Liebe Leser. Heute wieder ein paar wenig beachtete Meldungen aus den Klimawissenschaften. Für alle, die sprachliche Unterstützung benötigen: Adresse (URL) dieses Blogartikels mit den englischen Abschnitten kopieren. Dann zum Google Übersetzer Englisch-Deutsch gehen: https://translate.google.com/?hl=de&sl=en&tl=de&op=websites . Adresse (URL) des Blogartikels in das Feld kopieren und blauen Pfeil klicken. Fertig.
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Massive iceberg discharges during the last ice age had no impact on nearby Greenland
During the last ice age, massive icebergs periodically broke off from an ice sheet covering a large swath of North America and discharged rapidly melting ice into the North Atlantic Ocean around Greenland, triggering abrupt climate change impacts across the globe.
These sudden episodes, called Heinrich Events, occurred between 16,000 and 60,000 years ago. They altered the circulation of the world’s oceans, spurring cooling in the North Atlantic and impacting monsoon rainfall around the world.
But little was known about the events’ effect on nearby Greenland, which is thought to be very sensitive to events in the North Atlantic. A new study from Oregon State University researchers, just published in the journal Nature, provides a definitive answer.
“It turns out, nothing happened in Greenland. The temperature just stayed the same,” said the study’s lead author, Kaden Martin, a fourth-year doctoral candidate in OSU’s College of Earth, Ocean, and Atmospheric Sciences. “They had front-row seats to this action but didn’t see the show.”
Instead, the researchers found that these Heinrich events caused rapid warming in Antarctica, at the other end of the globe.
The researchers anticipated Greenland, in close proximity to the ice sheet, would have experienced some kind of cooling. To find that these Heinrich Events had no discernible impact on temperatures in Greenland is surprising and could have repercussions for scientists’ understanding of past climate dynamics, said study co-author Christo Buizert, an assistant professor in the College of Earth, Ocean, and Atmospheric Sciences.
“If anything, our findings raise more questions than answers,” said Buizert, a climate change specialist who uses ice cores from Greenland and Antarctica to reconstruct and understand the Earth’s climate history. “This really changes how we look at these massive events in the North Atlantic. It’s puzzling that far-flung Antarctica responds more strongly than nearby Greenland.”
Scientists drill and preserve ice cores to study past climate history through analysis of the dust and tiny air bubbles that have been trapped in the ice over time. Ice cores from Greenland and Antarctica provide important records of Earth’s atmospheric changes over hundreds of thousands of years.
Records from ice cores from those regions have served as pillars for scientists’ understanding of past climate events, with ice collected from both locations often telling similar stories, Martin said.
The impact of Heinrich Events on Greenland and Antarctica was not well understood, spurring Martin and Buizert to try to find out more about what was happening in those parts of the world.
The core used for the latest study was collected in 1992 from the highest point of Greenland, where the ice sheet is around 2 miles thick. Since then, the core has been in storage in the National Science Foundation Ice Core Facility in Denver.
Advancement in scientific tools and measurements over the last few decades gave Martin, Buizert and their colleagues the opportunity to re-examine the core using new methods.
The analysis shows that no changes in temperatures occurred in Greenland during Heinrich Events. But it also provides a very clear connection between Heinrich Events and the Antarctic response.
“When these big iceberg discharges happen in the Arctic, we now know that Antarctica responds right away,” Buizert said. “What happens in one part of the world has an effect on the rest of the world. This inter-hemispheric connection is likely caused by change in global wind patterns.”
The finding challenges the current understanding of global climate dynamics during these massive events and raises new questions for researchers, Buizert said. The researchers’ next step is to take the new information and run it through climate models to see if the models can replicate what occurred.
“There has to be a story that fits all of the evidence, something that connects all the dots,” he said. “Our discovery adds two new dots; it’s not the full story, and it may not be the main story. It is possible that the Pacific Ocean plays an important role that we haven’t figured out yet.”
The ultimate goal is to better understand how the climate system is connected and how the components all interact, the researchers said.
“While Heinrich Events are not going to happen in the future, abrupt changes in the globally interconnected climate system will happen again,” Martin said. “Understanding the global dynamics of the climate system can help us better project future impacts and inform how we respond and adapt.”
Paper: Kaden Martin, Bipolar impact and phasing of Heinrich-type climate variability, Nature (2023). DOI: 10.1038/s41586-023-05875-2. www.nature.com/articles/s41586-023-05875-2
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Joshua Howat Berger via phys.org:
Arson turns Amazon reforestation project to ashes
It was supposed to be a good-news story out of the damaged Amazon rainforest: a project that replanted hundreds of thousands of trees in an illegally deforested nature reserve in Brazil.
Then it went up in flames, allegedly torched by land-grabbers trying to reclaim the territory for cattle pasture.
Launched in 2019 by environmental research group Rioterra, the reforestation project took 270 hectares (665 acres) of forest that had been razed by cattle ranching on a protected nature reserve in the northern state of Rondonia and replanted it with 360,000 trees.
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120-year-old storm’s secrets could be key to judging weather risks
A severe windstorm that battered the U.K. more than a century ago produced some of the strongest winds that Britain has ever seen, a team of scientists have found after recovering old weather records.
Old weather measurements, first recorded on paper after Storm Ulysses hit the U.K. in February 1903, have shed new light on what was one of the most severe storms to have hit the British Isles.
By turning hand-written weather data into digital records, the research team has laid the way to better understand other historical storms, floods and heat waves. These observations from the past can help experts to understand the risks of extreme weather now and in the future.
Professor Ed Hawkins, a climate scientist at the University of Reading and the National Center for Atmospheric Science, led the research. He said, “We knew the storm we analyzed was a big one, but we didn’t know our rescued data would show that it is among the top four storms for strongest winds across England and Wales.
“This study is a great example of how rescuing old paper records can help us to better understand storms from decades gone by. Unlocking these secrets from the past could transform our understanding of extreme weather and the risks they pose to us today.”
Into the archives
Published in Natural Hazards and Earth System Sciences, the research indicates that many storms that occurred before 1950 are left unstudied as billions of pieces of data exist only on paper, stored in archives around the world.
But a team of scientists led by Professor Hawkins delved into the archives to convert hand-written observations relating to Storm Ulysses from paper to digital. The cyclone caused multiple deaths and heavily damaged infrastructure and ships when it passed across Ireland and the U.K. between 26 and 27 February 1903.
Using the new digital data, the research team was able to use techniques similar to modern weather forecasting to simulate the storm and accurately assess the strength of Storm Ulysses’ winds. Comparisons with independent weather observations, such as rainfall data, as well as photographs and written accounts from 1903 that outlined the devastation caused by the cyclone, helped to provide credibility for the reconstruction.
The reanalysis is beneficial for understanding the risks of extreme weather events as it showed that the winds experienced in some locations during Storm Ulysses would be rarer than once in 100 years. Having information about such a rare event provides valuable insight into the potential extra damage a similar storm could cause now in the future.
The 1903 storm is named Storm Ulysses because the damage to thousands of trees in Dublin is mentioned in the novel Ulysses by James Joyce, the events of which are set the year after the storm.
Rescuing the weather
The rescuing of atmospheric observations related to Storm Ulysses is not the first time Professor Ed Hawkins has led weather record recovery. National rainfall data from as far back as 1836 became available in 2022 after the University’s Department of Meteorology and 16,000 volunteers helped to restore 5.2 million observations.
The Rainfall Rescue project provided more context around recent changes in rainfall due to human-caused climate change.
Paper: Ed Hawkins et al, Rescuing historical weather observations improves quantification of severe windstorm risks, Natural Hazards and Earth System Sciences (2023). DOI: 10.5194/nhess-23-1465-2023
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Flood variability in the upper Yangtze River over the last millennium
A recent study led by Dr. Huo Ran (State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University) integrated reconstructed data and (global climate and hydrological) model simulations to better understand the variability of climate and hydrology over timescales ranging from decades to centuries.
They first drove hydrological models using the precipitation and temperature from four Global Climate Models (GCM), BCC-CSM1.1, MIROC, MRI-CGCM3, and CCSM4, to simulate daily discharge for the upper reach of the Yangtze River during the period of the last millennium (850–1849), historical period (1850–2005), and a future period (2006–2099).
The team found that:
(i) The MIROC model, differing from the other three GCM models, revealed positive temperature changes from the warm period (Medieval Climate Anomaly; MCA) to the cold period (Little Ice Age; LIA), while the temperature variability of the other models was similar to the records.
(ii) The BCC-CSM1.1 model performed better than the others regarding correlations between modeled precipitation and documented dry-wet periods.
(iii) Over most of the subbasins in the upper Yangtze River, the magnitude of extreme discharge in the BCC-CSM1.1 model results showed that there was a decrease from the MCA to the LIA period and an increase in the historical period relative to the cold period, while a future increase was projected by the four GCMs under the influence of climate change.
The paper is published in the journal Science China Earth Sciences.
Paper: Ran Huo et al, Flood variability in the upper Yangtze River over the last millennium—Insights from a comparison of climate-hydrological model simulated and reconstruction, Science China Earth Sciences (2023). DOI: 10.1007/s11430-022-1008-5