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- ItemReply to Bhowmik et al.: Democratic climate action and studying extreme climate risks are not in tension(Washington, DC : National Acad. of Sciences, 2022) Kemp, Luke; Xu, Chi; Depledge, Joanna; Ebi, Kristie L.; Gibbins, Goodwin; Kohler, Timothy A.; Rockström, Johan; Scheffer, Marten; Schellnhuber, Hans Joachim; Steffen, Will; Lenton, Timothy M.[no abstract available]
- ItemReply to Ruhl and Craig: Assessing and governing extreme climate risks needs to be legitimate and democratic(Washington, DC : National Acad. of Sciences, 2022) Kemp, Luke; Xu, Chi; Depledge, Joanna; Ebi, Kristie L.; Gibbins, Goodwin; Kohler, Timothy A.; Rockström, Johan; Scheffer, Marten; Schellnhuber, Hans Joachim; Steffen, Will; Lenton, Timothy M.[No abstract available]
- ItemStewardship of global collective behavior(Washington, DC : National Acad. of Sciences, 2021) Bak-Coleman, Joseph B.; Alfano, Mark; Barfuss, Wolfram; Bergstrom, Carl T.; Centeno, Miguel A.; Couzin, Iain D.; Donges, Jonathan F.; Galesic, Mirta; Gersick, Andrew S.; Jacquet, Jennifer; Kao, Albert B.; Moran, Rachel E.; Romanczuk, Pawel; Rubenstein, Daniel I.; Tombak, Kaia J.; Van Bavel, Jay J.; Weber, Elke U.Collective behavior provides a framework for understanding how the actions and properties of groups emerge from the way individuals generate and share information. In humans, information flows were initially shaped by natural selection yet are increasingly structured by emerging communication technologies. Our larger, more complex social networks now transfer high-fidelity information over vast distances at low cost. The digital age and the rise of social media have accelerated changes to our social systems, with poorly understood functional consequences. This gap in our knowledge represents a principal challenge to scientific progress, democracy, and actions to address global crises. We argue that the study of collective behavior must rise to a “crisis discipline” just as medicine, conservation, and climate science have, with a focus on providing actionable insight to policymakers and regulators for the stewardship of social systems.
- ItemReply to Smith et al.: Social tipping dynamics in a world constrained by conflicting interests(Washington, DC : National Acad. of Sciences, 2020) Otto, Ilona M.; Donges, Jonathan F.; Lucht, Wolfgang; Schellnhuber, Hans Joachim[No abstract available]
- ItemCommunicating sentiment and outlook reverses inaction against collective risks(Washington, DC : National Acad. of Sciences, 2020) Wang, Zhen; Jusup, Marko; Guo, Hao; Shi, Lei; Geček, Sunčana; Anand, Madhur; Perc, Matjaž; Bauch, Chris T.; Kurths, Jürgen; Boccaletti, Stefano; Schellnhuber, Hans JoachimCollective risks permeate society, triggering social dilemmas in which working toward a common goal is impeded by selfish interests. One such dilemma is mitigating runaway climate change. To study the social aspects of climate-change mitigation, we organized an experimental game and asked volunteer groups of three different sizes to invest toward a common mitigation goal. If investments reached a preset target, volunteers would avoid all consequences and convert their remaining capital into monetary payouts. In the opposite case, however, volunteers would lose all their capital with 50% probability. The dilemma was, therefore, whether to invest one's own capital or wait for others to step in. We find that communicating sentiment and outlook helps to resolve the dilemma by a fundamental shift in investment patterns. Groups in which communication is allowed invest persistently and hardly ever give up, even when their current investment deficits are substantial. The improved investment patterns are robust to group size, although larger groups are harder to coordinate, as evidenced by their overall lower success frequencies. A clustering algorithm reveals three behavioral types and shows that communication reduces the abundance of the free-riding type. Climate-change mitigation, however, is achieved mainly by cooperator and altruist types stepping up and increasing contributions as the failure looms. Meanwhile, contributions from free riders remain flat throughout the game. This reveals that the mechanisms behind avoiding collective risks depend on an interaction between behavioral type, communication, and timing.
- ItemEarly Last Interglacial ocean warming drove substantial ice mass loss from Antarctica(Washington, DC : National Acad. of Sciences, 2020) Turney, Chris S.M.; Fogwill, Christopher J.; Golledge, Nicholas R.; McKay, Nicholas P.; van Sebille, Erik; Jones, Richard T.; Etheridge, David; Rubino, Mauro; Thornton, David P.; Davies, Siwan M.; Ramsey, Christopher Bronk; Thomas, Zoë A.; Bird, Michael I.; Munksgaard, Niels C.; Kohno, Mika; Woodward, John; Winter, Kate; Weyrich, Laura S.; Rootes, Camilla M.; Millman, Helen; Albert, Paul G.; Rivera, Andres; van Ommen, Tas; Curran, Mark; Moy, Andrew; Rahmstorf, Stefan; Kawamura, Kenji; Hillenbrand, Claus-Dieter; Weber, Michael E.; Manning, Christina J.; Young, Jennifer; Cooper, AlanThe future response of the Antarctic ice sheet to rising temperatures remains highly uncertain. A useful period for assessing the sensitivity of Antarctica to warming is the Last Interglacial (LIG) (129 to 116 ky), which experienced warmer polar temperatures and higher global mean sea level (GMSL) (+6 to 9 m) relative to present day. LIG sea level cannot be fully explained by Greenland Ice Sheet melt (∼2 m), ocean thermal expansion, and melting mountain glaciers (∼1 m), suggesting substantial Antarctic mass loss was initiated by warming of Southern Ocean waters, resulting from a weakening Atlantic meridional overturning circulation in response to North Atlantic surface freshening. Here, we report a blue-ice record of ice sheet and environmental change from the Weddell Sea Embayment at the periphery of the marine-based West Antarctic Ice Sheet (WAIS), which is underlain by major methane hydrate reserves. Constrained by a widespread volcanic horizon and supported by ancient microbial DNA analyses, we provide evidence for substantial mass loss across the Weddell Sea Embayment during the LIG, most likely driven by ocean warming and associated with destabilization of subglacial hydrates. Ice sheet modeling supports this interpretation and suggests that millennial-scale warming of the Southern Ocean could have triggered a multimeter rise in global sea levels. Our data indicate that Antarctica is highly vulnerable to projected increases in ocean temperatures and may drive ice-climate feedbacks that further amplify warming.
- ItemWe need biosphere stewardship that protects carbon sinks and builds resilience(Washington, DC : National Acad. of Sciences, 2021) Rockström, Johan; Beringer, Tim; Hole, David; Griscom, Bronson; Mascia, Michael B.; Folke, Carl; Creutzig, Felix[no abstract available]
- ItemReply to Burgess et al: Catastrophic climate risks are neglected, plausible, and safe to study(Washington, DC : National Acad. of Sciences, 2022) Kemp, Luke; Xu, Chi; Depledge, Joanna; Ebi, Kristie L.; Gibbins, Goodwin; Kohler, Timothy A.; Rockström, Johan; Scheffer, Marten; Schellnhuber, Hans Joachim; Steffen, Will; Lenton, Timothy M.
- ItemReply to Kelman: The foundations for studying catastrophic climate risks(Washington, DC : National Acad. of Sciences, 2022) Kemp, Luke; Xu, Chi; Depledge, Joanna; Ebi, Kristie L.; Gibbins, Goodwin; Kohler, Timothy A.; Rockström, Johan; Scheffer, Marten; Schellnhuber, Hans Joachim; Steffen, Will; Lenton, Timothy M.
- ItemA regional nuclear conflict would compromise global food security(Washington, DC : National Acad. of Sciences, 2020) Jägermeyr, Jonas; Robock, Alan; Elliott, Joshua; Müller, Christoph; Xia, Lili; Khabarov, Nikolay; Folberth, Christian; Schmid, Erwin; Liu, Wenfeng; Zabel, Florian; Rabin, Sam S.; Puma, Michael J.; Heslin, Alison; Franke, James; Foster, Ian; Asseng, Senthold; Bardeen, Charles G.; Toon, Owen B.; Rosenzweig, CynthiaA limited nuclear war between India and Pakistan could ignite fires large enough to emit more than 5 Tg of soot into the stratosphere. Climate model simulations have shown severe resulting climate perturbations with declines in global mean temperature by 1.8 °C and precipitation by 8%, for at least 5 y. Here we evaluate impacts for the global food system. Six harmonized state-of-the-art crop models show that global caloric production from maize, wheat, rice, and soybean falls by 13 (±1)%, 11 (±8)%, 3 (±5)%, and 17 (±2)% over 5 y. Total single-year losses of 12 (±4)% quadruple the largest observed historical anomaly and exceed impacts caused by historic droughts and volcanic eruptions. Colder temperatures drive losses more than changes in precipitation and solar radiation, leading to strongest impacts in temperate regions poleward of 30°N, including the United States, Europe, and China for 10 to 15 y. Integrated food trade network analyses show that domestic reserves and global trade can largely buffer the production anomaly in the first year. Persistent multiyear losses, however, would constrain domestic food availability and propagate to the Global South, especially to food-insecure countries. By year 5, maize and wheat availability would decrease by 13% globally and by more than 20% in 71 countries with a cumulative population of 1.3 billion people. In view of increasing instability in South Asia, this study shows that a regional conflict using <1% of the worldwide nuclear arsenal could have adverse consequences for global food security unmatched in modern history.