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1.
Grassland is one of the most widespread vegetation types worldwide and plays a significant role in regional climate and global
carbon cycling. Understanding the sensitivity of Chinese grassland ecosystems to climate change and elevated atmospheric CO2 and the effect of these changes on the grassland ecosystems is a key issue in global carbon cycling. China encompasses vast
grassland areas of 354 million ha of 17 major grassland types, according to a national grassland survey. In this study, a
process-based terrestrial model the CENTURY model was used to simulate potential changes in net primary productivity (NPP)
and soil organic carbon (SOC) of the Leymus chinensis meadow steppe (LCMS) under different scenarios of climatic change and elevated atmospheric CO2. The LCMS sensitivities, its potential responses to climate change, and the change in capacity of carbon stock and sequestration
in the future are evaluated. The results showed that the LCMS NPP and SOC are sensitive to climatic change and elevated CO2. In the next 100 years, with doubled CO2 concentration, if temperature increases from 2.7-3.9˚C and precipitation increases by 10% NPP and SOC will increase by 7-21%
and 5-6% respectively. However, if temperature increases by 7.5-7.8˚C and precipitation increases by only 10% NPP and SOC
would decrease by 24% and 8% respectively. Therefore, changes in the NPP and SOC of the meadow steppe are attributed mainly
to the amount of temperature and precipitation change and the atmospheric CO2 concentration in the future. 相似文献
2.
Minimizing the future impacts of climate change requires reducing the greenhouse gas (GHG) load in the atmosphere. Anthropogenic emissions include many types of GHG’s as well as particulates such as black carbon and sulfate aerosols, each of which has a different effect on the atmosphere, and a different atmospheric lifetime. Several recent studies have advocated for the importance of short timescales when comparing the climate impact of different climate pollutants, placing a high relative value on short-lived pollutants, such as methane (CH4) and black carbon (BC) versus carbon dioxide (CO2). These studies have generated confusion over how to value changes in temperature that occur over short versus long timescales. We show the temperature changes that result from exchanging CO2 for CH4 using a variety of commonly suggested metrics to illustrate the trade-offs involved in potential carbon trading mechanisms that place a high value on CH4 emissions. Reducing CH4 emissions today would lead to a climate cooling of approximately ~0.5 °C, but this value will not change greatly if we delay reducing CH4 emissions by years or decades. This is not true for CO2, for which the climate is influenced by cumulative emissions. Any delay in reducing CO2 emissions is likely to lead to higher cumulative emissions, and more warming. The exact warming resulting from this delay depends on the trajectory of future CO2 emissions but using one business-as usual-projection we estimate an increase of 3/4 °C for every 15-year delay in CO2 mitigation. Overvaluing the influence of CH4 emissions on climate could easily result in our “locking” the earth into a warmer temperature trajectory, one that is temporarily masked by the short-term cooling effects of the CH4 reductions, but then persists for many generations. 相似文献
3.
Terrestrial carbon fluxes are an important factor in regulating concentrations of atmospheric carbon dioxide (CO2). In this study, we use a coupled climate model with interactive biogeochemistry to benchmark the simulation of net primary productivity (NPP) and its response to elevated atmospheric CO2. Short-term field experiments such as Free-Air Carbon Dioxide Enrichment (FACE) studies have examined this phenomenon but it is difficult to infer trends from only a few years of field data. Here, we employ the University of Victoria's Earth System Climate Model (UVic ESCM) version 2.8 to compare simulated changes in NPP due to an elevated atmospheric CO2 concentration of 550 ppm to observed increases in NPP of 23% ±2% from four temperate forest FACE studies between 1997 and 2002. We further compare two scenarios: elevated CO2 with climate change, and elevated CO2 without climate change, the latter being consistent with FACE methodology. In the climate change scenario global terrestrial and forest-only NPP increased by 24.5% and 27.9%, respectively, while these increases were 21.0% and 17.2%, respectively, in the latitude band most representative of the location of the FACE studies. In the scenario without climate change, terrestrial and forest-only NPP increased instead by 28.3% and 30.6%, respectively, while these increases were 24.3% and 14.4%, respectively, in the FACE latitudes. This suggests that the model may underestimate temperate forest NPP increases when compared to results from temperate forest FACE studies and highlights the need for both increased experimental study of other forest biomes and further model development. 相似文献
4.
The responses of the climate system to increase of atmospheric carbon dioxide(CO2)arestudied by using a new version of the Bureau of Meteorological Research Centre(BMRC)globalcoupled general circulation model(CGCM).Two simulations are run:one with atmospheric CO2concentration held constant at 330 ppm,the other with a tripling of atmospheric CO2(990 ppm).Results from the 41-year control coupled integration are applied to analyze the mean state,seasonal cycle and interannual variability in the model.Comparisons between the greenhouseexperiment and the control experiment then provide estimations of the influence of increased CO2on climate changes and climate variability.Especially discussed is the question on whether theclimate changes concerned with CO2 inerease will impact interannual variability in tropical Pacific,such as ENSO. 相似文献
5.
L. D. Danny Harvey 《Climatic change》2004,63(3):259-290
Carbon sequestration is increasingly being promoted as a potential response to the risks of unrestrained emissions of CO2, either in place of or as a complement to reductions in the use of fossil fuels. However, the potential role of carbon sequestration as an (at-least partial) substitute for reductions in fossil fuel use can be properly evaluated only in the context of a long-term acceptable limit (or range of limits) to the increase in atmospheric CO2 concentration, taking into account the response of the entire carbon cycle to artificial sequestration. Under highly stringent emission-reduction scenarios for non-CO2 greenhouse gases, 450 ppmv CO2 is the equivalent, in terms of radiative forcing of climate,to a doubling of the pre-industrial concentration of CO2. It is argued in this paper that compliance with the United Nations Framework Convention on Climate Change (henceforth, the UNFCCC) implies that atmospheric CO2 concentration should be limited, or quickly returned to, a concentration somewhere below 450 ppmv. A quasi-one-dimensional coupled climate-carbon cycle model is used to assess the response of the carbon cycle to idealized carbon sequestration scenarios. The impact on atmospheric CO2 concentration of sequestering a given amount of CO2 that would otherwise be emitted to the atmosphere, either in deep geological formations or in the deep ocean, rapidly decreases over time. This occurs as a result of a reduction in the rate of absorption of atmospheric CO2 by the natural carbon sinks (the terrestrial biosphere and oceans) in response to the slower buildup of atmospheric CO2 resulting from carbon sequestration. For 100 years of continuous carbon sequestration, the sequestration fraction (defined as the reduction in atmospheric CO2 divided by the cumulative sequestration) decreases to 14% 1000 years after the beginning of sequestration in geological formations with no leakage, and to 6% 1000 years after the beginning of sequestration in the deep oceans. The difference (8% of cumulative sequestration) is due to an eflux from the ocean to the atmosphere of some of the carbon injected into the deep ocean.The coupled climate-carbon cycle model is also used to assess the amount of sequestration needed to limit or return the atmospheric CO2 concentration to 350–400 ppmv after phasing out all use of fossil fuels by no later than 2100. Under such circumstances, sequestration of 1–2 Gt C/yr by the latter part of this century could limit the peak CO2 concentration to 420–460 ppmv, depending on how rapidly use of fossilfuels is terminated and the strength of positive climate-carbon cycle feedbacks. To draw down the atmospheric CO2 concentration requires creating negative emissions through sequestration of CO2 released as a byproduct of the production of gaseous fuels from biomass primary energy. Even if fossil fuel emissions fall to zero by 2100, it will be difficult to create a large enough negative emission using biomass energy to return atmospheric CO2 to 350 ppmv within 100 years of its peak. However, building up soil carbon could help in returning CO2 to 350 ppmv within 100 years of its peak. In any case, a 100-year period of climate corresponding to the equivalent of a doubled-CO2 concentration would occur before temperatures decreased. Nevertheless, returning the atmospheric CO2concentration to 350 ppmv would reduce longterm sea level rise due to thermal expansion and might be sufficient to prevent the irreversible total melting of the Greenland ice sheet, collapse of the West Antarctic ice sheet, and abrupt changes in ocean circulation that might otherwise occur given a prolonged doubled-CO2 climate. Recovery of coral reef ecosystems, if not already driven to extinction, could begin. 相似文献
6.
The increase of atmospheric CO2 concentrations due to anthropogenic activities is substantially damped by the ocean, whose CO2 uptake is determined by the state of the ocean, which in turn is influenced by climate change. We investigate the mechanisms of the ocean’s carbon uptake within the feedback loop of atmospheric CO2 concentration, climate change and atmosphere/ocean CO2 flux. We evaluate two transient simulations from 1860 until 2100, performed with a version of the Max Planck Institute Earth System Model (MPI-ESM) with the carbon cycle included. In both experiments observed anthropogenic CO2 emissions were prescribed until 2000, followed by the emissions according to the IPCC Scenario A2. In one simulation the radiative forcing of changing atmospheric CO2 is taken into account (coupled), in the other it is suppressed (uncoupled). In both simulations, the oceanic carbon uptake increases from 1 GT C/year in 1960 to 4.5 GT C/year in 2070. Afterwards, this trend weakens in the coupled simulation, leading to a reduced uptake rate of 10% in 2100 compared to the uncoupled simulation. This includes a partial offset due to higher atmospheric CO2 concentrations in the coupled simulation owing to reduced carbon uptake by the terrestrial biosphere. The difference of the oceanic carbon uptake between both simulations is primarily due to partial pressure difference and secondary to solubility changes. These contributions are widely offset by changes of gas transfer velocity due to sea ice melting and wind changes. The major differences appear in the Southern Ocean (?45%) and in the North Atlantic (?30%), related to reduced vertical mixing and North Atlantic meridional overturning circulation, respectively. In the polar areas, sea ice melting induces additional CO2 uptake (+20%). 相似文献
7.
Can Trees Buy Time? An Assessment of the Role of Vegetation Sinks as Part of the Global Carbon Cycle
Miko U. F. Kirschbaum 《Climatic change》2003,58(1-2):47-71
Atmospheric CO2 concentrations can be reduced by storing carbon in vegetation. However, this lowers the concentration gradient between the atmosphere and other potential carbon reservoirs, such as the oceans, and thereby reduces the subsequent inherent rate of removal of CO2 from the atmosphere. Hence, storage of carbon in temporary reservoirs can reduce atmospheric CO2 concentrations in the short term, but if the carbon is released again, it will increase concentrations in the long term. It must, therefore, be considered when, or, indeed whether, to store carbon in vegetation sinks.To determine an optimal strategy, the exact nature of climate-change impacts needs to be considered first. Impacts can be mediated by:1. the direct and instantaneous effect of CO2 and its associated temperature;2. the rate of change in CO2 and its associated temperature;3. the cumulative effect of CO2 and its associated temperature.Carbon stored in permanently maintained vegetation sinks can lower atmospheric CO2 concentrations, but this can be done most effectively if sequestration occurs close to the time when atmospheric concentrations are to be lowered. Similarly, maximal rates of change can be most effectively reduced by carbon sequestration close to the time of anticipated maximal rates of change. For reducing impacts via cumulative forcing, however, early sink activity would be more effective than delayed activity.Temporary carbon stores would only be beneficial for climate change impacts related to the cumulative impact of CO2, but it could even worsen impacts mediated via the instantaneous effect of temperature or those related to the rate of change. Hence, the planting of trees is only beneficial in reducing climate-change impacts if the most serious impacts are those related to the cumulative effect of increased temperature. If other impacts are more serious, then the planting of trees would bring greater benefits if it is delayed until closer to the time when the most severe impacts are to be expected. However, if serious land degradation would result from deforestation, or from a failure to plant trees in the near future, then trees should still be planted in order to maximise the amount of carbon stored on land. 相似文献
8.
Present and future surface climate in the western USA as simulated by 15 global climate models 总被引：3，自引：2，他引：1
We analyze results of 15 global climate simulations contributed to the Coupled Model Intercomparison Project (CMIP). Focusing on the western USA, we consider both present climate simulations and predicted responses to increasing atmospheric CO2. The models vary in their ability to predict the present climate. In the western USA, a few models produce a seasonal cycle for spatially averaged temperature and/or precipitation in good agreement with observational data. Other models tend to over-predict precipitation in the winter or exaggerate the amplitude of the seasonal cycle of temperature. The models also differ in their ability to reproduce the spatial patterns of temperature and precipitation in the USA. Considering the monthly mean precipitation responses to doubled atmospheric CO2, averaged over the western USA, we find some models predict increases while others predict decreases. The predicted temperature response, on the other hand, is invariably positive over this region; however, for each month, the range of values given by the different models is large compared to the mean model response. We look for possible relationships between the models temperature and precipitation responses to doubled CO2 concentration and their ability to simulate some aspects of the present climate. We find that these relationships are weak, at best. The precipitation response over the western USA in DJF and the precipitation response over the mid- and tropical latitudes seem to be correlated with the RMS error in simulated present-day precipitation, also calculated over the mid- and tropical latitudes. However, considering only the responses of the models with the smallest RMS errors does not provide a different estimate of the precipitation response to a doubled CO2 concentration, because even among the most accurate models, the range of model responses is so large. For temperature, we find that models that have smaller RMS errors in present-climate temperature in the north eastern Pacific region predict a higher temperature response in the western USA than the models with larger errors. A similar relation exists between the temperature response over Europe in DJF and the RMS error calculated over the Northern Atlantic. 相似文献
9.
SIMULATING THE RESPONSE OF NON-UNIFORMITY OF PRECIPITATION EXTREMES OVER CHINA TO CO2 INCREASING BY MIROC_HIRES MODEL 总被引：1，自引：0，他引：1
The response of non-uniformity of precipitation extremes over China to doubled CO2has been analyzed using the daily precipitation simulated by a coupled general circulation model,MIROC_Hires.The major conclusions are as follows:under the CO2increasing scenario(SRES A1B),the climatological precipitation extremes are concentrated over the southern China,while they are uniformly distributed over the northern China.For interannual variability,the concentration of precipitation extremes is small over the southern China,but it is opposite over the northern China.The warming effects on the horizontal and vertical scales are different over the northern and southern part of China.Furthermore,the atmospheric stability is also different between the two parts of China.The heterogeneous warming is one of the possible reasons for the changes in non-uniformity of precipitation extremes over China. 相似文献
10.
Influence of dynamic vegetation on climate change arising from increasing CO<Subscript>2</Subscript>
A dynamic global vegetation model (DGVM) is coupled to an atmospheric general circulation model (AGCM) to investigate the
influence of vegetation dynamics on climate change under conditions of global warming. The model results are largely in agreement
with observations and the results of previous studies in terms of the present climate, present potential vegetation, present
net primary productivity (NPP), and pre-industrial carbon budgets. The equilibrium state of climate properties are compared
among pre-industrial, doubled, and quadrupled atmospheric CO2 values using DGVM–AGCM and current AGCM with fixed vegetation to evaluate the influence of dynamic vegetation change. We
also separated the contributions of temperature, precipitation and CO2 fertilization on vegetation change. The results reveal an amplification of global warming climate sensitivity by 10% due
to the inclusion of dynamic vegetation. The total effects of elevated CO2 and climate change also lead to an increase in NPP and vegetation coverage globally. The reduction of albedo associated with
this greening results in enhanced global warming. Our separation analysis indicates that temperature alters vegetation at
high latitudes such as Siberia or Alaska, where there is a switch from tundra to forest. On the other hand, CO2 fertilization provides the largest contribution to greening in arid/semi-arid region. Precipitation change did not cause
any drastic vegetation shift. 相似文献
11.
Ocean acidification and climate change: synergies and challenges of addressing both under the UNFCCC
Ellycia R. Harrould-Kolieb 《Climate Policy》2013,13(3):378-389
Ocean acidification and climate change are linked by their common driver: CO2. Climate change is the consequence of a range of GHG emissions, but ocean acidification on a global scale is caused solely by increased concentrations of atmospheric CO2. Reducing CO2 emissions is therefore the most effective way to mitigate ocean acidification. Acting to prevent further ocean acidification by reducing CO2 emissions will also provide simultaneous benefits by alleviating future climate change. Although it is possible that reducing CO2 emissions to a level low enough to address ocean acidification will simultaneously address climate change, the reverse is unfortunately not necessarily true. Despite the ocean's integral role in the climate system and the potentially wide-ranging impacts on marine life and humans, the problem of ocean acidification is largely absent from most policy discussions pertaining to CO2 emissions. The linkages between ocean acidification, climate change and the United Nations Framework Convention on Climate Change (UNFCCC) are identified and possible scenarios for developing common solutions to reduce and adapt to ocean acidification and climate change are offered. Areas where the UNFCCC is currently lacking capacity to effectively tackle rising ocean acidity are also highlighted. 相似文献
12.
It is important to improve estimates of large-scale carbon fluxes over the boreal forest because the responses of this biome to global change may influence the dynamics of atmospheric carbon dioxide in ways that may influence the magnitude of climate change. Two methods currently being used to estimate these fluxes are process-based modeling by terrestrial biosphere models (TBMs), and atmospheric inversions in which fluxes are derived from a set of observations on atmospheric CO2 concentrations via an atmospheric transport model. Inversions do not reveal information about processes and therefore do not allow for predictions of future fluxes, while the process-based flux estimates are not necessarily consistent with atmospheric observations of CO2. In this study we combine the two methods by using the fluxes from four TBMs as a priori fluxes for an atmospheric Bayesian Synthesis Inversion. By doing so we learn about both approaches. The results from the inversion indicate where the results of the TBMs disagree with the atmospheric observations of CO2, and where the results of the inversion are poorly constrained by atmospheric data, the process-based estimates determine the flux results. The analysis indicates that the TBMs are modeling the spring uptake of CO2 too early, and that the inversion shows large uncertainty and more dependence on the initial conditions over Europe and Boreal Asia than Boreal North America. This uncertainty is related to the scarcity of data over the continents, and as this problem is not likely to be solved in the near future, TBMs will need to be developed and improved, as they are likely the best option for understanding the impact of climate variability in these regions. 相似文献
13.
Use of general circulation model output in the creation of climate change scenarios for impact analysis 总被引：1，自引：0，他引：1
Alan Robock Richard P. Turco Mark A. Harwell Thomas P. Ackerman Rigoberto Andressen Hsin-Shih Chang M. V. K. Sivakumar 《Climatic change》1993,23(4):293-335
Many scientific studies warn of a rapid global climate change during the next century. These changes are understood with much less certainty on a regional scale than on a global scale, but effects on ecosystems and society will occur at local and regional scales. Consequently, in order to study the true impacts of climate change, regional scenarios of future climate are needed. One of the most important sources of information for creating scenarios is the output from general circulation models (GCMs) of the climate system. However, current state-of-the-art GCMs are unable to simulate accurately even the current seasonal cycle of climate on a regional basis. Thus the simple technique of adding the difference between 2 × CO2 and 1 × CO2 GCM simulations to current climatic time series cannot produce scenarios with appropriate spatial and temporal details without corrections for model deficiencies. In this study a technique is developed to allow the information from GCM simulations to be used, while accommodating for the deficiencies. GCM output is combined with knowledge of the regional climate to produce scenarios of the equilibrium climate response to a doubling of the atmospheric CO2 concentration for three case study regions, China, Sub-Saharan Africa and Venezuela, for use in biological effects models. By combining the general climate change calculated with several GCMs with the observed patterns of interannual climate variability, reasonable scenarios of temperature and precipitation variations can be created. Generalizations of this procedure to other regions of the world are discussed. 相似文献
14.
Tom Mikunda Heleen de Coninck Morgan Bazilian Hilke Rösler Bob van der Zwaan 《Climate Policy》2013,13(5):665-676
Attaining deep greenhouse gas (GHG) emission reductions in industry in order to support a stringent climate change control target will be difficult without recourse to CO2 capture and storage (CCS). Using the insights from a long-term bottom-up energy systems model, and undertaking a sectoral assessment, we investigated the importance of CCS in the industrial sector. Under climate policy aimed at limiting atmospheric concentration of GHGs to 650 ppm CO2e, costs could increase fivefold when CCS is excluded from the portfolio of mitigation option measures in the industry sector as compared to when CCS is excluded in the power sector. This effect is driven largely by the lack of alternatives for deep emission reductions in industry. Our main policy conclusion is that a broader recognition of CCS in industrial applications in both current policy discussions and research, development, and demonstration funding programmes is justified. In recognition of the heterogeneity of the many types of industrial production processes, the size and location of industrial CO2 sources, the specific need for CCS-retrofitting, and the exposure of most industrial sectors to international trade, policies aimed at supporting CCS must distinguish between the different challenges faced by the power and industrial sectors. 相似文献
15.
长江三角洲地区净生态系统二氧化碳通量及浓度的数值模拟 总被引：1，自引：0，他引：1
净生态系统碳通量(NEE)的计算对于准确模拟区域碳通量和大气CO2浓度的时空变化至关重要。本文利用中尺度大气-温室气体耦合模式WRF-GHG(Weather Research and Forecasting Model with Greenhouse Gases Module),对2010年7月28日至2010年8月2日期间影响长江三角洲地区大气CO2浓度及时空分布的各种过程进行了详尽模拟。结果表明,植被光合呼吸模型(VPRM)能模拟不同植被下垫面NEE的日变化;WRF-GHG模拟的大气CO2浓度日变化与观测相吻合,但低估了大气CO2浓度5~15 ppm(ppm表示10-6),这可能与人为排放源的低估、VPRM参数的不确定性以及气象场模拟的不准确性有关。太湖和植被覆盖较好的地区如浙江北部山区是该地区的主要碳汇,而城市为CO2的主要排放源。太湖和陆地生态系统对区域内碳循环起到一定的调节作用,减缓区域大气CO2浓度的升高。此外,局地气象条件如湖陆风对太湖周边地区大气CO2浓度有显著影响。 相似文献
16.
Summary A novel multi-timescale analysis method, Empirical Mode Decomposition (EMD), is used to diagnose the variation of the annual
mean temperature data of the global, Northern Hemisphere (NH) and China from 1881 to 2002. The results show that: (1) Temperature
can be completely decomposed into four timescales quasi-periodic oscillations including an ENSO-like mode, a 6–8-year signal,
a 20-year signal and a 60-year signal, as well as a trend. With each contributing ration of the quasi-periodicity discussed,
the trend and the 60-year timescale oscillation of temperature variation are the most prominent. (2) It has been noticed that
whether on century-scale or 60-year scales, the global temperature tends to descend in the coming 20 years. (3) On quasi 60-year
timescale, temperature abrupt changes in China precede those in the global and NH, which provides a denotation for global
climate changes. Signs also show a drop in temperature in China on century scale in the next 20 years. (4) The dominant contribution
of CO2 concentration to global temperature variation is the trend. However, its influence weight on global temperature variation
accounts for no more than 40.19%, smaller than those of the natural climate changes on the rest four timescales. Despite the
increasing trend in atmospheric CO2 concentration, the patterns of 20-year and 60-year oscillation of global temperature are all in falling. Therefore, if CO2 concentration remains constant at present, the CO2 greenhouse effect will be deficient in counterchecking the natural cooling of global climate in the following 20 years. Even
though the CO2 greenhouse effect on global climate change is unsuspicious, it could have been excessively exaggerated. It is high time to
re-consider the trend of global climate changes. 相似文献
17.
Jian Ni 《Climatic change》2002,55(1-2):61-75
The BIOME3 model was used to simulate the distribution patterns and carbon storage of the horizontal, zonal boreal forests in northeast and northwest China using a mapping system for vegetation patterns combined with carbon density estimates from vegetation and soils. The BIOME3 prediction is in reasonable good agreement with the potential distribution of Chinese boreal forests. The effects of changing atmospheric CO2 concentration had a nonlinear effect on boreal forest distribution, with 3.5–10.8% reduced areas for both increasing and decreasing CO2. In contrast, the increased climate together with and without changing CO2 concentration showed dramatic changes in geographic patterns, with 70% reduction in area and disappearance of almost boreal forests in northeast China. The baseline carbon storage in boreal forests of China is 4.60 PgC (median estimate) based on the vegetation area of actual boreal forest distribution. If taking the large area of agricultural crops into account, the median value of potential carbon storage is 6.92 PgC. The increasing (340–500 ppmv) and decreasing CO2 concentration (340–200 ppmv) led to decrease of carbon storage, 0.33 PgC and 1.01 PgC respectively compared to BIOME3 potential prediction under present climate and CO2 conditions. Both climate change alone and climate change with CO2 enrichment (340–500 ppmv) reduced largely the carbon stored in vegetation and soils by ca. 6.5 PgC. The effect of climate change is more significant than the direct physiological effect of CO2 concentration on the boreal forests of China, showing a large reduction in both distribution area and carbon storage. 相似文献
18.
Global warming due to increased concentrations of atmospheric CO2 is expected to be amplified in middle and higher latitudes. Consequently, ecosystems in these latitudes will experience more pronounced climatic variations. This investigation attempts to assess the sensitivity of Canada's ecosystems to climatic change. Potential ecological impacts resulting from global warming are outlined. With this background, the effects of a doubled CO2 climate are applied to a classification model derived from the current ecological setting. Results reveal not only major shifts in ecological boundaries but also changes in the character of these broadly distributed ecosystems. 相似文献
19.
陆地生态系统碳汇显著降低大气CO2浓度上升和全球变暖的速率,受人类活动和气候变化的影响,陆地生态系统碳通量具有强烈的时空变化,其估算结果仍存在较大的不确定性,不同因子的贡献尚不清晰。为此,利用遥感驱动的陆地生态系统过程模型BEPS模拟分析了1981—2019年全球陆地生态系统碳通量的时空变化特征,评价了大气CO2浓度、叶面积指数（Leaf Area Index,LAI）、氮沉降、气候变化对全球陆地生态系统碳收支变化的贡献。1981—2019年全球陆地生态系统总初级生产力（Gross Primary Productivity,GPP）、净初级生产力（Net Primary Productivity,NPP）和净生态系统生产力（Net Ecosystem Productivity,NEP）的平均值分别为115.3、51.3和2.7 Pg·a-1（以碳质量计,下同）,上升速率分别为0.47、0.21和0.06 Pg·a-1。全球大部分区域GPP和NPP显著增加,NEP显著上升（p<0.05）的区域明显少于GPP和NPP。1981—2019年,全球NEP累积为105.2 Pg,森林、稀树草原及灌木、农田和草地的贡献分别为76.4、15.8、9.4和3.6 Pg。CO2浓度、LAI、氮沉降和气候变化各自对NEP的累积贡献分别为58.4、20.6、0.7和-43.6 Pg,全部4个因子变化对NEP的累积贡献为39.8 Pg,其中CO2浓度上升是近40 a全球陆地生态系统NEP上升的主要贡献因子,其次为LAI。 相似文献
20.
With advancing climate change there is a growing need to include short-lived climate forcings in cost-efficient mitigation strategies to achieve international climate policy targets. Tools are required to compare the climate impact of perturbations with distinctively different atmospheric lifetimes and atmospheric properties. We present a generic approach for relating the climate effect of short-lived climate forcers (SLCF) to that of CO2 emissions. We distinguish between three alternative types of metric-based factors that can be used to derive CO2 equivalences for SLCF: based on forcing, activity and fossil fuel consumption. We derive numerical values for a wide range of parameter assumptions and apply the resulting generalised approach to the practical example of aviation-induced cloudiness. The evaluation of CO2 equivalences for SLCF tends to be more sensitive to SLCF specific physical uncertainties and the normative choice of a discount rate than to the choice of a physical or economic metric approach. The ability of physical metrics to approximate economic-based metrics alters with changing atmospheric concentration levels and trends. Under reference conditions, physical CO2 equivalences for SLCF provide sufficient proxies for economic ones. The latter, however, allow detailed insight into structural uncertainties. They provide CO2 equivalences for SLCF in short term strategies in the face of failing climate policies, and a temporal evolution of CO2 equivalences over time that is noticeably better in line with cost-efficient climate stabilisation. 相似文献