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Author

Jim Haywood

Other affiliations: Met Office, Princeton University, University of Reading  ...read more
Bio: Jim Haywood is an academic researcher from University of Exeter. The author has contributed to research in topics: Aerosol & Radiative forcing. The author has an hindex of 67, co-authored 213 publications receiving 20503 citations. Previous affiliations of Jim Haywood include Met Office & Princeton University.


Papers
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Journal ArticleDOI
TL;DR: A review of the many developments in estimates of the direct and indirect global annual mean radiative forcing due to present-day concentra- tions of anthropogenic tropospheric aerosols since the Inter- governmental Panel on Climate Change (1996) is presented in this paper.
Abstract: This paper reviews the many developments in estimates of the direct and indirect global annual mean radiative forcing due to present-day concentra- tions of anthropogenic tropospheric aerosols since Inter- governmental Panel on Climate Change (1996). The range of estimates of the global mean direct radiative forcing due to six distinct aerosol types is presented. Addition- ally, the indirect effect is split into two components corresponding to the radiative forcing due to modifica- tion of the radiative properties of clouds (cloud albedo effect) and the effects of anthropogenic aerosols upon the lifetime of clouds (cloud lifetime effect). The radia- tive forcing for anthropogenic sulphate aerosol ranges from 20.26 to 20.82 W m 22 . For fossil fuel black carbon the radiative forcing ranges from 10.16 W m 22 for an external mixture to 10.42 W m 22 for where the black carbon is modeled as internally mixed with sulphate aerosol. For fossil fuel organic carbon the two estimates of the likely weakest limit of the direct radiative forcing are 20.02 and 20.04 W m 22 . For biomass-burning sources of black carbon and organic carbon the com-

1,868 citations

Journal ArticleDOI
TL;DR: In this paper, the impact of carbonaceous soot within the troposphere can significantly modify the clear-sky radiative forcing, and the effect of an assumed soot/sulfate mass ratio of between 0.05 and 0.1 is examined.
Abstract: Carbonaceous soot within the troposphere can significantly modify the clear-sky radiative forcing. Using an extension to a simple radiation calculation and two model-derived sulfate aerosol data sets, the impact of an assumed soot/sulfate mass ratio of between 0.05 and 0.1 is examined. Fossil fuel derived soot causes a positive global-mean radiative forcing which for one data set ranges from +0.03 to +0.24Wm−2; the lower estimate is for an external mixture with a soot/sulfate ratio of 0.05 and the upper estimate is for an internal mixture and a soot/sulfate ratio of 0.10. These values compare to a global-mean radiative forcing of −0.34Wm−2 due to sulfate aerosol. Soot also significantly reduces the interhemispherical difference in the radiative forcing due to sulfate aerosol. The nature and amount of soot must be well established if the climatic role of tropospheric aerosols is to be fully understood.

630 citations

Journal ArticleDOI
22 Dec 2005-Nature
TL;DR: Satellite-based measurements of aerosols and surface wind speed are used to estimate the clear-sky direct radiative forcing for 2002, suggesting future atmospheric warming greater than is presently predicted, as aerosol emissions continue to decline.
Abstract: Atmospheric aerosols cause scattering and absorption of incoming solar radiation. Additional anthropogenic aerosols released into the atmosphere thus exert a direct radiative forcing on the climate system. The degree of present-day aerosol forcing is estimated from global models that incorporate a representation of the aerosol cycles. Although the models are compared and validated against observations, these estimates remain uncertain. Previous satellite measurements of the direct effect of aerosols contained limited information about aerosol type, and were confined to oceans only. Here we use state-of-the-art satellite-based measurements of aerosols and surface wind speed to estimate the clear-sky direct radiative forcing for 2002, incorporating measurements over land and ocean. We use a Monte Carlo approach to account for uncertainties in aerosol measurements and in the algorithm used. Probability density functions obtained for the direct radiative forcing at the top of the atmosphere give a clear-sky, global, annual average of -1.9 W m(-2) with standard deviation, +/- 0.3 W m(-2). These results suggest that present-day direct radiative forcing is stronger than present model estimates, implying future atmospheric warming greater than is presently predicted, as aerosol emissions continue to decline.

461 citations

Journal ArticleDOI
TL;DR: In this article, the direct radiative forcing (DRF) of sulfate and black carbon (BC) aerosols is investigated using a new multispectral radiation code within the R30 Geophysical Fluid Dynamics Laboratory general circulation model (GCM).
Abstract: The direct radiative forcing (DRF) of sulfate and black carbon (BC) aerosols is investigated using a new multispectral radiation code within the R30 Geophysical Fluid Dynamics Laboratory general circulation model (GCM). Two independent sulfate climatologies from chemical transport models are applied to the GCM; each climatology has a different atmospheric burden, vertical profile, and seasonal cycle. The DRF is calculated to be approximately −0.6 and −0.8 W m−2 for the different sulfate climatologies. Additional sensitivity studies show that the vertical profile of the sulfate aerosol is important in determining the DRF; sulfate residing near the surface gives the strongest DRF due to the effects of relative humidity. Calculations of the DRF due to BC reveal that the DRF remains uncertain to approximately a factor of 3 due to uncertainties in the total atmospheric burden, the vertical profile of the BC, and the assumed size distribution. Because of the uncertainties in the total global mass of BC, the normalized DRF (the DRF per unit column mass of aerosol in watts per milligram (W mg−1)) due to BC is estimated; the range is +1.1 to + 1.9 W mg−1 due to uncertainties in the vertical profile. These values correspond to a DRF of approximately +0.4 W m−2 with a factor of 3 uncertainty when the uncertainty in the total global mass of BC is included. In contrast to sulfate aerosol, the contribution to the global DRF from cloudy regions is very significant, being estimated as approximately 60%. The vertical profile of the BC is, once again, important in determining the DRF, but the sensitivity is reversed from that of sulfate; BC near the surface gives the weakest DRF due to the shielding effects of overlying clouds. Although the uncertainty in the estimates of the DRF due to BC remains high, these results indicate that the DRF due to absorption by BC aerosol may contribute a significant positive radiative forcing and may consequently be important in determining climatic changes in the Earth-atmosphere system.

450 citations


Cited by
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01 Jan 2007
TL;DR: Drafting Authors: Neil Adger, Pramod Aggarwal, Shardul Agrawala, Joseph Alcamo, Abdelkader Allali, Oleg Anisimov, Nigel Arnell, Michel Boko, Osvaldo Canziani, Timothy Carter, Gino Casassa, Ulisses Confalonieri, Rex Victor Cruz, Edmundo de Alba Alcaraz, William Easterling, Christopher Field, Andreas Fischlin, Blair Fitzharris.
Abstract: Drafting Authors: Neil Adger, Pramod Aggarwal, Shardul Agrawala, Joseph Alcamo, Abdelkader Allali, Oleg Anisimov, Nigel Arnell, Michel Boko, Osvaldo Canziani, Timothy Carter, Gino Casassa, Ulisses Confalonieri, Rex Victor Cruz, Edmundo de Alba Alcaraz, William Easterling, Christopher Field, Andreas Fischlin, Blair Fitzharris, Carlos Gay García, Clair Hanson, Hideo Harasawa, Kevin Hennessy, Saleemul Huq, Roger Jones, Lucka Kajfež Bogataj, David Karoly, Richard Klein, Zbigniew Kundzewicz, Murari Lal, Rodel Lasco, Geoff Love, Xianfu Lu, Graciela Magrín, Luis José Mata, Roger McLean, Bettina Menne, Guy Midgley, Nobuo Mimura, Monirul Qader Mirza, José Moreno, Linda Mortsch, Isabelle Niang-Diop, Robert Nicholls, Béla Nováky, Leonard Nurse, Anthony Nyong, Michael Oppenheimer, Jean Palutikof, Martin Parry, Anand Patwardhan, Patricia Romero Lankao, Cynthia Rosenzweig, Stephen Schneider, Serguei Semenov, Joel Smith, John Stone, Jean-Pascal van Ypersele, David Vaughan, Coleen Vogel, Thomas Wilbanks, Poh Poh Wong, Shaohong Wu, Gary Yohe

7,720 citations

Journal ArticleDOI
TL;DR: In this paper, the authors provided an assessment of black-carbon climate forcing that is comprehensive in its inclusion of all known and relevant processes and that is quantitative in providing best estimates and uncertainties of the main forcing terms: direct solar absorption; influence on liquid, mixed phase, and ice clouds; and deposition on snow and ice.
Abstract: Black carbon aerosol plays a unique and important role in Earth's climate system. Black carbon is a type of carbonaceous material with a unique combination of physical properties. This assessment provides an evaluation of black-carbon climate forcing that is comprehensive in its inclusion of all known and relevant processes and that is quantitative in providing best estimates and uncertainties of the main forcing terms: direct solar absorption; influence on liquid, mixed phase, and ice clouds; and deposition on snow and ice. These effects are calculated with climate models, but when possible, they are evaluated with both microphysical measurements and field observations. Predominant sources are combustion related, namely, fossil fuels for transportation, solid fuels for industrial and residential uses, and open burning of biomass. Total global emissions of black carbon using bottom-up inventory methods are 7500 Gg yr−1 in the year 2000 with an uncertainty range of 2000 to 29000. However, global atmospheric absorption attributable to black carbon is too low in many models and should be increased by a factor of almost 3. After this scaling, the best estimate for the industrial-era (1750 to 2005) direct radiative forcing of atmospheric black carbon is +0.71 W m−2 with 90% uncertainty bounds of (+0.08, +1.27) W m−2. Total direct forcing by all black carbon sources, without subtracting the preindustrial background, is estimated as +0.88 (+0.17, +1.48) W m−2. Direct radiative forcing alone does not capture important rapid adjustment mechanisms. A framework is described and used for quantifying climate forcings, including rapid adjustments. The best estimate of industrial-era climate forcing of black carbon through all forcing mechanisms, including clouds and cryosphere forcing, is +1.1 W m−2 with 90% uncertainty bounds of +0.17 to +2.1 W m−2. Thus, there is a very high probability that black carbon emissions, independent of co-emitted species, have a positive forcing and warm the climate. We estimate that black carbon, with a total climate forcing of +1.1 W m−2, is the second most important human emission in terms of its climate forcing in the present-day atmosphere; only carbon dioxide is estimated to have a greater forcing. Sources that emit black carbon also emit other short-lived species that may either cool or warm climate. Climate forcings from co-emitted species are estimated and used in the framework described herein. When the principal effects of short-lived co-emissions, including cooling agents such as sulfur dioxide, are included in net forcing, energy-related sources (fossil fuel and biofuel) have an industrial-era climate forcing of +0.22 (−0.50 to +1.08) W m−2 during the first year after emission. For a few of these sources, such as diesel engines and possibly residential biofuels, warming is strong enough that eliminating all short-lived emissions from these sources would reduce net climate forcing (i.e., produce cooling). When open burning emissions, which emit high levels of organic matter, are included in the total, the best estimate of net industrial-era climate forcing by all short-lived species from black-carbon-rich sources becomes slightly negative (−0.06 W m−2 with 90% uncertainty bounds of −1.45 to +1.29 W m−2). The uncertainties in net climate forcing from black-carbon-rich sources are substantial, largely due to lack of knowledge about cloud interactions with both black carbon and co-emitted organic carbon. In prioritizing potential black-carbon mitigation actions, non-science factors, such as technical feasibility, costs, policy design, and implementation feasibility play important roles. The major sources of black carbon are presently in different stages with regard to the feasibility for near-term mitigation. This assessment, by evaluating the large number and complexity of the associated physical and radiative processes in black-carbon climate forcing, sets a baseline from which to improve future climate forcing estimates.

4,591 citations

Journal Article
TL;DR: In this article, the authors present a document, redatto, voted and pubblicato by the Ipcc -Comitato intergovernativo sui cambiamenti climatici - illustra la sintesi delle ricerche svolte su questo tema rilevante.
Abstract: Cause, conseguenze e strategie di mitigazione Proponiamo il primo di una serie di articoli in cui affronteremo l’attuale problema dei mutamenti climatici. Presentiamo il documento redatto, votato e pubblicato dall’Ipcc - Comitato intergovernativo sui cambiamenti climatici - che illustra la sintesi delle ricerche svolte su questo tema rilevante.

4,187 citations

Book ChapterDOI
01 Jan 2014
TL;DR: Myhre et al. as discussed by the authors presented the contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) 2013: Anthropogenic and Natural Radiative forcing.
Abstract: This chapter should be cited as: Myhre, G., D. Shindell, F.-M. Bréon, W. Collins, J. Fuglestvedt, J. Huang, D. Koch, J.-F. Lamarque, D. Lee, B. Mendoza, T. Nakajima, A. Robock, G. Stephens, T. Takemura and H. Zhang, 2013: Anthropogenic and Natural Radiative Forcing. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. Coordinating Lead Authors: Gunnar Myhre (Norway), Drew Shindell (USA)

3,684 citations