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Arindam Samanta, Bruce T. Anderson, Sangram Ganguly, Yuri Knyazikhin, Ramakrishna R. Nemani, and Ranga B. Myneni

roughly corresponds to the base year 1990 CO 2 concentration (355 ppmv) adopted by the Kyoto Protocol and the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) ( Solomon et al. 2007 ). The intervening 350-ppmv CO 2 increase corresponds to a radiative forcing of 3.6 W m −2 , which is well within the realm of what can be expected in the twenty-first century from anthropogenic contributions of radiatively active chemical constituents to the atmosphere, absent

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Bruce T. Anderson, Catherine Reifen, and Ralf Toumi

anthropogenic forcing, such that trends (positive or negative) increase with increased forcing; 2) decreased sensitivity to anthropogenic forcing, such that trends decrease with increased forcing; and 3) “turning point” behavior in which the short-term initial trends are of the opposite sign as the longer-term trends. Previous examples of such nonlinear behavior in historical and projected climate parameters include accelerated melting of arctic sea ice ( Winton 2006 ; Serreze and Francis 2006

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Bruce T. Anderson, Catherine Reifen, and Ralf Toumi

of anthropogenic forcing of climate change; from these we get estimates of what the possible “observed value” of gridpoint precipitation changes for the 2080–2100 period may be ( Räisänen and Palmer 2001 ). We then calculate the MMEM projection of 2080–2100 precipitation changes at each grid point and use this as the “forecast” value. We can then estimate how large the forecasted value skill is, given the range of plausible realizations of the climate system: where O i is the “observed” 2080

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W. L. Ellenburg, R. T. McNider, J. F. Cruise, and John R. Christy

surface fluxes at various spatial scales. As a result, the U.S. National Research Council ( Jacob et al. 2005 ) has recommended expanding research into the influence of land-cover processes on climate as a forcing. It has been conjectured that the climate response to land-use and land-cover change could possibly even exceed greenhouse gas contributions, making for very important local, regional, and even global implications ( Dirmeyer et al. 2010 ). While other studies have investigated the Southeast

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Yaqian He and Eungul Lee

vegetation with lower albedo compared with sand absorbed more solar radiation, which might create more rainfall over Africa. Los et al. (2006) concluded that vegetation effects accounted for about 30% of annual rainfall variation in the Sahel. It appears that both regional land surface and remote ocean forcings may be responsible for the variability of the Sahel rainfall. While the previous studies are concerned with the land and ocean factors separately, the relative contribution of the two different

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Julian C. Brimelow, John M. Hanesiak, and William R. Burrows

further elucidate how anomalies in NDVI can condition the convective boundary layer (CBL) so as to inhibit or facilitate thunderstorm activity while also considering the role of synoptic-scale forcing on modulating summer thunderstorm activity. Modeling studies have suggested that changes in low-level moisture and energy fluxes associated with soil moisture and vegetation anomalies can perpetuate drought conditions (e.g., Dirmeyer 1994 ; Beljaars et al. 1996 ; Seneviratne et al. 2010 ). Vegetation

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Michael E. Mann, Ed Gille, Jonathan Overpeck, Wendy Gross, Raymond S. Bradley, Frank T. Keimig, and Malcolm K. Hughes

studies have been spurred by hopes to better constrain the influences of natural and anthropogenic factors on long-term climate variability and change ( Lean et al., 1995; Overpeck et al., 1997; Mann et al., 1998 ), to estimate climate sensitivity to external radiative forcing ( Crowley and Kim, 1999; Waple et al., 2000 ), and to validate the behavior of climate models on multidecadal and longer timescales ( Barnett et al., 1996; Jones et al., 1998; Delworth and Mann, 2000 ). Most recently

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Avijit Gangopadhyay, Ayan H. Chaudhuri, and Arnold H. Taylor

propose to address a single primary question: Does the Gulf Stream system respond at different temporal scales east and west of 60°–65°W? And, if so, might these different time scales relate to the different forcing mechanisms mentioned above? We present evidence for an affirmative answer using past observations and available model results. The thermohaline linkage between the GS and the atmosphere is rather indirect. It is affected by convection in the Labrador Sea ( Myers et al. 1989 ; Dickson et

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David B. Lobell, Céline Bonfils, and Jean-Marc Faurès

1. Introduction Efforts to anticipate the impacts of climate change on crop production and food security depend critically on projections of future climate in agricultural regions. General circulation models (GCMs) commonly used to make these projections consider changes in atmospheric concentrations of carbon dioxide (CO 2 ) and other well-mixed greenhouse gases, and many also consider changes in anthropogenic aerosol levels. However, few consider climate forcing from land-use changes, which

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A. H. M. Siddique-E-Akbor, Faisal Hossain, Safat Sikder, C. K. Shum, Steven Tseng, Yuchan Yi, F. J. Turk, and Ashutosh Limaye

equally routine but easier to measure meteorological forcing data (e.g., precipitation, wind speed, temperature). A hydrological model can yield information on water availability at closer space–time resolutions, where it is very hard to place gauges. Thus, a hydrological model can bridge gaps in in situ measurement as well as keep track of the terrestrial component of the dynamic water cycle. As there is a general lack of in situ meteorological data availability for forcing a hydrological model

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