Surface air temperature response to increasing global industrial productivity: A beneficial greenhouse effect?

Summary Comparisons of trends of global industrial productivity, Northern Hemispheric and United States annual mean temperatures, U.S. annual and summer mean maximum and mean minimum temperatures, and U.S. cloud cover suggest that the net result of the CO₂/trace gas greenhouse effect and certain biologically-modulated negative feedbacks related to cloud characteristics may be a moderate increase in nighttime minimum temperatures with no change in daytime maximum values. Such a response, if verified by further studies, would likely be desirable, for it would reduce low temperature stresses on biological and mechanical systems, significantly amplify many of the positive botanical effects of atmospheric CO₂ enrichment, and produce few, if any, deleterious climatic effects. In a word, it may well be beneficial.With 4 Figures     

Vulnerability and adaptation assessments of agriculturalcrops under climate change in the Southeastern USA

Summary  It is expected that a change in climatic conditions due to global warming will directly impact agricultural production. Most climate change studies have been applied at very large scales, in which regions were represented by only one or two weather stations, which were mainly located at airports of major cities. The objective of this study was to determine the potential impact of climate change at a local level, taking into account weather data recorded at remote locations. Daily weather data for a 30-year period were obtained for more than 500 sites, representing the southeastern region of the USA. Climate change scenarios, using transient and equilibrium global circulation models (GCM), were defined, created and applied to the daily historical weather data. The modified temperature, precipitation and solar radiation databases corresponding to each of the climate change scenarios were used to run the CERES v.3.5 simulation model for maize and winter wheat and the CROPGRO v.3.5 model for soybean and peanut. The GCM scenarios projected a shorter duration of the crop-growing season. Under the current level of CO₂, the GCM scenarios projected a decrease of crop yields in the 2020s. When the direct effects of CO₂ were assumed in the study, the scenarios resulted in an increase in soybean and peanut yield. Under equilibrium , the GCM climate change scenarios projected a decrease of maize and winter wheat yield. The indirect effects of climate change also tended to decrease soybean and peanut yield. However, when the direct effects of CO₂ were included, most of the scenarios resulted in an increase in legume yields. Possible changes in sowing data, hybrids and cultivar selection, and fertilization were considered as adaptation options to mitigate the potential negative impact of potential warming. Received July 20, 1999/Revised April 18, 2000     

Effects of temperature rise and increase in CO2 concentration on simulated wheat yields in Europe

A crop-growth-simulation model based on SUCROS87 was used to study effects of temperature rise and increase of atmospheric CO₂ concentration on wheat yields in several regions in Europe. The model simulated potential and water-limited crop production (growth with ample supply of nutrients and in the absence of damage by pests, diseases and weeds). Historic daily weather data from 13 sites in Western Europe were used as starting point.For potential production (optimal water) a 3 °C temperature rise led to a yield decline due to a shortening of the growing period on all locations. Doubling of the CO₂ concentration caused an increase in yield of 40% due to higher assimilation rates. It was found that effects of higher temperature and higher CO₂ concentration were nearly additive and the combination of both led to a yield increase of 1–2 ton ha^-1. A very small CO₂-temperature interaction was found: the effect of doubled CO₂ concentration on crop yield was larger at higher temperatures. The inter-annual yield variability was hardly affected.When water was limiting crop-production effects of temperature rise and higher CO₂ levels were different than for the potential production. Rise in temperature led to a smaller yield reduction, doubled CO₂ concentration to a larger yield increase and combination of both led to a large yield increase (3 ton ha^-1) in comparison with yields simulated for the present situation. Both rise in temperature and increase in the CO₂ concentration reduced water requirements of the crop. Water shortages became smaller, leading to a reduction in inter-annual variability. It is concluded that when no major changes in precipitation pattern occur a climate change will not affect wheat yields since negative effects of higher temperatures are compensated by positive effects of CO₂ enrichment.     

Declining Temporal Effectiveness of Carbon Sequestration: Implications for Compliance with the United National Framework Convention on Climate Change

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.     

How is CO2 affecting yields and technological progress? A statistical analysis

This paper analyzes the impact of climate, crop production technology, and atmospheric carbon dioxide (CO₂) on current and future crop yields. The analysis of crop yields endeavors to advance the literature by estimating the effect of atmospheric CO₂ on observed crop yields. This is done using an econometric model estimated over pooled historical data for 1950–2009 and data from the free air CO₂ enrichment experiments. The main econometric findings are: 1) Yields of C3 crops (soybeans, cotton, and wheat) directly respond to the elevated CO₂, while yields of C4 crops (corn and sorghum) do not, but they are found to indirectly benefit from elevated CO₂ in times and places of drought stress; 2) The effect of technological progress on mean yields is non-linear; 3) Ignoring atmospheric CO₂ in an econometric model of crop yield likely leads to overestimates of the pure effects of technological progress on crop yields of about 51, 15, 17, 9, and 1 % of observed yield gain for cotton, soybeans, wheat, corn and sorghum, respectively; 4) Average climate conditions and climate variability contribute in a statistically significant way to average crop yields and their variability; and 5) The effect of CO₂ fertilization generally outweighs the effect of climate change on mean crop yields in many regions resulting in an increase of 7–22, 4–47, 5–26, 65–96, and 3–35 % for yields of corn, sorghum, soybeans, cotton, and wheat, respectively.     

Carbon dioxide sequestration: how much and when?

Carbon dioxide (CO₂) sequestration has been proposed as a key component in technological portfolios for managing anthropogenic climate change, since it may provide a faster and cheaper route to significant reductions in atmospheric CO₂ concentrations than abating CO₂ production. However, CO₂ sequestration is not a perfect substitute for CO₂ abatement because CO₂ may leak back into the atmosphere (thus imposing future climate change impacts) and because CO₂ sequestration requires energy (thus producing more CO₂ and depleting fossil fuel resources earlier). Here we use analytical and numerical models to assess the economic efficiency of CO₂ sequestration and analyze the optimal timing and extent of CO₂ sequestration. The economic efficiency factor of CO₂ sequestration can be expressed as the ratio of the marginal net benefits of sequestering CO₂ and avoiding CO₂ emissions. We derive an analytical solution for this efficiency factor for a simplified case in which we account for CO₂ leakage, discounting, the additional fossil fuel requirement of CO₂ sequestration, and the growth rate of carbon taxes. In this analytical model, the economic efficiency of CO₂ sequestration decreases as the CO₂ tax growth rate, leakage rates and energy requirements for CO₂ sequestration increase. Increasing discount rates increases the economic efficiency factor. In this simple model, short-term sequestration methods, such as afforestation, can even have negative economic efficiencies. We use a more realistic integrated-assessment model to additionally account for potentially important effects such as learning-by-doing and socio-economic inertia on optimal strategies. We measure the economic efficiency of CO₂ sequestration by the ratio of the marginal costs of CO₂ sequestration and CO₂ abatement along optimal trajectories. We show that the positive impacts of investments in CO₂ sequestration through the reduction of future marginal CO₂ sequestration costs and the alleviation of future inertia constraints can initially exceed the marginal sequestration costs. As a result, the economic efficiencies of CO₂ sequestration can exceed 100% and an optimal strategy will subsidize CO₂ sequestration that is initially more expensive than CO₂ abatement. The potential economic value of a feasible and acceptable CO₂ sequestration technology is equivalent – in the adopted utilitarian model – to a one-time investment of several percent of present gross world product. It is optimal in the chosen economic framework to sequester substantial CO₂ quantities into reservoirs with small or zero leakage, given published estimates of marginal costs and climate change impacts. The optimal CO₂ trajectories in the case of sequestration from air can approach the pre-industrial level, constituting geoengineering. Our analysis is silent on important questions (e.g., the effects of model and parametric uncertainty, the potential learning about these uncertainties, or ethical dimension of such geoengineering strategies), which need to be addressed before our findings can be translated into policy-relevant recommendations.     

Estimates of CO2 from wood fuel based on forest harvest data

Wood continues to be a major fuel source for vast numbers of the world's people. Even in the highly industrialized countries, use of wood and wood wastes as fuel produces a small (in comparison to fossil fuels) but non-negligible amount of CO₂. Although information on the worldwide harvest and use of wood is not as complete or as reliable as fossil fuel data, this paper uses what is available and develops annual estimates of CO₂ emissions for the period 1968–1983. Woods are separated into two types, coniferous and non-coniferous, and average content and carbon amounts are estimated for each type. Wood utilization is divided into several categories, e.g., fuelwood, lumber, poles, and use of wood wastes as fuels in the lumber and paper industries is included. Results are given for major world regions. In recent years the worldwide CO₂ emissions from wood used as fuels is estimated to be about one-tenth as much as CO₂ emissions from fossil fuels. This does not include fires in the forests, either associated with forest clearing or those from natural causes.     

Carbon Capture and Storage From Fossil Fuels and Biomass – Costs and Potential Role in Stabilizing the Atmosphere

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.     

全球农作物对大气CO2及其倍增的吸收量估算

根据农作物产量资料（ＦＡＯ１９９２年），计算出中国和全球各种作物对ＣＯ２的吸收总量分别为５．５×１０８ｔ／ａＣ和２８．９×１０８ｔ／ａＣ。同时以不同ＣＯ２浓度下小麦、玉米、大豆等全生育期光合速率实验数据直接计算的Ｃ吸收量为对照，与相应的中国产量资料计算结果比较，两者相差２．６％。从而进一步依据作物对ＣＯ２倍增反应诊断实验结果，推算出大气ＣＯ２浓度比目前倍增（７００ｐｐｍ）条件下，中国和全球农作物吸收ＣＯ２总量将增长２１％－２６％，分别为６．６×１０８ｔ／ａ—６．９×１０８ｔ／ａ和３４．１×１０８ｔ／ａ—３６．２×１０８ｔ／ａＣ。研究还表明，单位面积作物年吸Ｃ量全球（３．２ｔ／（ｈｍ２·８））比中国（４．２ｔ／（ｈｍ２·ａ））低２５．４％，而且Ｃ４作物普遍高于同类Ｃ３作物。     

Historical and future anthropogenic emission pathways derived from coupled climate�Ccarbon cycle simulations

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.     

Probabilistic simulations of the impact of increasing leaf-level atmospheric carbon dioxide on the global land surface

Using a climate model with a sophisticated land surface scheme, simulations were conducted to explore the impact of increases in leaf-level carbon dioxide (CO₂) on evaporation, temperature and other land surface quantities. Fifty-one realizations were run, for each of four Januarys and four Julys for CO₂ concentrations at leaf-level of 280, 375, 500, 650, 840 and 1,000 ppmv. Atmospheric CO₂ concentration was held constant at 375 ppmv in all experiments. Statistically significant decreases in evaporation and increases in temperature occur in specific regions as leaf-level CO₂ is increased from 280 to 375 ppmv. These same areas expand geographically, and the magnitude of the changes increase as leaf-level CO₂ is increased further suggesting that changes are caused by the increase in leaf-level CO₂ and are not internal model variability. As leaf-level CO₂ is increased further, larger areas of the continental surface are affected by increasing amounts and a statistically significant change in precipitation is seen. The increase in leaf-level CO₂ from 280 ppmv to 375 ppmv causes statistically significant changes in the evaporation over 12% of continental surfaces in July. This increases to 25% at 500 ppmv, 35% at 650 ppmv, 41% at 840 ppmv and 47% at 1,000 ppmv. This affects temperature and rainfall by similar amounts, generally in coincident regions. An analysis of these results over key regions shows that the probability density functions of the latent heat flux and temperature are affected non-uniformly. There is a shift in the latent heat flux probability density function to lower values, mainly through the reduction in the upper tail of the distribution. The temperature probability density function shifts to higher values, mainly through an increase in the upper tail of the distribution indicating that the impact is focussed on extremes. Given that there are a suite of well evaluated land surface models that include the biogeochemical effects of increasing CO₂ we suggest that the inclusion of such a model should be a recommended component of climate models used in future assessment reports by the Intergovernmental Panel on Climate Change.     

The millennial atmospheric lifetime of anthropogenic CO<Subscript>2</Subscript>

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.     

Climate change impacts on dryland cropping systems in the Central Great Plains,USA

Agricultural systems models are essential tools to assess potential climate change (CC) impacts on crop production and help guide policy decisions. In this study, impacts of projected CC on dryland crop rotations of wheat-fallow (WF), wheat-corn-fallow (WCF), and wheat-corn-millet (WCM) in the U.S. Central Great Plains (Akron, Colorado) were simulated using the CERES V4.0 crop modules in RZWQM2. The CC scenarios for CO₂, temperature and precipitation were based on a synthesis of Intergovernmental Panel on Climate Change (IPCC 2007) projections for Colorado. The CC for years 2025, 2050, 2075, and 2100 (CC projection years) were super-imposed on measured baseline climate data for 15–17 years collected during the long-term WF and WCF (1992–2008), and WCM (1994–2008) experiments at the location to provide inter-annual variability. For all the CC projection years, a decline in simulated wheat yield and an increase in actual transpiration were observed, but compared to the baseline these changes were not significant (p > 0.05) in all cases but one. However, corn and proso millet yields in all rotations and projection years declined significantly (p < 0.05), which resulted in decreased transpiration. Overall, the projected negative effects of rising temperatures on crop production dominated over any positive impacts of atmospheric CO₂ increases in these dryland cropping systems. Simulated adaptation via changes in planting dates did not mitigate the yield losses of the crops significantly. However, the no-tillage maintained higher wheat yields than the conventional tillage in the WF rotation to year 2075. Possible effects of historical CO₂ increases during the past century (from 300 to 380 ppm) on crop yields were also simulated using 96 years of measured climate data (1912–2008) at the location. On average the CO₂ increase enhanced wheat yields by about 30%, and millet yields by about 17%, with no significant changes in corn yields.     

CO2浓度倍增对中国主要作物影响的试验研究

根据自行设计的ＯＴＣ－１型开顶式气室及连续３年试验资料，在评述该套设备性能的基础上，分析了ＣＯ２浓度倍增对４种作物生长发育和产量的影响。结果表明：ＣＯ２浓度倍增，作物发育进程加快，株高增加，经济产量和生物产量增长明显，且Ｃ３作物的增长幅度大于Ｃ４作物；冬小麦、棉花品质呈良性变化，玉米品质可能有所下降，大豆品质变化不明显。上述初步结果尚待进一步研究     

The carbon dioxide/climate controversy: Some personal comments on two recent publications

The pervasive opinion on the relationship between the state of the climate and the increasing concentration of CO₂ is that a general global warming will occur with social, economical and environmental corollaries that may be adverse. However, there exist a number of dissenting arguments that call for a much smaller increase in global temperature or even an induced global cooling. Furthermore, the positive biological effects of a greater atmospheric CO₂ loading are emphasized.The difference of opinion is highlighted in two recent publications: CO ₂, Friend or Foe by Sherwood Idso and Carbon Dioxide: A Second Assessment by the National Academy of Science CO₂/Climate Review Committee. Using the two publications as focal points, some personal remarks are made regarding the controversy and the relative merits of the scientific arguments.     

Climate Change Impacts and Adaptation Strategies in Spring Barley Production in the Czech Republic

The crop model CERES-Barley was used to assess the impacts of increased concentration of atmospheric CO₂ on growth and development of the most important spring cereal in Central and Western Europe, i.e., spring barley, and to examine possible adaptation strategies. Three experimental regions were selected to compare the climate change impacts in various climatic and pedological conditions. The analysis was based on multi-year crop model simulations run with daily weather series obtained by stochastic weather generator and included two yield levels: stressed yields and potential yields. Four climate change scenarios based on global climate models and representing 2 × CO₂ climate were applied. Results: (i) The crop model is suitable for use in the given environment, e.g., the coefficient of determination between the simulated and experimental yields equals 0.88. (ii) The indirect effect related to changed weather conditions is mostly negative. Its magnitude ranges from ?19% to +5% for the four scenarios applied at the three regions. (iii) The magnitude of the direct effect of doubled CO₂ on the stressed yields for the three test sites is 35–55% in the present climate and 25–65% in the 2 × CO₂ climates. (iv) The stressed yields would increase in 2 × CO₂ conditions by 13–52% when both direct and indirect effects were considered. (v) The impacts of doubled CO₂ on potential yields are more uniform throughout the localities in comparison with the stressed yields. The magnitude of the indirect and direct effects ranges from ?1 to ?9% and from +31 to +33%, respectively. Superposition of both effects results in 19–30% increase of the potential yields. (vi) Application of the earlier planting date (up to 60 days) would result in 15–22% increase of the yields in 2 × CO₂ conditions. (vii) Use of a cultivar with longer vegetation duration would bring 1.5% yield increase per one extra day of the vegetation season. (viii) The initial water content in the soil water profile proved to be one of the key elements determining the spring barley yield. It causes the yields to increase by 54–101 kg.ha^?1 per 1% increase of the available soil water content on the sowing day.     

Changes in Soybean Yields in the Midwestern United States as a Result of Future Changes in Climate, Climate Variability, and CO2 Fertilization

This modeling study addresses the potential impacts of climate change and changing climate variability due to increased atmospheric CO₂ concentration on soybean (Glycine max (L.) Merrill) yields in theMidwestern Great Lakes Region. Nine representative farm locations and six future climate scenarios were analyzed using the crop growth model SOYGRO. Under the future climate scenarios earlierplanting dates produced soybean yield increases of up to 120% above current levels in the central and northern areas of the study region. In the southern areas, comparatively small increases (0.1 to 20%) and small decreases (–0.1 to–25%) in yield are found. The decreases in yield occurred under the Hadley Center greenhouse gas run (HadCM2-GHG), representing a greater warming, and the doubled climate variability scenario – a more extreme and variableclimate. Optimum planting dates become later in the southern regions. CO₂fertilization effects (555 ppmv) are found to be significant for soybean, increasing yields around 20% under future climate scenarios.For the study region as a whole the climate changes modeled in this research would have an overall beneficial effect, with mean soybean yield increases of 40% over current levels.     

The promise of carbon capture and storage: evaluating the capture-readiness of new EU fossil fuel power plants

To what degree are recently built and planned power plants in the EU ‘capture-ready’ for carbon capture and storage (CCS)? Survey results show that most recently built fossil fuel power plants have not been designed as capture-ready. For 20 planned coal-fired plants, 13 were said to be capture-ready (65%). For 31 planned gas-fired power plants, only 2 were indicated to be capture-ready (6%). Recently built or planned power plants are expected to cover a large share of fossil fuel capacity by 2030 and thereby have a large impact on the possibility to implement CCS after 2020. It is estimated that around 15–30% of fossil fuel capacity by 2030 can be capture-ready or have CO₂ capture implemented from the start. If CCS is implemented at these plants, 14–28% of baseline CO₂ emissions from fossil fuel power generation in 2030 could be mitigated, equivalent to 220–410 MtCO₂. A key reason indicated by utilities for building a capture-ready plant is (expected) national or EU policies. In addition, financial incentives and expected high CO₂ prices are important. The implementation of a long-term regulatory framework for CCS with clear definitions of ‘capture- readiness’ and policy requirements will be important challenges.     

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.     

Paper 2. agricultural impacts of and responses to climate change in the Missouri-Iowa-Nebraska-Kansas (MINK) region

The climate of the 1930s was used as an analog of the climate that might occur in Missouri, Iowa, Nebraska and Kansas (the MINK region) as a consequence of global warming. The analog climate was imposed on the agriculture of the region under technological and economic conditions prevailing in 1984/87 and again under a scenario of conditions that might prevail in 2030. The EPIC model of Williamset al. (1984), modified to allow consideration of the yield enhancing effects of CO₂ enrichment, was used to evaluate the impacts of the analog climate on the productivity and water use of some 50 representative farm enterprises. Before farm level adjustments and adaptations to the changed climate, and absent CO₂ enrichment (from 350 to 450 ppm), production of corn, sorghum and soybeans was depressed by the analog climate in about the same percent under both current and 2030 conditions. Production of dryland wheat was unaffected. Irrigated wheat production actually increased. Farm level adjustments using low-cost currently available technologies, combined with CO₂ enrichment, eliminated about 80% of the negative impact of the analog climate on 1984/87 baseline crop production. The same farm level adjustments, plus new technologies developed in response to the analog climate, when combined with CO₂ enrichment, converted the negative impact on 2030 crop production to a small increase. The analog climate would have little direct effect on animal production in MINK. The effect, if any, would be by way of the impact on production of feed-grains and soybeans. Since this impact would be small after on-farm adjustments and CO₂ enrichment, animal production in MINK would be little affected by the analog climate.