Tree Rings And Weather Data Warn Of Megadrought

Tree Rings And Weather Data Warn Of Megadrought

Drought blankets part of California in 2014. Image: By Pete Souza (public domain), via Wikimedia Commons

Farmers in the US West know they have a drought, but may not yet realise these arid years could become a megadrought.

Climate change could be pushing the US west and northern Mexico towards the most severe and most extended period of drought observed in a thousand years of US history, a full-blown megadrought.

Natural atmospheric forces have always triggered prolonged spells with little rain. But warming driven by profligate human use of fossil fuels could now be making a bad situation much worse.

The warning of what climate scientists call a megadrought – outlined in the journal Science – is based not on computer simulations but on direct testimony from more than a century of weather records and the much longer story told by 1200 consecutive years of evidence preserved in the annual growth rings of trees that provide a record of changing levels of soil moisture.

“Earlier studies were largely model projections of the future. We are no longer looking at projections, but at where we are now,” said Park Williams, a bioclimatologist at the Lamont Doherty Earth Observatory of Columbia University in the US.

“We now have enough observations of current drought and tree ring records of past drought to say we’re on the same trajectory as the worst prehistoric droughts.”

Repeating the past

Previous research has already linked catastrophic drought to turmoil among pre-Columbian civilisations in the American Southwest.

Studies by other groups have also warned that what happened in the past could happen again, as carbon dioxide emissions from fossil fuel combustion enrich the atmosphere, raise temperatures and parch the soils of the US West.

Global heating has been repeatedly linked to the last devastating drought in California, and to the possible return of Dust Bowl conditions in the Midwestern grain belt.

The latest study delivers a long-term analysis of conditions across nine US states, from Oregon and Montana in the north down to California, New Mexico and part of northern Mexico.

With the evidence preserved in old tree trunks, the scientists identified dozens of droughts in the region from 800 AD. They found four megadroughts – periods in which the conditions became extreme – between 800 and 1600. Since then there have been no droughts that could be matched with these – so far.

And then the researchers matched the megadrought tree ring evidence with soil moisture records collected in the first 19 years of this century, and compared this with any 19-year period in the prehistoric droughts.

“We’ll need more and more good luck to break out of drought, and less and less bad luck to get into drought”

They found that the current prolonged dry spell is already more pronounced than the three earliest records of megadrought. The fourth megadrought – it ran from 1575 to 1603 – may still have been the worst of all, but the match with the present years is so close that nobody can be sure.

But the team behind the Science study is sure of one thing. This drought right now is affecting wider stretches of landscape more consistently than any of the earlier megadroughts, and this, they say, is a signature of global heating. All the ancient megadroughts lasted longer, and sometimes much longer, than 19 years, but all began in a way very similar to the present.

The snowpack in the western high mountains has fallen dramatically, the flow of the rivers has dwindled, lake levels have fallen, farmers have been  hit and the wildfires have become more prolonged and more intense.

Drought and even the chance of megadrought may be a fact of life in the US West. During occasional natural atmospheric cycles, the tropical Pacific cools and storm tracks shift further north, taking rainfall away from the US drylands.

But since 2000, average air temperatures in the western states have risen by more than 1.2°C above the normal over earlier centuries. So soils already starved of rain began to lose their stored moisture at an ever-increasing rate.

Worsened by heating

Without the additional global heating, this drought might have happened anyway, and perhaps even been the 11th worst ever recorded, rather than almost the worst ever in human experience.

“It doesn’t matter if this is exactly the worst drought ever,” said Benjamin Cook, a co-author, from Nasa’s Goddard Institute for Space Studies. “What matters is that it has been made much worse than it could have been because of climate change.”

The researchers also found that the 20th century was the wettest century in the entire 1200 year record, and this relatively plentiful supply of water must have helped enrich the US West and make California, for instance, become the Golden State, the most populous in the US.

“Because the background is getting warmer, the dice are increasingly loaded towards longer and more severe droughts,” Professor Williams said. “We may get lucky, and natural variability will bring more precipitation for a while.

“But going forward, we’ll need more and more good luck to break out of drought, and less and less bad luck to get into drought.” – Climate News Network

About the Author

Tim Radford, freelance journalistTim Radford is a freelance journalist. He worked for The Guardian for 32 years, becoming (among other things) letters editor, arts editor, literary editor and science editor. He won the Association of British Science Writers award for science writer of the year four times. He served on the UK committee for the International Decade for Natural Disaster Reduction. He has lectured about science and the media in dozens of British and foreign cities. 

Science that Changed the World: The untold story of the other 1960s revolutionBook by this Author:

Science that Changed the World: The untold story of the other 1960s revolution
by Tim Radford.

Click here for more info and/or to order this book on Amazon. (Kindle book)

This Article Originally Appeared On Climate News Network

Related Books

Life After Carbon: The Next Global Transformation of Cities

by Peter Plastrik , John Cleveland
1610918495The future of our cities is not what it used to be. The modern-city model that took hold globally in the twentieth century has outlived its usefulness. It cannot solve the problems it helped to create—especially global warming. Fortunately, a new model for urban development is emerging in cities to aggressively tackle the realities of climate change. It transforms the way cities design and use physical space, generate economic wealth, consume and dispose of resources, exploit and sustain the natural ecosystems, and prepare for the future. Available On Amazon

The Sixth Extinction: An Unnatural History

by Elizabeth Kolbert
1250062187Over the last half-billion years, there have been Five mass extinctions, when the diversity of life on earth suddenly and dramatically contracted. Scientists around the world are currently monitoring the sixth extinction, predicted to be the most devastating extinction event since the asteroid impact that wiped out the dinosaurs. This time around, the cataclysm is us. In prose that is at once frank, entertaining, and deeply informed, New Yorker writer Elizabeth Kolbert tells us why and how human beings have altered life on the planet in a way no species has before. Interweaving research in half a dozen disciplines, descriptions of the fascinating species that have already been lost, and the history of extinction as a concept, Kolbert provides a moving and comprehensive account of the disappearances occurring before our very eyes. She shows that the sixth extinction is likely to be mankind's most lasting legacy, compelling us to rethink the fundamental question of what it means to be human. Available On Amazon

Climate Wars: The Fight for Survival as the World Overheats

by Gwynne Dyer
1851687181Waves of climate refugees. Dozens of failed states. All-out war. From one of the world’s great geopolitical analysts comes a terrifying glimpse of the strategic realities of the near future, when climate change drives the world’s powers towards the cut-throat politics of survival. Prescient and unflinching, Climate Wars will be one of the most important books of the coming years. Read it and find out what we’re heading for. Available On Amazon

From The Publisher:
Purchases on Amazon go to defray the cost of bringing you InnerSelf.comelf.com, MightyNatural.com, and ClimateImpactNews.com at no cost and without advertisers that track your browsing habits. Even if you click on a link but don't buy these selected products, anything else you buy in that same visit on Amazon pays us a small commission. There is no additional cost to you, so please contribute to the effort. You can also use this link to use to Amazon at any time so you can help support our efforts.

 

enafarzh-CNzh-TWdanltlfifrdeiwhihuiditjakomsnofaplptruesswsvthtrukurvi

follow InnerSelf on

facebook-icontwitter-iconrss-icon

 Get The Latest By Email

{emailcloak=off}

EVIDENCE

Will The Climate Warm As Much As Feared By Some?
Will The Climate Warm As Much As Feared By Some?
by Steven Sherwood et al
We know the climate changes as greenhouse gas concentrations rise, but the exact amount of expected warming remains…
Methane Emissions Hit Record Breaking Levels
Methane Emissions Hit Record Breaking Levels
by Josie Garthwaite
Global emissions of methane have reached the highest levels on record, research shows.
What The World Was Like The Last Time Carbon Dioxide Levels Were At 400ppm
What The World Was Like The Last Time Carbon Dioxide Levels Were At 400ppm
by James Shulmeister
The last time global carbon dioxide levels were consistently at or above 400 parts per million (ppm) was around four…
What An Ocean Hidden Under Antarctic Ice Reveals About Our Planet's Future Climate
What An Ocean Hidden Under Antarctic Ice Reveals About Our Planet's Future Climate
by Craig Stevens and Christina Hulbe
Jules Verne sent his fictional submarine, the Nautilus, to the South Pole through a hidden ocean beneath a thick ice…
Antarctic Ice Shelves Reveals A Missing Piece Of The Climate Puzzle
Antarctic Ice Shelves Reveals A Missing Piece Of The Climate Puzzle
by Katherine Hutchinson
Ice shelves, massive floating bodies of ice, are well-known for their buffering effect on land-based ice sheets as they…
Why We Won't Be Heading Into An Ice Age Any Time Soon
Why We Won't Be Heading Into An Ice Age Any Time Soon
by James Renwick
When I studied climate in my university geography course in the 1960s, I am sure we were told that the Earth was…
How Volcanoes Influence Climate And How Their Emissions Compare To What We Produce
How Volcanoes Influence Climate And How Their Emissions Compare To What We Produce
by Michael Petterson
Everyone is going on about reducing our carbon footprint, zero emissions, planting sustainable crops for biodiesel etc.
What Is Climate Sensitivity?
What Is Climate Sensitivity?
by Robert Colman and Karl Braganza
Humans are emitting CO2 and other greenhouse gases into the atmosphere. As these gases build up they trap extra heat…

LATEST VIDEOS

Methane Emissions Hit Record Breaking Levels
Methane Emissions Hit Record Breaking Levels
by Josie Garthwaite
Global emissions of methane have reached the highest levels on record, research shows.
kelp forrest 7 12
How The Forests Of The World’s Oceans Contribute To Alleviating The Climate Crisis
by Emma Bryce
Researchers are looking to kelp for help storing carbon dioxide far beneath the surface of the sea.
Tiny Plankton Drive Processes In The Ocean That Capture Twice As Much Carbon As Scientists Thought
Tiny Plankton Drive Processes In The Ocean That Capture Twice As Much Carbon As Scientists Thought
by Ken Buesseler
The ocean plays a major role in the global carbon cycle. The driving force comes from tiny plankton that produce…
Climate Change Threatens Drinking Water Quality Across The Great Lakes
Climate Change Threatens Drinking Water Quality Across The Great Lakes
by Gabriel Filippelli and Joseph D. Ortiz
“Do Not Drink/Do Not Boil” is not what anyone wants to hear about their city’s tap water. But the combined effects of…
Talking About Energy Change Could Break The Climate impasse
Talking About Energy Change Could Break The Climate Impasse
by InnerSelf Staff
Everyone has energy stories, whether they’re about a relative working on an oil rig, a parent teaching a child to turn…
Crops Could Face Double Trouble From Insects And A Warming Climate
Crops Could Face Double Trouble From Insects And A Warming Climate
by Gregg Howe and Nathan Havko
For millennia, insects and the plants they feed on have been engaged in a co-evolutionary battle: to eat or not be…
To Reach Zero Emissions Government Must Address Hurdles Putting People Off Electric Cars
To Reach Zero Emissions Government Must Address Hurdles Putting People Off Electric Cars
by Swapnesh Masrani
Ambitious targets have been set by the UK and Scottish governments to become net-zero carbon economies by 2050 and 2045…
Spring Is Arriving Earlier Across The US, And That's Not Always Good News
Spring Is Arriving Earlier Across The US, And That's Not Always Good News
by Theresa Crimmins
Across much of the United States, a warming climate has advanced the arrival of spring. This year is no exception.

LATEST ARTICLES

Two-thirds Of Glacier Ice In The Himalayas Could Be Lost By 2100
Two-thirds Of Glacier Ice In The Himalayas Could Be Lost By 2100
by Ann Rowan
In the world of glaciology, the year 2007 would go down in history. It was the year a seemingly small error in a major…
Rising Temps Could Kill Millions A Year By Century’s End
Rising Temps Could Kill Millions A Year By Century’s End
by Edward Lempinen
By the end of this century, tens of millions of people could die each year worldwide as a result of temperatures rising…
New Zealand Wants To Build A 100% Renewable Electricity Grid, But Massive Infrastructure Is Not The Best Option
New Zealand Wants To Build A 100% Renewable Electricity Grid, But Massive Infrastructure Is Not The Best Option
by Janet Stephenson
A proposed multibillion-dollar project to build a pumped hydro storage plant could make New Zealand’s electricity grid…
Wind Farms Built On Carbon-rich Peat Bogs Lose Their Ability To Fight Climate Change
Wind Farms Built On Carbon-rich Peat Bogs Lose Their Ability To Fight Climate Change
by Guaduneth Chico et al
Wind power in the UK now accounts for nearly 30% of all electricity production. Land-based wind turbines now produce…
Climate Denial Hasn't Gone Away – Here's How To Spot Arguments For Delaying Climate Action
Climate Denial Hasn't Gone Away – Here's How To Spot Arguments For Delaying Climate Action
by Stuart Capstick
In new research, we have identified what we call 12 “discourses of delay”. These are ways of speaking and writing about…
Routine Gas Flaring Is Wasteful, Polluting And Undermeasured
Routine Gas Flaring Is Wasteful, Polluting And Undermeasured
by Gunnar W. Schade
If you’ve driven through an area where companies extract oil and gas from shale formations, you’ve probably seen flames…
Flight Shaming: How To Spread The Campaign That Made Swedes Give Up Flying For Good
Flight Shaming: How To Spread The Campaign That Made Swedes Give Up Flying For Good
by Avit K Bhowmik
Europe’s major airlines are likely to see their turnover drop by 50% in 2020 as a result of the COVID-19 pandemic,…
Will The Climate Warm As Much As Feared By Some?
Will The Climate Warm As Much As Feared By Some?
by Steven Sherwood et al
We know the climate changes as greenhouse gas concentrations rise, but the exact amount of expected warming remains…