Archive for the ‘Ice ages’ Category

Rinksglacier

Rinks Glacier, West Greenland [image credit: NSIDC]

Interesting, but as we’ve had a temperature rise of about 1.2ºC since 1880, according to one source at least, comparisons with much bigger historical increases in shorter timescales seem somewhat ambitious, to say the least.
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Throughout the last ice age, the climate changed repeatedly and rapidly during so-called Dansgaard-Oeschger events, where Greenland temperatures rose between 5 and 16 degrees Celsius in decades, says Phys.org.

When certain parts of the climate system changed, other parts of the climate system followed like a series of dominos toppling in succession.

This is the conclusion from an analysis of ice-core data by a group of researchers that included postdoc Emilie Capron and associate professor Sune Olander Rasmussen from the Section for the Physics of Ice, Climate and Earth at the Niels Bohr Institute, University of Copenhagen, in Denmark.

This discovery, just published in the journal Nature Communications, is concerning because the extent of sea ice in the Arctic played an important part in these dramatic climate shifts of the past.

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Cloud formation [image credit:NASA]


‘Challenges’ is a polite way of putting it. Is the alleged human-caused climate problem really more of a human-caused climate models problem?
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Increased reflection of incoming sunlight by clouds led one current-generation climate model to predict unrealistically cold temperatures during the last ice age [Source: Geophysical Research Letters].

Key to the usefulness of climate models as tools for both scientists and policymakers is the models’ ability to connect changes in atmospheric greenhouse gas levels to corresponding shifts in temperature, says Eos.

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Image credit: ScienceDaily


This has echoes of the ice age dust/albedo theory – with no CO2 feedbacks – proposed by Ralph Ellis a few years ago. The article concludes: ‘The result thus has the potential to aid the understanding of the abrupt warming and cooling periods during the ice ages called Dansgaard/Oeschger events which bear the marks of climate tipping points.’

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Every late winter and early spring, huge dust storms swirled across the bare and frozen landscapes of Europe during the coldest periods of the latest ice age, says Phys.org.

These paleo-tempests, which are seldom matched in our modern climate frequently covered Western Europe in some of the thickest layers of ice-age dust found anywhere previously on Earth.

This is demonstrated by a series of new estimates of the sedimentation and accumulation rates of European loess layers obtained by Senior Research Scientist Denis-Didier Rousseau from Ecole Normale Supérieure in Paris, France, and colleagues.

The work, which is published in Quaternary Science Reviews is part of the TiPES project on tipping points in the Earth system, coordinated by The University of Copenhagen.

In the study Denis-Didier Rousseau and colleagues reinterpreted layers in loess from Nussloch, Germany.

Loess is a fine-silt-sized earth type found all over the world. It mainly consists of aeolian sediments, which are materials transported by the wind from dry areas without vegetation such as deserts of any type, moraines, or dried-out river beds.

Within the aeolian sediments, darker layers of paleosol alternate within the loess layers. Every layer in the loess represents a shift in climatic conditions.

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Ice core sample [image credit: Discovering Antarctica]


But they ignore the fact that historical changes in carbon dioxide levels always followed changes in temperatures, so could not be the cause of such changes. The article below asserts the opposite, and talks about ‘better understanding’ while promoting a greenhouse climate theory that says one minor trace gas is all that matters.
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A University of Arizona-led team has nailed down the temperature of the last ice age—the Last Glacial Maximum of 20,000 years ago—to about 46 degrees Fahrenheit (7.8 C), says Phys.org.

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.

The Last Glacial Maximum, or LGM, was a frigid period when huge 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,” said Jessica Tierney, associate professor in the UArizona Department of Geosciences. “But one question science has long wanted answers to is simple: How cold was the ice age?”

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Greenland ice sheet (east coast) [image credit: Hannes Grobe @ Wikipedia]


Of course the other question about the start of an ice age still remains.

New University of Melbourne research has revealed that ice ages over the last million years ended when the tilt angle of the Earth’s axis was approaching higher values, reports Phys.org.

During these times, longer and stronger summers melted the large Northern Hemisphere ice sheets, propelling the Earth’s climate into a warm ‘interglacial’ state, like the one we’ve experienced over the last 11,000 years.

The study by Ph.D. candidate, Petra Bajo, and colleagues also showed that summer energy levels at the time these ‘ice-age terminations’ were triggered controlled how long it took for the ice sheets to collapse, with higher energy levels producing fast collapse.

Researchers are still trying to understand how often these periods happen and how soon we can expect another one.

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image credit https://visitgreenland.com/

Mike Waite left the following comment over at Paul Homewood’s excellent not a lot of people know that blog yesterday:

There is an interesting paper by MacGuth et al (2013) which supports you :

From their summary:

-“We calculate the future sea-level rise contribution from the surface mass balance of all of

Greenland’s glaciers and ice caps (GICs, ca. 90 000 km2) using a simplified energy balance

model which is driven by three future climate scenarios from the regional climate models

HIRHAM5, RACMO2 and MAR. Glacier extent and surface elevation are modified during the

mass balance model runs according to a glacier retreat parameterization. Mass balance and glacier surface change are both calculated on a 250 m resolution digital elevation model yielding a high level of detail and ensuring that important feedback mechanisms are

considered. The mass loss of all GICs by 2098 is calculated to be

2016 +/- 129 Gt (HIRHAM5 forcing),

2584 +/-109 Gt (RACMO2)

and 3907+/- 108 Gt (MAR). This corresponds to a total contribution to sea-level rise of

5:8 +/- 0:4,

7:4 +/- 0:3

and 11:2 +/- 0:3 mm, respectively. “-

The future sea-level rise contribution of Greenland’s glaciers and ice caps

H Machguth1,2, P Rastner1, T Bolch1,3, N M¨olg1, L Sandberg Sørensen4,

G Aðalgeirsdottir5, J H van Angelen6, M R van den Broeke6 and

X Fettweis7

Online at stacks.iop.org/ERL/8/025005

Even if subsequent calculations modified these figures they are unlikely to be an order of magnitude higher and the sea level rise to 2098 calculated here is at most 11mm (not cm or feet or metres).

Can’t someone take these activists, sit them in a quet room and just read the literature to them since they seem incapable of such study themselves.

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Earth’s oldest asteroid crater found in Australia

Posted: January 22, 2020 by oldbrew in Ice ages, News, research
Tags:

Credit: earth.com


Theories abound, but the inevitable carbon dioxide one pops up at the end.

Scientists have identified the world’s oldest asteroid crater in Australia, adding it may explain how the planet was lifted from an ice age, reports BBC News.

The asteroid hit Yarrabubba in Western Australia about 2.2 billion years ago – making the crater about half the age of Earth, researchers say.

Their conclusion was reached by testing minerals found in rocks at the site.

The scientists say the find is exciting because it could account for a warming event during that era.

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The researchers do admit that ‘Snowball Earth is just a hypothesis’, but that period seems to have been an era of the most extreme long-term cold spell(s) ever detected on Earth.

There is very little life in Arctic tundras and glaciers. However that was the situation in a big portion of the world during Ice Ages, says Technology.org.

How did life survive these difficult periods? How didn’t everything just die, being cut off from any kind of sources of nutrition and oxygen?

Scientists examined the chemistry of the iron formations in Australia, Namibia, and California to get a window into the environmental conditions during the ice age. They selected rocks left there by the ice age, because they are representative of the conditions during that difficult period for life.

By analysing these rocks scientists from the McGill University were able to estimate the amount of oxygen in the oceans around 700 million years ago.

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‘Long-term’ here means really long-term. The 21k year precession period quoted looks like that of the perihelion.

In the past million years, the high-altitude winds of the southern westerly wind belt, which spans nearly half the globe, didn’t behave as uniformly over the Southern Pacific as previously assumed.

Instead, they varied cyclically over periods of ca. 21,000 years, reports ScienceDaily.

A new study has now confirmed close ties between the climate of the mid and high latitudes and that of the tropics in the South Pacific, which has consequences for the carbon budget of the Pacific Southern Ocean and the stability of the West Antarctic Ice Sheet.

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A reconstruction of the Anglian ice sheet in Precambrian North London (credit: BBC / The Natural History Museum, London)


This might rattle a few cages in climate-land.

An analysis of air up to 2 million years old, trapped in Antarctic ice, shows that a major shift in the periodicity of glacial cycles was probably not caused by a long-term decline in atmospheric levels of carbon dioxide, writes Eric W. Wolff in Nature.
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During the past 2.6 million years, Earth’s climate has alternated between warm periods known as interglacials, when conditions were similar to those of today, and cold glacials, when ice sheets spread across North America and northern Europe.

Before about 1 million years ago, the warm periods recurred every 40,000 years, but after that, the return period lengthened to an average of about 100,000 years.

It has often been suggested that a decline in the atmospheric concentration of carbon dioxide was responsible for this fundamental change.

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Ross Ice Shelf, Antarctica


Is there an element of circular reasoning here? Carbon dioxide levels have historically followed temperature changes, bringing any supposed causation into question.

Upside-down “rivers” of warm ocean water may be one of the causes of Antarctica’s ice shelves breaking up, leading to a rise in sea levels.

But a new study suggests an increase in sea ice may lead to a much more devastating change in the Earth’s climate — another ice age, reports Fox News.

Using computer simulations, the research suggests that an increase in sea ice could significantly alter the circulation of the ocean, ultimately leading to a reverse greenhouse effect as carbon dioxide levels in the ocean increase and levels in the air decrease.

“One key question in the field is still what caused the Earth to periodically cycle in and out of ice ages,” University of Chicago professor and the study’s co-author, Malte Jansen, said in a statement. “We are pretty confident that the carbon balance between the atmosphere and ocean must have changed, but we don’t quite know how or why.”

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‘Belief is in politics and religion, not science…follow the money’, says Professor Plimer.

Geologist and earth scientist Ian Plimer says the globe is not facing a climate emergency, telling Sky News Australia that “we are actually still living in an ice age.”

Professor Plimer’s comments come after Extinction Rebellion protesters have been calling on the government to declare a climate emergency – something the scientist said isn’t necessary.

“We live in horribly boring times,” he said.

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Credit: British Antarctic Survey


The EPICA ice cores clearly showed CO2 lagging behind temperature increases – probably by centuries. But observed effects aren’t supposed to precede alleged causes.

European scientists from 10 countries have spent years scouring the Antarctic ice sheet with one ambition in mind: to drill for the oldest-ever ice core.

Now, they have zeroed in on just the spot says IFL Science.

The team have chosen Little Dome C – one of the coldest, most barren places on Earth. For the next five years, they will drill for a 1.5-million-year-old ice core – a frozen timepiece of Earth’s climatic past.

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Glacier in Patagonia


The latest Ice Ages theory rolls off the production line. This one relies on ‘pulling enough carbon dioxide out of the atmosphere’, so we can see how they’re thinking. A possible problem there is that historical data from ice cores usually show carbon dioxide changes following temperature changes by a few hundred years, which seems to contradict the findings here. It’s the old chicken and egg conundrum – effects can’t precede causes. An important part of the carbon cycle is ocean outgassing of CO2 (response to warming) and absorption (response to cooling).

Over the last 540 million years, the Earth has weathered three major ice ages—periods during which global temperatures plummeted, producing extensive ice sheets and glaciers that have stretched beyond the polar caps.

Now scientists at MIT, the University of California at Santa Barbara, and the University of California at Berkeley have identified the likely trigger for these ice ages, reports Phys.org.

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Theorists take another look at the mechanisms that may or may not be important regulators of Earth’s ice ages.

Climate Etc.

by Donald Rapp, Ralf Ellis and Clive Best

A review of the relationship between the solar input to high latitudes and the global ice volume over the past 2.7 million years.

View original post 4,521 more words

Image credit: BBC


These climatic swings (cycles) were in sync with changes in the Earth’s tilt, say the researchers. They therefore believe ice ages are not the primary factor in these swings.

The Sahara desert is one of the harshest, most inhospitable places on the planet, covering much of North Africa in some 3.6 million square miles of rock and windswept dunes.

But it wasn’t always so desolate and parched, reports Phys.org.

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Ross Ice Shelf, Antarctica


The latest research comes up with a new addition to the list of possible ice age mechanisms.

Earth’s latest ice age may have been caused by changes deep inside the planet, reports ScienceDaily.

Based on evidence from the Pacific Ocean, including the position of the Hawaiian Islands, Rice University geophysicists have determined Earth shifted relative to its spin axis within the past 12 million years, which caused Greenland to move far enough toward the north pole to kick off the ice age that began about 3.2 million years ago.

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An interesting contribution to the ice age debate here. Problems with Milankovitch and CO2-related theories are discussed.

Thongchai Thailand

Gerald Marsh, retired Argonne National Laboratories Physicist, challenges the usual assumption that ice age cycles are initiated by Milankovich Cycles and driven by the Arrhenius effect of carbon dioxide. He says that the key variable here is “low altitude cloud cover” driven by cosmic rays. A paper worth reading.

ABSTRACT

  1. The existing understanding of interglacial periods is that they
    are initiated by Milankovitch cycles enhanced by rising atmospheric
    carbon dioxide concentrations. During interglacials, global temperature is
    also believed to be primarily controlled by carbon dioxide concentrations,
    modulated by internal processes such as the Pacific Decadal Oscillation
    and the North Atlantic Oscillation. Recent work challenges the
    fundamental basis of these conceptions.
  2. INTRODUCTION
    The history of the role of carbon dioxide in climate begins with the work of Tyndall 1861 and later in 1896 by Arrhenius. The concept that carbon dioxide controlled climate fell into disfavor for a variety of reasons until…

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Antarctic sea ice [image credit: BBC]


Have scientists been looking through the wrong end of the telescope, so to speak, regarding ice ages theory?

Ancient rainfall records stretching 550,000 years into the past may upend scientists’ understanding of what controls the Asian summer monsoon and other aspects of the Earth’s long-term climate, says EurekAlert.

Milankovitch theory says solar heating of the northernmost part of the globe drives the world’s climate swings between ice ages and warmer periods.

The new work turns Milankovitch on its head by suggesting climate is driven by differential heating of the Earth’s tropical and subtropical regions.

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Image credit: ScienceDaily


It seems there was ‘a distinct increase in sea ice extent’ at some point in time that led to a switch to longer ice age intervals, but the reason(s) for it are not known.

Researchers from Cardiff University have revealed how sea ice has been contributing to the waxing and waning of ice sheets over the last million years, says Phys.org.

In a new study published in the journal Nature Communications, the team have shown for the first time that ice ages, occurring every 100,000 years, are accompanied by a rapid build-up of sea ice in the Earth’s oceans.

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