The increase of devastating weather extremes in summer is likely linked to human-made climate change, mounting evidence shows. Giant airstreams are circling the Earth, waving up and down between the Arctic and the tropics. These planetary waves transport heat and moisture. When these planetary waves stall, droughts or floods can occur. Warming caused by greenhouse-gases from fossil fuels creates favorable conditions for such events, an international team of scientists now finds.
“The unprecedented 2016 California drought, the 2011 U.S. heatwave and 2010 Pakistan flood as well as the 2003 European hot spell all belong to a most worrying series of extremes,” says Michael Mann from the Pennsylvania State University in the U.S., lead-author of the study now to be published in Scientific Reports.
“The increased incidence of these events exceeds what we would expect from the direct effects of global warming alone, so there must be an additional climate change effect. In data from computer simulations as well as observations, we identify changes that favor unusually persistent, extreme meanders of the jet stream that support such extreme weather events. Human activity has been suspected of contributing to this pattern before, but now we uncover a clear fingerprint of human activity.”
+++ How sunny days can turn into a serious heat wave +++
“If the same weather persists for weeks on end in one region, then sunny days can turn into a serious heat wave and drought, or lasting rains can lead to flooding”, explains co-author Stefan Rahmstorf from the Potsdam Institute for Climate Impact Research (PIK) in Germany. “This occurs under specific conditions that favor what we call a quasi-resonant amplification that makes the north-south undulations of the jet stream grow very large. It also makes theses waves grind to a halt rather than moving from west to east. Identifying the human fingerprint on this process is advanced forensics.”
Air movements are largely driven by temperature differences between the Equator and the Poles. Since the Arctic is more rapidly warming than other regions, this temperature difference is decreasing. Also, land masses are warming more rapidly than the oceans, especially in summer. Both changes have an impact on those global air movements. This includes the giant airstreams that are called planetary waves because they circle Earth’s Northern hemisphere in huge turns between the tropics and the Arctic. The scientists detected a specific surface temperature distribution apparent during the episodes when the planetary waves eastward movement has been stalling, as seen in satellite data.
+++ Using temperature measurements since 1870 to confirm findings in satellite data +++
”Good satellite data exists only for a relatively short time – too short to robustly conclude how the stalling events have been changing over time. In contrast, high-quality temperature measurements are available since the 1870s, so we use this to reconstruct the changes over time,” says co-author Kai Kornhuber, also from PIK. “We looked into dozens of different climate models – computer simulations called CMIP5 of this past period – as well as into observation data, and it turns out that the temperature distribution favoring planetary wave airstream stalling increased in almost 70 percent of the simulations.”
Interestingly, most of the effect occured in the past four decades. “The more frequent persistent and meandering Jetstream states seems to be a relatively recent phenomenon, which makes it even more relevant,” says co-author Dim Coumou from the Department of Water and Climate Risk at VU University in Amsterdam (Netherlands). “We certainly need to further investigate this – there is some good evidence, but also many open questions. In any case, such non-linear responses of the Earth system to human-made warming should be avoided. We can limit the risks associated with increases in weather extremes if we limit greenhouse-gas emissions.”
Article: Michael E. Mann, Stefan Rahmstorf, Kai Kornhuber, Byron A. Steinman, Sonya K. Miller, Dim Coumou (2017): Influence of Anthropogenic Climate Change on Planetary Wave Resonance and Extreme Weather Events. Scientific Reports [DOI: 10.1038/srep45242]
Weblink to the article once it is published (which should be the case within 24 hours from now): www.nature.com/articles/srep45242
Weblink to video that explains the planetary waves phenomenon: https://www.youtube.com/watch?v=MzW5Isbv2A0
For further information please contact:
PIK press office
Phone: +49 331 288 25 07
Jonas Viering, Sarah Messina | Potsdam-Institut für Klimafolgenforschung
Ten-year anniversary of the Neumayer Station III
18.01.2019 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung
The pace at which the world’s permafrost soils are warming
16.01.2019 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung
The scientific and political community alike stress the importance of German Antarctic research
Joint Press Release from the BMBF and AWI
The Antarctic is a frigid continent south of the Antarctic Circle, where researchers are the only inhabitants. Despite the hostile conditions, here the Alfred...
World first experiments on sensor that may revolutionise everything from medical devices to unmanned vehicles
The new sensor - capable of detecting vibrations of living cells - may revolutionise everything from medical devices to unmanned vehicles.
Dead and alive at the same time? Researchers at the Max Planck Institute of Quantum Optics have implemented Erwin Schrödinger’s paradoxical gedanken experiment employing an entangled atom-light state.
In 1935 Erwin Schrödinger formulated a thought experiment designed to capture the paradoxical nature of quantum physics. The crucial element of this gedanken...
Cellulose obtained from wood has amazing material properties. Empa researchers are now equipping the biodegradable material with additional functionalities to produce implants for cartilage diseases using 3D printing.
It all starts with an ear. Empa researcher Michael Hausmann removes the object shaped like a human ear from the 3D printer and explains:
The phenomenon of so-called superlubricity is known, but so far the explanation at the atomic level has been missing: for example, how does extremely low friction occur in bearings? Researchers from the Fraunhofer Institutes IWM and IWS jointly deciphered a universal mechanism of superlubricity for certain diamond-like carbon layers in combination with organic lubricants. Based on this knowledge, it is now possible to formulate design rules for supra lubricating layer-lubricant combinations. The results are presented in an article in Nature Communications, volume 10.
One of the most important prerequisites for sustainable and environmentally friendly mobility is minimizing friction. Research and industry have been dedicated...
16.01.2019 | Event News
14.01.2019 | Event News
12.12.2018 | Event News
18.01.2019 | Materials Sciences
18.01.2019 | Life Sciences
18.01.2019 | Health and Medicine