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Sun, 21 Oct 2018
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Blackbox

Ice Ages Linked To Slight Shifts In Solar Radiation

Image
© Unknown
Sometime around now, scientists say, the Earth should be changing from a long interglacial period that has lasted the past 10,000 years and shifting back towards conditions that will ultimately lead to another ice age unless some other forces stop or slow it. But these are processes that literally move with glacial slowness, and due to greenhouse gas emissions the Earth has already warmed as much in about the past 200 years as it ordinarily might in several thousand years, Clark said.
A team of researchers says it has largely put to rest a long debate on the underlying mechanism that has caused periodic ice ages on Earth for the past 2.5 million years - they are ultimately linked to slight shifts in solar radiation caused by predictable changes in Earth's rotation and axis.

In a publication to be released Friday in the journal Science, researchers from Oregon State University and other institutions conclude that the known wobbles in Earth's rotation caused global ice levels to reach their peak about 26,000 years ago, stabilize for 7,000 years and then begin melting 19,000 years ago, eventually bringing to an end the last ice age.

The melting was first caused by more solar radiation, not changes in carbon dioxide levels or ocean temperatures, as some scientists have suggested in recent years.

"Solar radiation was the trigger that started the ice melting, that's now pretty certain," said Peter Clark, a professor of geosciences at OSU. "There were also changes in atmospheric carbon dioxide levels and ocean circulation, but those happened later and amplified a process that had already begun."

Sherlock

Peru: Global Warming freezes 20,000 alpaca

Climate change continues to wreck havoc in Peru's southern Altiplano, where the arrival of freezing temperatures since March - almost three months earlier than usual - have killed at least 20,000 alpaca, reported Peru's National Agriculture and Sanitation Service, or Senasa.

Since January, approximately 20,000 alpaca - a number that still remains within normal limits - have died, and 73,000 others have suffered from various illnesses due to the cold, said Senasa Director Reinaldo Llano Flores.

Alpacas, or vicugna pacos, is a domesticated species of South American camelid, and resembles a small llama. These animals are mostly kept in herds, and bred specifically for their high-quality fiber.

Magnify

At 9,000 years old, Britain's oldest house gives a glimpse of post-Ice Age domesticity

Built 3,000 years before the miracle of Stonehenge, this is Britain's oldest and best preserved house.

The remains of the strongly built shelter, discovered on the Isle of Man, provide a rare window into the domestic life of hunter-gatherers 9,000 years ago.

Unearthed by accident during extension work to the island's airport runway, the 23ft wide pit is giving up extraordinary archaeological secrets.

Most exciting is the revelation that the people of the mesolithic age, long regarded as nomads who wandered ancient Britain in search of food, were actually very good at settling down.
9000 Year old house
© Oxford Archaeology North
Excavation nears completion of the Mesolithic house, defined by a ring of holes which once contained wooden posts

Pumpkin

US: Nebraska tomatoes over a month late ripening

green tomatoes
© unknown
This year, the prize of gardening — a juicy tomato, ripe by the Fourth of July — has remained stubbornly green and hard.

Talk about frustration.

By now, many vegetable gardeners would be layering fat slices of tomatoes on a plate and eating them like watermelon.

But not this year.

The prize of gardening - a juicy tomato, ripe by the Fourth of July - has remained stubbornly green and hard.

"This is as slow as I've seen it, and I've been growing tomatoes since 1972," said Bob "The Tomato Man" Green.

A Sarpy County farmer, master gardener and longtime competitor at the county fair, Green has 67 plants - 27 varieties - this year at his farm outside Springfield, Neb. And they just aren't ripening.

Blame it on the cool weather, he said. Tomatoes need warm days and warm nights to ripen. So far, though, much of eastern Nebraska is running about 4 to 6 degrees below normal for July.

Bizarro Earth

Long debate ended over cause, demise of ice ages - may also help predict future

A team of researchers says it has largely put to rest a long debate on the underlying mechanism that has caused periodic ice ages on Earth for the past 2.5 million years - they are ultimately linked to slight shifts in solar radiation caused by predictable changes in Earth's rotation and axis.

In a publication to be released Friday in the journal Science, researchers from Oregon State University and other institutions conclude that the known wobbles in Earth's rotation caused global ice levels to reach their peak about 26,000 years ago, stabilize for 7,000 years and then begin melting 19,000 years ago, eventually bringing to an end the last ice age.

The melting was first caused by more solar radiation, not changes in carbon dioxide levels or ocean temperatures, as some scientists have suggested in recent years.

Blackbox

Did an ice age boost human brain size?

Image
© Doug Allan/Getty
Letting off some steam.
It is one of the biggest mysteries in human evolution. Why did we humans evolve such big brains, making us the unrivalled rulers of the world?

Some 2.5 million years ago, our ancestors' brains expanded from a mere 600 cubic centimetres to about a litre. Two new studies suggest it is no fluke that this brain boom coincided with the onset of an ice age. Cooler heads, it seems, allowed ancient human brains to let off steam and grow.

For all its advantages, the modern human brain is a huge energy glutton, accounting for nearly half of our resting metabolic rate. About a decade ago, biologists David Schwartzman and George Middendorf of Howard University in Washington DC hypothesised that our modern brain could not have evolved until the Quaternary ice age started, about 2.5 million years ago. They reckoned such a large brain would have generated heat faster than it could dissipate it in the warmer climate of earlier times, but they lacked evidence to back their hypothesis.

Now hints of that evidence are beginning to emerge. Climate researcher Axel Kleidon of the Max Planck Institute for Biogeochemistry in Jena, Germany, modelled present-day temperature, humidity and wind conditions around the world using an Earth-systems computer model. He used these factors to predict the maximum rate at which a modern human brain can lose heat in different regions. He found that, even today, the ability to dissipate heat should restrict the activity of people in many tropical regions (Climatic Change, vol 95, p 405).

Sherlock

When Did Humans Return After Last Ice Age?

Cave
© Natural History Museum
Gough's Cave.
The Cheddar Gorge in Somerset was one of the first sites to be inhabited by humans when they returned to Britain near the end of the last Ice Age. According to new radio carbon dating by Oxford University researchers, outlined in the latest issue of Quaternary Science Review, humans were living in Gough's Cave 14,700 years ago.

A number of stone artifacts as well as human and animal bones from excavations, spread over more than 100 years, shed further light on the nature as well as the timing of people to the cave.

Technological advances have allowed researchers at Oxford University and London's Natural History Museum to date the bones more accurately. Previous radiocarbon dates suggested a wide span of occupation of within 1000-1500 years. The new dates show a much narrower range of dates, corresponding precisely to climate warming, providing evidence that the archaeological material in the cave could have accumulated over perhaps as little as two to three human generations, centered on 14,700 years ago.

Bizarro Earth

I blame global warming! Michigan sweet corn, tomato crop delayed because of cold

corn
© unknown

Unusually cold weather in Michigan these days. Smack dab in the middle of July, we are having to close the windows because it's too cold outside. I still haven't run the ac yet this year. These weather patterns have other consequences. Just a couple of weeks ago, I reported that the Northern Michigan Cherry Festival was without northern Michigan cherries! (I blame Global Warming! Northern Michigan Cherry festival to be without Northern Michigan cherries. Not ripe yet because of cold!) I kid you not! They had to import cherries from elsewhere! And before that, the strawberry crop had been delayed (I blame global warming! Cool weather delays Michigan strawberry season). Is no crop safe from global warming? Er, I mean - climate change? Not corn or tomatoes apparently! From The Detroit Free Press: Ahh, summer. And we're chillin'?

Snowman

Solar Physicist Predicts Ice Age. What happened to global warming?

Timo Niroma, a physicist from Finland, publishes a Solar Report each month. He has given his permission to use it and distribute it to all so here it is. It will be a regular feature here and I hope you look forward to it as much as I do. The report is not written in the usual user-friendly way, but is rather intended for scientists that are familiar with the information contained in it. I will attempt to simplify and explain the details of the report and how it could impact you and, of course, Al Gore and company. As the predictions come true, as I assume they will, the green lobby will go on unemployment compensation. Let's start at the beginning and take it piece by piece.

"June Breaking News: The Cycle Goes at the Moment Below Dalton Level" gives away the punch line but let's see how he gets there.

Bell

Change In Ice Ages Not Caused By CO2

ice age
© unknown

Around 1.2 million years ago, a shift in global climate began that caused a change in the timing of the alternating warm and cold periods - called interglacials and glacials - that have persisted during the Pleistocene Ice Age. Prior to that time, ice age glacial periods lasted about 40,000 years but since ~700,000 years ago ice-age cycles have lasted for around 100,000 years. Orbital variations, called the Croll-Milankovitch cycles, do exert some forcing on the 100,000 year time scale, but it is relatively weak. Orbital cycles seem to many too feeble an explanation for the change in glacial-interglacial timing. Some scientists have attempted to attribute the timing shift to a drop in CO2 but a new study confirms that carbon dioxide levels were not the cause of the climate shift.

The dominant period of Pleistocene glacial cycles changed during the mid-Pleistocene from 40,000 years to 100,000 years, for reasons unknown to science. A new paper in the June 19, 2009, edition of Science investigates whether that shift could be attributed to changes in atmospheric CO2 levels. A group of researchers, led by Bärbel Hönisch, examined the factors that influenced the mid-Pleistocene transition (MPT) around 1250 to 700 thousand years ago. Here is the published abstract of the paper:
The dominant period of Pleistocene glacial cycles changed during the mid-Pleistocene from 40,000 years to 100,000 years, for as yet unknown reasons. Here we present a 2.1-million-year record of sea surface partial pressure of CO2 (PCO2), based on boron isotopes in planktic foraminifer shells, which suggests that the atmospheric partial pressure of CO2 (pCO2) was relatively stable before the mid-Pleistocene climate transition. Glacial PCO2 was ~31 microatmospheres higher before the transition (more than 1 million years ago), but interglacial PCO2 was similar to that of late Pleistocene interglacial cycles (<450,000 years ago). These estimates are consistent with a close linkage between atmospheric CO2 concentration and global climate, but the lack of a gradual decrease in interglacial PCO2 does not support the suggestion that a long-term drawdown of atmospheric CO2 was the main cause of the climate transition.