Abstracts on Global Climate Change

Nov 2006

Late Pliocene monsoon linkage in the tropical South China Sea

Tian, J Pak, DK Wang, PX Lea, D Cheng, XR Zhao, QH


The onset of Northern Hemisphere Glaciation (NHG) similar to 2.7 Ma ago coincided with prominent climate changes in the tropical regions such as the African and the Asian monsoons. However, the relationship between tropical and sub-tropical monsoonal variations and high northern latitude ice sheet expansion as well as processes such as late Pliocene tropical sea surface temperature (SST) change is not clear. Our late Pliocene (2.5-3.3 Ma) monsoon proxy records and Mg/Ca derived SST records at Ocean Drilling Program (ODP) Site 1143 from the southern South China Sea (SCS) reveal that while tropical SST shows a stepwise decrease of 2-3 degrees C during this period, the East Asian monsoon gradually strengthens in response to the onset of the NHG. At the 41-kyr and 23-kyr bands, ice volume change lags tropical SST by similar to 4 kyr, but leads the East Asian monsoon by similar to 12-17 kyr. Our finding highlights the significant role of the tropical Pacific region in driving global climate change in the late Pliocene, which has invariable leading phase relative to the ice volume change as in the late Pleistocene. However, the East Asian monsoon shows a linear response to the onset: of the NHG in the late Pliocene, with much bigger phase lagged at the 41-kyr and 23-kyr bands than in the Pleistocene, which suggests that at the obliquity and precession bands the phases of the Plio-Pleistocene East Asian monsoon variations relative to the global ice volume changes are not constant, but variable. Therefore, the East Asian monsoons are not only simply driven by northern summer insolation at the precession period but also modulated by global ice volume change in high latitudes. (c) 2006 Elsevier B.V. All rights reserved.

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An atmosphere-ocean time series model of global climate change

Stern, DI


Time series models of global climate change tend to estimate a low climate-sensitivity (equilibrium effect on global temperature of doubling carbon dioxide concentrations) and a fast adjustment rate to equilibrium. These results may be biased by omission of a key variable-heat stored in the ocean. A time series model of the atmosphere-ocean climate system is developed, in which surface temperature (atmospheric temperature over land and sea surface temperature) moves towards a long-run equilibrium with both radiative forcing and ocean heat content, while ocean heat content accumulates the deviations from atmospheric equilibrium. This model is closely related to Granger and Lee’s multicointegration model. As there are only 55 years of observations on ocean heat content, the Kalman filter is used to estimate heat content as a latent state variable, which is constrained by the available observations. This method could be applied to other climate change problems where there are only limited observations on key variables. The final model adopted relates surface temperature to the heat content of the upper 300m of the ocean. The resulting parameter estimates are closer to theoretically expected values than those of previous time series models and the estimated climate sensitivity to a doubling of carbon dioxide is 4.4 K. (c) 2005 Published by Elsevier B.V.

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The influence of the possible global climate change on the properties of Mexican soils

Nikol’skii, YN Castillo-Alvarez, M Bakhlaeva, OS Roma-Calleros, XA Maslov, BS


To estimate the changes in the integral fertility index of virgin soils in Mexico upon the expected global climate changes, we applied a method based on revealing the quantitative relationship between the Budyko radiation index of dryness and the modal values of the regional agrochemical properties of soils located on a nearly horizontal surface (with slope of less than 0.001) at elevations ranging from 0 to 2500 m a.s.l. The results of existing forecasts of the alteration of the global air temperature, radiation, and precipitation were also used. In the case that the carbon dioxide content is doubled in the atmosphere by the end of the 21st century, a medium and weak decrease in the soil fertility will be observed in the central (cereal) regions of Mexico; furthermore, a significant (over 20%) decrease in fertility will be observed in the tropical regions, where sugar cane is cultivated.

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The elevation history of the Tibetan Plateau and its implications for the Asian monsoon

Harris, N


The determination of the evolving palaeoaltitude of the Tibetan Plateau, since the India-Eurasia collision underpins our understanding of how orography in central Asia affects the intensity of the monsoon and hence global climate change. Palacoaltitudes, however, cannot be measured directly and need to be inferred from proxy observations that are usually model-dependent. Differing tectonic models for the behaviour of the lithosphere during continental collision have contrasting implications for the elevation of the plateau. However, two techniques recently employed for determining palaeo-elevation are independent of tectonic models, the first involving the variation with altitude of oxygen isotopes in precipitation and the second involving the change of leaf morphology with moist static energy of the atmosphere. Elevation studies have focused on southern Tibet, largely due to the relative ease of access to the region. There is a remarkable unanimity amongst the diverse techniques applied that the altitude of the southern plateau has not significantly changed since at least the mid Miocene (ca. 15 Ma) arguing for an onset of the monsoon system during or before the early Miocene. A range of tectonic studies suggest that the northern and eastern parts of the plateau are younger geornorphological features, but there are few quantitative constraints of the timing of elevation from these regions of Tibet. Since both the elevation and the surface area of the plateau impact on atmospheric circulation, palacoaltitude studies need to be extended to chart the increasing areas of elevated land surface through time. (c) 2006 Elsevier B.V All rights reserved.

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Optimal endogenous carbon taxes for electric power supply chains with power plants

Nagurney, A Liu, ZG Woolley, T


In this paper, we develop a modeling and computational framework that allows for the determination of optimal carbon taxes applied to electric power plants in the context of electric power supply chain (generation/distribution/consumption) networks. The adoption of carbon/pollution taxes both internationally and regionally has been fueled by global climate change and fuel security risks, with a significant portion of such policy interventions directed at the electric power industry. The general framework that we develop allows for three distinct types of carbon taxation environmental policies, beginning with a completely decentralized scheme in which taxes can be applied to each individual power generator/power plant in order to guarantee that each assigned emission bound is not exceeded, to two versions of a centralized scheme, one which assumes a fixed bound over the entire electric power supply chain in terms of total carbon emissions and the other which allows the bound to be a function of the tax. The behavior of the various decision-makers in the electric power supply chain network is described, along with the three taxation schemes, and the governing equilibrium conditions, which are formulated as finite-dimensional variational inequality problems. Twelve numerical examples are presented in which the optimal carbon taxes, as well as the equilibrium electric power flows and demands, are computed. The numerical results demonstrate, as the theory predicts, that the carbon taxes achieve the desired goal, in that the imposed bounds on the carbon emissions are not exceeded. Moreover, they illustrate the spectrum of scenarios that can be explored in terms of changes in the bounds on the carbon emissions; changes in emission factors; changes in the demand price functions, etc. (c) 2006 Elsevier Ltd. All rights reserved.

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Study on the trace species in the stratosphere and their impact on climate

Chen, YJ Zhou, RJ Shi, CH Bi, Y


The trace gases (O-3, HCl, CH4, H2O, NO, NO2) in the stratosphere play an important role, not only in the photochemical processes in which the ozone layer destroyed, but also in the radiative processes. In this paper, we review the works on the distribution and variation of the trace gases in the stratosphere and their impact on climate, which have been carried out at the University of Science and Technology of China in the recent 20 years. The Halogen Occultation Experiment (HALOE) data were used to analyse the distribution and variation of the mixing ratio of these trace gases and the temperature trends in the stratosphere in the most recent decade. And the reanalyzed National Centers of Environmental Prediction (NCEP)/NCAR data were also used to give the temperature trends and compared with the results from HALOE data. Numerical simulations were also carried out to study the impact of ozone depletion on the global climate. In this review, the distributions of the trace gases, especially those over the Qinghai-Xizang Plateau, are discussed, and the variations and trends for the trace gases in various levels in the stratosphere have been given for the most recent decade. The temperature variation and the cooling trend obtained from HALOE data in the middle and lower stratosphere for the last 13 years are significant, which agree well with the results from NCEP/NCAR data. While the temperature trend in the upper stratosphere in this period do not seem to have much cooling. The numerical simulations show that either the Antarctic ozone hole or the ozone valley over Qinghai-Xizang Plateau affect not only the temperature and circulation in the stratosphere, but also the temperature, pressure and wind fields in the troposphere, then lead to the global climate change.

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Oceanic implications for climate change policy

McNeil, BI


Under the United Nations convention on the law of the sea (1982), each participating country maintains exclusive economic and environmental rights within the oceanic region extending 200 nm from its territorial sea, known as the exclusive economic zone (EEZ). Although the ocean within each EEZ is undoubtedly an anthropogenic CO2 sink, it has been overlooked within international climate policy. In this paper I use an area-weighted scaling argument to show that the inclusion of the EEZ CO2 sink within national carbon accounts would have significant implications in tracking national greenhouse commitments to any future climate change policy initiative. The advantages and disadvantages for inclusion of the EEZ CO2 sink into global climate change policy are also explored. The most compelling argument for including the EEZ CO2 sink is that it would enhance the equity and resources among coastal nations to combat and adapt against future climate change that will inherently impact coastal nations more so than land locked nations. If included, the funds raised could be used for either monitoring or adaptive coastal infrastructure among the most vulnerable nations. On the other hand, the EEZ anthropogenic CO2 sink cannot be directly controlled by human activities and could be used as a disincentive for some developed nations to reduce fossil-fuel related greenhouse gas emissions. This may therefore dampen efforts to ultimately reduce atmospheric greenhouse gas concentrations. In consideration of these arguments it is therefore suggested that an “EEZ clause” be added to Kyoto and any future international climate policy that explicitly excludes its use within national carbon accounts under these international climate frameworks. (c) 2006 Elsevier Ltd. All rights reserved.

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Soil respiration of forest ecosystems in Japan and global implications

Lee, MS Mo, WH Koizumi, H


Within terrestrial ecosystems, soil respiration is one of the largest carbon flux components. We discuss the factors controlling soil respiration, while focusing on research conducted at the Takayama Experimental Site. Soil respiration was affected by soil temperature, soil moisture, rainfall events, typhoons, and root respiration. We consider the temporal and spatial variability of soil respiration at the Takayama Experimental Site and review the variability of annual soil respiration in Japanese forests. In the 26 compiled studies, the values of annual soil respiration ranged from 203 to 1,290 g C m(-2) year(-1), with a mean value of 669 g C m(-2) year(-1) (SD = 264, CV = 40). We note the need for more studies and data synthesis for the accurate prediction of soil respiration and soil carbon dynamics in Japanese forests. Finally, several methods for measuring soil respiration rates are compared and the implications of soil respiration rates for global climate change are discussed.

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Atypical delta N-15 variations at the southern boundary of the East Pacific oxygen minimum zone over the last 50 ka

Martinez, P Lamy, F Robinson, RR Pichevin, L Billy, I


We report a nitrogen isotope record (ODP Site 1233) from the southern Chile margin at 41 degrees S. The site is located slightly south of the southern boundary of the Peru-Chile upwelling system and the associated oxygen minimum zone off Peru and northern Chile. We show that our nitrogen isotope record, from the time interval 0-50 calendar kiloyears before present (ka B.P.), bears an atypical pattern both in shape and timing when compared with records obtained from either the continental margin of the eastern Pacific or the Subantarctic Zone (SAZ) of the Southern Ocean. The delta N-15 values at Site 1233 are relatively high throughout the record, varying between 9 parts per thousand. and 13 parts per thousand. The iriajor features are a pronounced delta N-15 increase at the beginning of the deglaciation, a maximum from 19 to 10 ka B.P.; thereafter a large decrease during the early Holocene, and millenial scale oscillations showing an Antarctic timing. We propose that the record results from an amalgam of low-latitude and high-latitude processes. Low-latitude processes, including a stronger advection signal of heavy nitrates from the denitrifying zones off Peru and northern Chile, would explain the timing of the deglaciation rise and the heaviest values found over this interval, excluding the Antarctic Cold Reversal period. The overall differences between site 1233 and records from Peru and northwest American margins suggest however that the origin of the delta N-15 signal off Chile is largely controlled by hydrologic and climatic changes in the Southern Ocean. We propose that the interplay between nutrient demand in the SAZ and latitudinal shifts of hydrologic fronts controlled both the concentrations and the isotopic signature of the remaining nitrate delivered to the Chile margin. Then, the glacial surface waters of the southern Chile margin were likely lower in nitrate concentration and bear a higher delta N-15 than during interglacial periods. (c) 2006 Elsevier Ltd. All rights reserved.

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Enhancement of lidar backscatters signal-to-noise ratio using empirical mode decomposition method

Wu, SH Liu, ZS Liu, BY


Lidar is being widely used to monitor meteorological parameters and atmospheric constituents. Applications include meteorology, environmental pollution, atmospheric dynamics and global climate change. Signal processing for lidar applications involve highly nonlinear models and consequently nonlinear filtering. In this paper, we applied a new method, empirical mode decomposition to the lidar signal processing. The denoising approach is done by removal of the proper intrinsic mode functions. The data from the simulation and measurements are analyzed to evaluate this method comparing with the traditional low-pass filter and the multi-pulse averaging. Results show that it is effective-and superior to the band-pass filter and the averaging method. The denoising method also allows less averaging laser shots which is important for the real-time monitoring and for the low cost laser transmitter. (c) 2006 Elsevier B.V. All rights reserved.

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Low clouds and cloud immersion enhance photosynthesis in understory species of a southern Appalachian spruce-fir forest (USA)

Johnson, DM Smith, WK


High-attitude forests of the southern Appalachian Mountains (USA) are frequently immersed in clouds, as are many mountain forests. They may be particularly sensitive to predicted increases in cloud base altitude with global warming. However, few studies have addressed the impacts of immersion on incident sunlight and photosynthesis. Understory sunlight (photosynthetically active radiation, PAR) was measured during clear, low cloud, and cloud-immersed conditions at Mount Mitchell and Roan Mountain, NC (USA) along with accompanying photosynthesis in four representative understory species. Understory PAR was substantially less variable on immersed vs. clear days. Photosynthesis became light-saturated between similar to 100 and 400 mu mol center dot m(-2). s(-1) PAR for all species measured, corresponding closely to the sunlight environment measured during immersion. Estimated daily carbon gain was 26% greater on clear days at a more open canopy site but was 22% greater on immersed/cloudy days at a more closed canopy site. F-v/F-m (maximum photosystem II efficiency) in Abies fraseri seedlings exposed to 2.5 min full sunlight was significantly reduced (10%), indicating potential reductions in photosynthesis on clear days. In addition, photosynthesis in microsites with canopy cover was nearly 3-fold greater under immersed (2.6 mmol center dot m(-2) center dot h(-1)) vs. clear conditions (0.9 mmol center dot m(-2) center dot h(-1)). Thus, cloud immersion provided more constant PAR regimes that enhanced photosynthesis, especially in shaded microsites. Future studies are needed to predict the survival of these refugial forests under potential changes in cloud regimes.

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Prognosis of the impact of global climate change on zonal ecosystems of the Volga river basin

Kolomyts, EG


On the basis of the GISS prognostic climatic model, landscape-ecological scenarios concerning the immediate future of the region are considered in the forms of cartographic and analytical models. These scenarios predict a growing thermoarid bioclimatic trend accompanied by a general northward displacement of zonal boundaries, with corresponding acceleration of the biological cycle and increase in the productivity of boreal forests.

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Evidence for carbon dioxide and moisture interactions from the leaf cell up to global scales: Perspective on human-caused climate change

Alpert, P Niyogi, D Pielke, RA Eastman, JL Xue, YK Raman, S


It is of utmost interest to further understand the mechanisms behind the potential interactions or synergies between the greenhouse gases (GHG) forcing(s), particularly as represented by CO2, and water processes and through different climatic scales down to the leaf scale. Toward this goal, the factor separation methodology introduced by Stein and Alpert [Stein U. and Alpert, P. 1993. Factor separation in numerical simulations, J. Atmos. Sci., 50, 2107-2115.] that allows an explicit separation of atmospheric synergies among different factors, is employed. Three independent experiments carried out recently by the present authors, are reported here, all strongly suggest the existence of a significant CO2-water synergy in all the involved scales. The experiments employed a very wide range of up-to-date atmospheric models that complement the physics currently introduced in most Global Circulation Models (GCMs) for global climate change prediction. Three modeling experiments that go from the small/micro scale (leaf scale and soil moisture) to mesoscale (land-use change and CO2 effects) and to global scale (greenhouse gases and cloudiness) all show that synergies between water and CO2 are essential in predicting carbon assimilation, minimum daily temperature and the global Earth temperature, respectively. The study also highlights the importance of including the physics associated with carbon-water synergy which is mostly unresolved in global climate models suggesting that significant carbon-water interactions are not incorporated or at least well parameterized in current climate models. Hence, there is a need for integrative climate models. As shown in earlier studies, the climate involves physical, chemical and biological processes. To only include a subset of these processes limits the skill of local, regional and global models to simulate the real climate system. In addition, our results provide explicit determination of the direct and the interactive effect of the CO2 response on the terrestrial biosphere response. There is also an implicit scale interactive effect that can be deduced from the multiscale effects discussed in the three examples. Processes at each scale-leaf, regional and global will all synergistically contribute to increase the feedbacks-which can decrease or increase the overall system’s uncertainty depending on specific case/setup and needs to be examined in future coupled, multiscale studies. (C) 2006 Elsevier B.V. All rights reserved.

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