedia.org/wiki/Jessica_Tierney
    A lead author for the sixth assessment report of the Intergovernmental Panel on Climate Change (IPCC), 2018
    https://www.youtube.com/watch?v=2TnkJ8_BmSI

  8. the continents werent in the same spots
    otherise antarctica and the arctic would never of had trees etc tthere
    what made ME laugh about this?
    the aussie aboriginals keep pushing claims of inhabitation back from 20 n 30k yrs ago to now saying 60k yrs
    well even taking avg temps a race with little use of clothing living in caves or bark humpies etc
    really wouldnt have done too well at all. some of the “top-end “near tropical(now) spots in qld NT and WA might have scraped by but…elsewhere?
    doubtful.
    and from what ive heard(too much lately) they dont seem to have dreamtime tales of extreme cold/ice etc at all

  9. I am not convinced. The Alaska area was green about 20,000 years ago. Also, Greenland has yet to get out of its ice age. Much of Russia shows hardly any signs of glaciation even if the permafrost is still a hindrance to agriculture. Much doesn’t add up. All I can say is that the climate is very eccentric and it has always changed. Get over it.
    Am I worried? No. Not anywhere near as worried as I tend to get regarding political mismanagement of things like Covid and how Greta became a celebrity just for repeating a few lies of politicians.
    Life marches on and changes affect us all. This morning I am freezing as I wake up compared to a month ago in which I slept with no covering and windows all open. The only failure is failure to adapt to the new normal in the wider sense.
    A person locked into the past is his own demise.
    You can never stand in the same river twice.
    Mark my words.

  10. More twaddle masquerading as science. It works like this, work out the conclusion you seek then reverse engineer the “science” to fit.

  11. Of note in the image of the Earth above, is that also reflected is that sea levels are shown to be 400 ft lower at the same time, which we all know.

    Curious – anyone ever seen an image of what the Galapagos would have appeared w/ SL 400 ft lower.There’s a lot of less than 400 ft deep ocean surrounding them.

Comments are closed.