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+--- Thread: Research Study predicts catastrophic river change threats + Global temps over half billion yrs (/thread-16533.html)
Study predicts catastrophic river change threats + Global temps over half billion yrs - C C - Sep 21, 2024
Breakthrough study predicts catastrophic river shifts that threaten millions worldwide
https://www.eurekalert.org/news-releases/1058637
INTRO: Indiana University researchers have uncovered key insights into the dangerous phenomenon of “river avulsion,” offering a way to predict when and where rivers may suddenly and dramatically change course. Published in Nature, this breakthrough study sheds light on a process that has shaped human history through devastating floods and continues to threaten millions of people worldwide.
Led by James “Jake” Gearon, a Ph.D. candidate in the Department of Earth and Atmospheric Sciences (EAS) within the College of Arts and Sciences at Indiana University Bloomington, the research team has outlined for the first time the conditions that create river avulsions. Co-authors include Harrison Martin (Ph.D. EAS ’23), a post-doctoral fellow now at CalTech, Clarke DeLisle (Ph.D. EAS ’23) now at EVS, Inc, Eric Barefoot, a post-doctoral researcher at IU Bloomington and now a faculty member at UC-Riverside, and Professor Douglas Edmonds, the Malcolm and Sylvia Boyce Chair in Geological Sciences in the Earth and Atmospheric Sciences department.
Using advanced satellite technology, the team mapped how certain landscape features make avulsions more likely. “Measuring topography around a river is difficult and time-consuming because of the dense vegetation,” said Gearon. “We took advantage of a new satellite that uses lasers to measure topography.” This technology, called lidar, penetrates vegetation to find bare-earth elevations, allowing for accurate topographical measurements.
The study presents a novel framework for predicting when avulsions will occur, a problem humanity has dealt with for millennia. “Avulsions which are possibly the inspirations for ancient flood myths, have created the largest floods in human history, and continue to threaten millions of people today,” explained Edmonds. “As climate change alters global water cycles and human expansion into flood-prone areas increases, understanding and predicting avulsions has never been more critical.” (MORE - details, no ads)
Study: Over nearly half a billion years, Earth’s global temperature has changed drastically, driven by carbon dioxide
https://www.eurekalert.org/news-releases/1058221
INTRO: A new study co-led by the University of Arizona and the Smithsonian offers the most detailed glimpse yet into how Earth's surface temperature has changed over the past 485 million years.
Published in the journal Science, the study presents a curve of global mean surface temperature that reveals Earth's temperature has varied more than previously thought over much of the Phanerozoic Eon a period of geologic time when life diversified, populated land and endured multiple mass extinctions. The curve also confirms Earth's temperature is strongly correlated to the amount of carbon dioxide in the atmosphere.
The start of the Phanerozoic Eon 540 million years ago is marked by the Cambrian Explosion, a point in time when complex, hard-shelled organisms first appeared in the fossil record. Although researchers can create simulations all the way back to 540 million years ago, the temperature curve in the study focuses on the last 485 million years since there is limited geological data of temperature before then.
"It's hard to find rocks that are that old and have temperature indicators preserved in them – even at 485 million years ago we don't have that many. We were limited with how far back we could go,” said study co-author Jessica Tierney, a paleoclimatologist at the University of Arizona.
The researchers created the temperature curve using an approach called data assimilation. This allowed them to combine data from the geologic record and climate models to create a more cohesive understanding of ancient climates.
"This method was originally developed for weather forecasting," said Emily Judd, lead author of the paper and a former postdoctoral researcher at the Smithsonian National Museum of Natural History and the U of A. "Instead of using it to forecast future weather, here we're using it to hindcast ancient climates."
Refining scientists' understanding of how Earth's temperature has fluctuated over time provides crucial context for understanding modern climate change.
"If you're studying the last couple of million years, you won't find anything that looks like what we expect in 2100 or 2500," said Scott Wing, a co-author on the paper and a curator of paleobotany at the Smithsonian National Museum of Natural History. "You need to go back even further to periods when the Earth was really warm, because that's the only way we're going to get a better understanding of how the climate might change in the future."
The new curve reveals that temperature varied more greatly during the past 485 million years than previously thought. Over the eon, the global temperature spanned 52 to 97 degrees Fahrenheit. Periods of extreme heat were most often linked to elevated levels of the greenhouse gas carbon dioxide in the atmosphere.
"This research illustrates clearly that carbon dioxide is the dominant control on global temperatures across geological time," said Tierney. "When CO2 is low, the temperature is cold; when CO2 is high, the temperature is warm."
The findings also reveal that the Earth's current global temperature of 59 degrees Fahrenheit is cooler than Earth has been over much of the Phanerozoic. But greenhouse gas emissions from human-caused climate change are currently warming the planet at a much faster rate than even the fastest warming events of the Phanerozoic, the reseaerchers say. The speed of warming puts species and ecosystems around the world at risk and is causing a rapid rise in sea level. Some other episodes of rapid climate change during the Phanerozoic have sparked mass extinctions... (MORE - details, no ads)