What causes an ice age to end?

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.

‘Melting Greenland’ likely to add up to half an inch to global sea levels by 2098

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.

Earth’s oldest asteroid crater found in Australia

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.

How did life survive in the Snowball Earth? Scientists might have cracked the mystery

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.

Changes in high-altitude winds over the South Pacific produce long-term effects

‘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.

Ancient air challenges carbon dioxide explanation for a shift in glacial cycles

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.
– – –
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.

Explosion in Antarctic sea ice levels may cause another ice age

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.”

Prof. Ian Plimer: Earth is ‘not in a period of extinction’

‘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.

Scientists Drill For “Oldest Ice On Earth” To Unlock Mystery Of Ancient Earth’s Changing Climate

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.

Tectonics in the tropics trigger Earth’s ice ages, says study

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.

Solar input to high latitudes and the global ice volume

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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

Study shows the Sahara swung between lush and desert conditions every 20,000 years, in sync with monsoon activity

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.

‘True polar wander’ may have caused ice age

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.

Gerald Marsh, A Theory of Ice Ages

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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…

View original post 1,929 more words

Dusty rainfall records reveal new understanding of Earth’s long-term climate

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.

Unravelling the mystery of ice ages using ancient molecules

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.

Glaciers in Mongolia’s Gobi Desert actually shrank during the last ice age

Tavan Bogd Mountains in Mongolia [imagecredit: Altaihunters @ Wikipedia]

Why glaciers are not always climate thermometers.

High in Mongolia’s Gobi Desert, the climate is so dry and cold that glaciers shrank during the last ice age. Dating of rock deposits shows how glaciers in this less-studied region behave very differently as the climate shifts.

The simple story says that during the last ice age, temperatures were colder and ice sheets expanded around the planet, says EurekAlert.

That may hold true for most of Europe and North America, but new research from the University of Washington tells a different story in the high-altitude, desert climates of Mongolia.

Key to predicting climate change could be blowing in the wind

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

This isn’t the first time a dust-related theory of long-term climate change has been put forward. But this one looks at what could have caused the Earth to go into cycles of glacial and interglacial periods in the first place.

Dust that blew into the North Pacific Ocean could help explain why the Earth’s climate cooled 2.7 million years ago, according to a new study, reports ScienceDaily.

One of the co-authors was Alex Pullen, an assistant professor of environmental engineering and earth sciences at Clemson University.

“Why study the past? It’s a great predictor of the future,” he said. “The findings of this study were both interesting and very unexpected.”

Matt Ridley: The mysterious cycles of ice ages

US winter storm 2018 [image credit: NASA]

A sort of review of leading ice age theories. A paper by Ralph Ellis that was featured at the Talkshop gets a mention. A point not mentioned: the carbon cycle dictates that cooling leads to the oceans absorbing more CO2, while warming leads to more outgassing of it to the atmosphere.

Record cold in America has brought temperatures as low as minus 44C in North Dakota, frozen sharks in Massachusetts and iguanas falling from trees in Florida, writes Matt Ridley.

Al Gore blames global warming, citing one scientist to the effect that this is “exactly what we should expect from the climate crisis”. Others beg to differ: Kevin Trenberth, of America’s National Centre for Atmospheric Research, insists that “winter storms are a manifestation of winter, not climate change”.

Forty-five years ago a run of cold winters caused a “global cooling” scare.

Ice sheets may melt rapidly in response to distant volcanoes

This is the finding from a new research paper entitled ‘Enhanced ice sheet melting driven by volcanic eruptions during the last deglaciation.’

Another very recently published paper (‘Very large release of mostly volcanic carbon during the Palaeocene–Eocene Thermal Maximum’) says something similar:
‘The Palaeocene–Eocene Thermal Maximum [PETM], was a global warming event that occurred about 56 million years ago, and is commonly thought to have been driven primarily by the destabilization of carbon from surface sedimentary reservoirs such as methane hydrates. However, it remains controversial whether such reservoirs were indeed the source of the carbon that drove the warming…[We] identify volcanism associated with the North Atlantic Igneous Province rather than carbon from a surface reservoir, as the main driver of the PETM. This finding implies that climate-driven amplification of organic carbon feedbacks probably played only a minor part in driving the event.’

So two papers saying volcanic ash on the ice, not carbon dioxide in the air, was the main player in PETM deglaciation.
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Volcanic eruptions have been known to cool the global climate, but they can also exacerbate the melting of ice sheets, according to a paper published today in Nature Communications, says Phys.org.

Researchers who analyzed ice cores and meltwater deposits found that ancient eruptions caused immediate and significant melting of the ice sheet that covered much of northern Europe at the end of the last ice age, some 12,000 to 13,000 years ago.