Foliage temperature increases in water hyacinth caused by atmospheric CO2 enrichment

Summary Atmospheric CO₂ enrichment tends to induce partial stomatal closure in most higher plants. This phenomenon reduces per-unit-leaf-area plant transpirational water loss rates, which in turn leads to higher plant temperatures. Working in the field with water hyacinths maintained in open-top, clear-plastic wall, CO₂ -enrichment chambers at Phoenix, Arizona, we have quantified this relationship for a plant species which has been shown previously to react like most land plants in this regard. Our results indicate that in some parts of the world this non-greenhouse mechanism for surface temperature change may play an important role in determining future climate. Under sunlit and well-watered conditions conducive to active growth, for instance, we found water hyacinth foliage temperatures to increase by 2.7 K in response to a 300 to 600 ppm doubling of the atmospheric CO₂ concentration.

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Erhöhungen der Blattemperatur von Wasserhyazinthen durch atmosphärische CO₂-Anreicherung

Zusammenfassung Erhöhter CO₂ -Gehalt neigt dazu, teilweises Schließen der Spaltöffnungen höherer Pflanzen zu verursachen. Das reduziert den Wasserverlust durch Transpiration und führt zu höheren Pflanzentemperaturen. Bei Feldarbeiten an Wasserhyazinthen in oben offenen Klarplastikkammern mit CO₂ -Anreicherung bei Phoenix, Arizona wurde diese Beziehung für eine Pflanzenart quantifiziert, die sich in diesem Zusammenhang den meisten Landpflanzen als ähnlich erwiesen hat. Die Ergebnisse liegen nahe, daß dieser, vom Glashauseffekt unabhängige, Mechanismus der änderung der Oberflächemtemperatur in einigen Teilen der Welt eine bedeutende Rolle bei der Bestimmung des zukünftigen Klimas spielen könnte. Es konnte z.B. unter für das Wachstum günstigen Strahlungs- und Wasserverhältnissen eine Erhöhung der Blattemperatur der Wasserhyazinthen um 2,7 K durch eine Verdoppelung der atmosphärischen CO₂ -Konzentration von 300 auf 600 ppm nachgewiesen werden.

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Contribution from th Agricultural Research Service, U.S. Department of Agriculture.

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With 3 Figures     

大气CO2富集对根际NaCl盐渍的人参果植株干物质生产和水分利用的影响

对单株砂培盆栽的半木质化枝条扦插生根的一月龄人生果（Solanum muricatum Ait.）栽培品种＂Xotus＂,每周浇两次200mL NaCl质量浓度分别为0mg·L-1和25mg·L-1的Hoagland营养液处理2个月,第二个月在控制空气CO2体积分数为（350±10）×10-6、（700±10）×10-6和（1050±10）×10-6的植物生长箱内试验。结果表明,人参果植株干物质生产量和耗水量受根际NaCl盐渍而下降,又随大气CO2升高而增加。根际NaCl盐渍能增大植株叶片蒸腾系数、根/冠比和干物质向枝干和根部分配的比例及积累量,降低根系吸收水分的效率和耗水量。升高大气CO2能促进叶片发育及干物质向地上部其他器官和地下部组织分配,增加总叶面积、比叶干重和各种器官中干物质增长量,提高干物质生产率和水分利用率。根际经25mg·L-1NaCl盐渍处理的植株,总干物质增长量和水分利用率相应下降50%～54%和24%～37%;与350×10-6CO2的处理的植株相比,700×10-6及1050×10-6CO2的处理分别使这两项指标提高到79%～106%和61%～88%以及133%～189%和99%～142%。大气CO2富集能改善受NaCl盐渍的植株干物质生产力、提高水分利用率。根际NaCl盐渍和大气CO2富集对人参果植株干物质生产和水分利用有生物互作效应。它们的共同作用会促进植株干物质的增长及叶片中合成的干物质向其他器官分配,提高干物质生产率和水分利用率,同时减少总叶面积、枝条和根系干重、根系吸水效率、植株耗水量和叶片蒸腾系数。因此,全球大气CO2富集将有利于该作物的干物质生产和水分利用。     

Regional hydrologic consequences of increases in atmospheric CO2 and other trace gases

Concern over changes in global climate caused by growing atmospheric concentrations of carbon dioxide and other trace gases has increased in recent years as our understanding of atmospheric dynamics and global climate systems has improved. Yet despite a growing understanding of climatic processes, many of the effects of human-induced climatic changes are still poorly understood. Major alterations in regional hydrologic cycles and subsequent changes in regional water availability may be the most important effects of such climatic changes. Unfortunately, these are among the least well-understood impact. Water-balance modeling techniques - modified for assessing climatic impacts - were developed and tested for a major watershed in northern California using climate-change scenarios from both state-of-the-art general circulation models and from a series of hypothetical scenarios. Results of this research suggest strongly that plausible changes in temperature and precipitation caused by increases in atmospheric trace-gas concentrations could have major impacts on both the timing and magnitude of runoff and soil moisture in important agricultural areas. Of particular importance are predicted patterns of summer soil-moisture drying that are consistent across the entire range of tested scenarios. The decreases in summer soil moisture range from 8 to 44%. In addition, consistent changes were observed in the timing of runoff-specifically dramatic increases in winter runoff and decreases in summer runoff. These hydrologic results raise the possibility of major environmental and socioeconomic difficulties and they will have significant implications for future water-resource planning and management.     

Managing atmospheric CO2

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.     

二维能量平衡模式中大气温度对二氧化碳增温效应的响应

利用一个考虑了辐射能传输的二维能量平衡气候模式,解析地分析了二氧化碳浓度改变后冰界纬度的变化,得到了冰界纬度随CO2浓度变化的关系以及全球平均温度的变化曲线.结果表明,当CO2浓度由工业革命前的280×10-6增加到700×10-6时,冰界仅后退(北半球向北)几个纬度;当CO2的浓度继续增加时,冰界纬度会加速向极地退缩,直至出现全球无极冰覆盖的现象.同样地,当CO2浓度由280×10-6增加到700×10-6时,全球地表平均温度虽然在增加,但增加的速率很小,并且增加的速率在减小,而当大于700×10-6之后,温度增加的速率会快速增大,温度将加速上升.对不同反照率进行敏感性试验,发现当反照率从0.1到0.32时,结果并没有显著地改变,即结果对反照率的变化并不敏感.这一计算结果表明,在目前的状态下,由CO2引起的增温作用似乎处于变化很小的准饱和状态,即目前气候不会因为CO2浓度的增加而迅速变暖.较为实际的情形可能是大气温度在缓慢增加到一定程度后才会迅速升高.这并不意味着可以忽视CO2的增温效应,因为根据计算结果,这个临界值大概在700×10-6左右,当CO2浓度增加到超过临界值之后,气温会剧烈上升,气候将会处在一个非常温暖的阶段.     

Siberian CO2 efflux in winter as a CO2 source and cause of seasonality in atmospheric CO2

Over three years, we found a consistent CO₂ efflux from forest tundra of the Russian North throughout the year, including a large (89 g C m^–2 yr^–1) efflux during winter. Our results provide one explanation for the observations that the highest atmospheric CO₂ concentration and greatest seasonal amplitude occur at high latitudes rather than over the mid-latitudes, where fossil fuel sources are large, and where high summer productivity offset by winter respiration should give large seasonal oscillations in atmospheric CO₂. Winter respiration probably contributed substantially to the boreal winter CO₂ efflux. Respiration is an exothermic process that produces enough heat to warm soils and promote further decomposition. We suggest that, as a result of this positive feedback, small changes in surface heat flux, associated with human activities in the North or with regional or global warming, could release large quantities of organic carbon that are presently stored in permafrost.     

Interannual variation of atmospheric CO2 concentration

A method is described for the analysis of the interannual variability of background atmospheric carbon dioxide concentration. The analysis is carried out on the data from 6 observatories for which records of >8 years were available.A global-scale interannual variation of CO₂ concentration in the troposphere with a characteristic time-scale of 2–3 years has been confirmed throughout the period of the records. These variations are estimated to be associated with carbon cycle imbalances of 2–3 Gt or annual net exchanges between the atmosphere and another carbon reservoir(s) at a rate of about 1.2 Gt of carbon per year. Lag correlations and amplitude comparisons between the records suggests a low latitude southern hemisphere origin to this phenomenon.The interannual variations of CO₂ increase are found to be correlated with those observed in data for Pacific sea surface temperatures and Pacific witd stress, the Southern Oscillation Index and the Quasi-Biennial Oscillation. However multiple regression studies found that once the Southern Oscillation index is used as an explanatory variable for CO₂ variations, the inclusion of additional geophysical variables does not give any significant improvement in the regression.     

Equilibrium and transient climatic warming induced by increased atmospheric CO2

The change in the Earth's equilibrium global mean surface temperature induced by a doubling of the CO₂ concentration has been estimated as 0.2 to 10 K by surface energy balance models, 0.5 to 4.2 K by radiative-convective models, and 1.3 to 4.2 K by general circulation models. These wide ranges are interpreted and quantified here in terms of the direct radiative, forcing of the increased CO₂, the response of the climate system in the absence of feedback processes, and the feedbacks of the climate system. It is the range in the values of these feedbacks that leads to the ranges in the projections of the global mean surface warming. The time required for a CO₂-induced climate change to reach equilibrium has been characterized by an e-folding time _e with values estimated by a variety of climate/ocean models as 10 to 100 years. Analytical and numerical studies show that this wide range is due to the strong dependence of _e on the equilibrium sensitivity of the climate model and on the effective vertical thermal diffusivity of the ocean model. A coupled atmosphere-ocean general circulation model simulation for doubled CO₂ suggestes that, as a result of the transport of the CO₂-induced surface heating into the interior of the ocean, _e 50 to 100 years. Theoretical studies for a realistic CO₂ increase between 1850 and 1980 indicate that this sequestering of heat into the ocean's interior is responsible for the concomittant warming being only about half that which would have occurred in the absence of the ocean. These studies also indicate that the climate sytem will continue to warm towards its as yet unrealized equilibrium temperature change, even if there is no further increase in the CO₂ concentration.     

景德镇地区大气CO2浓度变化特征

利用景德镇温室气体监测站CO_2观测数据,分析了景德镇地区2017年12月—2018年11月大气CO_2浓度变化特征,同时对其浓度进行了筛分,以剔除污染数据,使其更具区域代表性。研究表明:景德镇地区大气CO_2浓度昼降夜升,早上最高,傍晚最低;春季最高,秋季最低;春、夏季NNE、NE、ENE风向,秋季NE、ENE风向以及冬季W、WSW、SW、SSW、S风向上CO_2浓度较高。同时,春、夏和秋季大气CO_2浓度大致随风速的增加而不断降低,冬季风速对大气CO_2浓度无明显影响。筛分后数据显示景德镇地区年均大气CO_2浓度为422.1×10~(-6),浓度日均值年振幅73.96×10~(-6),夏半年CO_2浓度低于冬半年。     

Constraints on the temperature sensitivity of global soil respiration from the observed interannual variability in atmospheric CO2

Carbon cycle feedbacks have been shown to be very important in predicting climate change over the next century. The response of the terrestrial carbon cycle to climate change depends on the competition between increased respiration due to warmer temperatures and increased uptake due to elevated CO₂levels. Whether the terrestrial carbon cycle remains a sink for anthropogenic carbon, or switches to become a source, depends particularly on the response of soil respiration to temperature. Here we use observed global atmospheric CO₂concentration to constrain the behaviour of soil respiration in a coupled climate–carbon cycle GCM.     

Effects of high CO2 levels on surface temperature and atmospheric oxidation state of the early Earth

One-dimensional radiative-convective and photochemical models are used to examine the effects of enhanced CO₂ concentrations on the surface temperature of the early Earth and the composition of the prebiotic atmosphere. Carbon dioxide concentrations of the order of 100–1000 times the present level are required to compensate for an expected solar luminosity decrease of 25–30%, if CO₂ and H₂O were the only greenhouse gases present. The primitive stratosphere was cold and dry, with a maximum H₂O volume mixing ratio of 10^–6. The atmospheric oxidation state was controlled by the balance between volcanic emission of reduced gases, photo-stimulated oxidation of dissolved Fe⁺² in the oceans, escape of hydrogen to space, and rainout of H₂O₂ and H₂CO. At high CO₂ levels, production of hydrogen owing to rainout of H₂O₂ would have kept the H₂ mixing ratio above 2×10^–4 and the ground-level O₂ mixing ratio below 10^–11, even if no other sources of hydrogen were present. Increased solar UV fluxes could have led to small changes in the ground-level mixing ratios of both O₂ and H₂.     

A robust sequential CO2 emissions strategy based on optimal control of atmospheric CO2 concentrations

This paper formally introduces the concept of mitigation as a stochastic control problem. This is illustrated by applying a digital state variable feedback control approach known as Non-Minimum State Space (NMSS) control to the problem of specifying carbon emissions to control atmospheric CO₂ concentrations in the presence of uncertainty. It is shown that the control approach naturally lends itself to integrating both anticipatory and reflexive mitigation strategies within a single unified framework. The framework explicitly considers the closed-loop nature of climate mitigation, and employs a policy orientated optimisation procedure to specify the properties of this closed-loop system. The product of this exercise is a control law that is suitably conditioned to regulate atmospheric CO₂ concentrations through assimilating online information within a 25-year review cycle framework. It is shown that the optimal control law is also robust when faced with significant levels of uncertainty about the functioning of the global carbon cycle.     

Effect of ocean thermal diffusivity on global warming induced by increasing atmospheric CO2

A global mean ocean model including atmospheric heating, heat capacity of the mixed layer ocean, and vertical thermal diffusivity in the lower ocean, proposed by Cess and Goldenberg (1981), is used in this paper to study the sen-sitivity of global warming to the vertical diffusivity. The results suggest that the behaviour of upper ocean tempera-ture is mainly determined by the magnitude of upper layer diffusivity and an ocean with a larger diffusivity leads to a less increase of sea surface temperature and a longer time delay for the global warming induced by increasing CO2 than that with smaller one. The global warming relative to four scenarios of CO2 emission assumed by Intergovernmental Panel of Climate Change (IPCC) is also estimated by using the model with two kinds of thermal diffusivities. The result shows that for various combinations of the CO2 emission scenarios and the diffusivities, the oceanic time delay to the global warming varies from 15 years to 70 years.     

大气CO2富集对根际NaCl盐渍的人参果植株干物质生产和水分利用的影响

对单株砂培盆栽的半木质化枝条扦插生根的一月龄人生果(Solanum muricatum Ait.)栽培品种"Xotus",每周浇两次200mL NaCl质量浓度分别为0mg·L^-1和25mg·L^-1的Hoagland营养液处理2个月,第二个月在控制空气CO₂体积分数为(350±10)×10^-6、(700±10)×10^-6和(1050±10)×10^-6的植物生长箱内试验。结果表明,人参果植株干物质生产量和耗水量受根际NaCl盐渍而下降,又随大气CO₂升高而增加。根际NaCl盐渍能增大植株叶片蒸腾系数、根/冠比和干物质向枝干和根部分配的比例及积累量,降低根系吸收水分的效率和耗水量。升高大气CO₂能促进叶片发育及干物质向地上部其他器官和地下部组织分配,增加总叶面积、比叶干重和各种器官中干物质增长量,提高干物质生产率和水分利用率。根际经25mg·L^-1NaCl盐渍处理的植株,总干物质增长量和水分利用率相应下降50%～54%和24%～37%;与350×10^-6CO₂的处理的植株相比,700×10^-6及1050×10^-6CO₂的处理分别使这两项指标提高到79%～106%和61%～88%以及133%～189%和99%～142%。大气CO₂富集能改善受NaCl盐渍的植株干物质生产力、提高水分利用率。根际NaCl盐渍和大气CO₂富集对人参果植株干物质生产和水分利用有生物互作效应。它们的共同作用会促进植株干物质的增长及叶片中合成的干物质向其他器官分配,提高干物质生产率和水分利用率,同时减少总叶面积、枝条和根系干重、根系吸水效率、植株耗水量和叶片蒸腾系数。因此,全球大气CO₂富集将有利于该作物的干物质生产和水分利用。     

Implications of atmospheric CO2 enrichment and climatic change for the geographical distribution of two introduced vines in the U.S.A.

The continuing increase in the atmospheric carbon dioxide concentration resulting from fossil fuel combustion and deforestation may change the ecological impact and geographical distribution of kudzu (Pueraria lobata Ohwi) and Japanese honeysuckle (Lonicera japonica Thunb.) in the U.S.A. Both vines were introduced about a century ago from Japan and have become naturalized weeds. Westward range expansion is currently limited by drought during seedling establishment, while northward range expansion is limited by low temperature sensitivity of overwintering stems.Direct effects of CO₂ enrichment on growth were assessed by growing the plants in controlled environment chambers at 350, 675, or 1000 l/L CO₂. In both species, CO₂ enrichment increased instantaneous water use efficiency by increasing photosynthetic rates and reducing transpiration rates. During a drought stress, CO₂ enrichment delayed significant decline in total water potential of kudzu by several days. When grown in a cool temperature regime of 18/12 °C day/night, the CO₂ enrichment significantly increased leaf area and total biomass of both species and plants were taller and had more branches. These results suggested that atmospheric CO₂ enrichment may allow westward and northward spread of both species in the U.S.A.Indirect effects of CO₂ induced climate change (Greenhouse Effect) on the vines' distribution were assessed. Predictions based on current models of climatic response were used to project changes in winter temperatures at doubled CO₂ concentrations. Increases in average and minimum winter temperatures by 3 °C could allow northward spread of both species by several hundred kilometers. Projected decreases in summer precipitation may minimize westward spread, despite improved water use efficiency and increased drought tolerance.This study was supported by NSF Grant No. BSR82-15533 and Contract No. DEAS05-83ER06177 from the Carbon Dioxide Research Office, Dept. of Energy to B. R. Strain and NSF Grant No. BSR83-14925 for the Duke University Phytotron.     

One-year temperature records in the atmospheric surface layer above sea ice and open water

Temperature observations of three buoys drifting in the Weddell Sea for one year and covering the ice-water-ice cycle from July 1986 to July 1987 are presented. Significant differences between winter and summer are shown to be a consequence of the air-sea heat exchange being drastically modified by the sea ice cover. Over ice, prevailing variance is in the synoptic scale (periods 3 to 5 days) with amplitudes of 25 °C, whereas over water, the diurnal wave dominates with amplitudes of less than 1 °C.     

Summer dryness due to an increase of atmospheric CO2 concentration

To investigate the hydrologic changes of climate in response to an increase of CO₂-concentration in the atmosphere, the results from numerical experiments with three climate models are analyzed and compared with each other. All three models consist of an atmospheric general circulation model and a simple mixed layer ocean with a horizontally uniform heat capacity. The first model has a limited computational domain and simple geography with a flat land surface. The second model has a global computational domain with realistic geography. The third model is identical to the second model except that it has a higher computational resolution. In each numerical experiment, the CO₂-induced change of climate is evaluated based upon a comparison between the two climates of a model with normal and four times the normal concentration of carbon dioxide in air. It is noted that the zonal mean value of soil moisture in summer reduces significantly in two separate zones of middle and high latitudes in response to the increase of the CO₂-concentration in air. This CO₂-induced summer dryness results not only from the earlier ending of the snowmelt season, but also from the earlier occurrence of the spring to summer reduction in rainfall rate. The former effect is particularly important in high latitudes, whereas the latter effect becomes important in middle latitudes. Other statistically significant changes include large increases in both soil moisture and runoff rate in high latitudes of a model during most of the annual cycle with the exception of the summer season. The penetration of moisture-rich, warm air into high latitudes is responsible for these increases.