Download or read book Comparing Oceanic Heat Uptake in Atmosphere ocean General Circulation Model Transient Climate Change Experiments written by Andrei P. Sokolov and published by . This book was released on 2003 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: The transient response of both surface air temperature and deep ocean temperature to an increasing external forcing strongly depends on climate sensitivity and the rate of the heat mixing into the deep ocean, estimates for both of which have large uncertainty. In this paper a method for estimating rates of oceanic heat uptake for coupled atmosphere-ocean general circulation models from results of transient climate change simulations is described. For models considered in this study, the estimates vary by a factor of 2 1/2. Nevertheless, values of oceanic heat uptake for all models fall in the range implied by the climate record for the last century. It is worth noting that the range of the model values is narrower than that consistent with observations and thus does not provide a full measure of the uncertainty in the rate of oceanic heat uptake.
Download or read book A Comparison of the Behavior of Different AOGCMs in Transient Climate Change Experiments written by Andrei P. Sokolov and published by . This book was released on 2001 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: The transient response of both surface air temperature and deep ocean temperature to an increasing external forcing strongly depends on climate sensitivity and the rate of the heat mixing into the deep ocean, estimates for both of which have large uncertainty. In this paper we describe a method for estimating rates of oceanic heat uptake for coupled atmosphere/ocean general circulation models from results of transient climate change simulations. For models considered in this study, the estimates vary more than threefold. Nevertheless, values for all models fall in the 5-95% interval of the range implied by the climate record for the last century. The MIT 2D climate model, with an appropriate choice of parameters, matches changes in surface air temperature and sea level rise simulated by different models. It also reproduces the overall range of changes in precipitation.
Download or read book The Deep ocean Heat Uptake in Transient Climate Change written by Boyin Huang and published by . This book was released on 2002 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt: The deep-ocean heat uptake (DOHU) in transient climate changes is studied using an ocean general circulation model (OGCM) and its adjoint. The model configuration consists of idealized Pacific and Atlantic basins. The model is forced with the anomalies of surface heat and freshwater fluxes from a global warming scenario with a coupled model using the same ocean configuration. In the scenario CO2 concentration increases 1% per year. The heat uptake calculated from the coupled model and from the adjoint are virtually identical, showing that the heat uptake by the OGCM is a linear process. After 70 years the ocean heat uptake is almost evenly distributed within the layers above 200 m, between 200 and 700 m, and below 700 m (about 20 x 1022 J in each). The effect of anomalous surface fresh water flux on the DOHU is negligible. Analysis of CMIP-2 data for the same global warming scenario shows that qualitatively similar results apply to coupled atmosphere-ocean GCMs. The penetration of surface heat flux to the deep ocean in our OGCM occurs mainly in the North Atlantic and the Southern Ocean, since both the sensitivity of DOHU to the surface heat flux and the magnitude of anomalous surface heat flux are large in these two regions. The DOHU relies on the reduction of convection and Gent-McWilliams-Redi mixing in the North Atlantic, and the reduction of Gent-McWilliams- Redi mixing in the Southern Ocean.
Download or read book The Role of High latitude Oceans in Transient Climate Change written by Yavor Krasimirov Kostov and published by . This book was released on 2016 with total page 119 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis we explore the role of the large-scale ocean circulation in the North Atlantic and the Southern Ocean (SO) in setting the regional and globally averaged sea surface temperature (SST) response to atmospheric forcing. We focus on the impact of anthropogenic greenhouse gases (AGHGs) and the Antarctic ozone hole and use output from general circulation models (GCMs) to estimate the corresponding climate response functions (CRFs). We show that the strength and the vertical extent of the time-mean Atlantic Meridional Overturning Circulation (AMOC) set the effective heat capacity of the World Ocean and affect the global CRF to greenhouse gas (GHG) forcing. A large fraction of the anomalous surface heat uptake induced by GHGs takes place over the North Atlantic. However, the SO also plays a significant role in removing excess heat from the atmosphere. Compared to the rest of the World Ocean, the SO warms at a much slower rate under GHG forcing. In this region the background Meridional Overturning Circulation (MOC) upwells unmodified deep water masses to the surface where they take up atmospheric heat. The modified water masses are then advected northward and subducted in the mid-latitudes. This geographical imprint of the MOC is reflected in the regional CRFs to GHGs, as seen in idealized numerical experiments with GCMs. However, GHGs are not the only major source of anthropogenic forcing on the SO. Stratospheric ozone depletion around Antarctica gives rise to an atmospheric pattern similar to the positive phase of the Southern Annular Mode (SAM): a strengthening and a southward shift of the westerlies. This poleward intensification of the winds changes the ocean circulation and gives rise to an SST response. We examine the SO CRF to a SAM pattern that arises either in the form of natural variability in unforced control experiments or as a result of imposed ozone perturbations. We analyze the SO SST response to SAM on multiple timescales and across an ensemble of GCMs from the Climate Modeling Intercomparison Project phase 5 (CMIP5). We show that the corresponding SO CRF is governed by the anomalous wind-driven MOC redistributing the background heat reservoir. The intermodel diversity in the fast and slow SST responses to SAM is partly explained by differences in the climatological thermal stratification across the ensemble of GCMs. Furthermore, we demonstrate that the sea ice response to SAM in models is very well correlated with the geographic pattern of the SST anomalies. Finally, we convolve our estimated CRFs with timeseries of historical forcing to recover the SO SST trends in numerical simulations and in observations. We contrast the multidecadal SO cooling trends against the SST warming rate in the Northern Hemisphere high latitudes. Our results imply that the recent cooling in the SO may be explained by the Antarctic ozone hole projecting on a positive SAM trend. We furthermore attempt to understand why CMIP5 models have been unable to reproduce the observed negative SST trends in the SO and instead predict regional warming. Many GCM simulations underestimate the historical SAM evolution. Another subset of CMIP5 models have biases in their climatological SO stratification, which affects their SO CRFs to SAM. The successful application of the CRF framework in the context of observed and simulated SST trends validates the results of our analysis. We are thus able to interpret the CRFs as inherent characteristics of the climate system and elucidate the importance of the high latitude oceans in transient climate change.
Download or read book Uncertainty in the Oceanic Heat and Carbon Uptake and Its Impact on Climate Projections written by Andrei P. Sokolov and published by . This book was released on 1998 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: The impact of uncertainty in the rate of heat and carbon uptake by the deep ocean on climate response to increases in greenhouse gas concentrations is studied by means of numerical simulations with the two-dimensional climate-chemistry model developed in the framework of the MIT Global Change Joint Program. This model incorporates parameterizations of most physical processes, includes fully interactive atmospheric chemistry and calculates carbon uptake by the ocean and, therefore, simulates the main nonlinear interactions taking place in the climate system. At the same time, it is much more computationally efficient than coupled atmosphere-ocean general circulation models. Results of the simulations with calculated CO2 concentrations are compared with those of simulations with a prescribed CO2 increase. This comparison shows that the uncertainty in the increase in global mean surface temperature due to uncertainty in the rate of oceanic heat uptake is enhanced by taking into account the related uncertainty in oceanic carbon uptake, while the uncertainty in sea level rise is decreased.
Download or read book Assessment of Approaches to Updating the Social Cost of Carbon written by National Academies of Sciences, Engineering, and Medicine and published by National Academies Press. This book was released on 2016-03-26 with total page 73 pages. Available in PDF, EPUB and Kindle. Book excerpt: The social cost of carbon (SCC) for a given year is an estimate, in dollars, of the present discounted value of the damage caused by a 1-metric ton increase in CO2 emissions into the atmosphere in that year; or equivalently, the benefits of reducing CO2 emissions by the same amount in that given year. The SCC is intended to provide a comprehensive measure of the monetized value of the net damages from global climate change from an additional unit of CO2, including, but not limited to, changes in net agricultural productivity, energy use, human health effects, and property damages from increased flood risk. Federal agencies use the SCC to value the CO2 emissions impacts of various policies including emission and fuel economy standards for vehicles, regulations of industrial air pollutants from industrial manufacturing, emission standards for power plants and solid waste incineration, and appliance energy efficiency standards. There are significant challenges to estimating a dollar value that reflects all the physical, human, ecological, and economic impacts of climate change. Recognizing that the models and scientific data underlying the SCC estimates evolve and improve over time, the federal government made a commitment to provide regular updates to the estimates. To assist with future revisions of the SCC, the Interagency Working Group on the Social Cost of Carbon (IWG) requested the National Academies of Sciences, Engineering, and Medicine complete a study that assessed the merits and challenges of a limited near-term update to the SCC and of a comprehensive update of the SCC to ensure that the estimates reflect the best available science. This interim report focuses on near-term updates to the SCC estimates.
Download or read book Climate Stabilization Targets written by National Research Council and published by National Academies Press. This book was released on 2011-02-11 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt: Emissions of carbon dioxide from the burning of fossil fuels have ushered in a new epoch where human activities will largely determine the evolution of Earth's climate. Because carbon dioxide in the atmosphere is long lived, it can effectively lock the Earth and future generations into a range of impacts, some of which could become very severe. Emissions reductions decisions made today matter in determining impacts experienced not just over the next few decades, but in the coming centuries and millennia. According to Climate Stabilization Targets: Emissions, Concentrations, and Impacts Over Decades to Millennia, important policy decisions can be informed by recent advances in climate science that quantify the relationships between increases in carbon dioxide and global warming, related climate changes, and resulting impacts, such as changes in streamflow, wildfires, crop productivity, extreme hot summers, and sea level rise. One way to inform these choices is to consider the projected climate changes and impacts that would occur if greenhouse gases in the atmosphere were stabilized at a particular concentration level. The book quantifies the outcomes of different stabilization targets for greenhouse gas concentrations using analyses and information drawn from the scientific literature. Although it does not recommend or justify any particular stabilization target, it does provide important scientific insights about the relationships among emissions, greenhouse gas concentrations, temperatures, and impacts. Climate Stabilization Targets emphasizes the importance of 21st century choices regarding long-term climate stabilization. It is a useful resource for scientists, educators and policy makers, among others.
Download or read book Modelling Oceanic Climate Interactions written by Jürgen Willebrand and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 477 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ocean plays a central role in determining the climate of the earth. The oceanic circulation largely controls the temporal evolution of cli mate changes resulting from human activities such as the increase of greenhouse gases in the atmosphere, and also affects the magnitude and regional distribution of those changes. On interannual and longer time scales the ocean is, through its interaction with the atmosphere, a source of important natural climate variations which we are only now beginning to recognise but whose cause has yet to be properly determined. Chem ical and biological processes in the ocean are linked to climate change, particularly through interaction with the global carbon cycle. A quantitative understanding of the oceanic role in the climate system requires models which include many complex processes and interactions, and which are systematically verified with observations. This is the ob jective of global research programs such as TOGA, WOCE, and JGOFS. Coupled numerical models of the oceanic and atmospheric circulation constitute the basis of every climate simulation. Increasingly it is recog nized that in addition a biological/chemical component is necessary to capture the pathways of carbon and other trace gases. The development of such coupled models is a challenging task which needs scientists who must be cognizant of several other disciplines beyond their own specialty.
Download or read book The Oceans and Rapid Climate Change written by Dan Seidov and published by John Wiley & Sons. This book was released on 2001-01-09 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt: Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 126. Until a few decades ago, scientists generally believed that significant large-scale past global and regional climate changes occurred at a gradual pace within a time scale of many centuries or millennia. A secondary assumption followed: climate change was scarcely perceptible during a human lifetime. Recent paleoclimatic studies, however, have proven otherwise: that global climate can change extremely rapidly. In fact, there is good evidence that in the past at least regional mean annual temperatures changed by several degrees Celsius on a time scale of several centuries to several decades.
Download or read book Adjusting to Policy Expectations in Climate Change Modeling written by and published by . This book was released on 1998 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper surveys and interprets the attitudes of scientists to the use of flux adjustments in climate projections with coupled Atmosphere Ocean General Circulation Models. The survey is based largely on the responses of 19 climate modellers to several questions and a discussion document circulated in 1995. We interpret the responses in terms of the following factors: the implicit assumptions which scientists hold about how the environmental policy process deals with scientific uncertainty over human-related global warming; the different scientific styles that exist in climate research; and the influence of organisations, institutions, and policy upon research agendas. We find evidence that scientists' perceptions of the policy process do play a role in shaping their scientific practices. In particular, many of our respondents expressed a preference for keeping discussion of the issue of flux adjustments within the climate modeling community, apparently fearing that climate contrarians would exploit the issue in the public domain. While this may be true, we point to the risk that such an approach may backfire. We also identify assumptions and cultural commitments lying at a deeper level which play at least as important a role as perceptions of the policy process in shaping scientific practices. This leads us to identify two groups of scientists, 'pragmatists' and 'purists, ' who have different implicit standards for model adequacy, and correspondingly are or are not willing to use flux adjustments.
Download or read book Ocean Mixing written by Michael Meredith and published by Elsevier. This book was released on 2021-09-16 with total page 386 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ocean Mixing: Drivers, Mechanisms and Impacts presents a broad panorama of one of the most rapidly-developing areas of marine science. It highlights the state-of-the-art concerning knowledge of the causes of ocean mixing, and a perspective on the implications for ocean circulation, climate, biogeochemistry and the marine ecosystem. This edited volume places a particular emphasis on elucidating the key future questions relating to ocean mixing, and emerging ideas and activities to address them, including innovative technology developments and advances in methodology. Ocean Mixing is a key reference for those entering the field, and for those seeking a comprehensive overview of how the key current issues are being addressed and what the priorities for future research are. Each chapter is written by established leaders in ocean mixing research; the volume is thus suitable for those seeking specific detailed information on sub-topics, as well as those seeking a broad synopsis of current understanding. It provides useful ammunition for those pursuing funding for specific future research campaigns, by being an authoritative source concerning key scientific goals in the short, medium and long term. Additionally, the chapters contain bespoke and informative graphics that can be used in teaching and science communication to convey the complex concepts and phenomena in easily accessible ways. - Presents a coherent overview of the state-of-the-art research concerning ocean mixing - Provides an in-depth discussion of how ocean mixing impacts all scales of the planetary system - Includes elucidation of the grand challenges in ocean mixing, and how they might be addressed
Download or read book Ocean Circulation and Climate written by and published by Elsevier. This book was released on 2001-03-27 with total page 737 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book represents all the knowledge we currently have on ocean circulation. It presents an up-to-date summary of the state of the science relating to the role of the oceans in the physical climate system.The book is structured to guide the reader through the wide range of World Ocean Circulation Experiment (WOCE) science in a consistent way. Cross-references between contributors have been added, and the book has a comprehensive index and unified reference list.The book is simple to read, at the undergraduate level. It was written by the best scientists in the world who have collaborated to carry out years of experiments to better understand ocean circulation.
Download or read book Ocean Heat Uptake in Transient Climate Change written by Boyin Huang and published by . This book was released on 2003 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: (Cont.) Experiments are carried out with values of the diffusivity of 500, 1000, and 2000 m2/sec. The total OHU is insensitive to these changes. The insensitivity is mainly due to the changes in the vertical heat flux by GMR mixing being compensated by changes in the other vertical heat flux components. In the Atlantic when the diffusivity is reduced from 1000 to 500 m2/sec, the surface warming can penetrate deeper. Therefore, the warming decreases by about 0.158C above 2000 m but increases by about 0.158C below 2500 m. Similarly, when the diffusivity is increased from 1000 to 2000 m2 s21, the surface warming becomes shallower; the warming increases by about 0.28C above 1000 m but decreases by about 0.28C below 1000 m. These changes in the vertical distribution of the OHU also contribute to the insensitivity of the total OHU to changes in the GMR mixing ...
Download or read book Ocean Biogeochemistry written by Michael J.R. Fasham and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt: Oceans account for 50% of the anthropogenic CO2 released into the atmosphere. During the past 15 years an international programme, the Joint Global Ocean Flux Study (JGOFS), has been studying the ocean carbon cycle to quantify and model the biological and physical processes whereby CO2 is pumped from the ocean's surface to the depths of the ocean, where it can remain for hundreds of years. This project is one of the largest multi-disciplinary studies of the oceans ever carried out and this book synthesises the results. It covers all aspects of the topic ranging from air-sea exchange with CO2, the role of physical mixing, the uptake of CO2 by marine algae, the fluxes of carbon and nitrogen through the marine food chain to the subsequent export of carbon to the depths of the ocean. Special emphasis is laid on predicting future climatic change.
Download or read book Variability of Ocean Heat Uptake written by and published by . This book was released on 2005 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study examines the temporal variability of ocean heat uptake in observations and in climate models. Previous work suggests that coupled Atmosphere-Ocean General Circulation Models (A-OGCMs) may have underestimated the observed natural variability of ocean heat content, particularly on decadal and longer timescales. To address this issue, we rely on observed estimates of heat content from the 2004 World Ocean Atlas (WOA-2004) compiled by Levitus et al. (2005). Given information about the distribution of observations in WOA-2004, we evaluate the effects of sparse observational coverage and the infilling that Levitus et al. use to produce the spatially-complete temperature fields required to compute heat content variations. We first show that in ocean basins with limited observational coverage, there are important differences between ocean temperature variability estimated from observed and infilled portions of the basin. We then employ data from control simulations performed with eight different A-OGCMs as a test-bed for studying the effects of sparse, space- and time-varying observational coverage. Subsampling model data with actual observational coverage has a large impact on the inferred temperature variability in the top 300 and 3000 meters of the ocean. This arises from changes in both sampling depth and in the geographical areas sampled. Our results illustrate that subsampling model data at the locations of available observations increases the variability, reducing the discrepancy between models and observations.
Download or read book A Numerical Simulation of CO2 induced Transient Climate Change with a Coupled Atmosphere ocean General Circulation Model written by M. E. Schlesinger and published by . This book was released on 1985 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ocean General Circulation Models written by and published by . This book was released on 1988 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt:
