DOCSLIB.ORG

Abrupt Climate Change in the Computer: Is It Real?

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Abrupt Climate Change in the Computer: Is It Real? Perspective Abrupt climate change in the computer: Is it real? Thomas F. Stocker* and Olivier Marchal Climate and Environmental Physics, Physics Institute, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland Models suggest that dramatic changes in the ocean circulation are responsible for abrupt climate changes during the last ice age and may possibly alter the relative climate stability of the last 10,000 years. mong the archives recording past cli- the air–sea fluxes of heat and freshwater. In freshwater balance of the North Atlantic. By Amate and environmental changes, ice the Pacific there is no such circulation, be- discharging freshwater, the thermohaline cores, marine and lacustrine sediments in cause the surface waters are too fresh: even circulation reduces or collapses completely, anoxic environments, and tree rings have if cooled to the freezing point, they would but the response depends on the location, seasonal to annual resolution. Changes in not acquire enough density to sink down and amplitude and duration of the perturbation dust level (1), snow accumulation (2), sum- establish a large-scale THC. This is caused (11, 12, 14, 15, 17, 18). All three responses mer temperature (3), and indicators of the by a combination of several factors, includ- shown in Fig. 1 can be generated in such productivity of marine life (4) suggest that ing reduced evaporation in the Pacific, models, albeit at different threshold values. some of the climate changes have evolved on fresher surface waters flowing northward, The Younger Dryas cold event (12,700– time scales as short as a few years to decades. and a different basin geometry (8). 11,550 years before present) is the most Such changes appear abrupt in comparison The Atlantic THC is a self-sustaining recent and best documented of the family of with the classical view of climate change. phenomenon and thus prone to instability. abrupt climate changes of the past. Large The understanding of the mechanisms re- If the northward flow of saline tropical amounts of freshwater entered the ocean sponsible for abrupt change has long relied waters decreases (e.g., by increased river before Younger Dryas (19), which may have on qualitative reasoning. However, climate runoff, ice melt, changes in precipitation, triggered this cold event. Models indicate research now increasingly makes use of nu- etc.), the density of high latitude waters is that a full stop (10) or a reduction of the merical models as a tool to interpret and reduced so that these waters are no longer water flux associated with the THC to Ϸ integrate results. Projections of anticipated able to sink: the circulation stops. The result 20% of the modern value (11) both pro- climate change also rely on such models. is a very cool and fresh northern North duce a drop in sea surface temperature in Ϸ Abrupt climate change, as recorded in many Atlantic. This process, first described by the the North Atlantic of 8°C and a substantial paleoclimatic archives (5), provides a chal- late Henry Stommel (9), is now well under- cooling over Greenland of 4–10°C. Al- lenge to these models. Their task is to stood and found by most climate models though the resolution of these coupled elucidate the processes that are involved in (10–12). The thermohaline circulation can ocean–atmosphere models is still coarse, abrupt change. If validated by the past, these thus exhibit more than one stable equilib- there is quantitative agreement with recent models may be able to quantify the likeli- rium, a feature that is typical of a non-linear paleoclimatic estimates of temperature hood of future surprises in the climate physical system. changes during that event (20). system. The concept of hysteresis illustrates the Climate models provide much additional possible responses of the ocean–atmosphere information if they also predict changes in Ocean Circulation and Abrupt Change. Ocean system to perturbations in the surface fresh- the global carbon cycle. Recently, results currents cause significant geographical dif- water balance. More freshwater in the sink- from a climate–carbon cycle model have ferences in the supply of heat to the atmo- ing regions reduces the THC (13–15) (Fig. been directly compared with paleoclimatic sphere (6). Regions around the North At- 1). The system is stable and reacts in a linear data of the Younger Dryas (21). In response lantic Ocean have a mean annual surface air fashion as long as threshold values are not to a meltwater pulse (Fig. 2a), the model temperature that is 5–7°C warmer than crossed (Fig. 1a). An abrupt change with an simulates a collapse of the THC in the those at the same latitude in the Pacific. This amplitude that no longer scales with the Atlantic and a cooling whose timing agrees is due to the thermohaline circulation perturbation occurs if threshold values are well with the Greenland ice core record (THC) of the Atlantic Ocean which is mov- crossed (Fig. 1b). If the initial state of the (Fig. 2b). The amplitude of the cooling is too ing warm, saline tropical waters northward; ocean–atmosphere system is a unique equi- small by a factor of 4 because of the zonal averaging of the model. Slight warming dur- the Gulf Stream is part of this basin-scale librium, the system jumps back to the orig- ing the northern cold event is simulated in circulation. These tropical waters then give inal state once the perturbation has ceased: the far south, evidencing the ‘‘bipolar see- off their heat to the atmosphere north of the abrupt change is reversible. However, if saw’’ (22, 23) between northern and south- Iceland, become denser and sink to the other equilibria exist, the perturbation ern hemispheres (Fig. 2c). The atmospheric abyss, and flow southward in the form of a causes an irreversible change (Fig. 1c). Hys- CO concentration increases during the deep western boundary current (7). The two teresis is well known in climate models, but 2 abrupt event, but the amplitudes do not major locations of deep water formation in its structure is highly model-dependent (16). exceed 30 parts per million by volume (Fig. the Atlantic are in the Greenland-Iceland- A burning question is, Where are we now on 2d); this corresponds well with the CO Norwegian (GIN) Sea and in the Labrador the hysteresis, and what is its structure? 2 changes measured on ice cores (21, 24). Sea, both of which contribute to the forma- tion of North Atlantic Deep Water. The Where Models Agree with the Climate Record. THC is driven by differences in the density Abrupt change is triggered in almost all *To whom reprint requests should be addressed. E-mail: of sea water and therefore is controlled by climate models by perturbing the surface [email protected]. 1362–1365 ͉ PNAS ͉ February 15, 2000 ͉ vol. 97 ͉ no. 4 Downloaded by guest on September 29, 2021 Fig. 1. The ocean–atmosphere system is a nonlinear physical sys- tem that can exhibit hysteresis behavior (13). The upper branch of the hysteresis is characterized by warm North Atlantic sea sur- face temperatures (SST), the lower branch by cold sea surface temperatures. A given perturba- tion (indicated by the blue and red arrows) in the freshwater bal- ance of the North Atlantic (pre- cipitation ϩ runoff Ϫ evapora- tion) causes transitions from an initial state 1 to states 2 and/or 3. Three structurally different responses are possible depending on whether threshold values (dashed line) are crossed: (a) Linear, reversible response. (b) Nonlinear, reversible response. (c) Nonlinear, irreversible response. The stable isotopes of dissolved inorganic because surface waters rich in 13C no longer surface to the abyss. Because the THC carbon in the ocean (␦13C) are further im- sink to depth. This is in agreement with contributes to this transport, a collapsed portant variables in climate models that can marine records that have sufficient resolu- THC would result in an accumulation of 14C be directly compared with the paleoclimatic tion to identify this event (25). By contrast, in the atmosphere. The paleoclimatic data record. In the deep North Atlantic, the ␦13C changes in the Southern Ocean are show the expected increase of 14Catthe climate–carbon cycle model simulates a de- minor, again in agreement with the few beginning of the Younger Dryas, but 14C crease in ␦13C when the THC is reduced available records (26). decreases already a few centuries later, long It should be noted that the simulated before the end of the event. This early changes to a given freshwater flux pertur- decrease could be attributable to a signifi- bation are strongly model-dependent, and cantly reduced production of radiocarbon in mixing parameters like vertical diffusivities the stratosphere or a substantial increase in in the ocean models appear to be most deep water formation in the Southern influential (16). Ocean or elsewhere. No climate model is able to simulate this 14C decrease at present. Where Models Disagree with the Climate Third, a full sequence of abrupt climate Record. Models still have substantial difficul- change such as seen in the Greenland ice ties in simulating important aspects of core record (29) has not yet been simulated abrupt change when confronted with the with climate models. Here the problems are hard evidence from the paleoclimatic ar- twofold: (i) the initialization of such a model chives. All current models respond instan- is an unresolved problem; and (ii) models of taneously to a large perturbation in the continental ice sheets, which will supply freshwater balance, such as that used in Fig. freshwater pulses, are only now being in- 2. Yet, the sea level records tell us that the corporated into comprehensive climate first meltwater peak during the deglaciation models.
Load more

Recommended publications
  • An Abrupt Climate Change Scenario and Its Implications for United States National Security October 2003
    An Abrupt Climate Change Scenario and Its Implications for United States National Security October 2003 By Peter Schwartz and Doug Randall Imagining the Unthinkable The purpose of this report is to imagine the unthinkable – to push the boundaries of current research on climate change so we may better understand the potential implications on United States national security. We have interviewed leading climate change scientists, conducted additional research, and reviewed several iterations of the scenario with these experts. The scientists support this project, but caution that the scenario depicted is extreme in two fundamental ways. First, they suggest the occurrences we outline would most likely happen in a few regions, rather than on globally. Second, they say the magnitude of the event may be considerably smaller. We have created a climate change scenario that although not the most likely, is plausible, and would challenge United States national security in ways that should be considered immediately. Executive Summary There is substantial evidence to indicate that significant global warming will occur during the 21st century. Because changes have been gradual so far, and are projected to be similarly gradual in the future, the effects of global warming have the potential to be manageable for most nations. Recent research, however, suggests that there is a possibility that this gradual global warming could lead to a relatively abrupt slowing of the ocean’s thermohaline conveyor, which could lead to harsher winter weather conditions, sharply reduced soil moisture, and more intense winds in certain regions that currently provide a significant fraction of the world’s food production.
    [Show full text]
  • Abrupt Climate Transitions
    City University of New York (CUNY) CUNY Academic Works All Dissertations, Theses, and Capstone Projects Dissertations, Theses, and Capstone Projects 9-2019 Abrupt Climate Transitions Christine J. Ramadhin The Graduate Center, City University of New York How does access to this work benefit ou?y Let us know! More information about this work at: https://academicworks.cuny.edu/gc_etds/3350 Discover additional works at: https://academicworks.cuny.edu This work is made publicly available by the City University of New York (CUNY). Contact: [email protected] Abrupt Climate Transitions By Christine Ramadhin A dissertation submitted to the Graduate Faculty in Earth and Environmental Sciences in partial fulfillment of the requirements for the degree of Doctor of Philosophy, The City University of New York 2019 i © 2019 Christine Ramadhin All Rights Reserved ii Abrupt Climate Transitions by Christine Ramadhin This manuscript has been read and accepted for the Graduate Faculty in Earth and Environmental Sciences in satisfaction of the dissertation requirements for the degree of Doctor of Philosophy. Date Prof. Chuixiang Yi Chair of Examining Committee Date Prof. Monica Varsanyi Executive Officer Supervisory Committee: Prof. George Hendrey Prof. Cecilia McHugh Prof. Gary Hemming Prof. Nir Krakauer THE CITY UNIVERSITY OF NEW YORK iii Abstract Abrupt Climate Transitions By Christine Ramadhin Advisor: Dr. Chuixiang Yi The Earth’s climate system displays a long history of nonlinear abrupt transitions which have resulted in significant ecosystem disruption and are recorded in the geologic data. Today significant anthropogenic changes are occurring in many Earth systems that seem to be pushing these toward critical thresholds. Thus, increasing the possibility of a transition to alternative states which can have unfavorable consequences.
    [Show full text]
  • Abrupt Climate Changeby Richard B
    Abrupt Climate ChangeBy Richard B. Alley n the Hollywood disaster thriller Inevitable, too, are the potential chal- The Day after Tomorrow, a climate lenges to humanity. Unexpected warm Winter temperatures catastrophe of ice age proportions spells may make certain regions more catches the world unprepared. Mil- hospitable, but they could magnify swel- plummeting six degrees lions of North Americans fl ee to tering conditions elsewhere. Cold snaps sunny Mexico as wolves stalk the could make winters numbingly harsh Celsius and sudden last few people huddled in freeze- and clog key navigation routes with ice. dried New York City. Tornadoes rav- Severe droughts could render once fertile droughts scorching I age California. Giant hailstones pound land agriculturally barren. These conse- farmland around the Tokyo. quences would be particularly tough to Are overwhelmingly abrupt climate bear because climate changes that oc- globe are not just the changes likely to happen anytime soon, cur suddenly often persist for centuries or did Fox Studios exaggerate wildly? or even thousands of years. Indeed, the stuff of scary movies. The answer to both questions appears collapses of some ancient societies—once to be yes. Most climate experts agree attributed to social, economic and politi- Such striking climate that we need not fear a full-fl edged ice cal forces—are now being blamed largely age in the coming decades. But sudden, on rapid shifts in climate. jumps have happened dramatic climate changes have struck The specter of abrupt climate change many times in the past, and they could has attracted serious scientifi c investiga- before—sometimes happen again.
    [Show full text]
  • NONLINEARITIES, FEEDBACKS and CRITICAL THRESHOLDS WITHIN the EARTH's CLIMATE SYSTEM 1. Introduction Nonlinear Phenomena Charac
    NONLINEARITIES, FEEDBACKS AND CRITICAL THRESHOLDS WITHIN THE EARTH’S CLIMATE SYSTEM JOSÉ A. RIAL 1,ROGERA.PIELKESR.2, MARTIN BENISTON 3, MARTIN CLAUSSEN 4, JOSEP CANADELL 5, PETER COX 6, HERMANN HELD 4, NATHALIE DE NOBLET-DUCOUDRÉ 7, RONALD PRINN 8, JAMES F. REYNOLDS 9 and JOSÉ D. SALAS 10 1Wave Propagation Laboratory, Department of Geological Sciences CB#3315, University of North Carolina, Chapel Hill, NC 27599-3315, U.S.A. E-mail: [email protected] 2Atmospheric Science Dept., Colorado State University, Fort Collins, CO 80523, U.S.A. 3Dept. of Geosciences, Geography, Univ. of Fribourg, Pérolles, Ch-1700 Fribourg, Switzerland 4Potsdam Institute for Climate Impact Research, Telegrafenberg C4, 14473 Potsdam, P.O. Box 601203, Potsdam, Germany 5GCP-IPO, Earth Observation Centre, CSIRO, GPO Box 3023, Canberra, ACT 2601, Australia 6Met Office Hadley Centre, London Road, Bracknell, Berkshire RG12 2SY, U.K. 7DSM/LSCE, Laboratoire des Sciences du Climat et de l’Environnement, Unité mixte de Recherche CEA-CNRS, Bat. 709 Orme des Merisiers, 91191 Gif-sur-Yvette, France 8Dept. of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139-4307, U.S.A. 9Department of Biology and Nicholas School of the Environmental and Earth Sciences, Phytotron Bldg., Science Dr., Box 90340, Duke University, Durham, NC 27708, U.S.A. 10Dept. of Civil Engineering, Colorado State University, Fort Collins, CO 80523, U.S.A. Abstract. The Earth’s climate system is highly nonlinear: inputs and outputs are not proportional, change is often episodic and abrupt, rather than slow and gradual, and multiple equilibria are the norm.
    [Show full text]
  • Abrupt Climate Changes: Past, Present and Future
    Abrupt Climate Changes: Past, Present and Future Lonnie G. Thompson* The Earth's tropical regions are very important for understanding current and past climate change as 50% of the Earth's surface lies between. 30'N and 30 'S, and it is these regions where most of the sun's energy that drives the climate system is absorbed. The tropics and subtropics are also the most populated regions on the planet. Paleoclimate records reveal that in the past, natural disruptions of the climate system driven by such processes as large explosive volcanic eruptions' and variations in the El Nifio-Southern Oscillation 2 have affected the climate over much of the planet.3 Changes in the vertical temperature profile in the tropics also affect the climate on large-spatial scales. While land surface temperatures and sea surface temperatures show great spatial variability, tropical temperatures are quite uniform at mid-tropospheric elevations where most glaciers and ice caps exist. Observational data before, during and after a major El Nifio event demonstrate that within four months of its onset, the energy from the sea surface is distributed throughout the tropical mid-troposphere.4 Thus, the observation that virtually all tropical regions are retreating 5 under the current climate regime strongly indicates that a large-scale warming of the Earth system is currently underway. * University Distinguished Professor, School of Earth Sciences, Senior Research Scientist, Byrd Polar Research Center, The Ohio State University. The Journal of Land, Resources & Environmental Law would also like to thank Dr. Ellen Mosely-Thompson who significantly assisted the journal staff and editorial board in preparing this manuscript while Dr.
    [Show full text]
  • Abrupt Cold Events in the North Atlantic Ocean in a Transient Holocene Simulation
    Clim. Past, 14, 1165–1178, 2018 https://doi.org/10.5194/cp-14-1165-2018 © Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License. Abrupt cold events in the North Atlantic Ocean in a transient Holocene simulation Andrea Klus1, Matthias Prange1, Vidya Varma2, Louis Bruno Tremblay3, and Michael Schulz1 1MARUM – Center for Marine Environmental Sciences and Faculty of Geosciences, University of Bremen, Bremen, Germany 2National Institute of Water and Atmospheric Research, Wellington, New Zealand 3Department of Atmospheric and Oceanic Sciences, McGill University, Montreal, Canada Correspondence: Andrea Klus ([email protected]) Received: 25 August 2017 – Discussion started: 25 September 2017 Accepted: 16 July 2018 – Published: 14 August 2018 Abstract. Abrupt cold events have been detected in nu- 1 Introduction merous North Atlantic climate records from the Holocene. Several mechanisms have been discussed as possible trig- Holocene climate variability in the North Atlantic at differ- gers for these climate shifts persisting decades to centuries. ent timescales has been discussed extensively during the past Here, we describe two abrupt cold events that occurred dur- decades (e.g., Kleppin et al., 2015; Drijfhout et al., 2013; ing an orbitally forced transient Holocene simulation us- Hall et al., 2004; Schulz and Paul, 2002; Hall and Stouffer, ing the Community Climate System Model version 3. Both 2001; Bond et al., 1997, 2001; O’Brien et al., 1995; Wanner events occurred during the late Holocene (4305–4267 BP and et al., 2001, 2011). North Atlantic cold events can be accom- 3046–3018 BP for event 1 and event 2, respectively). They panied by sea ice drift from the Nordic Seas and the Labrador were characterized by substantial surface cooling (−2.3 and Sea towards the Iceland Basin as well as by changes in the −1.8 ◦C, respectively) and freshening (−0.6 and −0.5 PSU, Atlantic Meridional Overturning Circulation (AMOC).
    [Show full text]
  • Early Younger Dryas Glacier Culmination in Southern Alaska: Implications for North Atlantic Climate Change During the Last Deglaciation Nicolás E
    https://doi.org/10.1130/G46058.1 Manuscript received 30 January 2019 Revised manuscript received 26 March 2019 Manuscript accepted 27 March 2019 © 2019 Geological Society of America. For permission to copy, contact [email protected]. Published online XX Month 2019 Early Younger Dryas glacier culmination in southern Alaska: Implications for North Atlantic climate change during the last deglaciation Nicolás E. Young1, Jason P. Briner2, Joerg Schaefer1, Susan Zimmerman3, and Robert C. Finkel3 1Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA 2Department of Geology, University at Buffalo, Buffalo, New York 14260, USA 3Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, California 94550, USA ABSTRACT ongoing climate change event, however, leaves climate forcing of glacier change during the last The transition from the glacial period to the uncertainty regarding its teleconnections around deglaciation (Clark et al., 2012; Shakun et al., Holocene was characterized by a dramatic re- the globe and its regional manifestation in the 2012; Bereiter et al., 2018). organization of Earth’s climate system linked coming decades and centuries. A longer view of Methodological advances in cosmogenic- to abrupt changes in atmospheric and oceanic Earth-system response to abrupt climate change nuclide exposure dating over the past 15+ yr circulation. In particular, considerable effort is contained within the paleoclimate record from now provide an opportunity to determine the has been placed on constraining the magni- the last deglaciation. Often considered the quint- finer structure of Arctic climate change dis- tude, timing, and spatial variability of climatic essential example of abrupt climate change, played within moraine records, and in particular changes during the Younger Dryas stadial the Younger Dryas stadial (YD; 12.9–11.7 ka) glacier response to the YD stadial.
    [Show full text]
  • Physical Climate Processes and Feedbacks
    7 Physical Climate Processes and Feedbacks Co-ordinating Lead Author T.F. Stocker Lead Authors G.K.C. Clarke, H. Le Treut, R.S. Lindzen, V.P. Meleshko, R.K. Mugara, T.N. Palmer, R.T. Pierrehumbert, P.J. Sellers, K.E. Trenberth, J. Willebrand Contributing Authors R.B. Alley, O.E. Anisimov, C. Appenzeller, R.G. Barry, J.J. Bates, R. Bindschadler, G.B. Bonan, C.W. Böning, S. Bony, H. Bryden, M.A. Cane, J.A. Curry, T. Delworth, A.S. Denning, R.E. Dickinson, K. Echelmeyer, K. Emanuel, G. Flato, I. Fung, M. Geller, P.R. Gent, S.M. Griffies, I. Held, A. Henderson-Sellers, A.A.M. Holtslag, F. Hourdin, J.W. Hurrell, V.M. Kattsov, P.D. Killworth, Y. Kushnir, W.G. Large, M. Latif, P. Lemke, M.E. Mann, G. Meehl, U. Mikolajewicz, W. O’Hirok, C.L. Parkinson, A. Payne, A. Pitman, J. Polcher, I. Polyakov, V. Ramaswamy, P.J. Rasch, E.P. Salathe, C. Schär, R.W. Schmitt, T.G. Shepherd, B.J. Soden, R.W. Spencer, P. Taylor, A. Timmermann, K.Y. Vinnikov, M. Visbeck, S.E. Wijffels, M. Wild Review Editors S. Manabe, P. Mason Contents Executive Summary 419 7.3 Oceanic Processes and Feedbacks 435 7.3.1 Surface Mixed Layer 436 7.1 Introduction 421 7.3.2 Convection 436 7.1.1 Issues of Continuing Interest 421 7.3.3 Interior Ocean Mixing 437 7.1.2 New Results since the SAR 422 7.3.4 Mesoscale Eddies 437 7.1.3 Predictability of the Climate System 422 7.3.5 Flows over Sills and through Straits 438 7.3.6 Horizontal Circulation and Boundary 7.2 Atmospheric Processes and Feedbacks 423 Currents 439 7.2.1 Physics of the Water Vapour and Cloud 7.3.7 Thermohaline Circulation
    [Show full text]
  • Methane Hydrate Stability and Anthropogenic Climate Change
    Biogeosciences, 4, 521–544, 2007 www.biogeosciences.net/4/521/2007/ Biogeosciences © Author(s) 2007. This work is licensed under a Creative Commons License. Methane hydrate stability and anthropogenic climate change D. Archer University of Chicago, Department of the Geophysical Sciences, USA Received: 20 March 2007 – Published in Biogeosciences Discuss.: 3 April 2007 Revised: 14 June 2007 – Accepted: 19 July 2007 – Published: 25 July 2007 Abstract. Methane frozen into hydrate makes up a large 1 Methane in the carbon cycle reservoir of potentially volatile carbon below the sea floor and associated with permafrost soils. This reservoir intu- 1.1 Sources of methane itively seems precarious, because hydrate ice floats in water, and melts at Earth surface conditions. The hydrate reservoir 1.1.1 Juvenile methane is so large that if 10% of the methane were released to the at- Methane, CH , is the most chemically reduced form of car- mosphere within a few years, it would have an impact on the 4 bon. In the atmosphere and in parts of the biosphere con- Earth’s radiation budget equivalent to a factor of 10 increase trolled by the atmosphere, oxidized forms of carbon, such as in atmospheric CO . 2 CO , the carbonate ions in seawater, and CaCO , are most Hydrates are releasing methane to the atmosphere today in 2 3 stable. Methane is therefore a transient species in our at- response to anthropogenic warming, for example along the mosphere; its concentration must be maintained by ongoing Arctic coastline of Siberia. However most of the hydrates release. One source of methane to the atmosphere is the re- are located at depths in soils and ocean sediments where an- duced interior of the Earth, via volcanic gases and hydrother- thropogenic warming and any possible methane release will mal vents.
    [Show full text]
  • Abrupt Climate Changes: Oceans, Ice, and Us by RICHARD B
    THE ROGER REVELLE COMMEMORATIVE LECTURE SERIES Abrupt Climate Changes: Oceans, Ice, and Us BY RICHARD B. ALLEY Presenting the Sixth Annual Roger Revelle Commemorative Lecture given November 10, 2004 at the Baird Auditorium at the Smithsonian Museum of Natural History in Washington, D.C. This lecture series was created in 1999 by the National Research Council’s Ocean Studies Board in honor of the late Dr. Roger Revelle, a leader in the field of Oceanography for almost a half a century, in order to highlight the important links between ocean sciences and public policy. SYNOPSIS change. Although a major, potentially community recognized that variabil- Modern climate science indicates that rapid change in climate is a daunting ity includes very large and widespread rising carbon dioxide levels in the at- prospect, I am convinced that today’s abrupt climate changes. The relatively re- mosphere and other effects of human students, if given suffi cient training and cent revelations gleaned from the climate activities will cause large climate changes fi nancial support, will be able to address record tell us that change will occur in requiring signifi cant adaptation by hu- the climate challenges of the future. fi ts and starts, with potentially large and man societies around the globe. Climate rapid jumps and detours along the way. records and human history provide in- INTRODUCTION: A CHALLENGE After presenting some of the evidence sight into the nature of climate change How should we handle our climate fu- for abrupt climate changes and describ- and the types of challenges a shifting ture? In trying to decide what if anything ing the likely causes, I will discuss wheth- environment will pose for humankind.
    [Show full text]
  • Abrupt Climate Change: the Next Major Challenge
    Abrupt Climate Change: The Next Major Challenge Paul Andrew Mayewski, Director, Climate Change Institute, University of Maine Introduction Prior to the early 1990’s the concept of dramatic changes in climate characterized by onset and decay of less than a decade was suspected, but definitely not demonstrated. Today we know that even “milder” versions of abrupt climate change are significant enough to radically alter the course of civilizations and ecosystems (eg., Buckland et al. 1995, Mayewski and White, 2002; Gill et al., 2008) and that these events are taken seriously enough to be the subject of numerous governmental scientific and security reports (eg., NRC, 1999; 2003). To understand the mechanisms, the timing, and probable regions of impact of future abrupt climate change requires detailed examination of the pre-instrumental era record since analogs for abrupt climate change pre-date the short ~100 years of northern hemisphere and shorter southern hemisphere instrumental era. What is known about abrupt climate change does not preclude the occurrence of these events in the near future. In fact, as warming progresses climate will likely become less stable, increasing the probability for abrupt climate change events. Projections for future climate change suggest that many developing areas may experience the most adverse impacts of warming, drought, and sea level rise. As demonstrated in the following understanding of abrupt climate change is primarily dependant on paleo-analogs. While future abrupt climate change may or may not operate in a similar fashion to naturally occurring abrupt change events the paleo-record has and still does offer the most significant potential for understanding these events.
    [Show full text]
  • NSF and Arctic Oceans Science
    NSFNSF andand ArcticArctic OceansOceans sciencescience SimonSimon StephensonStephenson NSFNSF DivisionDivision ofof ArcticArctic SciencesSciences DriversDrivers FollowingFollowing NSFNSF strategicstrategic planplan formatformat DiscoveryDiscovery LearningLearning ResearchResearch InfrastructureInfrastructure StewardshipStewardship DiscoveryDiscovery HealthyHealthy foundationalfoundational researchresearch inin thethe socialsocial andand naturalnatural sciencessciences concerningconcerning elementselements ofof thethe ArcticArctic system.system. ThematicThematic (next(next slide)slide) ArcticArctic systemsystem andand itsits globalglobal linkageslinkages ModelingModeling andand synthesissynthesis GlobalGlobal contextcontext andand connectionsconnections DiscoveryDiscovery (continued)(continued) Thematic Bering Sea studies – strengthening the social science component Abrupt climate change Glacier & sea-level Ocean acidification A warming tundra/permafrost and the carbon cycle Sustainability, adaptation & resilience Black carbon Sea-ice vulnerability Human eco-dynamics DiscoveryDiscovery (continued)(continued) Thematic Bering Sea studies – strengthening the social science component Abrupt climate change Glacier & sea-level Ocean acidification A warming tundra/permafrost and the carbon cycle Sustainability, adaptation & resilience Black carbon Sea-ice vulnerability Human eco-dynamics LearningLearning MaintainMaintain thethe scopescope establishedestablished duringduring thethe InternationalInternational PolarPolar
    [Show full text]