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1.
Using a global carbon cycle model (GLOCO) that considers seven terrestrial biomes, surface and deep ocean layers based on the HILDA model and a single mixed atmosphere, we analyzed the response of atmospheric CO2 concentration and oceanic DIC and DOC depth profiles to additions of carbon to the atmosphere and ocean. The rate of transport of carbon to the deepest oceanic layers is rather insensitive to the atmosphereic-ocean surface gas exchange coefficient over a wide range, hence discrepancies between researchers on the precise global average value of this coefficient do not significantly affect predictions of atmospheric response to anthropogenic inputs. Upwelling velocity, on the other hand, amplifies oceanic response by increasing primary production in the upper ocean layers, resulting in a larger flux into DOC and sediments and increased carbon storage; experiments to reduce the uncertainty in this parameter would be valuable.The location of the carbon addition, whether it is released in the atmosphere or in the middle of the oceanic thermocline, has a significant impact on the maximum atmospheric CO2 concentration (pCO2) subsequently reached, suggesting that oceanic burial of a significant fraction of carbon emissions (e.g. via clathrate hydrides) may be an important management option for limiting pCO2 buildup. Our analysis indicates that the effectiveness of ocean burial decreases asymptotically below about 1000 m depth. With a constant emissions scenario (at 1990 levels), pCO2 at year 2100 is reduced from 501 ppmv considering all emissions go to the atmosphere, to 422 ppmv with ocean burial at a depth of 1000 m of 50% of the fossil fuel emissions. An alternative scenario looks at stabilizing pCO2 at 450 ppmv; with no ocean burial of fossil fuel emissions, the rate of emissions has to be cut drastically after the year 2010, whereas oceanic burial of 2 GtC/yr allows for a smoother transition to alternative energy sources.  相似文献   

2.
The simulation model accounts for four major compartments in the global carbon cycle: atmosphere, ocean, terrestrial biosphere and fossil carbon reservoir. The ocean is further compartmentalized into a high and a low latitude surface layer, and into 10 deep sea strata. The oceanic carbon fluxes are caused by massflow of descending and upwelling water, by precipitation of organic material and by diffusion exchange.The biosphere is horizontally subdivided into six ecosystems and vertically into leaves, branches, stemwood, roots, litter, young humus and stable soil carbon. Deforestation, slash and burn agriculture, rangeland burning and shifts in land use have been included. The atmosphere is treated as one well mixed reservoir. Fossil fuel consumption is simulated with historic data, and with IIASA scenario's for the future. Using the low IIASA scenario an atmospheric CO2 concentration of 431 ppmv is simulated for 2030 AD. A sensitivity analysis shows the importance of different parameters and of human behaviour. Notwithstanding the large size of the biosphere fluxes, the atmospheric CO2 concentration in the next century will be predominantly determined by the growth rate of fossil fuel consumption.  相似文献   

3.
We use a coupled climate–carbon cycle model of intermediate complexity to investigate scenarios of stratospheric sulfur injections as a measure to compensate for CO2-induced global warming. The baseline scenario includes the burning of 5,000 GtC of fossil fuels. A full compensation of CO2-induced warming requires a load of about 13 MtS in the stratosphere at the peak of atmospheric CO2 concentration. Keeping global warming below 2°C reduces this load to 9 MtS. Compensation of CO2 forcing by stratospheric aerosols leads to a global reduction in precipitation, warmer winters in the high northern latitudes and cooler summers over northern hemisphere landmasses. The average surface ocean pH decreases by 0.7, reducing the calcifying ability of marine organisms. Because of the millennial persistence of the fossil fuel CO2 in the atmosphere, high levels of stratospheric aerosol loading would have to continue for thousands of years until CO2 was removed from the atmosphere. A termination of stratospheric aerosol loading results in abrupt global warming of up to 5°C within several decades, a vulnerability of the Earth system to technological failure.  相似文献   

4.
Increasing concentrations of atmospheric CO2 influence climate, terrestrial biosphere productivity and ecosystem carbon storage through its radiative, physiological and fertilization effects. In this paper, we quantify these effects for a doubling of CO2 using a low resolution configuration of the coupled model NCAR CCSM4. In contrast to previous coupled climate-carbon modeling studies, we focus on the near-equilibrium response of the terrestrial carbon cycle. For a doubling of CO2, the radiative effect on the physical climate system causes global mean surface air temperature to increase by 2.14 K, whereas the physiological and fertilization on the land biosphere effects cause a warming of 0.22 K, suggesting that these later effects increase global warming by about 10 % as found in many recent studies. The CO2-fertilization leads to total ecosystem carbon gain of 371 Gt-C (28 %) while the radiative effect causes a loss of 131 Gt-C (~10 %) indicating that climate warming damps the fertilization-induced carbon uptake over land. Our model-based estimate for the maximum potential terrestrial carbon uptake resulting from a doubling of atmospheric CO2 concentration (285–570 ppm) is only 242 Gt-C. This highlights the limited storage capacity of the terrestrial carbon reservoir. We also find that the terrestrial carbon storage sensitivity to changes in CO2 and temperature have been estimated to be lower in previous transient simulations because of lags in the climate-carbon system. Our model simulations indicate that the time scale of terrestrial carbon cycle response is greater than 500 years for CO2-fertilization and about 200 years for temperature perturbations. We also find that dynamic changes in vegetation amplify the terrestrial carbon storage sensitivity relative to a static vegetation case: because of changes in tree cover, changes in total ecosystem carbon for CO2-direct and climate effects are amplified by 88 and 72 %, respectively, in simulations with dynamic vegetation when compared to static vegetation simulations.  相似文献   

5.
The capture and storage of CO2 from combustion of fossil fuels is gaining attraction as a means to deal with climate change. CO2 emissions from biomass conversion processes can also be captured. If that is done, biomass energy with CO2 capture and storage (BECS) would become a technology that removes CO2 from the atmosphere and at the same time deliver CO2-neutral energy carriers (heat, electricity or hydrogen) to society. Here we present estimates of the costs and conversion efficiency of electricity, hydrogen and heat generation from fossil fuels and biomass with CO2 capture and storage. We then insert these technology characteristics into a global energy and transportation model (GET 5.0), and calculate costs of stabilizing atmospheric CO2 concentration at 350 and 450 ppm. We find that carbon capture and storage technologies applied to fossil fuels have the potential to reduce the cost of meeting the 350 ppm stabilisation targets by 50% compared to a case where these technologies are not available and by 80% when BECS is allowed. For the 450 ppm scenario, the reduction in costs is 40 and 42%, respectively. Thus, the difference in costs between cases where BECS technologies are allowed and where they are not is marginal for the 450 ppm stabilization target. It is for very low stabilization targets that negative emissions become warranted, and this makes BECS more valuable than in cases with higher stabilization targets. Systematic and stochastic sensitivity analysis is performed. Finally, BECS opens up the possibility to remove CO2 from the atmosphere. But this option should not be seen as an argument in favour of doing nothing about the climate problem now and then switching on this technology if climate change turns out to be a significant problem. It is not likely that BECS can be initiated sufficiently rapidly at a sufficient scale to follow this path to avoiding abrupt and serious climate changes if that would happen.  相似文献   

6.
Summary The first GCM climate change projections to include dynamic vegetation and an interactive carbon cycle produced a very significant amplification of global warming over the 21st century. Under the IS92a business as usual emissions scenario CO2 concentrations reached about 980ppmv by 2100, which is about 280ppmv higher than when these feedbacks were ignored. The major contribution to the increased CO2 arose from reductions in soil carbon because global warming is assumed to accelerate respiration. However, there was also a lesser contribution from an alarming loss of the Amazonian rainforest. This paper describes the phenomenon of Amazonian forest dieback under elevated CO2 in the Hadley Centre climate-carbon cycle model.  相似文献   

7.
Ocean iron fertilization has been proposed as a method to mitigate anthropogenic climate change, and there is continued commercial interest in using iron fertilization to generate carbon credits. It has been further speculated that ocean iron fertilization could help mitigate ocean acidification. Here, using a global ocean carbon cycle model, we performed idealized ocean iron fertilization simulations to place an upper bound on the effect of iron fertilization on atmospheric CO2 and ocean acidification. Under the IPCC A2 CO2 emission scenario, at year 2100 the model simulates an atmospheric CO2 concentration of 965 ppm with the mean surface ocean pH 0.44 units less than its pre-industrial value of 8.18. A globally sustained ocean iron fertilization could not diminish CO2 concentrations below 833 ppm or reduce the mean surface ocean pH change to less than 0.38 units. This maximum of 0.06 unit mitigation in surface pH change by the end of this century is achieved at the cost of storing more anthropogenic CO2 in the ocean interior, furthering acidifying the deep-ocean. If the amount of net carbon storage in the deep ocean by iron fertilization produces an equivalent amount of emission credits, ocean iron fertilization further acidifies the deep ocean without conferring any chemical benefit to the surface ocean.  相似文献   

8.
Article 2 of the United Nations Framework Convention on Climate Change (UNFCCC) calls for stabilization of greenhouse gas (GHG) concentrations at levels that prevent dangerous anthropogenic interference (DAI) in the climate system. However, some of the recent policy literature has focused on dangerous climatic change (DCC) rather than on DAI. DAI is a set of increases in GHGs concentrations that has a non-negligible possibility of provoking changes in climate that in turn have a non-negligible possibility of causing unacceptable harm, including harm to one or more of ecosystems, food production systems, and sustainable socio-economic systems, whereas DCC is a change of climate that has actually occurred or is assumed to occur and that has a non-negligible possibility of causing unacceptable harm. If the goal of climate policy is to prevent DAI, then the determination of allowable GHG concentrations requires three inputs: the probability distribution function (pdf) for climate sensitivity, the pdf for the temperature change at which significant harm occurs, and the allowed probability (“risk”) of incurring harm previously deemed to be unacceptable. If the goal of climate policy is to prevent DCC, then one must know what the correct climate sensitivity is (along with the harm pdf and risk tolerance) in order to determine allowable GHG concentrations. DAI from elevated atmospheric CO2 also arises through its impact on ocean chemistry as the ocean absorbs CO2. The primary chemical impact is a reduction in the degree of supersaturation of ocean water with respect to calcium carbonate, the structural building material for coral and for calcareous phytoplankton at the base of the marine food chain. Here, the probability of significant harm (in particular, impacts violating the subsidiary conditions in Article 2 of the UNFCCC) is computed as a function of the ratio of total GHG radiative forcing to the radiative forcing for a CO2 doubling, using two alternative pdfs for climate sensitivity and three alternative pdfs for the harm temperature threshold. The allowable radiative forcing ratio depends on the probability of significant harm that is tolerated, and can be translated into allowable CO2 concentrations given some assumption concerning the future change in total non-CO2 GHG radiative forcing. If future non-CO2 GHG forcing is reduced to half of the present non-CO2 GHG forcing, then the allowable CO2 concentration is 290–430 ppmv for a 10% risk tolerance (depending on the chosen pdfs) and 300–500 ppmv for a 25% risk tolerance (assuming a pre-industrial CO2 concentration of 280 ppmv). For future non-CO2 GHG forcing frozen at the present value, and for a 10% risk threshold, the allowable CO2 concentration is 257–384 ppmv. The implications of these results are that (1) emissions of GHGs need to be reduced as quickly as possible, not in order to comply with the UNFCCC, but in order to minimize the extent and duration of non-compliance; (2) we do not have the luxury of trading off reductions in emissions of non-CO2 GHGs against smaller reductions in CO2 emissions, and (3) preparations should begin soon for the creation of negative CO2 emissions through the sequestration of biomass carbon.  相似文献   

9.
Summary A suite of simulations with the HadCM3LC coupled climate-carbon cycle model is used to examine the various forcings and feedbacks involved in the simulated precipitation decrease and forest dieback. Rising atmospheric CO2 is found to contribute 20% to the precipitation reduction through the physiological forcing of stomatal closure, with 80% of the reduction being seen when stomatal closure was excluded and only radiative forcing by CO2 was included. The forest dieback exerts two positive feedbacks on the precipitation reduction; a biogeophysical feedback through reduced forest cover suppressing local evaporative water recycling, and a biogeochemical feedback through the release of CO2 contributing to an accelerated global warming. The precipitation reduction is enhanced by 20% by the biogeophysical feedback, and 5% by the carbon cycle feedback from the forest dieback. This analysis helps to explain why the Amazonian precipitation reduction simulated by HadCM3LC is more extreme than that simulated in other GCMs; in the fully-coupled, climate-carbon cycle simulation, approximately half of the precipitation reduction in Amazonia is attributable to a combination of physiological forcing and biogeophysical and global carbon cycle feedbacks, which are generally not included in other GCM simulations of future climate change. The analysis also demonstrates the potential contribution of regional-scale climate and ecosystem change to uncertainties in global CO2 and climate change projections. Moreover, the importance of feedbacks suggests that a human-induced increase in forest vulnerability to climate change may have implications for regional and global scale climate sensitivity.  相似文献   

10.
A two-dimensional model of global atmospheric transport is used to relate estimated air-to-surface exchanges of carbon dioxide (CO2) to spatial and temporal variations of atmospheric CO2 concentrations and isotopic composition. The atmospheric model coupled with models of the biosphere and mixed layer of the ocean describes the gross features of the global carbon cycle. In particular this paper considers the change in isotopic composition due to interreservoir exchanges and thus the potential application and measurement requirements of new isotopic observational programs.A comparison is made between the model-generated CO2 concentration variation and those observed on secular, interannual and seasonal time scales and spatially through the depth of the troposphere and meridionally from pole-to-pole.The relationship between isotopic and concentration variation on a seasonal time-scale is discussed and it is shown how this can be used to quantitatively estimate relative contributions of biospheric and oceanic CO2 exchange. Further, it is shown that the interhemispheric gradient of concentration and isotopic ratio results primarily from the redistribution of fossil fuel CO2. Both isotopic and concentration data indicate that tropical deforestation contributes less than 2 Gt yr-1 of carbon to the atmosphere.The study suggests that changes in the rate of change of the ratio of 13C to 12C in the atmosphere of less than 0.03 yr-1 might be expected if net exchanges with the biosphere are the cause of interannual variations of CO2 concentrations.  相似文献   

11.
The notion is pervasive in the climate science community and in the public at large that the climate impacts of fossil fuel CO2 release will only persist for a few centuries. This conclusion has no basis in theory or models of the atmosphere/ocean carbon cycle, which we review here. The largest fraction of the CO2 recovery will take place on time scales of centuries, as CO2 invades the ocean, but a significant fraction of the fossil fuel CO2, ranging in published models in the literature from 20–60%, remains airborne for a thousand years or longer. Ultimate recovery takes place on time scales of hundreds of thousands of years, a geologic longevity typically associated in public perceptions with nuclear waste. The glacial/interglacial climate cycles demonstrate that ice sheets and sea level respond dramatically to millennial-timescale changes in climate forcing. There are also potential positive feedbacks in the carbon cycle, including methane hydrates in the ocean, and peat frozen in permafrost, that are most sensitive to the long tail of the fossil fuel CO2 in the atmosphere.  相似文献   

12.
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   

13.
A new Earth system model, GENIE-1, is presented which comprises a 3-D frictional geostrophic ocean, phosphate-restoring marine biogeochemistry, dynamic and thermodynamic sea-ice, land surface physics and carbon cycling, and a seasonal 2-D energy-moisture balance atmosphere. Three sets of model climate parameters are used to explore the robustness of the results and for traceability to earlier work. The model versions have climate sensitivity of 2.8–3.3°C and predict atmospheric CO2 close to present observations. Six idealized total fossil fuel CO2 emissions scenarios are used to explore a range of 1,100–15,000 GtC total emissions and the effect of rate of emissions. Atmospheric CO2 approaches equilibrium in year 3000 at 420–5,660 ppmv, giving 1.5–12.5°C global warming. The ocean is a robust carbon sink of up to 6.5 GtC year−1. Under ‘business as usual’, the land becomes a carbon source around year 2100 which peaks at up to 2.5 GtC year−1. Soil carbon is lost globally, boreal vegetation generally increases, whilst under extreme forcing, dieback of some tropical and sub-tropical vegetation occurs. Average ocean surface pH drops by up to 1.15 units. A Greenland ice sheet melt threshold of 2.6°C local warming is only briefly exceeded if total emissions are limited to 1,100 GtC, whilst 15,000 GtC emissions cause complete Greenland melt by year 3000, contributing 7 m to sea level rise. Total sea-level rise, including thermal expansion, is 0.4–10 m in year 3000 and ongoing. The Atlantic meridional overturning circulation shuts down in two out of three model versions, but only under extreme emissions including exotic fossil fuel resources.  相似文献   

14.
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   

15.
The sensitivity of the last glacial-inception (around 115 kyr BP, 115,000 years before present) to different feedback mechanisms has been analysed by using the Earth system model of intermediate complexity CLIMBER-2. CLIMBER-2 includes dynamic modules of the atmosphere, ocean, terrestrial biosphere and inland ice, the last of which was added recently by utilising the three-dimensonal polythermal ice-sheet model SICOPOLIS. We performed a set of transient experiments starting at the middle of the Eemiam interglacial and ran the model for 26,000 years with time-dependent orbital forcing and observed changes in atmospheric CO2 concentration (CO2 forcing). The role of vegetation and ocean feedback, CO2 forcing, mineral dust, thermohaline circulation and orbital insolation were closely investigated. In our model, glacial inception, as a bifurcation in the climate system, appears in nearly all sensitivity runs including a run with constant atmospheric CO2 concentration of 280 ppmv, a typical interglacial value, and simulations with prescribed present-day sea-surface temperatures or vegetation cover—although the rate of the growth of ice-sheets growth is smaller than in the case of the fully interactive model. Only if we run the fully interactive model with constant present-day insolation and apply present-day CO2 forcing does no glacial inception appear at all. This implies that, within our model, the orbital forcing alone is sufficient to trigger the interglacial–glacial transition, while vegetation, ocean and atmospheric CO2 concentration only provide additional, although important, positive feedbacks. In addition, we found that possible reorganisations of the thermohaline circulation influence the distribution of inland ice.  相似文献   

16.
A coupled carbon cycle-climate model is used to compute global atmospheric CO2 and temperature variation that would result from several future CO2 emission scenarios. The model includes temperature and CO2 feedbacks on the terrestrial biosphere, and temperature feedback on the oceanic uptake of CO2. The scenarios used include cases in which fossil fuel CO2 emissions are held constant at the 1986 value or increase by 1% yr–1 until either 2000 or 2020, followed by a gradual transition to a rate of decrease of 1 or 2% yr–1. The climatic effect of increases in non-CO2 trace gases is included, and scenarios are considered in which these gases increase until 2075 or are stabilized once CO2 emission reductions begin. Low and high deforestation scenarios are also considered. In all cases, results are computed for equilibrium climatic sensitivities to CO2 doubling of 2.0 and 4.0 °C.Peak atmospheric CO2 concentrations of 400–500 ppmv and global mean warming after 1980 of 0.6–3.2 °C occur, with maximum rates of global mean warming of 0.2–0.3 °C decade–1. The peak CO2 concentrations in these scenarios are significantly below that commonly regarded as unavoidable; further sensitivity analyses suggest that limiting atmospheric CO2 to as little as 400 ppmv is a credible option.Two factors in the model are important in limiting atmospheric CO2: (1) the airborne fraction falls rapidly once emissions begin to decrease, so that total emissions (fossil fuel + land use-induced) need initially fall to only about half their present value in order to stabilize atmospheric CO2, and (2) changes in rates of deforestation have an immediate and proportional effect on gross emissions from the biosphere, whereas the CO2 sink due to regrowth of forests responds more slowly, so that decreases in the rate of deforestation have a disproportionately large effect on net emission.If fossil fuel emissions were to decrease at 1–2% yr–1 beginning early in the next century, emissions could decrease to the rate of CO2 uptake by the predominantly oceanic sink within 50–100 yrs. Simulation results suggest that if subsequent emission reductions were tied to the rate of CO2 uptake by natural CO2 sinks, these reductions could proceed more slowly than initially while preventing further CO2 increases, since the natural CO2 sink strength decreases on time scales of one to several centuries. The model used here does not account for the possible effect on atmospheric CO2 concentration of possible changes in oceanic circulation. Based on past rates of atmospheric CO2 variation determined from polar ice cores, it appears that the largest plausible perturbation in ocean-air CO2 flux due to changes of oceanic circulation is substantially smaller than the permitted fossil fuel CO2 emissions under the above strategy, so tieing fossil fuel emissions to the total sink strength could provide adequate flexibility for responding to unexpected changes in oceanic CO2 uptake caused by climatic warming-induced changes of oceanic circulation.  相似文献   

17.
Using a coupled climate?Ccarbon cycle model, fossil fuel carbon dioxide (CO2) emissions are derived through a reverse approach of prescribing atmospheric CO2 concentrations according to observations and future projections, respectively. In the second half of the twentieth century, the implied fossil fuel emissions, and also the carbon uptake by land and ocean, are within the range of observational estimates. Larger discrepancies exist in the earlier period (1860?C1960), with small fossil fuel emissions and uncertain emissions from anthropogenic land cover change. In the IPCC SRES A1B scenario, the simulated fossil fuel emissions more than double until 2050 (17 GtC/year) and then decrease to 12 GtC/year by 2100. In addition to A1B, an aggressive mitigation scenario was employed, developed within the European ENSEMBLES project, that peaks at 530 ppm CO2(equiv) around 2050 and then decreases to approach 450 ppm during the twenty-second century. Consistent with the prescribed pathway of atmospheric CO2 in E1, the implied fossil fuel emissions increase from currently 8 GtC/year to about 10 by 2015 and decrease thereafter. In the 2050s (2090s) the emissions decrease to 3.4 (0.5) GtC/year, respectively. As in previous studies, our model simulates a positive climate?Ccarbon cycle feedback which tends to reduce the implied emissions by roughly 1 GtC/year per degree global warming. Further, our results suggest that the 450 ppm stabilization scenario may not be sufficient to fulfill the European Union climate policy goal of limiting the global temperature increase to a maximum of 2°C compared to pre-industrial levels.  相似文献   

18.
The uptake and storage of anthropogenic carbon in the North Atlantic is investigated using different configurations of ocean general circulation/carbon cycle models. We investigate how different representations of the ocean physics in the models, which represent the range of models currently in use, affect the evolution of CO2 uptake in the North Atlantic. The buffer effect of the ocean carbon system would be expected to reduce ocean CO2 uptake as the ocean absorbs increasing amounts of CO2. We find that the strength of the buffer effect is very dependent on the model ocean state, as it affects both the magnitude and timing of the changes in uptake. The timescale over which uptake of CO2 in the North Atlantic drops to below preindustrial levels is particularly sensitive to the ocean state which sets the degree of buffering; it is less sensitive to the choice of atmospheric CO2 forcing scenario. Neglecting physical climate change effects, North Atlantic CO2 uptake drops below preindustrial levels between 50 and 300 years after stabilisation of atmospheric CO2 in different model configurations. Storage of anthropogenic carbon in the North Atlantic varies much less among the different model configurations, as differences in ocean transport of dissolved inorganic carbon and uptake of CO2 compensate each other. This supports the idea that measured inventories of anthropogenic carbon in the real ocean cannot be used to constrain the surface uptake. Including physical climate change effects reduces anthropogenic CO2 uptake and storage in the North Atlantic further, due to the combined effects of surface warming, increased freshwater input, and a slowdown of the meridional overturning circulation. The timescale over which North Atlantic CO2 uptake drops to below preindustrial levels is reduced by about one-third, leading to an estimate of this timescale for the real world of about 50 years after the stabilisation of atmospheric CO2. In the climate change experiment, a shallowing of the mixed layer depths in the North Atlantic results in a significant reduction in primary production, reducing the potential role for biology in drawing down anthropogenic CO2.  相似文献   

19.
Nearly all scenarios for future U.S. energy supply systems show heavy dependence on coal. The magnitude depends on assumptions as to reliance on nuclear fission, degree of electrification, and rate of GNP growth, and ranges from 700 million tons to 2300 million tons per year. However, potential climate change resulting from increasing atmospheric carbon dioxide concentrations may prevent coal from playing a major role. The carbon in the carbon dioxide produced from fossil fuels each year is about 1/10 the net primary production by terrestrial plants, but the fossil fuel production has been growing exponentially at 4.3% per year. Observed atmospheric CO2 concentrations have increased from 315 ppm in 1958 to 330 ppm in 1974 - in 1900, before much fossil fuel was burned, it was about 290–295 ppm. Slightly over one-half the CO2 released from fossil fuels is accounted for by the increase observed in the atmosphere; at present growth rates the quantities are doubling every 15–18 years. Atmospheric models suggest a global warming of about 2 K if the concentration were to rise to two times its pre-1900 value - enough to change the global climate in major (but largely unknown) ways. With the current rate of increase in fossil fuel use, the atmospheric concentration should reach these levels by about 2030. A shift to coal as a replacement for oil and gas gives more carbon dioxide per unit of energy; thus if energy growth continues with a concurrent shift toward coal, high concentrations can be reached somewhat earlier. Even projections with very heavy reliance on non-fossil energy (Neihaus) after 2000 show atmospheric carbon dioxide concentrations reaching 475 ppm.First presented to the symposium, Coal Science and our National Expectations, Annual Meeting of the American Association for the Advancement of Science, Boston, Massachusetts, February 20, 1976.  相似文献   

20.
较全面地介绍了北京气候中心气候系统模式(BCC_CSM)研发所取得的一些进展及其在气候变化研究中的应用,重点介绍了全球近280 km较低分辨率的全球海-陆-气-冰-生物多圈层耦合的气候系统模式BCC_CSM1.1和110 km中等大气分辨率的BCC_CSM1.1(m),以及大气、陆面、海洋、海冰各分量模式的发展。BCC_CSM1.1和BCC_CSM1.1(m)气候系统模式均包含了全球碳循环和动态植被过程。当给定全球人类活动导致的碳源排放后,就可以模拟和预估人类活动对气候变化的影响。BCC_CSM1.1和BCC_CSM1.1(m)已应用于IPCC AR5模式比较,为中外开展气候变化机理分析和未来气候变化预估提供了大量的试验数据。还介绍了BCC_CSM1.1和BCC_CSM1.1(m)参与国际耦合模式比较计划(CMIP5)的大量试验分析评估结果,BCC_CSM能够较好地模拟20世纪气温和降水等气候平均态和季节变化特征,以及近1000年的历史气候变化,所预估的未来100年气候变化与国际上其他模式的CMIP5试验预估结果相当。初步的分析表明,分辨率相对高的BCC_CSM1.1(m)在区域气候平均态的模拟上优于分辨率较低的BCC_CSM1.1。  相似文献   

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