DOCSLIB.ORG

Cumulus Microphysics and Climate Sensitivity

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Cumulus Microphysics and Climate Sensitivity 2376 JOURNAL OF CLIMATE VOLUME 18 Cumulus Microphysics and Climate Sensitivity ANTHONY D. DEL GENIO NASA Goddard Institute for Space Studies, New York, New York WILLIAM KOVARI Center for Climate Systems Research, Columbia University, New York, New York MAO-SUNG YAO SGT, Inc., Institute for Space Studies, New York, New York JEFFREY JONAS Center for Climate Systems Research, Columbia University, New York, New York (Manuscript received 24 May 2004, in final form 15 October 2004) ABSTRACT Precipitation processes in convective storms are potentially a major regulator of cloud feedback. An unresolved issue is how the partitioning of convective condensate between precipitation-size particles that fall out of updrafts and smaller particles that are detrained to form anvil clouds will change as the climate warms. Tropical Rainfall Measuring Mission (TRMM) observations of tropical oceanic convective storms indicate higher precipitation efficiency at warmer sea surface temperature (SST) but also suggest that cumulus anvil sizes, albedos, and ice water paths become insensitive to warming at high temperatures. International Satellite Cloud Climatology Project (ISCCP) data show that instantaneous cirrus and deep convective cloud fractions are positively correlated and increase with SST except at the highest tempera- tures, but are sensitive to variations in large-scale vertical velocity. A simple conceptual model based on a Marshall–Palmer drop size distribution, empirical terminal velocity–particle size relationships, and assumed cumulus updraft speeds reproduces the observed tendency for detrained condensate to approach a limiting value at high SST. These results suggest that the climatic behavior of observed tropical convective clouds is intermediate between the extremes required to support the thermostat and adaptive iris hypotheses. 1. Introduction cloud types. This is possible because few observational constraints exist to ascertain the sign of specific cloud State-of-the-art general circulation models (GCMs) feedbacks. subjected to external climate forcings produce global A good example of this uncertainty is the role of net cloud feedbacks ranging from moderately negative convective systems in cloud and water vapor feedback. to strongly positive, and individual shortwave (SW) and Deep convective clouds occupy a small area but are longwave (LW) cloud feedback components often dif- often accompanied by areally extensive anvils that fer in sign among models with similar net cloud feed- dominate tropical planetary albedo and thinner cirrus back (Cess et al. 1996). This implies that different clouds that modulate outgoing longwave radiation GCMs often predict different but compensating (OLR). Convective cirrus clouds and anvils form from changes in the occurrence and properties of different detrainment of condensate formed in cumulus updrafts and from in situ mesoscale vertical motions within the anvils. Some anvil ice sublimes and along with de- Corresponding author address: Anthony D. Del Genio, NASA Goddard Institute for Space Studies, 2880 Broadway, New York, trained water vapor from the updraft provides a signifi- NY 10025. cant source of water vapor to the upper troposphere. E-mail: [email protected] The complexity of the dynamics and microphysics in Unauthenticated | Downloaded 09/24/21 08:45 PM UTC JCLI3413 1JULY 2005 D E L G E N I O E T A L . 2377 convective updrafts makes it difficult to correctly char- anomalies than do SST perturbation simulations, nor- acterize the water cycle of convective systems in nu- malized by the column-integrated heating. Further- merical models, that is, the balance between the pre- more, natural and forced variability in general will have cipitation sink that reduces updraft condensate and the different horizontal patterns of change and thus differ- nonprecipitating condensate that represents the major ent dynamical responses in several parameters that af- source for the anvil cloud. fect clouds. We therefore feel that the most prudent use Two diametrically opposed ideas about the competi- of satellite data is to provide useful physical property tion between precipitation and detrainment in a climate and process constraints that can serve as the basis for change have appeared in the literature. The thermostat the design and/or evaluation of global climate model hypothesis (Ramanathan and Collins 1991) suggests parameterizations that are used to predict cloud feed- that in a warmer climate, increased boundary layer wa- back. ter vapor will increase condensation in convective This paper extends the results of Del Genio and Ko- clouds and thus increase detrainment, leading to more vari (2002) to all high cloud types and explores the extensive and thicker anvils. Because the shortwave implications of observed convective storm behavior for cloud forcing (SWCF) of tropical convective systems cloud feedback. Section 2 describes the data sources slightly exceeds their longwave cloud forcing (LWCF), and analysis methods. Sections 3 and 4 explore the SST this suggests a negative cloud feedback, although the and vertical velocity dependences of TRMM storm additional water vapor source for the upper tropo- properties and ISCCP high cloud types, respectively. sphere implies a positive water vapor feedback. The Section 5 describes a simple conceptual model that cap- adaptive iris hypothesis (Lindzen et al. 2001) argues tures the essentials of the TRMM-observed behavior and might serve as the basis for an improved param- that increased precipitation efficiency because of in- eterization of convective microphysics in GCMs. Impli- creased convective condensate in a warmer climate will cations of our work are discussed in section 6. reduce detrainment, leading to a negative water vapor feedback and a slightly positive cloud feedback once the radiative properties of tropical clouds are properly 2. Data accounted for (Lin et al. 2002). The analysis of TRMM data follows the procedure Both analyses fail to account for vertical velocity ef- described fully in Del Genio and Kovari (2002). Instan- fects, since warm sea surface temperatures (SSTs) are taneous TRMM Microwave Imager (TMI) product 2A- often accompanied by upward mean motion that pro- 12 rain rates and hydrometeor profiles (Kummerow et motes high cloud formation (cf. Fu et al. 1992; Hart- al. 2001) for the period 1–5 February 1998 are used to mann and Michelsen 2002). Del Genio and Kovari define storms as contiguous raining areas with cloud (2002) analyzed the hydrological and radiative proper- water above the 5-km level in the Ϯ15° latitude band. ties of tropical precipitating storms in Tropical Rainfall Storm area-averaged rain rates and ice water paths Measuring Mission (TRMM) data and separated them (IWP) are calculated for each of 6765 storms detected according to monthly mean SST and vertical velocity. over ocean. Coincident Clouds and the Earth’s Radiant They found that SW albedos and ice water paths of Energy System (CERES) data provide storm-averaged convective storms were insensitive to SST variations at SW albedos and OLR. Del Genio and Kovari (2002) warm temperatures. These results apply only to the used the original CERES ES-8 [Earth Radiation Bud- precipitating area of the storms, however; the more ex- get Experiment (ERBE)-like] products, but for this pa- tensive nonprecipitating areas of cirrus and cirrostratus per we have redone the analysis using the more accu- were not explored. rate CERES Single Scanner Footprint (SSF) retrievals Drawing inferences about cloud feedback in a forced (Wielicki et al. 1996). climate change from such observed variability is risky. International Satellite Cloud Climatology Project Current climate variability is typically driven at the air– (ISCCP) D1 retrievals (Rossow and Schiffer 1999) pro- sea interface, and anomalies in vertical structure may vide joint distributions of visible optical thickness (␶) be qualitatively different from those associated with and cloud-top pressure (p)atϳ5 km resolution forced climate changes, which are driven at the atmo- sampled to 30 km and aggregated over 2.5° ϫ 2.5° lati- spheric emission level. For example, doubled CO2 ex- tude–longitude areas. For this study we use the high periments with the Goddard Institute for Space Studies cloud types (p Ͻ 440 mb) defined by ISCCP as follows: (GISS) GCM predict stronger upper-level radiative cirrus, Ci (␶ Ͻ 3.6), cirrostratus, Cs (3.6 Ͻ ␶ Ͻ 23), and cooling, mid- and upper-level convective heating, and deep convective clouds, DCC (␶ Ͼ 23). The Cs category boundary layer convective and radiative heating generally includes the transition from precipitating to Unauthenticated | Downloaded 09/24/21 08:45 PM UTC 2378 JOURNAL OF CLIMATE VOLUME 18 FIG. 1. (top left) Storm-averaged TMI rainwater path per hour, (top right) TMI ice water path, (bottom left) CERES albedo, and (bottom right) CERES OLR vs SST for three 500-mb ␻ ranges: ϽϪ0.04 Pa sϪ1 (solid), Ϫ0.04 to0PasϪ1 (dashed), and Ͼ0PasϪ1 (dash–dot). (top) The solid line with diamonds shows the estimated boundary layer precipitable water vapor. nonprecipitating portions of cumulus anvils, so TRMM 3. Storm hydrological and radiative properties raining areas are combinations of DCC and some Cs Figure 1 (upper left) shows TMI rainwater paths per ISCCP pixels. Ci pixels represent the only high clouds hour of storm lifetime versus SST for each ␻ category, with positive net cloud forcing in the ISCCP dataset. while Fig. 1 (upper right) shows mean storm IWP ver- Storm and high cloud property
Load more

Recommended publications
  • Climate Models and Their Evaluation
    8 Climate Models and Their Evaluation Coordinating Lead Authors: David A. Randall (USA), Richard A. Wood (UK) Lead Authors: Sandrine Bony (France), Robert Colman (Australia), Thierry Fichefet (Belgium), John Fyfe (Canada), Vladimir Kattsov (Russian Federation), Andrew Pitman (Australia), Jagadish Shukla (USA), Jayaraman Srinivasan (India), Ronald J. Stouffer (USA), Akimasa Sumi (Japan), Karl E. Taylor (USA) Contributing Authors: K. AchutaRao (USA), R. Allan (UK), A. Berger (Belgium), H. Blatter (Switzerland), C. Bonfi ls (USA, France), A. Boone (France, USA), C. Bretherton (USA), A. Broccoli (USA), V. Brovkin (Germany, Russian Federation), W. Cai (Australia), M. Claussen (Germany), P. Dirmeyer (USA), C. Doutriaux (USA, France), H. Drange (Norway), J.-L. Dufresne (France), S. Emori (Japan), P. Forster (UK), A. Frei (USA), A. Ganopolski (Germany), P. Gent (USA), P. Gleckler (USA), H. Goosse (Belgium), R. Graham (UK), J.M. Gregory (UK), R. Gudgel (USA), A. Hall (USA), S. Hallegatte (USA, France), H. Hasumi (Japan), A. Henderson-Sellers (Switzerland), H. Hendon (Australia), K. Hodges (UK), M. Holland (USA), A.A.M. Holtslag (Netherlands), E. Hunke (USA), P. Huybrechts (Belgium), W. Ingram (UK), F. Joos (Switzerland), B. Kirtman (USA), S. Klein (USA), R. Koster (USA), P. Kushner (Canada), J. Lanzante (USA), M. Latif (Germany), N.-C. Lau (USA), M. Meinshausen (Germany), A. Monahan (Canada), J.M. Murphy (UK), T. Osborn (UK), T. Pavlova (Russian Federationi), V. Petoukhov (Germany), T. Phillips (USA), S. Power (Australia), S. Rahmstorf (Germany), S.C.B. Raper (UK), H. Renssen (Netherlands), D. Rind (USA), M. Roberts (UK), A. Rosati (USA), C. Schär (Switzerland), A. Schmittner (USA, Germany), J. Scinocca (Canada), D. Seidov (USA), A.G.
    [Show full text]
  • Climate Change: Addressing the Major Skeptic Arguments
    Climate Change: Addressing the Major Skeptic Arguments September 2010 Whitepaper available online: http://www.dbcca.com/research Carbon Counter widget available for download at: www.Know-The-Number.com Research Team Authors Mary-Elena Carr, Ph.D. Kate Brash Associate Director Assistant Director Columbia Climate Center, Earth Institute Columbia Climate Center, Earth Institute Columbia University Columbia University Robert F. Anderson, Ph.D. Ewing-Lamont Research Professor Lamont-Doherty Earth Observatory Columbia University DB Climate Change Advisors – Climate Change Investment Research Mark Fulton Bruce M. Kahn, Ph.D. Managing Director Director Global Head of Climate Change Investment Research Senior Investment Analyst Nils Mellquist Emily Soong Vice President Associate Senior Research Analyst Jake Baker Lucy Cotter Associate Research Analyst 2 Climate Change: Addressing the Major Skeptic Arguments Editorial Mark Fulton Global Head of Climate Change Investment Research Addressing the Climate Change Skeptics The purpose of this paper is to examine the many claims and counter-claims being made in the public debate about climate change science. For most of this year, the volume of this debate has turned way up as the ‘skeptics’ launched a determined assault on the climate findings accepted by the overwhelming majority of the scientific community. Unfortunately, the increased noise has only made it harder for people to untangle the arguments and form their own opinions. This is problematic because the way the public’s views are shaped is critical to future political action on climate change. For investors in particular, the implications are huge. While there are many arguments in favor of clean energy, water and sustainable agriculture – for instance, energy security, economic growth, and job opportunities – we at DB Climate Change Advisors (DBCCA) have always said that the science is one essential foundation of the whole climate change investment thesis.
    [Show full text]
  • A Prediction Market for Climate Outcomes
    Florida State University College of Law Scholarship Repository Scholarly Publications 2011 A Prediction Market for Climate Outcomes Shi-Ling Hsu Florida State University College of Law Follow this and additional works at: https://ir.law.fsu.edu/articles Part of the Environmental Law Commons, Law and Politics Commons, Natural Resources Law Commons, and the Oil, Gas, and Mineral Law Commons Recommended Citation Shi-Ling Hsu, A Prediction Market for Climate Outcomes, 83 U. COLO. L. REV. 179 (2011), Available at: https://ir.law.fsu.edu/articles/497 This Article is brought to you for free and open access by Scholarship Repository. It has been accepted for inclusion in Scholarly Publications by an authorized administrator of Scholarship Repository. For more information, please contact [email protected]. A PREDICTION MARKET FOR CLIMATE OUTCOMES * SHI-LING HSU This Article proposes a way of introducing some organization and tractability in climate science, generating more widely credible evaluations of climate science, and imposing some discipline on the processing and interpretation of climate information. I propose a two-part policy instrument consisting of (1) a carbon tax that is indexed to a “basket” of climate outcomes, and (2) a cap-and- trade system of emissions permits that can be redeemed in the future in lieu of paying the carbon tax. The amount of the carbon tax in this proposal (per ton of CO2) would be set each year on the basis of some objective, non-manipulable climate indices, such as temperature and mean sea level, and also on the number of certain climate events, such as flood events or droughts, that occurred in the previous year (or some moving average of previous years).
    [Show full text]
  • Is There a Basis for Global Warming Alarm? Richard S. Lindzen
    Is there a basis for global warming alarm? Richard S. Lindzen Alfred P. Sloan Professor of Atmospheric Science Massachusetts Institute of Technology Yale Center for the Study of Globalization October 21, 2005 These slides are available as a pdf file from [email protected] 1 The reality of global warming is frequently attested to by reference to a scientific consensus: Tony Blair: “The overwhelming view of experts is that climate change, to a greater or lesser extent, is man-made, and, without action, will get worse.” Elizabeth Kolbert in New Yorker: “All that the theory of global warming says is that if you increase the concentration of greenhouse gases in the atmosphere, you will also increase the earth's average temperature. It's indisputable that we have increased greenhouse-gas concentrations in the air as a result of human activity, and it's also indisputable that over the last few decades average global temperatures have gone up.” 2 These references fail to note that there are many sources of climate change, and that profound climate change occurred many times both before and after man appeared on earth. Given the ubiquity of climate change, it is implausible that all change is for the worse. Moreover, the coincidence of increasing CO2 and the small warming over the past century hardly establishes causality. Nevertheless, for the most part I do not personally disagree with the Consensus (though the absence of any quantitive considerations should be disturbing). Indeed, I know of no serious split, and suspect that the claim that there is opposition to this consensus amounts to no more than setting up a straw man to scoff at.
    [Show full text]
  • Cloud Feedback Mechanisms and Their Representation in Global Climate Models Paulo Ceppi ,1* Florent Brient ,2 Mark D
    Advanced Review Cloud feedback mechanisms and their representation in global climate models Paulo Ceppi ,1* Florent Brient ,2 Mark D. Zelinka 3 and Dennis L. Hartmann 4 Edited by Eduardo Zorita, Domain Editor and Editor-in-Chief Cloud feedback—the change in top-of-atmosphere radiative flux resulting from the cloud response to warming—constitutes by far the largest source of uncer- tainty in the climate response to CO2 forcing simulated by global climate models (GCMs). We review the main mechanisms for cloud feedbacks, and discuss their representation in climate models and the sources of intermodel spread. Global- mean cloud feedback in GCMs results from three main effects: (1) rising free- tropospheric clouds (a positive longwave effect); (2) decreasing tropical low cloud amount (a positive shortwave [SW] effect); (3) increasing high-latitude low cloud optical depth (a negative SW effect). These cloud responses simulated by GCMs are qualitatively supported by theory, high-resolution modeling, and observa- tions. Rising high clouds are consistent with the fixed anvil temperature (FAT) hypothesis, whereby enhanced upper-tropospheric radiative cooling causes anvil cloud tops to remain at a nearly fixed temperature as the atmosphere warms. Tropical low cloud amount decreases are driven by a delicate balance between the effects of vertical turbulent fluxes, radiative cooling, large-scale subsidence, and lower-tropospheric stability on the boundary-layer moisture budget. High- latitude low cloud optical depth increases are dominated by phase changes in mixed-phase clouds. The causes of intermodel spread in cloud feedback are dis- cussed, focusing particularly on the role of unresolved parameterized processes such as cloud microphysics, turbulence, and convection.
    [Show full text]
  • Lindzen Iris
    The Iris Effect; its strange and disturbing history Richard S. Lindzen Massachusetts Institute of Technology Goddard Space Flight Center May 19, 2004 A pdf file of these slides is available upon request to [email protected]. Original papers can be found at the following URL: www-eaps.mit.edu/faculty/lindzen.htm 1 This talk focuses on what is often considered the most fundamental question in the field of climate change (namely, what is the sensitivity of global mean temperature to global radiative forcing?), and the response of the climate change community to this question. My work with M.-D. Chou and A.Y. Hou on the Iris Effect will be discussed as an explicit example. 2 This would appear to be an important and well defined question. If the climate sensitivity is low, then presumably the problem of global warming is limited; if it is high, then urgency would appear justified. Relatedly, if the sensitivity is low, the need for subsidiary studies of impacts may also be limited. Since at least 1979, the common measure of sensitivity has been the change in global mean temperature that would be expected from a doubling of CO2 once the climate system reaches equilibrium. 3 In 1979, the National Research Council’s Charney Report offered a ‘guesstimate’ of about 1.5-4.5oC. Note that there was no real basis for these bounds. The range could have been extended at both ends. The latest IPCC WG 1 report claims that the range of model results continues to show the very same range. The low end is officially reckoned to be tolerable, while the high end is judged to be ominous.
    [Show full text]
  • Climate Models an Assessment of Strengths and Limitations
    Climate Models An Assessment of Strengths and Limitations U.S. Climate Change Science Program Synthesis and Assessment Product 3.1 July 2008 FEDERAL EXECUTIVE TEAM Acting Director, Climate Change Science Program ......................................................William J. Brennan Director, Climate Change Science Program Office.......................................................Peter A. Schultz Lead Agency Principal Representative to CCSP; Associate Director, Department of Energy, Office of Biological and Environmental Research .........................................................................................Anna Palmisano Product Lead; Department of Energy, Office of Biological and Environmental Research ........................................................Anjuli S. Bamzai Synthesis and Assessment Product Advisory Group Chair; Associate Director, EPA National Center for Environmental Assessment.....................................................................................................................Michael W. Slimak Synthesis and Assessment Product Coordinator, Climate Change Science Program Office ......................................................................Fabien J.G. Laurier OTHER AGENCY REPRESENTATIVES National Aeronautics and Space Administration ...........................................................Donald Anderson National Oceanic and Atmospheric Administration ......................................................Brian D. Gross National Science Foundation .........................................................................................Jay
    [Show full text]
  • Revisiting the Iris Effect of Tropical Cirrus Clouds with TRMM and A
    PUBLICATIONS Journal of Geophysical Research: Atmospheres RESEARCH ARTICLE Revisiting the iris effect of tropical cirrus clouds 10.1002/2016JD025827 with TRMM and A-Train satellite data Key Points: Yong-Sang Choi1,2 , WonMoo Kim3 , Sang-Wook Yeh4 , Hirohiko Masunaga5 , • Satellite observations reveal the iris 6 7 2,8 effect of tropical cirrus clouds Min-Jae Kwon , Hyun-Su Jo , and Lei Huang • The concentration of cloud systems 1 2 very likely contributes to the iris effect Department of Environmental Science and Engineering, Ewha Womans University, Seoul, South Korea, NASA Jet 3 • Climate models show that the Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA, Climate Prediction Department, APEC cirrus-precipitation relationship Climate Center, Busan, South Korea, 4Marine Sciences and Convergent Technology, Hanyang University, Seoul, South strongly linked to climate sensitivity Korea, 5Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, Japan, 6Department of Atmospheric Science and Engineering, Ewha Womans University, Seoul, South Korea, 7CSIRO Oceans and Atmosphere, Aspendale, Victoria, Australia, 8Joint Institute for Regional Earth System Science and Engineering, University of California, Los Angeles, Correspondence to: California, USA Y.-S. Choi, [email protected] Abstract Just as the iris of human eye controls the light influx (iris effect), tropical anvil cirrus clouds may ’ Citation: regulate the Earth s surface warming by controlling outgoing longwave radiation. This study examines this Choi, Y.-S., W. Kim, S.-W. Yeh, H. possible effect with monthly satellite observations such as Tropical Rainfall Measuring Mission (TRMM) Masunaga, M.-J. Kwon, H.-S. Jo, and L. precipitation, Moderate Resolution Imaging Spectroradiometer cirrus fraction, and Clouds and the Earth’s Huang (2017), Revisiting the iris effect of fl tropical cirrus clouds with TRMM and Radiant Energy System top-of-the-atmosphere radiative uxes averaged over different tropical domains from A-Train satellite data, J.
    [Show full text]
  • Climate Science: Is It Currently Designed to Answer Questions?1
    Climate Science: Is it currently designed to answer questions?1 Richard S. Lindzen Program in Atmospheres, Oceans and Climate Massachusetts Institute of Technology November 29, 2008 Revised: September 21, 2012 Abstract For a variety of inter-related cultural, organizational, and political reasons, progress in climate science and the actual solution of scientific problems in this field have moved at a much slower rate than would normally be possible. Not all these factors are unique to climate science, but the heavy influence of politics has served to amplify the role of the other factors. By cultural factors, I primarily refer to the change in the scientific paradigm from a dialectic opposition between theory and observation to an emphasis on simulation and observational programs. The latter serves to almost eliminate the dialectical focus of the former. Whereas the former had the potential for convergence, the latter is much less effective. The institutional factor has many components. One is the inordinate growth of administration in universities and the consequent increase in importance of grant overhead. This leads to an emphasis on large programs that never end. Another is the hierarchical nature of formal scientific organizations whereby a small executive council can speak on behalf of thousands of scientists as well as govern the distribution of ‘carrots and sticks’ whereby reputations are made and broken. The above factors are all amplified by the need for government funding. When an issue becomes a vital part of a political agenda, as is the case with climate, then the politically desired position becomes a goal rather than a consequence of scientific research.
    [Show full text]
  • Tightening of Tropical Ascent and High Clouds Key to Precipitation Change in a Warmer Climate
    ARTICLE Received 20 Jun 2016 | Accepted 27 Apr 2017 | Published 7 Jun 2017 DOI: 10.1038/ncomms15771 OPEN Tightening of tropical ascent and high clouds key to precipitation change in a warmer climate Hui Su1, Jonathan H. Jiang1, J. David Neelin2, T. Janice Shen1, Chengxing Zhai1, Qing Yue1, Zhien Wang3, Lei Huang1,4, Yong-Sang Choi5, Graeme L. Stephens1 & Yuk L. Yung6 The change of global-mean precipitation under global warming and interannual variability is predominantly controlled by the change of atmospheric longwave radiative cooling. Here we show that tightening of the ascending branch of the Hadley Circulation coupled with a decrease in tropical high cloud fraction is key in modulating precipitation response to surface warming. The magnitude of high cloud shrinkage is a primary contributor to the intermodel spread in the changes of tropical-mean outgoing longwave radiation (OLR) and global-mean precipitation per unit surface warming (dP/dTs) for both interannual variability and global warming. Compared to observations, most Coupled Model Inter-comparison Project Phase 5 models underestimate the rates of interannual tropical-mean dOLR/dTs and global-mean dP/dTs, consistent with the muted tropical high cloud shrinkage. We find that the five models that agree with the observation-based interannual dP/dTs all predict dP/dTs under global warming higher than the ensemble mean dP/dTs from the B20 models analysed in this study. 1 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Mail Stop 183-701, Pasadena, California 91109-8099, USA. 2 Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, Los Angeles, California 90095, USA.
    [Show full text]
  • Zelinka and Hartmann 2011
    JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 116, D23103, doi:10.1029/2011JD016459, 2011 The observed sensitivity of high clouds to mean surface temperature anomalies in the tropics Mark D. Zelinka1,2 and Dennis L. Hartmann1 Received 23 June 2011; revised 9 September 2011; accepted 28 September 2011; published 2 December 2011. [1] Cloud feedback represents the source of largest diversity in projections of future warming. Observational constraints on both the sign and magnitude of the feedback are limited, since it is unclear how the natural variability that can be observed is related to secular climate change, and analyses have rarely been focused on testable physical theories for how clouds should respond to climate change. In this study we use observations from a suite of satellite instruments to assess the sensitivity of tropical high clouds to interannual tropical mean surface temperature anomalies. We relate cloud changes to a physical governing mechanism that is sensitive to the vertical structure of warming. Specifically, we demonstrate that the mean and interannual variability in both the altitude and fractional coverage of tropical high clouds as measured by CloudSat, the Moderate Resolution Imaging Spectroradiometer, the Atmospheric Infrared Sounder, and the International Satellite Cloud Climatology Project are well diagnosed by upper tropospheric convergence computed from the mass and energy budget of the clear‐sky atmosphere. Observed high clouds rise approximately isothermally in accordance with theory and exhibit an overall reduction in coverage when the tropics warms, similar to their behavior in global warming simulations. Such cloud changes cause absorbed solar radiation to increase more than does outgoing longwave radiation, resulting in a positive but statistically insignificant net high cloud feedback in response to El Niño–Southern Oscillation.
    [Show full text]
  • Bibliography Agriculture and Climate Change
    BIBLIOGRAPHY AGRICULTURE AND CLIMATE CHANGE KLAUS AMMANN, OUT OF WEB OF SCIENCE AND OTHER SOURCES, SUMMARY AND FULL TEXT LINKS P. AERNI (2011) Lock-in situations in the global debates on climate change, biotechnology and international trade: Evidence from a global stakeholder survey, draft report, NCCR Trade Regulation Swiss National Centre of Competence in Research, 21, 38 The problem of man-made global climate change is strongly related to land-use practices and the global dependence on fossil fuels. Biotechnology is a platform technology that may help reduce greenhouse gas emissions in agriculture, improve adaptation to climate change, offer new sources of renewable energy and transform the current petrochemical industry into a less energy intensive biological industry. Yet, this potential is hardly ever discussed in the public debate on climate change because it is currently not associated with the term ‘cleantech’ that is used to describe climate-friendly technology. In our study we investigate the perceptions and interests of the main stakeholders involved in the global debate on biotechnology and climate change in order to better understand why ‘cleantech’ is currently not linked to ‘biotech’. For that purpose, we designed a global stakeholder survey which was completed online by 59 respondents representing 40 core institutions in the global sustainability debate. The response rate was above 80%. The survey results reveal that most stakeholders even in the climate change debate regard the potential of biotechnology to be significant. Yet, the results also show that one of the stakeholders that is assessed to be key in the biotechnology as well as the climate change debate and of central importance in the formation of global public opinion is also firmly opposed to the use of modern biotechnology to address climate change problems.
    [Show full text]