Ice Ages Blamed on Tilted Earth

  1. https://www.livescience.com/6937-ice-ages-blamed-tilted-earth.html

Ice Ages Blamed on Tilted Earth

In the past million years, the Earth experienced a major ice age about every 100,000 years. Scientists have several theories to explain this glacial cycle, but new research suggests the primary driving force is all in how the planet leans.

The Earth’s rotation axis is not perpendicular to the plane in which it orbits the Sun. It’s offset by 23.5 degrees. This tilt, or obliquity, explains why we have seasons and why places above the Arctic Circle have 24-hour darkness in winter and constant sunlight in the summer.

But the angle is not constant – it is currently decreasing from a maximum of 24 degrees towards a minimum of 22.5 degrees. This variation goes in a 40,000-year cycle.

Peter Huybers of Woods Hole Oceanographic Institution and Carl Wunsch of the Massachusetts Institute of Technology have compared the timing of the tilt variations with that of the last seven ice ages. They found that the ends of those periods – called glacial terminations – corresponded to times of greatest tilt.

“The apparent reason for this is that the annual average sunlight in the higher latitudes is greater when the tilt is at maximum,” Huybers told LiveScience in a telephone interview.

More sunlight seasonally hitting polar regions would help to melt the ice sheets. This tilt effect seems to explain why ice ages came more quickly – every 40,000 years, just like the tilt variations — between two and one million years ago.

“Obliquity clearly was important at one point,” Huybers said.

Colder planet

The researchers speculate that the glacier period has become longer in the last million years because the Earth has gotten slightly colder – the upshot being that every once in a while the planet misses a chance to thaw out.

The glacial cycles can be measured indirectly in the ratio of heavy to light oxygen in ocean sediments. Simply put, the more ice there is on Earth, the less light oxygen there is in the ocean. The oxygen ratio is recorded in the fossils of small organisms – called foraminifera, or forams for short – that make shells out of the available oxygen in the ocean.

“These ‘bugs’ have been around for a long time – living all across the ocean,” Huybers said. “When they die, they fall to the seafloor and become part of the sediment.”

Drilled out sediment cores from the seafloor show variations with depth in the ratio of heavy to light oxygen – an indication of changes in the amount of ice over time. This record of climate change goes back tens of millions of years.

By improving the dating of these sediments, Huybers and Wunsch have showed that rapid decreases in the oxygen ratio – corresponding to an abrupt melting of ice – occurred when the Earth had its largest tilt.

Other orbital oddities

The significance of this relationship calls into question other explanations for the frequency of ice ages.

One popular theory has been that the noncircular shape, or eccentricity, of Earth’s orbit around the Sun could be driving the glacial cycle, since the variations in the eccentricity have a 100,000-year period. Curiously different, but interesting.

Variation in Orbit Period
Tilt 40,000 yr
Wobble 20,000 yr
Eccentricity 100,000 yr

By itself, though, the eccentricity is too small of an effect. According to Huybers, changes in the orbit shape cause less than a tenth of a percent difference in the amount of sunlight striking the planet.

But some scientists believe a larger effect could be generated if the eccentricity fluctuations are coupled with the precession, or wobble of the Earth’s axis. It’s like what is seen with a spinning top as it slows down.

Earth’s axis is currently pointing at the North Star, Polaris, but it is always rotating around in a conical pattern. In about 10,000 years, it will point toward the star Vega, which will mean that winter in the Northern Hemisphere will begin in June instead of January. After 20,000 years, the axis will again point at Polaris.

Huybers said that the seasonal shift from the precession added to the eccentricity fluctuations could have an important effect on glacier melting, but he and Wunsch found that the combined model could not match the timing in the sediment data.

Skipping beats

The question, then, that Huybers and Wunsch had to answer: How does the 40,000-year tilt cycle make a 100,000-year glacial cycle? A more careful sediment dating has shown is that the time between ice ages may on average be 100,000 years, but the durations are sometimes 80,000 years, sometimes 120,000 years — both numbers are divisible by 40,000. It appears there was not a mass melting every time the tilt reached its maximum.

“The Earth is skipping obliquity beats,” Huybers explained.

The planet only recently started missing melting opportunities. Although the researchers have no corroborating evidence, they hypothesize that the skipping is due to an overall cooling of the planet.

The last major glacial thaw was 10,000 years ago, which means that the Earth is scheduled to head into another ice age. Whether human influences could reverse this, Huybers was hesitant to speculate. Other researchers have found evidence that the process of climate warming can set up conditions that create a global chill.

“What we have here is a great laboratory for seeing how climate changes naturally,” he said. “But this is a 100,000-year cycle, whereas global warming is happening a thousand times faster.”

Seven Worlds, One Planet review – breathtaking, moving, harrowing

David Attenborough and the BBC play us like pianos – and at this point in the evolution of natural history TV, they are maestros. Prepare to weep

A face-off between a penguin and a giant leopard seal in Seven Worlds, One Planet.
 A face-off between a penguin and a giant leopard seal in Seven Worlds, One Planet. Photograph: BBC NHU

Any nature programme is now, in essence, just a list of things we’re killing. A record for posterity (whatever that looks like) of what we once had and fished, boiled and starved to death via climate breakdown. But if you can set aside the growing sense of fiddling with the remote control while Rome and every single other point on the globe burns, there is still much to enjoy in the latest offering from the BBC: Seven Worlds, One Planet.

Each earthly continent gets an episode narrated by David Attenborough (can you imagine the calls from the agent of any land mass whose wasn’t?), beginning with the one we only noticed 200 years ago – Antarctica. In spring, king penguin chicks, endlessly adorable and absurd, mass on St Andrew’s Bay beach in South Georgia under strict instructions from their parents (who are no more able to tell them apart than we are, unless they can hear their voices) not to move, but toddle off to investigate seedheads and elephant seals regardless.

In summer, humpback whales blow spiralling walls of bubbles in the southern ocean to corral some of the 400 trillion krill in existence into banquet-sized groups so they can survive the rest of the year. In autumn, teenage chicks and pups do their best to avoid predators and grow to adulthood. In winter, only the deep sea life continues unperturbed as the sea above them freezes at a rate of 40,000 sq miles a day. Sea anemones catch jellyfish and feast for four days. Three-metre-long worms ripple across rocks. Hermaphroditic white frills known as nudibranchs fertilise each other. Blue and orange starfish continue to starfish as they have for millennia.

David Attenborough in Seven Worlds, One Planet.
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 David Attenborough in Seven Worlds, One Planet. Photograph: Alex Board/BBC NHU

As ever, the makers play us like pianos and at this stage of natural history television’s evolution they are maestros. Majesty – snowy wastelands! The largest congregation of feeding whales ever filmed! – is followed by melancholy. Warming glaciers are calving so rapidly that their floating rubble masks the penguins’ enemies from them – and the depredations against the environment and its wildlife are putting their function as a massive carbon sponge for the world in jeopardy.

Triumph is followed by disaster, or as close to the latter as they think we can bear. And there is the emotionally pulverising set piece. This one was provided by the albatross chick blown out of its nest by one of the increasingly violent storms (for which we and our climate-convulsing ways are also responsible) and its desperate attempts, amid the lifeless bodies of even less fortunate babies, to clamber back in. It chirped uselessly at its mother, who ignored it utterly. Adult albatross recognise their offspring only by virtue of them being on the nests where they left them. Watching the chick flail at the feet of its oblivious parent was every childhood nightmare made flesh. At last, it got there, and was tucked under the warm maternal belly once more. The creatures around which the mini-narratives centre have an almost suspiciously uniform tendency to survive while their compatriots die, but if there are shenanigans or filmic sleight-of-hand going on here, let the record show that I consider this very much in the tradition of public service.

The show concludes, as is customary, on a hopeful note: the recovery of the southern right whales.
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 The show concludes, as is customary, on a hopeful note: the recovery of the southern right whales. Photograph: Stephen Bradley/BBC NHU

It was all as gorgeous, breathtaking, moving and harrowing as we have come to expect from this world-leading branch of the BBC. There is nothing to criticise or cavil at here, unless you consider yourself to be on sufficiently high moral ground to whine that it and Attenborough could have started leveraging their power to highlight the environmental crisis some time before they did.

We exited, as is customary, on a hopeful note: the recovery of the southern right whales since the ban on commercial whaling (adhered to, the programme noted with a level of detail unusual enough to be considered pointed, by all except Japan, Norway and Iceland) in 1986. 35 remaining females have become a population of 2,000.

So on, possibly, we go.

Amazon Wildfires Are Horrifying, But They’re Not Destroying Earth’s Oxygen Supply

wildfires burn the amazon rainforest

(Image: © iStock / Getty Images Plus)

Fires in the Amazon rainforest have captured attention worldwide in recent days. Brazilian President Jair Bolsonaro, who took office in 2019, pledged in his campaign to reduce environmental protection and increase agricultural development in the Amazon, and he appears to have followed through on that promise.

The resurgence of forest clearing in the Amazon, which had decreased more than 80% following a peak in 2004, is alarming for many reasons. Tropical forests harbor many species of plants and animals found nowhere else. They are important refuges for indigenous people, and contain enormous stores of carbon as wood and other organic matter that would otherwise contribute to the climate crisis.

Some media accounts have suggested that fires in the Amazon also threaten the atmospheric oxygen that we breathe. French President Emmanuel Macron tweeted on Aug. 22 that “the Amazon rain forest — the lungs which produces 20% of our planet’s oxygen — is on fire.”

The oft-repeated claim that the Amazon rainforest produces 20% of our planet’s oxygen is based on a misunderstanding. In fact nearly all of Earth’s breathable oxygen originated in the oceans, and there is enough of it to last for millions of years. There are many reasons to be appalled by this year’s Amazon fires, but depleting Earth’s oxygen supply is not one of them.

Oxygen from plants

As an atmospheric scientist, much of my work focuses on exchanges of various gases between Earth’s surface and the atmosphere. Many elements, including oxygen, constantly cycle between land-based ecosystems, the oceans and the atmosphere in ways that can be measured and quantified.

Nearly all free oxygen in the air is produced by plants through photosynthesis. About one-third of land photosynthesis occurs in tropical forests, the largest of which is located in the Amazon Basin.

But virtually all of the oxygen produced by photosynthesis each year is consumed by living organisms and fires. Trees constantly shed dead leaves, twigs, roots and other litter, which feeds a rich ecosystem of organisms, mostly insects and microbes. The microbes consume oxygen in that process.

Forest plants produce lots of oxygen, and forest microbes consume a lot of oxygen. As a result, net production of oxygen by forests — and indeed, all land plants — is very close to zero.

Oxygen production in the oceans

For oxygen to accumulate in the air, some of the organic matter that plants produce through photosynthesis must be removed from circulation before it can be consumed. Usually this happens when it is rapidly buried in places without oxygen — most commonly in deep sea mud, under waters that have already been depleted of oxygen.

This happens in areas of the ocean where high levels of nutrients fertilize large blooms of algae. Dead algae and other detritus sink into dark waters, where microbes feed on it. Like their counterparts on land, they consume oxygen to do this, depleting it from the water around them.

Below depths where microbes have stripped waters of oxygen, leftover organic matter falls to the ocean floor and is buried there. Oxygen that the algae produced at the surface as it grew remains in the air because it is not consumed by decomposers.

This buried plant matter at the bottom of the ocean is the source of oil and gas. A smaller amount of plant matter gets buried in oxygen-free conditions on land, mostly in peat bogs where the water table prevents microbial decomposition. This is the source material for coal.

Only a tiny fraction — perhaps 0.0001% — of global photosynthesis is diverted by burial in this way, and thus adds to atmospheric oxygen. But over millions of years, the residual oxygen left by this tiny imbalance between growth and decomposition has accumulated to form the reservoir of breathable oxygen on which all animal life depends. It has hovered around 21% of the volume of the atmosphere for millions of years.

Some of this oxygen returns to the planet’s surface through chemical reactions with metals, sulfur and other compounds in Earth’s crust. For example, when iron is exposed to air in the presence of water, it reacts with oxygen in the air to form iron oxide, a compound commonly known as rust. This process, which is called oxidation, helps regulate oxygen levels in the atmosphere.

Don’t hold your breath

Even though plant photosynthesis is ultimately responsible for breathable oxygen, only a vanishingly tiny fraction of that plant growth actually adds to the store of oxygen in the air. Even if all organic matter on Earth were burned at once, less than 1% of the world’s oxygen would be consumed.

In sum, Brazil’s reversal on protecting the Amazon does not meaningfully threaten atmospheric oxygen. Even a huge increase in forest fires would produce changes in oxygen that are difficult to measure. There’s enough oxygen in the air to last for millions of years, and the amount is set by geology rather than land use. The fact that this upsurge in deforestation threatens some of the most biodiverse and carbon-rich landscapes on Earth is reason enough to oppose it.

Original article published on The Conversation.

Massive supernova could have made humans walk upright, study says

Researchers claim cosmic particles bombarded Earth’s surface at such high levels forests turned to savannah

Exploding stars 2.6 million years ago may have caused ancient humans to walk upright, a new scientific paper claims.

Cosmic particles from these supernovae bombarded Earth’s surface at such high levels that they caused global forest fires, researchers from the University of Kansas suggest.

This led to the creation of large swathes of savannahs in places that would previously have been forested. Early hominins in northeast Africa had to learn to walk on two legs to cross these vast areas, according to the study, published in the Journal of Geology.

The theory was laid out by a team led by physicist Professor Adrian Melott in an attempt to join together different strands of research.

“It is thought there was already some tendency for hominins to walk on two legs, even before this event. But they were mainly adapted for climbing around in trees,” he said.

“After this conversion to savannah, they would much more often have to walk from one tree to another across the grassland, and so they become better at walking upright. They could see over the tops of grass and watch for predators.”

Professor Melott arrived at this hypothesis by drawing on research about historic supernovae and evidence for the impact they had on Earth. Ancient seabed deposits of iron-60 isotopes – radioactive forms of iron – provided a crucial clue.

Professor Melott said these materials must have arrived on Earth from a supernova, which would have exploded 163 light years away during the transition from the Pliocene Epoch to the Ice Age.

“We calculated the ionisation of the atmosphere from cosmic rays which would come from a supernova about as far away as the iron-60 deposits indicate,” he said.

“We contend it would increase the ionisation of the lower atmosphere by 50-fold. Usually, you don’t get lower-atmosphere ionisation because cosmic rays don’t penetrate that far, but the more energetic ones from supernovae come right down to the surface – so there would be a lot of electrons being knocked out of the atmosphere.”

They suggest ionisation in the lower atmosphere meant there were more pathways for lightning strikes which led to widespread fires.

Professor Melott also said he believed his theory was supported by the discovery of carbon deposits in soils at around the same time as this cosmic-ray bombardment was happening. 

“The observation is that there’s a lot more charcoal and soot in the world starting a few million years ago. It’s all over the place, and nobody has any explanation for why it would have happened all over the world in different climate zones. This could be an explanation,” he said.

“That increase in fires is thought to have stimulated the transition from woodland to savannah in a lot of places – where you had forests, now you had mostly open grassland with shrubby things here and there.”

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Professor Melott said no similar event was expected to happen any time soon. The nearest star capable of exploding into a supernova in the next million years is Betelgeuse, which is 652 light years from Earth.

“Betelgeuse is too far away to have effects anywhere near this strong,” he said.

At the end of last year Professor Melott led another study that found supernovae 2.6 million years ago could have swept Earth’s prehistoric oceans wiping out creatures like the giant shark known as the Megalodon.

His research suggested that particles from these exploding stars could have caused cancers in large marine mammals to spike.

It’s Hard to Believe How Close This Asteroid Is Going to Get to Earth

A simulation showing 99942 Apophis’s expected path past Earth. The blue dots represent orbiting satellites, and the pink line represents the International Space Station.
GIF: NASA

While space agencies simulate an asteroid impact this week at the 2019 Planetary Defense Conference, there’s a real asteroid they’re monitoring that will make a close appearance in just 10 years.

99942 Apophis is among the most infamous near-Earth objects. When astronomers at Kitt Peak National Observatory discovered it in 2004, they initially calculated a 2.7 percent chance that it would hit Earth and assigned it a level 4 on the Torino Scale, the highest assignment for a near-Earth object ever. Though it has since been downgraded and is expected to pose no threat to the planet, it’s a real-life version of the simulated asteroid scenarios that scientists are currently playing out.

“The Apophis close approach in 2029 will be an incredible opportunity for science,” Marina Brozovic, a radar scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California said in a press release.

When Apophis flies by on April 13, 2029, the 1,100-foot-wide (340-meter) asteroid will come shockingly close, coming within 20,000 miles (33,000 kilometers) of the Earth’s surface. By comparison, the average distance between the Moon and Earth is 238,855 miles (384,400 km). This will be a rare opportunity to study an asteroid up close.

You might wonder how scientists go from predicting a 2.7 percent chance of impact to ruling out danger from such a large asteroid, and whether you should be worried. Single observations and models have error bars, a spread of potential locations the asteroid will pass. You can see how only a few observations of an object that will come within 20,000 miles of the Earth might suggest a potential strike. But more observations shrink the error bars and the number of potential paths.

By now, researchers have made enough observations of Apophis to rule out a strike in 2029 as well as when it passes the planet again in 2036. The odds are harder to calculate for close approaches further down the line, but for the moment, this particular asteroid is not worth worrying over. Instead, scientists will be discussing what value they can glean from the close approach and whether they should send a mission to study the asteroid.

But asteroid impacts more generally are a real concern. At the Planetary Defense Conference this week, NASA, FEMA, and other agencies are simulating a situation quite similar to the 2004 Apophis discovery. But they’re discussing more than just how best to observe the asteroid—they’re also puzzling over what to do if a real threat to Earth becomes imminent.

Humanity has a long way to go before feeling confident in our ability to handle an impending asteroid strike. As we’ve written, there are a load of asteroids we haven’t discovered, and potential inaccuracies in the data that scientists have already collected. But for now, I guess we should be thankful that scientists are take potential asteroid strikes seriously.

Huge ‘God of Chaos’ asteroid to pass near Earth in 2029: report

A 1,110-foot-wide asteroid named for the Egyptian god of chaos will fly past Earth in 2029 within the distance of some orbiting spacecraft, according to reports.

The asteroid, 99942 Apophis, will come within 19,000 miles of Earth on April 13, a decade from now, but scientists at the Planetary Defense Conference are already preparing for the encounter, Newsweek reported. They plan to discuss the asteroid’s effects on Earth’s gravity, potential research opportunities and even how to deflect an incoming asteroid in a theoretical scenario.

NASA CHIEF WARNS ASTEROID THREAT IS REAL: ‘IT’S ABOUT PROTECTING THE ONLY PLANET WE KNOW TO HOST LIFE’

Scientists say most asteroids that pass near Earth aren’t more than 30 feet wide, making Apophis, named for an Egyptian god of chaos, a rare opportunity for research.

The asteroid will be visible to the naked eye and will look like a moving star point of light, according to NASA. It will pass over the United States in the early evening, according to WUSA 9.

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Apophis was discovered in 2004 and, after tracking it for 15 years, scientists say the asteroid has a 1 in 100,000 chance of striking Earth decades in the future – after 2060, Newsweek reported.

Earth is ‘In Midst of Mass Extinction’, Sir David Attenborough Warns

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The renowned academic speculated on the development phase that Earth is at today, drawing a parallel with one that saw the dinosaurs, which lived on our planet throughout the Mesozoic Era, being completely wiped out.

Renowned British natural historian Sir David Attenborough has warned in an explicit way that Earth is facing a mass extinction, much like the one that caused the dinosaurs to die out. Speaking at the launch of his new Netflix series titled “Out Planet”, the 92-year-old researcher and broadcaster was quoted by British media as saying:

“Right now we are in the midst of the Earth’s sixth mass extinction — one every bit as profound and far reaching as that which wiped out the dinosaurs”, expressing fear that millions of living organisms will disappear into thin air as their habitats are increasingly affected by climate change.

Sir David, the holder of an unrivalled 32 honorary degrees from Britain’s universities, told the audience at the Natural History Museum, which hosted the event, that mankind has shattered the Earth’s natural order as a result of a massive environmental pollution.

“Consider these facts — 96% of the mass of mammals on our planet today are us and the livestock we’ve domesticated. Only 4% is everything else”, Sir David noted, going on to speculate on the interconnections between humans and their natural habitat:

“Nature once determined how we survive. Now we determine how nature survives”.

Another speaker at the event was notably the royal environmental campaigner Prince Charles, who took the floor drawing attention to the educational aspect:

“Education about what we have, what we have destroyed and what can and must be regenerated could not be more timely or more urgently needed”.

https://sputniknews.com/science/201904061073886029-earth-extinction-warns-attenborough/

Save the Earth: Pray for a Pandemic

August 14, 2014

 

by Jim Robertson from the blog Exposing the Big Game

I don’t mean to sound like some hateful misanthrope who wants to see humanity suffer for all its crimes against the environment. Rather, my misanthropy stems from a profound love of nature and a will to save non-humans from the cruelty and exploitation they’re routinely subjected to by the one species fully capable of causing a mass extinction.

Indeed, the species Homo sapiens is currently in the process of putting an end to the most biologically diverse period the Earth has ever known—the Age of Mammals, a class in which the human race must reluctantly find itself included.

Being nothing more than mere mammals themselves, humans are ultimately at the mercy of Mother Nature’s self-preserving tactics. And what better way to reign in her errant child than with a major global pandemic that takes down only humans? Let’s face it, are humans ever going to effectively reverse the ill-effects of climate change, for example? Oh, world leaders sometimes give it lip service, but they never mention the parallel scourge of overpopulation any more. It seems it’s hard to be “green” and keep 7,185,322,300 (as of this writing) people fed, clothed, sheltered and transported in the manner they’re currently accustomed.

If people want to come out of this alive, they’re going to have to make some serious lifestyle changes. That means no more oil-dependent cars, trains, jet airplanes, no more Walmarts full of plastic trinkets built with coal power in Chinese factories, then sent overseas in gargantuan container ships. No offshore oil wells, no fracking, no tar sands pipelines; no freeways, no commuter traffic, no immensely-popular sporting events selling factory-farmed hot dogs by the billions. No people by the billions, for that matter. No more breeding period until humans have figured out how to live alongside the rest of the Earth’s inhabitants without wiping them out or making slaves of them.

No more! Starting right now! No false-starts or baby steps. Time to change or be changed!

It’s not just the politicians who lack the will to do what it would take to soften the blow of climate change. But while humans debate their role in causing relatively dependable weather systems to go topsy-turvy worldwide, Nature is poised to unleash a pandemic or two from her bag of tricks and take care of the human problem herself. I’m not talking about Ebola, that’s too slow and nasty.

When Nature gets serious, I’m hoping it’ll be quick and painless for all.  By the time humans know what hit ‘em, there’ll be no one left to test the experimental vaccine on the animals–who’ll be too busy inheriting the Earth anyway.

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