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The Intergovernmental Panel on Climate Change (IPCC), which is the United Nations body for assessing the science related to climate change, has recently recognized the natural carbonation process as a way of carbon offsetting with mortar and concrete. Accordingly, this activity could be recognized as a carbon removal process for which certification should be granted. The aim of the certification of carbon removal is to promote the development of adequate and efficient new carbon removal processes. Therefore, the main objective of this study is to provide reliable results on carbon dioxide uptake by cement-based materials in Spain. Yearly, greenhouse gas emissions are reported to the United Nations Framework Convention on Climate Change (UNFCCC) by each country, and the natural carbonation should be added up to the carbon accounting. Therefore, natural carbonation should be included in the IPCC Guidelines for National Greenhouse Gas Inventories, and such accounting information should be made available promptly to the national regulatory authorities. This paper provides the results of carbon dioxide uptake by Spanish cement-based materials from 1990 to 2020 by using an easy method of estimating the net carbon dioxide emissions (simplified method) considering the carbon dioxide released by the calcination during clinker production (process emissions). The outcome of this study reveals that there was 93,556,000 tons of carbon dioxide uptake by the mortar and concrete manufactured in Spain from 1990 to 2020. [ABSTRACT FROM AUTHOR]

Broadband (spectrally‐integrated) radiation calculations are dominated by the expense of spectral integration, and many applications require fast parameterizations for computing radiative flux. Here we describe a novel approach using a linear weighted sum of monochromatic calculations at a small set of optimally‐chosen frequencies. The empirically‐optimized quadrature method is used to compute atmospheric boundary fluxes, net flux profiles throughout the atmosphere, heating rate profiles, and top‐of‐the‐atmosphere forcing by CO2, in the longwave for clear skies. We evaluate the method against two modern correlated k‐distribution models and find that we can achieve comparable errors with 32 spectral points. We also examine the effect of minimizing different cost functions, and find that in order to accurately represent heating rates and CO2 forcing, these quantities must be included in the cost function. Plain Language Summary: Quantifying the way radiation flows through the atmosphere is computationally expensive, and most applications require fast approximation. In this paper, we develop an empirically‐optimized quadrature method that can compute quantities of interest in climate science and weather prediction such as radiative flux throughout the atmosphere, heating rates, and forcing by carbon dioxide. The method uses a simple optimization algorithm, combined with a linear model, to achieve accuracy and computational cost of similar order of magnitude to the modern correlated k‐distribution models. Depending on the focus of the application, the algorithm can easily be adapted to prioritize desired quantities. Key Points: Spectrally integrated radiative quantities can be estimated from a small weighted set of monochromatic calculationsTradeoffs between computational cost and accuracy are commensurate with correlated k‐distribution modelsOptimization priorities can be tailored to a specific applications [ABSTRACT FROM AUTHOR]

By combining Solar Cycle Lengths (SCL) and CO 2 this paper predicts a global average surface temperature (GAST) anomaly of 1.5K in the year 2100 compared to 0.42K in 1996–2006. This assumes a continuing CO 2 increase of 2 ppm per year and our derived form of Transient Climate Response (TCR), whose value 1.93 ± 0.26 K (K) per CO 2 doubling would be 1.23 times higher if the Sun were ignored. After the CO 2 effect has been subtracted out, the SCL explains a healthy 55% of the remaining variance. It also estimates that 37% of the recent warming from 1980 to 2001 was due to solar effects. We then compare with models created from Scafetta (2010, 2013) (the first of which has the best fit of all) and from radiative forcings estimated by Myhre et al. (2001) and Skeie et al. (2011). The latter confirms the solar contribution to 1980–2001 warming as 33%, in contrast to the negligible value given by Benestad & Schmidt (2009). It also gives a TCR of 1.3K if only CO 2 continues to rise, and 2.0K if CH 4 and NO 2 also rise proportionately. Likewise this model estimates the ratio between the sensitivities of forcings from the Sun and greenhouse gases as 2.9 (versus 1.0 for Benestad & Schmidt (2009)). We develop a negative exponential model for post-forced warming to derive a ratio between Equilibrium Climate Sensitivity (ECS) and TCR, estimated to be 1.15. Two statistical novelties of the paper are the computation of the exact left tail probability of the Durbin-Watson statistic, and the demonstration of an approximate relationship between the Akaike Information Criterion and the tail probability of the F-statistic. [ABSTRACT FROM AUTHOR]

The practice of using climate metrics to estimate carbon dioxide equivalent emissions has long been subject to scientific discussion. One strand of this literature has analysed whether the choice of metric affects the relative cost-effectiveness of options for climate change abatement, but there has been little discussion on the effect of metric choices on cost-effective abatement of near-term climate forcers (NTCFs). These NTCFs are air pollutants primarily regulated by policies outside the climate policy arena and their estimated carbon dioxide equivalent emissions are not typically considered in the evaluation of cost-effective abatement. However, the attention to NTCFs as climate forcers has increased during the last decade. The objective of this paper is to identify whether the relative cost-effectiveness of different NTCF abatement options is robust to climate metric choices. We assess nine plausible NTCF abatement options available in Sweden (with negligible effect on long-lived GHG emissions) and evaluate the robustness of the ranking of these, according to their estimated cost-effectiveness. Different metric designs are considered as well as climate impact uncertainty of NTCFs, with corresponding uncertainty in metric values. The results indicate that the choice of metric has little effect on the ranking of the options according to their cost-effectiveness, with options affecting NOx indicated as an exception. This suggests that the choice of metric utilised when calculating cost-effectiveness of NTCF abatement options is likely to have minor effect on which NTCF abatement options should be targeted for policy interventions (if NOx emissions are not significantly affected). [ABSTRACT FROM AUTHOR]

This paper investigates patterns of daily evolutions of CO in the lower atmosphere at a rural site over 2 years. The first part is devoted to observation analysis using a clustering procedure. However, direct application of the average-linkage method yielded undesirable results. In order to improve this procedure, data were previously processed using three smoothing procedures: the kernel smoothing method, the elliptical procedure, and the second-order cylindrical model. These procedures successfully revealed that clusters were based on daily concentration and range. However, the unequal distribution of frequencies in the clusters proved to be a noticeable disadvantage. Four alternative and simpler schemes for grouping observations were proposed in the second part of this paper. The first, comprising groups following fixed values of daily range and mean concentration, provided a sharp contrast between spring, with a marked daily cycle linked to the biological peak, and summer with a smooth daily cycle and low concentration when the biological minimum was reached. The second scheme is based on isopleth analysis and considers observation groups of similar frequencies following an increasing order of mean concentration and daily range. As a result, seasonal evolution was less marked. Straight lines were the borders for groups in the third scheme, which was similar and simpler than the second. The final scheme divided observations by means of equations of daily range as a quadratic function of daily concentration. The groups formed may be linked to seasons, with the group prevailing in summer presenting a noticeable daily range. [ABSTRACT FROM AUTHOR]

The Orbiting Carbon Observatory-2 (OCO-2) collects infrared spectra from which atmospheric properties are retrieved. OCO-2 operational data processing uses optimal estimation (OE), a state-of-the-art approach to inference of atmospheric properties from satellite measurements. One of the main advantages of the OE approach is computational efficiency, but it only characterizes the first two moments of the posterior distribution of interest. Here we obtain samples from the posterior using a Markov Chain Monte Carlo (MCMC) algorithm and compare this empirical estimate of the true posterior to the OE results. We focus on 600 simulated soundings that represent the variability of physical conditions encountered by OCO-2 between November 2014 and January 2016. We treat the two retrieval methods as ensemble and density probabilistic forecasts, where the MCMC yields an ensemble from the posterior and the OE retrieval result provide the first two moments of a normal distribution. To compare these methods, we apply both univariate and multivariate diagnostic tools and proper scoring rules. The general impression from our study is that when compared to MCMC, the OE retrieval performs reasonably well for the main quantity of interest, the column-averaged CO2 concentration XCO2, but not for the full state vector X which includes a profile of CO2 concentrations over 20 pressure levels, as well as several other atmospheric properties.Supplementary materials accompanying this paper appear on-line. [ABSTRACT FROM AUTHOR]

The potential for carbon dioxide (CO2) in the atmosphere to influence global surface temperatures was first recognized in the mid-nineteenth century. Even so, high-precision measurements of atmospheric CO2 concentration were not commenced until the International Geophysical Year (1957-8), following concerns of the climatic impact of increased use of fossil fuels and the concomitant release of CO2 into the atmosphere. In Australia, an early (1960s-70s) interest in the high-precision measurement of CO2 concentration was stimulated by a study of the photosynthesis and respiration of a wheat crop. This study conducted in north-easternVictoria during 1971-2 led two young CSIRO scientists, J. R. Garratt and G. I. Pearman, encouraged by their Chief, C. H. B. Priestley, to extend micro-environment CO2 studies to larger-scale measurements of CO2 concentration in the background atmosphere. The significant extension of the observation programme required refined measurement techniques to improve both the precision and absolute comparability with observations made by laboratories overseas. Joined in 1974 by P. J. Fraser, they identified the impact of pressure broadening on calibration techniques used in the non-dispersive infrared absorption method of CO2 concentration measurement. This, in turn, led to improved inter-comparability of CO2 concentration data collected around the globe. A comprehensive aircraft-based air sampling programme was established in the early 1970s, leading to increased understanding of the time and space variability of CO2 concentration throughout the depth of the troposphere and lower stratosphere in the mid-latitudes of the Southern Hemisphere. In turn this led to: (i) the establishment of a permanent ground-based observatory at Cape Grim, north-western Tasmania; (ii) the development of carbon cycle models; and (iii) measurements of 12CO2, 13CO2 and 14CO2 relative abundances in current and past atmospheres, the last from air samples trapped in ice cores (described in Part 2, the companion paper). The accumulated data from these studies, together with those collected by international colleagues, form the basis of our understanding of the changes of CO2 concentration over thousands of years. In addition, the data have contributed to our understanding of the mechanisms of past and present biogeochemical cycling of CO2 that provides the predictive basis for future changes in CO2 concentration. [ABSTRACT FROM AUTHOR]

This article builds on the premise that human consumption of goods, food and transport are the ultimate drivers of climate change. However, the nature of the climate change problem (well described as a tragedy of the commons) makes it difficult for individuals to recognise their personal duty to implement behavioural changes to reduce greenhouse gas emissions. Consequently, this article aims to analyse the climate change issue from a human-scale perspective, in which each of us has a clearly defined personal quota of CO2 emissions that limits our activity and there is a finite time during which CO2 emissions must be eliminated to achieve the “well below 2°C” warming limit set by the Paris Agreement of 2015 (COP21). Thus, this work’s primary contribution is to connect an equal per capita fairness approach to a global carbon budget, linking personal levels with planetary levels. Here, we show that a personal quota of 5.0 tons of CO2 yr-1 p-1 is a representative value for both past and future emissions; for this level of a constant per-capita emissions and without considering any mitigation, the global accumulated emissions compatible with the “well below 2°C” and 2°C targets will be exhausted by 2030 and 2050, respectively. These are references years that provide an order of magnitude of the time that is left to reverse the global warming trend. More realistic scenarios that consider a smooth transition toward a zero-emission world show that the global accumulated emissions compatible with the “well below 2°C” and 2°C targets will be exhausted by 2040 and 2080, respectively. Implications of this paper include a return to personal responsibility following equity principles among individuals, and a definition of boundaries to the personal emissions of CO2. [ABSTRACT FROM AUTHOR]

This paper investigates changes in the tropical tropopause layer (TTL) in response to carbon dioxide increase and surface warming separately in an atmospheric general circulation model, finding that both effects lead to a warmer tropical tropopause. Surface warming also results in an upward shift of the tropopause. A detailed heat budget analysis is performed to quantify the contributions from different radiative and dynamic processes to changes in the TTL temperature. When carbon dioxide increases with fixed surface temperature, a warmer TTL mainly results from the direct radiative effect of carbon dioxide increase. With surface warming, the largest contribution to the TTL warming comes from the radiative effect of the warmer troposphere, which is partly canceled by the radiative effect of the moistening at the TTL. Strengthening of the stratospheric circulation following surface warming cools the lower stratosphere dynamically and radiatively via changes in ozone. These two effects are of comparable magnitudes. This circulation change is the main cause of temperature changes near 63 hPa but is weak near 100 hPa. Contributions from changes in convection and clouds are also quantified. These results illustrate the heat budget analysis as a useful tool to disentangle the radiative-dynamical-chemical-convective coupling at the TTL and to facilitate an understanding of intermodel difference. [ABSTRACT FROM AUTHOR]

In this paper, the authors address the impact of uncertainty on estimates of transient climate sensitivity (TCS) of the globally averaged surface temperature, including both uncertainty in past forcing and internal variability in the climate record. This study provides a range of probabilistic estimates of the TCS that combine these two sources of uncertainty for various underlying assumptions about the nature of the uncertainty. The authors also provide estimates of how quickly the uncertainty in the TCS may be expected to diminish in the future as additional observations become available. These estimates are made using a nonlinear Kalman filter coupled to a stochastic, global energy balance model, using the filter and observations to constrain the model parameters. This study verifies that model and filter are able to emulate the evolution of a comprehensive, state-of-the-art atmosphere-ocean general circulation model and to accurately predict the TCS of the model, and then apply the methodology to observed temperature and forcing records of the twentieth century. For uncertainty assumptions best supported by global surface temperature data up to the present time, this paper finds a most likely present-day estimate of the transient climate sensitivity to be 1.6 K, with 90%% confidence the response will fall between 1.3 and 2.6 K, and it is estimated that this interval may be 45%% smaller by the year 2030. The authors calculate that emissions levels equivalent to forcing of less than 475 ppmv CO2 concentration are needed to ensure that the transient temperature response will not exceed 2 K with 95%% confidence. This is an assessment for the short-to-medium term and not a recommendation for long-term stabilization forcing; the equilibrium temperature response to this level of CO2 may be much greater. The flat temperature trend of the last decade has a detectable but small influence on TCS. This study describes how the results vary if different uncertainty assumptions are made and shows they are robust to variations in the initial prior probability assumptions. [ABSTRACT FROM AUTHOR]

A full understanding of the causes of the severe drought seen in the Sahel in the latter part of the twentieth-century remains elusive some 25 yr after the height of the event. Previous studies have suggested that this drying trend may be explained by either decadal modes of natural variability or by human-driven emissions (primarily aerosols), but these studies lacked a sufficiently large number of models to attribute one cause over the other. In this paper, signatures of both aerosol and greenhouse gas changes on Sahel rainfall are illustrated. These idealized responses are used to interpret the results of historical Sahel rainfall changes from two very large ensembles of fully coupled climate models, which both sample uncertainties arising from internal variability and model formulation. The sizes of these ensembles enable the relative role of human-driven changes and natural variability on historic Sahel rainfall to be assessed. The paper demonstrates that historic aerosol changes are likely to explain most of the underlying 1940-80 drying signal and a notable proportion of the more pronounced 1950-80 drying. [ABSTRACT FROM AUTHOR]

The interrelationship between the cryosphere and the climate is not always operating on Earth over a scale of billions or millions of years. Indeed, most of the time, the Earth is regulated at temperatures such that no ice sheet exists. Nevertheless, it is very fruitful to understand the conditions where and when ice sheets were triggered during the Earth's history. This paper deals with the paleoclimate and the cryosphere in the last 4.6 Ga and explains the different processes that make the climate of the first 4 billion years warm despite the weaker solar luminosity. We also describe the more recent evolution in the last 65 million years when a global decrease in atmospheric CO from around 4 PAL to 1 PAL was associated with a global cooling (1 PAL present atmospheric level = 280 ppm). It is in this context that the Quaternary occurred characterized by low atmospheric CO and the presence of two perennial ice sheets in Greenland and Antarctica. The last million years are certainly the most documented since direct and reliable CO measurements are available. They are characterized by a complex climate/cryosphere dynamics leading to oscillations between long glacial periods with four ice sheets and shorter ones with only two ice sheets (interglacial). We are currently living in one of those interglacials, generally associated with a CO level of 280 ppm. Presently, anthropogenic activities are seriously perturbing the carbon cycle and the atmospheric CO content and therefore the climate. The last but not least question raised in this paper is to investigate whether the anthropogenic perturbation may lead to a melting of the ice sheets. [ABSTRACT FROM AUTHOR]

The exchange of CO_{2} between the atmosphere and the ocean surface is a problem that has become increasingly important due to its impact on climatic behavior. Given the large quantity of sources of information available for studying the CO_{2} problem, it is necessary to provide innovative solutions that facilitate the automation of certain tasks and incorporate decision support systems to obtain a better understanding of this phenomenon. This paper presents a multiagent architecture aimed at providing solutions for monitoring the interaction between the atmosphere and the ocean. The ocean surface and the atmosphere exchange carbon dioxide. This process is can be modeled by a multiagent system with advanced learning and adaption capabilities. The proposed multiagent architecture incorporates CBR-agents that integrate novel strategies that both monitor the parameters that affect the interaction, and facilitate the creation of models. The system was tested and this paper presents the results obtained. [ABSTRACT FROM AUTHOR]

The primary focus of this paper is the analysis of the roles of long-term increases in carbon dioxide (CO2) and sea surface temperatures (used as indicators of climate change) and man-made halocarbons (indicators of chemical ozone depletion linked to halogens) in explaining the observed trend of ozone in the tropical lower stratosphere and implications for related variables including temperature and tropopause height. Published estimates indicate a decrease of approximately 10% in observed ozone concentrations in this region between 1979 and 2005. Using a coupled chemistry–climate atmosphere model forced by observed sea surface temperatures and surface concentrations of long-lived greenhouse gases and halocarbons, the authors show that the simulations display substantial decreases in tropical ozone that compare well in both latitudinal and vertical structure with those observed. Based on sensitivity simulations, the analysis indicates that the decreases in the lower stratospheric (85–50 hPa) tropical ozone distribution are mostly associated with increases in CO2 and sea surface temperatures, in contrast to those at higher latitudes, which are largely driven by halocarbon increases. Factors influencing temperature trends and tropopause heights in this region are also probed. It is shown that the modeled temperature trends in the lower tropical stratosphere are also associated with increases in CO2 and sea surface temperatures. Following the analysis of lower stratospheric tropical temperature trends, the secondary focus of this paper is on related changes in tropopause height. Much of the simulated tropopause rise in the tropical zone as measured by tropopause height is found to be linked to increases in sea surface temperatures and CO2, while increases in halocarbons dominate the tropopause height changes in the subtropics near 30°; both drivers thus affect different regions of the simulated changes in the position of the tropopause. Finally, it is shown that halocarbon increases dominate the changes in the width of the region where modeled total ozone displays tropical character (as indicated by low values of the column abundance). Hence the findings suggest that climate changes and halocarbon changes make different contributions to different metrics used to characterize tropical change. [ABSTRACT FROM AUTHOR]

Researchers have proposed that a significant portion of the post-glacial rise in atmospheric CO could be due to the respiration of permafrost carbon stocks that formed over the course of glaciation. In this paper, we used the University of Victoria Earth System Climate Model v. 2.9 to simulate the deglacial and interglacial carbon cycle from the last glacial maximum to the present. The model's sensitivity to mid and high latitude terrestrial carbon storage is evaluated by including a 600 Pg C carbon pool parameterized to respire in concert with decreases in ice sheet surface area. The respiration of this stored carbon during the early stages of deglaciation had a large effect on the carbon cycle in these simulations, allowing atmospheric CO to increase by 40 ppmv in the model, with an additional 20 ppmv increase occurring in the case of a more realistic, prescribed CO radiative warming. These increases occurred prior to large-scale carbon uptake due to the reestablishment of boreal forests and peatlands in the proxy record (beginning in the early Holocene). Surprisingly, the large external carbon input to the atmosphere and oceans did not increase sediment dissolution and mean ocean alkalinity relative to a control simulation without the high latitude carbon reservoir. In addition, our simulations suggest that an early deglacial terrestrial carbon release may come closer to explaining some observed deglacial changes in deep-ocean carbonate concentrations than simulations without such a release. We conclude that the respiration of glacial soil carbon stores may have been an important contributor to the deglacial CO rise, particularly in the early stages of deglaciation. [ABSTRACT FROM AUTHOR]

This paper reports the pros and cons of co-management (i.e. concerted actions towards climate change and air quality management) through local sustainability initiatives using three case studies, each encompassing the planning and management issues at local government levels. Case study I is policy-based and reports the outcome of a consultation exercise while case studies II and III have greater scientific bearing. These case studies pave the way for development of a more integrated Climate Change Strategy Action Plan at local scales, specifically regarding policies on emissions sources from transportation and decentralised energy. They highlight the merits and the trade-offs of implementing local scale co-management practices, using a more integrated planning framework than what is currently under offer. We recognise that delivery of such ambitious, cross-cutting agenda may be impeded, primarily owing to limited expertise in assessing the synergies and the expected outcomes from cross-fertility between these two arenas. This calls for a step-change through more cohesive, cross-disciplinary policy frameworks, going beyond the local administrative spheres to maximise the co-management potentials while mitigating the wider environmental impacts. [ABSTRACT FROM AUTHOR]

This paper designs a comprehensive approach based on the engineering machine/ system concept, to model, analyze, and assess the level of carbon dioxide (CO) exchange between the atmosphere and terrestrial ecosystems, which is an important factor in understanding changes in global climate. The focus of this article is on spatial patterns and on the correlation between levels of CO fluxes and a variety of influencing factors in eco-environments. The engineering/machine concept used is a system protocol that includes the sequential activities of design, test, observe, and model. This concept is applied to explicitly include various influencing factors and interactions associated with CO fluxes. To formulate effective models of a large and complex climate system, this article introduces a modeling technique that will be referred to as stochastic filtering analysis of variance (SF-ANOVA). The CO flux data observed from some sites of AmeriFlux are used to illustrate and validate the analysis, prediction, and globalization capabilities of the proposed engineering approach and the SF-ANOVA technique. The SF-ANOVA modeling approach was compared to stepwise regression, ridge regression, and neural networks. The comparison indicated that the proposed approach is a valid and effective tool with similar accuracy and less complexity than the other procedures. [ABSTRACT FROM AUTHOR]

Abstract: In photovoltaic (PV) water pumping design, the accurate prediction of the water flow is a key step for optimized implementation and system robustness. This paper presents a model to characterize the motor-pumps subsystems used in PV pumping installations. The model expresses the water flow output (Q) directly as a function of the electrical power input (P) to the motor-pump, for different total heads. The actual model is developed using the experimental results obtained by the use of several motor-pump subsystems of different types and technologies. This work details the investigations concerning centrifugal and positive displacement motor-pump subsystems. The experimental tests are used to validate the developed model. Based on the motor-pump subsystem model, a method is proposed to estimate the amount of carbon dioxide (CO2) emissions saved by the use of water pumping facilities powered by a photovoltaic array instead of diesel fuelled generators. This work shows that the dissemination of PV water systems not only improves the living conditions in remote areas, but is also environment friendly. [ABSTRACT FROM AUTHOR]

Uncertainty about biases common across models and about unknown and unmodeled feedbacks is important for the tails of temperature change distributions and thus for climate risk assessments. This paper develops a hierarchical Bayes framework that explicitly represents these and other sources of uncertainty. It then uses models’ estimates of albedo, carbon cycle, cloud, and water vapor–lapse rate feedbacks to generate posterior probability distributions for feedback strength and equilibrium temperature change. The posterior distributions are especially sensitive to prior beliefs about models’ shared structural biases: nonzero probability of shared bias moves some probability mass toward lower values for climate sensitivity even as it thickens the distribution’s positive tail. Obtaining additional models of these feedbacks would not constrain the posterior distributions as much as narrowing prior beliefs about shared biases or, potentially, obtaining feedback estimates having biases uncorrelated with those impacting climate models. Carbon dioxide concentrations may need to fall below current levels to maintain only a 10% chance of exceeding official 2°C limits on global average temperature change. [ABSTRACT FROM AUTHOR]

Abstract: A climatological mean distribution for the surface water pCO2 over the global oceans in non-El Niño conditions has been constructed with spatial resolution of 4° (latitude) ×5° (longitude) for a reference year 2000 based upon about 3 million measurements of surface water pCO2 obtained from 1970 to 2007. The database used for this study is about 3 times larger than the 0.94 million used for our earlier paper [Takahashi et al., 2002. Global sea–air CO2 flux based on climatological surface ocean pCO2, and seasonal biological and temperature effects. Deep-Sea Res. II, 49, 1601–1622]. A time-trend analysis using deseasonalized surface water pCO2 data in portions of the North Atlantic, North and South Pacific and Southern Oceans (which cover about 27% of the global ocean areas) indicates that the surface water pCO2 over these oceanic areas has increased on average at a mean rate of 1.5μatmy−1 with basin-specific rates varying between 1.2±0.5 and 2.1±0.4μatmy−1. A global ocean database for a single reference year 2000 is assembled using this mean rate for correcting observations made in different years to the reference year. The observations made during El Niño periods in the equatorial Pacific and those made in coastal zones are excluded from the database. Seasonal changes in the surface water pCO2 and the sea-air pCO2 difference over four climatic zones in the Atlantic, Pacific, Indian and Southern Oceans are presented. Over the Southern Ocean seasonal ice zone, the seasonality is complex. Although it cannot be thoroughly documented due to the limited extent of observations, seasonal changes in pCO2 are approximated by using the data for under-ice waters during austral winter and those for the marginal ice and ice-free zones. The net air–sea CO2 flux is estimated using the sea–air pCO2 difference and the air–sea gas transfer rate that is parameterized as a function of (wind speed)2 with a scaling factor of 0.26. This is estimated by inverting the bomb 14C data using Ocean General Circulation models and the 1979–2005 NCEP-DOE AMIP-II Reanalysis (R-2) wind speed data. The equatorial Pacific (14°N–14°S) is the major source for atmospheric CO2, emitting about +0.48Pg-Cy−1, and the temperate oceans between 14° and 50° in the both hemispheres are the major sink zones with an uptake flux of −0.70Pg-Cy−1 for the northern and −1.05Pg-Cy−1 for the southern zone. The high-latitude North Atlantic, including the Nordic Seas and portion of the Arctic Sea, is the most intense CO2 sink area on the basis of per unit area, with a mean of −2.5tons-Cmonth−1 km−2. This is due to the combination of the low pCO2 in seawater and high gas exchange rates. In the ice-free zone of the Southern Ocean (50°–62°S), the mean annual flux is small (−0.06Pg-Cy−1) because of a cancellation of the summer uptake CO2 flux with the winter release of CO2 caused by deepwater upwelling. The annual mean for the contemporary net CO2 uptake flux over the global oceans is estimated to be −1.6±0.9Pg-Cy−1, which includes an undersampling correction to the direct estimate of −1.4±0.7Pg-Cy−1. Taking the pre-industrial steady-state ocean source of 0.4±0.2Pg-Cy−1 into account, the total ocean uptake flux including the anthropogenic CO2 is estimated to be −2.0±1.0Pg-Cy−1 in 2000. [Copyright &y& Elsevier]

It has been shown previously that the awareness and concern of the general public about global warming is not only a function of scientific information. Both psychological and sociological factors affect the willingness of laypeople to acknowledge the reality of global warming, and to support climate policies of their home countries. In this paper, I analyse a cross-national dataset of public concern about global warming, utilising data from 46 countries. Based on earlier results at the national and regional level, I expect concern to be negatively correlated to national measures of wealth and carbon dioxide emissions. I find that gross domestic product is indeed negatively correlated to the proportion of a population that regards global warming as a serious problem. There is also a marginally significant tendency that nations’ per capita carbon dioxide emissions are negatively correlated to public concern. These findings suggest that the willingness of a nation to contribute to reductions in greenhouse gas emissions decreases with its share of these emissions. This is in accordance with psychological findings, but poses a problem for political decision-makers. When communicating with the public, scientists ought to be aware of their responsibility to use a language that is understood by laypeople. [ABSTRACT FROM AUTHOR]

Since 1990 carbon dioxide emissions in Africa have increased by about 50%. The total carbon dioxide emissions of the entire African continent are not, however, anywhere near those of countries such as India or China. Yet certain African countries have per capita emissions comparable to some European countries. What is the outlook for Africa? How should African countries respond as it becomes increasingly likely that climate change is occurring? Increased industrial growth and more foreign investment in Africa, especially in countries that are politically and economically stable, have led to huge commercial developments such as the In Salah gas project in Algeria, which releases more than a million tons of carbon dioxide annually; and synthetic fuel plants and power stations in South Africa that generate more than 350 million tons per year. In this perspective should some African countries be required to limit greenhouse gas emissions or should they be immune to 'environmental taxation'? This paper critically reviews the carbon dioxide problem in some parts of Africa and its role in climate change. [ABSTRACT FROM AUTHOR]

This paper examines the implications of uncertainty in the carbon cycle for the cost of stabilizing carbon dioxide concentrations. Using a state of the art integrated assessment model, we find that uncertainty in our understanding of the carbon cycle has significant implications for the costs of a climate stabilization policy, with cost differences denominated in trillions of dollars. Uncertainty in the carbon cycle is equivalent to a change in concentration target of up to 100 ppmv. The impact of carbon cycle uncertainties are smaller than those for climate sensitivity, and broadly comparable to the effect of uncertainty in technology availability. [ABSTRACT FROM AUTHOR]

This paper summarizes results from ten global economy-energy-environment models implementing mechanisms of endogenous technological change (ETC). Climate policy goals represented as different CO2 stabilization levels are imposed, and the contribution of induced technological change (ITC) to meeting the goals is assessed. Findings indicate that climate policy induces additional technological change, in some models substantially. Its effect is a reduction of abatement costs in all participating models. The majority of models calculate abatement costs below 1 percent of present value aggregate gross world product for the period 2000-2100. The models predict different dynamics for rising carbon costs, with some showing a decline in carbon costs towards the end of the century. There are a number of reasons for differences in results between models; however four major drivers of differences are identified. First, the extent of the necessary CO2 reduction which depends mainly on predicted baseline emissions, determines how much a model is challenged to comply with climate policy. Second, when climate policy can offset market distortions, some models show that not costs but benefits accrue from climate policy. Third, assumptions about long-term investment behavior, e.g. foresight of actors and number of available investment options, exert a major influence. Finally whether and how options for carbon-free energy are implemented (backstop and end-of-the-pipe technologies) strongly affects both the mitigation strategy and the abatement costs. [ABSTRACT FROM AUTHOR]

The greenhouse gas emissions scenarios published by the IPCC in the Special Report on Emission Scenarios (SRES) continue to serve as a primary basis for assessing future climate change and possible response strategies. These scenarios were developed between 1996 and 1999 and sufficient time has now passed to make it worth examining their consistency with more recent data and projections. The comparison performed in this paper includes population, GDP, energy use, and emissions of CO2, non-CO2 gases and sulfur. We find the SRES scenarios to be largely consistent with historical data for the 1990-2000 period and with recent projections. Exceptions to this general observation include (1) in the long-term, relatively high population growth assumptions in some regions, particularly in the A2 scenario; (2) in the medium-term, relatively high economic growth assumptions in the LAM (Latin America, Africa and Middle East) region in the A1 scenario; (3) in the short-term, CO2 emissions projections in Al that are somewhat higher than the range of current scenarios; and (4) substantially higher sulfur emissions in some scenarios than in historical data and recent projections. In conclusion, given the relatively small inconsistencies for use as global scenarios there seems to be no immediate need for a large-scale IPCC-led update of the SRES scenarios that is solely based on the SRES scenario performance vis-a-vis data for the 1990-2000 period and/or more recent projections. Based on reported findings, individual research teams could make, and in some cases already have made, useful updates of the scenarios. [ABSTRACT FROM AUTHOR]

Across many dryland regions, historically grass-dominated ecosystems have been encroached upon by woody-plant species. In this paper, we compare ecosystem water and carbon dioxide (CO2) fluxes over a grassland, a grassland–shrubland mosaic, and a fully developed woodland to evaluate potential consequences of woody-plant encroachment on important ecosystem processes. All three sites were located in the riparian corridor of a river in the southwest US. As such, plants in these ecosystems may have access to moisture at the capillary fringe of the near-surface water table. Using fluxes measured by eddy covariance in 2003 we found that ecosystem evapotranspiration (ET) and net ecosystem exchange of carbon dioxide (NEE) increased with increasing woody-plant dominance. Growing season ET totals were 407, 450, and 639 mm in the grassland, shrubland, and woodland, respectively, and in excess of precipitation by 227, 265, and 473 mm. This excess was derived from groundwater, especially during the extremely dry premonsoon period when this was the only source of moisture available to plants. Access to groundwater by the deep-rooted woody plants apparently decouples ecosystem ET from gross ecosystem production (GEP) with respect to precipitation. Compared with grasses, the woody plants were better able to use the stable groundwater source and had an increased net CO2 gain during the dry periods. This enhanced plant activity resulted in substantial accumulation of leaf litter on the soil surface that, during rainy periods, may lead to high microbial respiration rates that offset these photosynthetic fluxes. March–December (primary growing season) totals of NEE were −63, −212, and −233 g C m−2 in the grassland, shrubland, and woodland, respectively. Thus, there was a greater disparity between ecosystem water use and the strength of the CO2 sink as woody plants increased across the encroachment gradient. Despite a higher density of woody plants and a greater plant productivity in the woodland than in the shrubland, the woodland produced a larger respiration response to rainfall that largely offset its higher photosynthetic potential. These data suggest that the capacity for woody plants to exploit water resources in riparian areas results in enhanced carbon sequestration at the expense of increased groundwater use under current climate conditions, but the potential does not scale specifically as a function of woody-plant abundance. These results highlight the important roles of water sources and ecosystem structure on the control of water and carbon balances in dryland areas. [ABSTRACT FROM AUTHOR]

The effects of elevated carbon dioxide on plant–herbivore interactions have been summarized in a number of narrative reviews and metaanalyses, while accompanying elevation of temperature has not received sufficient attention. The goal of our study is to search, by means of metaanalysis, for a general pattern in responses of herbivores, and plant characteristics important for herbivores, to simultaneous experimental increase of carbon dioxide and temperature (ECET) in comparison with both ambient conditions and responses to elevated CO2 (EC) and temperature (ET) applied separately. Our database includes 42 papers describing studies of 31 plant species and seven herbivore species. Nitrogen concentration and C/N ratio in plants decreased under both EC and ECET treatments, whereas ET had no significant effect. Concentrations of nonstructural carbohydrates and phenolics increased in EC, decreased in ET and did not change in ECET treatments, whereas terpenes did not respond to EC but increased in both ET and ECET; leaf toughness increased in both EC and ECET. Responses of defensive secondary compounds to treatments differed between woody and green tissues as well as between gymnosperm and angiosperm plants. Insect herbivore performance was adversely affected by EC, favoured by ET, and not modified by ECET. Our analysis allowed to distinguish three types of relationships between CO2 and temperature elevation: (1) responses to EC do not depend on temperature (nitrogen, C/N, leaf toughness, phenolics in angiosperm leaves), (2) responses to EC are mitigated by ET (sugars and starch, terpenes in needles of gymnosperms, insect performance) and (3) effects emerge only under ECET (nitrogen in gymnosperms, and phenolics and terpenes in woody tissues). This result indicates that conclusions of CO2 elevation studies cannot be directly extrapolated to a more realistic climate change scenario. The predicted negative effects of CO2 elevation on herbivores are likely to be mitigated by temperature increase. [ABSTRACT FROM AUTHOR]

The aim of this paper is to investigate the longevity and diversity of the Amazonian rainforest and to assess its likely future. Palaeoclimate and palaeoecological records suggest that the Amazon rainforest originated in the late Cretaceous and has been a permanent feature of South America for at least the last 55 million years. The Amazon rainforest has survived the high temperatures of the Early Eocene climate optimum, the gradual Cenozoic cooling, and the drier and lower carbon dioxide levels of the Quaternary glacial periods. Two new theories for the great diversity of the Amazon rainforest are discussed – the canopy density hypothesis and the precessional-forced seasonality hypothesis. We suggest the Amazon rainforest should not be viewed as a geologically ephemeral feature of South America, but rather as a constant feature of the global Cenozoic biosphere. The forest is now, however, entering a set of climatic conditions with no past analogue. The predicted future hotter and more arid tropical climates may have a disastrous effect on the Amazon rainforest. [ABSTRACT FROM AUTHOR]

This paper presents results of 1 year (from March 25, 2003 to March 24, 2004, 366 days) of continuous measurements of net ecosystem CO2 exchange (NEE) above a steppe in Mongolia using the eddy covariance technique. The steppe, typical of central Mongolia, is dominated by C3 plants adapted to the continental climate. The following two questions are addressed: (1) how do NEE and its components: gross ecosystem production (GEP) and total ecosystem respiration ( Reco) vary seasonally? (2) how do NEE, GEP, and Reco respond to biotic and abiotic factors? The hourly minimal NEE and the hourly maximal Reco were −3.6 and 1.2 μmol m−2 s−1, respectively (negative values denoting net carbon uptake by the canopy from the atmosphere). Peak daily sums of NEE, GEP, and Reco were −2.3, 3.5, and 1.5 g C m−2 day−1, respectively. The annual sums of GEP, Reco, and NEE were 179, 138, and −41 g C m−2, respectively. The carbon removal by sheep was estimated to range between 10 and 82 g C m−2 yr−1 using four different approaches. Including these estimates in the overall carbon budget yielded net ecosystem productivity of −23 to +20 g C m−2 yr−1. Thus, within the remaining experimental uncertainty the carbon budget at this steppe site can be considered to be balanced. For the growing period (from April 23 to October 21, 2003), 26% and 53% of the variation in daily NEE and GEP, respectively, could be explained by the changes in leaf area index. Seasonality of GEP, Reco, and NEE was closely associated with precipitation, especially in the peak growing season when GEP and Reco were largest. Water stress was observed in late July to early August, which switched the steppe from a carbon sink to a carbon source. For the entire growing period, the light response curves of daytime NEE showed a rather low apparent quantum yield ( α=−0.0047 μmol CO2 μmol−1 photons of photosynthetically active radiation). However, the α values varied with air temperature ( Ta), vapor pressure deficit, and soil water content. [ABSTRACT FROM AUTHOR]

A review of the present status of the global warming science is presented in this paper. The term global warming is now popularly used to refer to the recent reported increase in the mean surface temperature of the earth; this increase being attributed to increasing human activity and in particular to the increased concentration of greenhouse gases (carbon dioxide, methane and nitrous oxide) in the atmosphere. Since the mid to late 1980s there has been an intense and often emotional debate on this topic. The various climate change reports (1996, 2001) prepared by the IPCC (Intergovernmental Panel on Climate Change), have provided the scientific framework that ultimately led to the Kyoto protocol on the reduction of greenhouse gas emissions (particularly carbon dioxide) due to the burning of fossil fuels. Numerous peer-reviewed studies reported in recent literature have attempted to verify several of the projections on climate change that have been detailed by the IPCC reports. The global warming debate as presented by the media usually focuses on the increasing mean temperature of the earth, associated extreme weather events and future climate projections of increasing frequency of extreme weather events worldwide. In reality, the climate change issue is considerably more complex than an increase in the earth’s mean temperature and in extreme weather events. Several recent studies have questioned many of the projections of climate change made by the IPCC reports and at present there is an emerging dissenting view of the global warming science which is at odds with the IPCC view of the cause and consequence of global warming. Our review suggests that the dissenting view offered by the skeptics or opponents of global warming appears substantially more credible than the supporting view put forth by the proponents of global warming. Further, the projections of future climate change over the next fifty to one hundred years is based on insufficiently verified climate models and are therefore not considered reliable at this point in time. [ABSTRACT FROM AUTHOR]

Adaptation of a greenhouse climate management strategy to local climate conditions is important for the improvement of resource use efficiency of greenhouse crop production. In this paper the optimal greenhouse climate management under hot, humid, subtropical summer conditions was investigated through simulation analysis based on the Greenhouse Process (KASPRO) model, previously validated under this particular conditions. The study was limited to affordable means of greenhouse design, crop and climate management such as ventilation capacity, canopy size and whitewashing, in a greenhouse without injection of carbon dioxide. Obviously, the increase of greenhouse ventilation capacity leads to an increase of carbon dioxide concentration in the greenhouse air, canopy transpiration, and thus evaporative cooling of the greenhouse air and crop canopy, and in turn to an increase of crop biomass production. The results show, however, that there is a rather sharp ceiling beyond which there is little gain in increasing ventilation capacity. For a cucumber crop under the summer conditions typical of Shanghai, the ventilation capacity of the greenhouse should be about 40 volume changes per hour. The balance of assimilation, respiration and evaporative cooling ensure that crop biomass production is maximal at a canopy leaf area index of 4. [Copyright &y& Elsevier]

A regional coupled soil–vegetation–atmosphere model is used to study changes and interactions between climate and the ecosystem in East Asia due to increased atmospheric CO[sub 2] . The largest simulated climate changes are due to the radiative influence of CO[sub 2] , modified slightly by vegetation feedbacks. Annual precipitation increases by about 20% in coastal areas of northern China and in central China, but only by 8% in southern China. The strongest warming of up to 4°C occurs in summer in northern China. Generally, the climate tends to be warmer and wetter under doubled CO[sub 2] except for inland areas of northern China, where it becomes warmer and drier. Most of the changes discussed in this paper are associated with changes in the East Asian monsoon, which is intensified under doubled CO[sub 2] . The largest changes and feedbacks between vegetation and climate occur in northern China. In some coastal and central areas around 40°N, temperate deciduous forests expand northward, replacing grassland due to warmer and wetter climate. Evergreen taiga retreats in the coastal northeast, causing extra cooling feedback due to less snow masking. The largest changes occur in extensive inland regions northward of 40°N, where deserts and shrub land expand due to warmer and drier conditions, and water supply is a critical factor for vegetation. These northern inland ecosystems experience considerable degradation and desertification, indicating a marked sensitivity and vulnerability to climatic change. [ABSTRACT FROM AUTHOR]

Many energy systems models have sought to develop pathways for deep decarbonization of the global energy system. Most often, these pathways minimize system costs or greenhouse gas emissions; with few exceptions, they ignore the constraints imposed by political, social, and economic factors that slow transition processes, making them prone to producing implausible decarbonization pathways. This paper integrates a key socio-technical factor—social acceptance of low-carbon nuclear power—into an energy systems model to illustrate how it alters the optimal energy generation mix. The United States was chosen as the example, but the approach itself is designed to be general and applicable to any region of interest. An empirically grounded risk tolerance model is developed to characterize acceptance of nuclear power and estimate an upper-bound deployment limit for the technology. Illustrative scenarios are presented to improve our understanding of how the socio-technical constraints that exist in the real world can alter deep decarbonization pathways. The cost-optimal generation portfolio to achieve net zero CO 2 emissions by 2050 primarily relies on nuclear power. If risk tolerance concerns constrain nuclear deployment to socially acceptable levels, deep decarbonization scenarios are up to 11% more expensive than the reference scenario and require low-carbon options to be available and replace the reduced nuclear share. Results from this novel framework improve our representation of the effect of social acceptance on the adoption and diffusion of energy technologies. They also contribute to a growing literature that seeks to firmly embed the social sciences in climate and energy policy. • Plausible decarbonization pathways must also account for social constraints. • We combine a social risk tolerance model with an energy system optimization model. • We assess the role of social acceptance in constraining nuclear power's deployment. • Social acceptance limits nuclear's share by as much as 71% in CO 2 reduction pathways. • Decision-making can be strengthened with integration of socio-technical analyses. [ABSTRACT FROM AUTHOR]

This paper analyzes four methods for estimating the spatial degrees of freedom (dof ) of a climate field: the x 2 method, the Z method, the S method, and the B method. The results show that the B method provides the most accurate estimate of the dof. The x 2 method, S method, and Z method yield underestimates when the number of realizations of the field is not sufficiently large or the field's mean and variance vary with respect to spatial location. The dof of the monthly surface temperature field is studied numerically. The B method shows that the dof of the Northern Hemisphere (NH) has an obvious annual cycle, which is around 60 in the winter months and 90 in the summer months. The dof for the Southern Hemisphere (SH) varies between 35 and 50, with large values during its winter months and small ones during its summer months. The dof of the global temperature field demonstrates a similar annual cycle to that of the NH. The dof estimated from the observational data is smaller than that from the GFDL GCM model output of the surface air temperature. In addition, the model output for the SH shows the opposite phase of the seasonal cycle of the dof: large dof in summer and small ones in winter. [ABSTRACT FROM AUTHOR]

Climate policy is often discussed as a lever with which to bring about climate-friendly technical innovation and diffusion. However, quantitative policy assessments routinely treat technological change as a factor that is independent of policy. Stabilizing atmospheric concentrations of CO2 cannot be achieved through marginal changes in the way we supply and use energy. The only path to stabilization of climate over the next century that is consistent with widely accepted population and economic-growth scenarios involves substantial decoupling of energy services from carbon emissions. The required rate of structural and technical change for such a goal has been experienced only in the wake of economic and resource crises and for periods of a decade or less. Historic rates of structural and technical change averaged over a century are far from adequate for stabilizing climate. In this paper, we review technical changes in the energy system and a few instances in which energy economic models have begun to include technical change as an endogenous feature of their assessments. Finally, we consider the implications of considering endogenous technical change for critical climate policy questions, such as the cost of control and the appropriate timing of the emissions mitigation effort. [ABSTRACT FROM AUTHOR]

Good-quality CO 2 emission data are fundamental for effective climate policy and governance. Data manipulation should be deterred, while developing countries are generally weaker than developed countries in compiling bottom-up CO 2 emission inventories due to less adequate data collection capacity. This paper assesses the capabilities of CO 2 satellites as objective, independent, potentially low-cost and external data sources for monitoring energy-related anthropogenic CO 2 emissions at regional/national, megacity and point-source geographical scales. After overviewing all major CO 2 satellites, SCIAMACHY, GOSAT and OCO-2 are focused on due to their wider research applications and higher CO 2 sensitivity in total column measurements that include near surface emissions. Nighttime light satellite data for proxy CO 2 monitoring are also brought into comparison to distinguish the importance of direct CO 2 satellite monitoring. Studies are reviewed from the perspectives of spatial and temporal capability and accuracy to comprehend the current statuses of applications, assess the strengths and weaknesses of research methods, investigate major challenges and propose suggestions for future progress. We conclude that CO 2 satellite monitoring can strengthen the data foundation for implementing international climate treaties and domestic climate policies. • We review CO 2 satellites for climate governance as independent data sources. • CO 2 satellites are compared with nighttime light satellites as proxy monitoring. • We examine applications at national/regional, megacity and point-source levels. • The assessment specifically focuses on SCIAMACHY, GOSAT and OCO-2 satellites. • CO 2 satellite monitoring strengthens the data foundation for climate governance. [ABSTRACT FROM AUTHOR]

Based on a mixed-methods study of Norwegian second home users, this paper addresses travel distances, modes and carbon dioxide emissions from second home mobility, with a particular focus on reasons for choosing relevant modes of transportation to second home areas and while staying there. The questionnaire data show that the climate impacts are particularly high for trips to second homes located abroad, but due to their higher number, mobility when visiting domestic Norwegian second homes is also a sizeable source of CO 2 emissions. Qualitative interviews with 18 participants illustrate important reasons why the car is often considered the default mode of travel when going to Norwegian second homes. These findings provide foundations for proposing land use and transport policies to reduce the climate impact of second home mobility. [ABSTRACT FROM AUTHOR]

Focuses on the support of the Royal Society for the nuclear option in the energy White Paper. Reduction of carbon dioxide emissions; Risks in the pursuit for non-nuclear energy; Relation of carbon emissions to climate change.