Niederschläge im Amazonasgebiet werden von der interdekadischen pazifischen Oszillation bestimmt
Im Amazonasbecken herrschte in den 2010er Jahren eine lang anhaltende Dürre. Die Analyse eines Klimamodells, die in diesem Beitrag vorgestellt wird, zeigt, dass ein negativer bis positiver Phasenübergang der interdekadischen pazifischen Oszillation (IPO) etwa 45 % der beobachteten Dürre seit 2010 erklärt, was weitaus größer ist als die Rolle des externen Einflusses von etwa 12 %. Die IPO-Entwicklung beeinflusst die kurzfristige Projektion der Niederschläge im Amazonasgebiet erheblich und führt zu großen Unsicherheiten in der kurzfristigen Projektion. Diese Unsicherheit verringert sich um etwa38 %, nachdem der Einfluss des IPO aus der Computersimulation entfernt wurde. Somit würde die Vorhersage des kurzfristigen Phasenübergangs des IPO die Projektion der Niederschlagsveränderungen in Amazonien in den kommenden Jahrzehnten erheblich verbessern. Der IPO ist definiert als das 9-Jahres-Mittel der Differenz zwischen der Anomalie der Meeresoberflächentemperatur (SST) von Dezember bis April (D-A), gemittelt über den zentral-östlichen äquatorialen Pazifik, und dem Durchschnitt der SST-Anomalie von Dezember bis April im nordwestlichen und südwestlichen Pazifik.
Hier das dazugehörige Paper von Yi Liu et al. 2024:
Near-term projection of Amazon rainfall dominated by phase transition of the Interdecadal Pacific Oscillation
The Amazon basin experienced a prolonged drought condition during the 2010s, leading to a large-scale forest degradation destructive to ecosystems and human society. Elusive are issues as to whether the decadal drought is driven by external forcing or internal variability, and whether the drought will continue or recover soon. Using large ensemble simulations from a state-of-the-art climate model, here we find a negative-to-positive phase transition of the Interdecadal Pacific Oscillation (IPO) explains ~45% (~40–49%) of the observed decadal drought of Amazon rainfall since 2010, much greater than the role of external forcing (~12%). Constraining future IPO phase transition reduces the uncertainty by ~38% from a range of −0.73 to + 0.31 mm day−1 decade−1 to a range of −0.42 to + 0.23 mm day−1 decade−1, of the near-term Amazon rainfall projection before 2040 under a mid-intensity emission scenario. Thus, the IPO plays a crucial role in the post-2010 drying and the near-term rainfall projection.
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Alexandra Witze in Nature:
Geologists reject the Anthropocene as Earth’s new epoch — after 15 years of debate
But some are now challenging the vote, saying there were ‘procedural irregularities’.
After 15 years of discussion and exploration, a committee of researchers has decided that the Anthropocene — generally understood to be the age of irreversible human impacts on the planet — will not become an official epoch in Earth’s geological timeline. The ruling, first reported by The New York Times, is meant to be final, but is being challenged by two leading members of the committee that ran the vote.
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Dr. Willie Soon wurde kürzlich von Dr. Saifedean Ammous interviewt. Hier geht’s zum Podcast.
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Bob Yirka , Phys.org:
Migration of hominins out of Africa may have been driven by the first major glaciation of the Pleistocene
A pair of planetary scientists, one with the University of Milan, the other with Columbia University, has found evidence that the exodus of hominins out of Africa approximately 1 million years ago may have been driven by the first major glaciation of the Pleistocene.
n their study, reported in Proceedings of the National Academy of Sciences, Giovanni Muttonia and Dennis Kent more accurately dated the onset of the first major Pleistocene ice age and compared it with genetic evidence of a hominin population bottleneck described in prior research efforts.
Weiterlesen auf Phys.org
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Hannah Hickey, University of Washington:
AI analysis of satellite images shows 1990s USSR collapse increased methane emissions, despite lower oil, gas production
The collapse of the former Soviet Union in 1991 yielded social, political and economic effects worldwide. Among them was a suspected role in slowing human-generated methane emissions. Methane had been rising steadily in the atmosphere until about 1990. Atmospheric scientists theorized that economic collapse in the former USSR led to less oil and gas production, and thus a slowdown in the rise of global methane levels, which has since resumed.
But new University of Washington research uses early satellite records to dispute that assumption. The study, published in the Proceedings of the National Academy of Sciences, finds that methane emissions in Turkmenistan, a former Soviet republic and major oil producer, actually increased in the years following the dissolution of the Soviet Union.
„Methane has these enigmatic trends that we don’t really understand,“ said senior author Alex Turner, a UW assistant professor of atmospheric sciences. „One that has always been fascinating is this slowdown in 1992. We find that the collapse of the Soviet Union seems to result, surprisingly, in an increase in methane emissions.“
Carbon dioxide is more important than methane for long-term global warming, but methane plays an important role in the shorter term. One molecule of methane has more heat-trapping power than CO2, and its half-life in the atmosphere is just a decade, meaning its levels can fluctuate.
In recent years, the rise of methane accelerated during COVID-19 lockdowns. Turner’s previous research showed that less driving and thus fewer vehicle emissions containing reactive nitrogen (an air pollutant) likely played a role, because pollution was no longer able to combine with methane molecules to remove them from the atmosphere.
Weiterlesen bei der University of Washington:
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Rochelle GLUZMAN auf phy.org:
Sinking US cities more exposed to rising seas: Study
Sea level rise could hit major US cities like New Orleans and San Francisco harder than expected by mid-century because coastal land is sinking, researchers said Wednesday, warning current flood defenses leave people and property at risk.
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After decades of Arctic sea ice getting faster, models suggest a dramatic reversal is coming
Will ice floating in the Arctic Ocean move faster or slower over the coming decades? The answer to this question will tell us whether marine transportation can be expected to get more or less hazardous. It might also have important implications for the rate of ice cover loss, which is hugely consequential for Northern Indigenous communities, ecosystems, and the global climate system.
While observational data suggest the trend has been towards faster sea ice speeds, climate models project that those speeds will slow down during the summer season. This contrast has led to some questions about the plausibility of the model projections.
In a new paper published today in The Cryosphere, Lassonde School of Engineering Associate Professor Neil Tandon and Postdoctoral Visitor Jamie Ward found that, while the mechanisms driving the ice slowdown remain plausible, questions remain regarding the timing of the slowdown.
„Understanding how sea ice motion is going to change is clearly of interest, and yet we didn’t really know if what the models were projecting was reasonable,“ says Tandon, who is also with the Centre for Research in Earth and Space Science (CRESS) at York University. „It seems that we can expect sea ice to continue to speed up for some time, but there will be a point in the coming decades when the dynamics will shift.“
Floating sea ice presents a particular hazard for marine transportation, says Tandon, pointing to a dramatic example from 2017 when sea ice trapped and sunk two fishing boats around Newfoundland. And the faster the ice, the more hazardous the conditions.
To understand why sea ice has been speeding up, Tandon says a spring can be a useful analogy. As temperatures warm and the ice thins, it can expand and contract more readily, just as a spring made of thinner metal can expand and contract more easily compared to a spring made of thicker metal.
„As the thinner sea ice expands and contracts more, it generates more momentum for the sea ice, just like one of those spring-loaded toy cars goes faster the farther back you pull it,“ explains Tandon.
However, this is not the only force acting on the ice, and when the ice gets thin enough, the internal stresses that produce „springiness“ start to fade, and other forces start to dominate.
„As ice enters what they call a free drift state, the internal stress becomes negligible, and the external forces of wind and the ocean surface tilt start to dominate. The models suggest that changes in the wind and ocean surface tilt will drive a slowdown of the sea ice during the summer season.“
Tandon says that while the models generally agree that this summertime slowdown will occur, they do not agree on when this slowdown will start. Some models suggest that the slowdown will start within the next decade, while others suggest it will start toward the end of this century.
Faster ice drifts can create hazardous conditions for marine transport, so in that sense, an ice slowdown could be seen as a positive, but Tandon says there are bigger considerations.
„It doesn’t change the fact that sea ice cover is steadily declining, right? This is a concern because of the impact on ecosystems, the Indigenous populations that rely on being able to hunt certain animals, the animals‘ ability to survive the changing habitat, and the overall effect on the global climate,“ says Tandon. „But, I would say it’s marginally good news in that the models are suggesting that some of the worst aspects we were expecting about ice cover decline are not being projected.“
Paper: Jamie L. Ward et al, Why is summertime Arctic sea ice drift speed projected to decrease?, The Cryosphere (2024). DOI: 10.5194/tc-18-995-2024