21/02/2021

Earth’s Magnetic Field Broke Down 42,000 Years Ago And Caused Massive Sudden Climate Change

The Conversation -  |  |  | 

vchal / shutterstock

Authors
  •  is Professor of Glaciology and Palaeoclimatology, Head of School Geography, Geology and the Environment and Director of the Institute for Sustainable Futures, Keele University
  •  is Professor, Director, Carbon Dating Laboratory, University of Waikato
  •  is Professor of Earth Science and Climate Change, Director of the Earth and Sustainability Science Research Centre, Director of Chronos 14Carbon-Cycle Facility, and UNSW Director of ARC Centre for Excellence in Australian Biodiversity and Heritage, UNSW
  •  is ARC DECRA Fellow, UNSW
The world experienced a few centuries of apocalyptic conditions 42,000 years ago, triggered by a reversal of the Earth’s magnetic poles combined with changes in the Sun’s behaviour. That’s the key finding of our new multidisciplinary study, published in Science. 

This last major geomagnetic reversal triggered a series of dramatic events that have far-reaching consequences for our planet.

They read like the plot of a horror movie: the ozone layer was destroyed, electrical storms raged across the tropics, solar winds generated spectacular light shows (auroras), Arctic air poured across North America, ice sheets and glaciers surged and weather patterns shifted violently.

During these events, life on earth was exposed to intense ultraviolet light, Neanderthals and giant animals known as megafauna went extinct, while modern humans sought protection in caves.

The magnetic north pole – where a compass needle points to – does not have a permanent location. Instead, it usually wobbles around close to the geographic north pole – the point around which the Earth spins – over time due to movements within the Earth’s core.

For reasons still not entirely clear, magnetic pole movements can sometimes be more extreme than a wobble. One of the most dramatic of these pole migrations took place some 42,000 years ago and is known as the Laschamps Excursion – named after the village where it was discovered in the French Massif Central.

The Laschamps Excursion has been recognised around the world, including most recently in Tasmania, Australia. But up until now, it has not been clear whether such magnetic changes had any impacts on climate and life on the planet. Our new work draws together multiple lines of evidence that strongly suggest the effects were indeed global and far-reaching.

Ancient trees

To investigate what happened, we analysed ancient New Zealand kauri trees that had been preserved in peat bogs and other sediments for more than 40,000 years. Using the annual growth rings in the kauri trees, we have been able to create a detailed timescale of how Earth’s atmosphere changed over this time.

The trees revealed a prolonged spike in atmospheric radiocarbon levels caused by the collapse of Earth’s magnetic field as the poles switched, providing a way of precisely linking widely geographically dispersed records.

Ancient trees point to turning point in Earth's history 42,000 years ago

How the tree analysis works. The temporary breakdown of Earth’s magnetic field 42,000 years ago sparked major climate shifts that led to environmental change and mass extinctions, a new international study co-led by UNSW Sydney shows.

 “The kauri trees are like the Rosetta Stone, helping us tie together records of environmental change in caves, ice cores, and peat bogs around the world,” says professor Alan Cooper, who co-lead this research project.

Using the newly-created timescale, we were able to show that tropical Pacific rain belts and the Southern Ocean westerly winds abruptly shifted at the same time, bringing arid conditions to places like Australia at the same time as a range of megafauna, including giant kangaroos and giant wombats went extinct. Further north, the vast Laurentide Ice Sheet rapidly grew across the eastern US and Canada, while in Europe the Neanderthals spiralled into extinction.

Climate modelling

Working with a computer programme that simulated the global interactions between chemistry and the climate, we investigated the impact of a weaker magnetic field and changes in the Sun’s strength. Importantly, during the magnetic switch, the strength of the magnetic field plummeted to less than 6% of what it is today. A compass back then would struggle to even find north.

An ancient kauri tree log from Ngāwhā, New Zealand. Nelson Parker, Author provided

With essentially no magnetic field, our planet totally lost its very effective shield against cosmic radiation, and many more of these very penetrating particles from space could access the top of the atmosphere.

On top of this, the Sun experienced several “grand solar minima” throughout this period, during which the overall solar activity was generally much lower but also more unstable, sending out numerous massive solar flares that allowed more powerful ionising cosmic rays to reach Earth.

Our models showed that this combination of factors had an amplifying effect. The high energy cosmic rays from the galaxy and also enormous bursts of cosmic rays from solar flares were able to penetrate the upper atmosphere, charging the particles in the air and causing chemical changes that drove the loss of stratospheric ozone.

The modelled chemistry-climate simulations are consistent with the environmental shifts observed in many natural climate and environmental change archives. These conditions would have also extended the dazzling light shows of the aurora across the world – at times, nights would have been as bright as daytime. We suggest the dramatic changes and unprecedented high UV levels caused early humans to seek shelter in caves, explaining the apparent sudden flowering of cave art across the world 42,000 years ago.

It must have seemed like the end of days.

The Adams Event

Because of the coincidence of seemingly random cosmic events and the extreme environmental changes found around the world 42,000 years ago, we have called this period the “Adams Event” – a tribute to the great science fiction writer Douglas Adams, who wrote The Hitchhiker’s Guide to the Galaxy and identified “42” as the answer to life, the universe and everything. Douglas Adams really was onto something big, and the remaining mystery is how he knew?

Paleopocalypse! - Narrated by Stephen Fry
Stephen Fry brings to life the story of the 'Adams event' and just like in The Hitchhiker’s Guide to the Galaxy, the answer comes back to 42.

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(USA) US Makes Official Return To Paris Climate Pact

The Guardian - Associated Press

World leaders expect Washington to prove commitment to accord after four years of inaction

Smog blankets the Los Angeles skyline. The US return to the Paris agreement became official on Friday. Photograph: Justin Lambert/Getty Images

The US is back in the Paris climate accord, just 107 days after it left.

While Friday’s return is heavily symbolic, world leaders say they expect the US to prove its seriousness after four years of being mostly absent.

They are especially keen to hear an announcement from Washington in the coming months on the US’s goal for cutting emissions of heat-trapping gases by 2030.

The US return to the Paris agreement became official on Friday, almost a month after Joe Biden told the UN that the US intended to rejoin.

“A cry for survival comes from the planet itself,” Biden said in his inaugural address. “A cry that can’t be any more desperate or any more clear now.”

The president signed an executive order on his first day in office that reversed the withdrawal ordered by his immediate predecessor, Donald Trump.

The Trump administration had announced its departure from the Paris accord in 2019 but it did not become effective until 4 November 2020, the day after the election, because of provisions in the agreement.

The UN secretary general, António Guterres, said on Thursday the official US re-entry “is itself very important”, as was Biden’s announcement that the US would return to providing climate aid to poorer countries, as promised in 2009.

“It’s the political message that is being sent,” said Christiana Figueres, the former UN climate chief. She was one of the leading forces in hammering out the 2015 mostly voluntary agreement where countries set their own goals to reduce greenhouse gases.

One fear was that other countries would follow the US in abandoning the climate fight, but none did, Figueres said. She said the real issue was four years of climate inaction by the Trump administration. US cities, states and businesses still worked to reduce heat-trapping carbon dioxide, but without the federal government.

“From a political symbolism perspective, whether it’s 100 days or four years, it is basically the same thing,” Figueres said. “It’s not about how many days. It’s the political symbolism that the largest economy refuses to see the opportunity of addressing climate change. We’ve lost too much time,” Figueres said.

The UN Environment Programme director, Inger Andersen, said the US had to prove its leadership to the rest of the world, but she said she had no doubt it would when it submits its required emissions-cutting targets. The Biden administration promises to announce them before a summit in April.

“We hope they will translate into a very meaningful reduction of emissions and they will be an example for other countries to follow,” Guterres said.

More than 120 countries, including the world’s biggest emitter, China, have promised to have net zero carbon emissions around mid-century.

The University of Maryland environment professor Nathan Hultman, who worked on the Obama administration’s Paris goal, said he expected a 2030 target of reducing carbon dioxide emissions between 40% and 50% from the 2005 baseline levels.

A longtime international target, included in the Paris accord with an even more stringent goal, is to keep warming below 2C above pre-industrial levels. The world has already warmed about 1.2C since that time. 

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(USA) Ice, Fire, Floods: Extreme Weather And Climate Change

Bloomberg Green -   | 

Snow covered Zilker Park in Austin, Texas, U.S., on Feb. 18. Photographer: Thomas Ryan Allison/Bloomberg

Not that many years ago, a senator used a snowball gathered outside the U.S. Capitol to stand as conclusive proof that global warming didn’t exist. That’s not an argument heard much any more, even as a severe cold snap has created emergency conditions in Texas and other southern states.

The connections between warming trends and extreme weather aren’t completely understood, but it’s becoming increasingly apparent that there’s a connection between climate change and rising damage from hurricanes, typhoons, rainstorms, wildfires and heat and cold.

1. What’s the connection to the Southern freeze?

The Earth’s poles are warming faster than anywhere on the planet: The North Pole has been heating up about twice as fast as the rest of Earth for the last 30 years, according to the National Snow & Ice Data Center. In the Northern Hemisphere’s summer, this has led to a decrease in the contrast between the heat of the equator and the cold of North Pole.

The strength of the summer jet stream, a river of wind that propels weather systems around the globe, depends on extreme temperature differences between these two regions. As the planet warms and this contrast diminishes, the jet stream weakens and can no longer push large weather patterns out of the way.

2. How did this send cold air south?

3. Can scientists prove that climate change caused this?

No. Similar events happen about six times per decade, according to the National Oceanic and Atmospheric Administration. But Judah Cohen, director of seasonal forecasting at Atmospheric and Environmental Research, part of risk analytics firm Verisk, who’s spent more than a decade studying Arctic warming, maintains that climate change has increased the frequency with which the polar vortex weakens and allow the cold to air to run amok.

Texas has certainly seen snow before, said Bob Henson, a meteorologist with Yale Climate Connections. But he urged observers not to be distracted by individual anomalies. “We know the climate of the central U.S. can produce events like this,” he said. “The point is, when you sum up all the events that are happening 365 days a year, that is when you see climate change most vividly.”

4. What other kind of weather do scientists tie to climate change?

The blackouts in Texas marked the second time in six months that extreme temperatures have brought grids to their knees — a heatwave across California in August caused a spike in energy demand for cooling equipment, forcing rolling blackouts for the first time since 2001. Across the U.S., severe thunderstorms and hail damage have been rising for decades. Some of that is due to increasing population, but that doesn’t explain the full extent of the increase.

While scientists aren’t sure about the precise cause, there’s broad agreement that the weather is changing. In the past year, many parts of the world’s oceans reached record warm temperatures. The Atlantic produced an all-time high of 30 hurricanes and tropical storms in 2020. Vast areas the west were consumed by wildfires, including parts of Oregon and Washington that were once too wet to produce the required dry brush as fuel.

Studies by reinsurers Munich Re and Aon both show weather-related natural disasters around the world increasing over the years, while damage from other events such as earthquakes and volcanoes has remained the same.

It depends on what kind of disaster is being discussed. Solid correlation between global warming projections made in the 1970s or even earlier with rising temperatures make heat waves some of the most straightforward events to connect to to humanity’s greenhouse gas pollution. Forest fires are the product of heat, drought and wind, which is why scientists have become so confident that climate change is making wildfires in the western U.S., Australia, and elsewhere much worse.

In the U.S. fire season is now two months longer than it was in the 1970s and 80s. Since the beginning of this century, the West has seen a 75% increase in forest area with a high fire risk, and from 1984 to 2015, the area lost to forest fires almost doubled. Hurricanes are harder to pin down, given their meteorologically complex nature and how quickly they form and dissipate.

But warmer water and wetter air — both realized as complements of global warming — provide added fuel to tropical cyclones, which are expected to become more intense as the century wears on.

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