Irrigated afforestation of the Sahara and Australian Outback to end global warming

Each year, irrigated Saharan- and Australian-desert forests could sequester amounts of atmospheric CO₂ at least equal to that from burning fossil fuels. Without any rain, to capture CO₂ produced from gasoline requires adding about $1 to the per-gallon pump-price to cover irrigation costs, using reverse osmosis (RO), desalinated, sea water. Such mature technology is economically competitive with the currently favored, untested, power-plant Carbon Capture (and deep underground, or under-ocean) Sequestration (CCS). Afforestation sequesters CO₂, mostly as easily stored wood, both from distributed sources (automotive, aviation, etc., that CCS cannot address) and from power plants. Climatological feasibility and sustainability of such irrigated forests, and their potential global impacts are explored using a general circulation model (GCM). Biogeophysical feedback is shown to stimulate considerable rainfall over these forests, reducing desalination and irrigation costs; economic value of marketed, renewable, forest biomass, further reduces costs; and separately, energy conservation also reduces the size of the required forests and therefore their total capital and operating costs. The few negative climate impacts outside of the forests are discussed, with caveats. If confirmed with other GCMs, such irrigated, subtropical afforestation probably provides the best, near-term route to complete control of green-house-gas-induced, global warming.     

Ionospheric potential as a proxy index for global temperature

Since the global circuit is maintained by currents from thunderstorms and electrified clouds, which are controlled by temperature, we are investigating the use of ionospheric potential (V_I) as a measure of the variation of global temperature. We report positive correlation between V_I and global temperature obtained from three different data sets. V_I is also positively correlated with an inferred global lightning/deep cloud index which is positively correlated with global temperature. Thus, there is a consistent picture of warmer temperatures leading to more deep convection and higher V_I. Since a series of single V_I soundings at any appropriate location may provide a globally representative measure of temperature variation in real time, it is suggested that routine monitoring of this parameter could provide considerable cost and operational advantages compared to current methodology involving observations at thousands of ground stations and satellite radiation measurements.     

Satellite-derived estimates of potential carbon sequestration through afforestation of agricultural lands in the United States

Afforestation of marginal agricultural lands represents a promising option for carbon sequestration in terrestrial ecosystems. An ecosystem carbon model was used to generate new national maps of annual net primary production (NPP), one each for continuous land covers of ‘forest’, ‘crop’, and ‘rangeland’ over the entire U. S. continental area. Direct inputs of satellite “greenness” data from the Advanced Very High Resolution Radiometer (AVHRR) sensor into the NASA-CASA carbon model at 8-km spatial resolution were used to estimate spatial variability in monthly NPP and potential biomass accumulation rates in a uniquely detailed manner. The model predictions of regrowth forest production lead to a conservative national projection of 0.3 Pg C as potential carbon stored each year on relatively low-production crop or rangeland areas. On a regional level, the top five states for total crop afforestation potential were: Texas, Minnesota, Iowa, Illinois, and Missouri, whereas the top five states for total rangeland afforestation potential are: Texas, California, Montana, New Mexico, and Colorado. Afforestation at this level of intensity has the capacity to offset at least one-fifth of annual fossil fuel emission of carbon in the United States. These projected afforestation carbon gains also match or exceed recent estimates of the annual sink for atmospheric CO₂ in currently forested area of the country.     

The European and global potential of carbon dioxide sequestration in tackling climate change

Although, it has received relatively little attention as a potential method of combating climate change in comparison to energy reduction measures and development of carbon-free energy technologies, sequestration of carbon dioxide in geologic or biospheric sinks has enormous potential. This paper reviews the potential for sequestration using geological and ocean storage as a means of reducing carbon dioxide emissions.Considerable quantities of carbon dioxide separated from natural gas deposits and from hydrogen production from steam reforming of methane are already used in enhanced oil recovery and in extraction of coalbed methane, the carbon dioxide remaining sequestered at the end of the process. A number of barriers lie in the way of its implementation on a large scale. There are concerns about possible environmental effects of large-scale injection of carbon dioxide especially into the oceans. Available technologies, especially of separating and capturing the carbon dioxide from waste stream, have high costs at present, perhaps representing an additional 40–100% onto the costs of generating electricity. In most of the world there are no mechanisms to encourage firms to consider sequestration.Considerable R&D is required to bring down the costs of the process, to elucidate the environmental effects of storage and to ensure that carbon dioxide will not escape from stores in unacceptably short timescales. However, the potential of sequestration should not be underestimated as a contribution to global climate change mitigation measures.     

六种HFCs的辐射强迫与全球增温潜能

采用最新分子吸收数据集HITRAN2004中6种氢氟碳化物（HFCs）的吸收截面数据,建立了它们的相关K-分布的辐射计算方案,研究了这些长寿命温室气体浓度变化引起的辐射强迫,比较了它们的全球增温潜能。结果表明,从1750年到2005年由于这些气体浓度变化引起的总的辐射强迫约为0、0066Wm^-2,未来100a的辐射强迫结果说明它们对未来全球变暖的贡献不容忽视。     

The biogeophysical effects of extreme afforestation in modeling future climate

Afforestation has been deployed as a mitigation strategy for global warming due to its substantial carbon sequestration, which is partly counterbalanced with its biogeophysical effects through modifying the fluxes of energy, water, and momentum at the land surface. To assess the potential biophysical effects of afforestation, a set of extreme experiments in an Earth system model of intermediate complexity, the McGill Paleoclimate Model-2 (MPM-2), is designed. Model results show that latitudinal afforestation not only has a local warming effect but also induces global and remote warming over regions beyond the forcing originating areas. Precipitation increases in the northern hemisphere and decreases in southern hemisphere in response to afforestation. The local surface warming over the forcing originating areas in northern hemisphere is driven by decreases in surface albedo and increases in precipitation. The remote surface warming in southern hemisphere is induced by decreases in surface albedo and precipitation. The results suggest that the potential impact of afforestation on regional and global climate depended critically on the location of the forest expansion. That is, afforestation in 0°–15°N leaves a relatively minor impact on global and regional temperature; afforestation in 45°–60°N results in a significant global warming, while afforestation in 30°–45°N results in a prominent regional warming. In addition, the afforestation leads to a decrease in annual mean meridional oceanic heat transport with a maximum decrease in forest expansion of 30°–45°N. These results can help to compare afforestation effects and find areas where afforestation mitigates climate change most effectively combined with its carbon drawdown effects.     

The global warming potential of two healthy Nordic diets compared with the average Danish diet

The potential greenhouse gas (GHG) emissions from the production of food for three different diets are compared using consequential Life Cycle Assessment. Diet 1 is an Average Danish Diet (ADD); diet 2 is based on the Nordic Nutritional Recommendations (NNR), whilst diet 3 is a New Nordic Diet (NND) developed by the OPUS project. The NND contains locally produced Nordic foods where more than 75 % is organically produced. NNR and NND include less meat and more fruit and vegetables than the ADD. All diets were adjusted to contain a similar energy and protein content. The GHG emissions from the provision of NNR and NND were lower than for ADD, 8 % and 7 % respectively. If GHG emissions from transport (locally produced versus imported food) are also taken into account, the difference in GHG emissions between NND and ADD increases to 12 %. If the production method (organic versus conventional) is taken into account so that the ADD contains the actual ratio of organically produced food (6.6 %) and the NND contains 80 %, the GHG emissions for the NND are only 6 % less than for the ADD. When the NND was optimised to be more climate friendly, the global warming potential of the NND was 27 % lower than it was for the ADD. This was achieved by including less beef, and only including organic produce if the GHG emissions are lower than for the conventional version, or by substituting all meat with legumes, dairy products and eggs.     

Historical and potential future contributions of power technologies to global warming

Using the mathematical formalism of the Brazilian Proposal to the IPCC, we analyse eight power technologies with regard to their past and potential future contributions to global warming. Taking into account detailed bottom-up technology characteristics we define the mitigation potential of each technology in terms of avoided temperature increase by comparing a “coal-only” reference scenario and an alternative low-carbon scenario. Future mitigation potentials are mainly determined by the magnitude of installed capacity and the temporal deployment profile. A general conclusion is that early technology deployment matters, at least within a period of 50–100?years. Our results conclusively show that avoided temperature increase is a better proxy for comparing technologies with regard to their impact on climate change, and that numerous short-term comparisons based on annual or even cumulative emissions may be misleading. Thus, our results support and extend the policy relevance of the Brazilian Proposal in the sense that not only comparisons between countries, but also comparisons between technologies could be undertaken on the basis of avoided temperature increase rather than on the basis of annual emissions as is practiced today.     

Estimating the global potential of water harvesting from successful case studies

Water harvesting has been widely applied in different social-ecological contexts, proving to be a valuable approach to sustainable intensification of agriculture. Global estimates of the potential of water harvesting are generally based on purely biophysical assessments and mostly neglect the socioeconomic dimension of agriculture. This neglect becomes a critical factor for the feasibility and effectiveness of policy and funding efforts to mainstream this practice. This study uses archetype analysis to systematically identify social-ecological regions worldwide based on >160 successful cases of local water harvesting implementation. We delineate six archetypal regions which capture the specific social-ecological conditions of the case studies. The archetypes cover 19% of current global croplands with hotspots in large portions of East Africa and Southeast Asia. We estimate that the adoption of water harvesting in these cropland areas can increase crop production up to 60–100% in Uganda, Burundi, Tanzania and India. The results of this study can complement conventional biophysical analysis on the potential of these practices and guide policy development at global and regional scales. The methodological approach can be also replicated at finer scales to guide the improvement of rainfed agricultural.     

The global energy balance from a surface perspective

In the framework of the global energy balance, the radiative energy exchanges between Sun, Earth and space are now accurately quantified from new satellite missions. Much less is known about the magnitude of the energy flows within the climate system and at the Earth surface, which cannot be directly measured by satellites. In addition to satellite observations, here we make extensive use of the growing number of surface observations to constrain the global energy balance not only from space, but also from the surface. We combine these observations with the latest modeling efforts performed for the 5th IPCC assessment report to infer best estimates for the global mean surface radiative components. Our analyses favor global mean downward surface solar and thermal radiation values near 185 and 342 Wm^?2, respectively, which are most compatible with surface observations. Combined with an estimated surface absorbed solar radiation and thermal emission of 161 and 397 Wm^?2, respectively, this leaves 106 Wm^?2 of surface net radiation available globally for distribution amongst the non-radiative surface energy balance components. The climate models overestimate the downward solar and underestimate the downward thermal radiation, thereby simulating nevertheless an adequate global mean surface net radiation by error compensation. This also suggests that, globally, the simulated surface sensible and latent heat fluxes, around 20 and 85 Wm^?2 on average, state realistic values. The findings of this study are compiled into a new global energy balance diagram, which may be able to reconcile currently disputed inconsistencies between energy and water cycle estimates.     

Change of tropical cyclone heat potential in response to global warming

Tropical cyclone heat potential (TCHP) in the ocean can affect tropical cyclone intensity and intensification. In this paper, TCHP change under global warming is presented based on 35 models from CMIP5 (Coupled Model Intercomparison Project, Phase 5). As the upper ocean warms up, the TCHP of the global ocean is projected to increase by 140.6% in the 21st century under the RCP4.5 (+4.5 W m^-2 Representative Concentration Pathway) scenario. The increase is particularly significant in the western Pacific, northwestern Indian and western tropical Atlantic oceans. The increase of TCHP results from the ocean temperature warming above the depth of the 26°C isotherm (D26), the deepening of D26, and the horizontal area expansion of SST above 26°C. Their contributions are 69.4%, 22.5% and 8.1%, respectively. Further, a suite of numerical experiments with an Ocean General Circulation Model (OGCM) is conducted to investigate the relative importance of wind stress and buoyancy forcing to the TCHP change under global warming. Results show that sea surface warming is the dominant forcing for the TCHP change, while wind stress and sea surface salinity change are secondary.     

具有热力-动力耦合的二维能量平衡气候模式

本文设计了一个热力—动力耦合的理论模式,所得到温度场和运动场的平均气候状态基本上与实况接近.分析表明,温度场和速度场是相互制约的,温度分布在纬向上的不均匀形成了垂直经圈环流,此种流场又把赤道的热量往极地输送,其结果与没有运动场耦合的情况相比,可使赤道温度降低而极地温度升高. 研究模式气候对太阳常数变化的敏感性后指出,要使冰界线从现在的72°N南移到冰河期的50°N,太阳常数要减小15％左右.这在考虑或不考虑流场耦合的模式中都是差不多的.     

《巴黎协定》实施细则评估与全球气候治理展望

《巴黎协定》在确立2020年后应对气候变化框架性制度安排的同时也给出了一系列留待解决的后续任务,包括制定《巴黎协定》实施细则,细化相应规则、制度和指南等。经过3年的谈判,2018年年底在卡托维兹举行的第24次缔约方会议对《巴黎协定》涉及的除市场机制外的众多议题做出了一揽子安排,建立了一系列指导和帮助各方在2020年后落实和履行《巴黎协定》的实施细则,为全面有效实施《巴黎协定》提供了更明确的指导。本研究致力对《巴黎协定》实施细则的内容和特点、对中国的潜在影响和要求、后续谈判走向以及中国的对策等进行全面深入的梳理和分析。评估发现,实施细则继续保持了《巴黎协定》的“精妙平衡”,严格恪守并充分体现了“自下而上”的《巴黎协定》模式,在为发展中国家保留一定灵活性的基础上统一了报告和审评的“度量衡”,并进一步明确了以五年为周期提高行动和支持力度的序贯决策机制。细则可能给中国引领全球气候治理和国内履约带来新的机遇和挑战。中国需要从观念认识、责任担当、业务协调上做好新的布局,根据国内外新趋势、新特点构建中国特色的气候治理新体系。     

The global carbon budget: a conflicting claims problem

An effective climate agreement is urgently required, yet conflict between parties prevails over cooperation. Thanks to advances in science it is now possible to quantify the global carbon budget, the amount of available cumulative CO₂ emissions before crossing the 2 ^°C threshold (Meinshausen et al. Nature 458(7242):1158–1162, 2009). Countries carbon claims, however, exceed this. Historically such situations have been tackled with bankruptcy division rules. We argue that framing climate negotiations as a classical conflicting claims problem (O’Neill Math Soc Sci 2(4):345–371, 1982) may provide for an effective climate policy. We analyze the allocation of the global carbon budget among parties claiming the maximum emissions rights possible. Based on the selection of some desirable principles, we propose an efficient and sustainable allocation of the available carbon budget for the period 2000 to 2050 taking into account different risk scenarios.     

Potential vorticity and eddy potential enstrophy in the North Atlantic Ocean simulated by a global eddy-resolving model

Eight-year daily mean output of a quasi-global eddy-resolving model is examined with a focus on the large-scale dynamical characteristics of the North Atlantic Ocean in a framework of potential vorticity (PV) and its derivatives. The model has reproduced some of the observed features of the mean potential vorticity field well. The three-dimensional structure of the mean potential vorticity supports baroclinic instability in most of the basin. Eddies are found to play important roles in the formation and maintenance of the mean potential vorticity fields. The contribution of relative vorticity to the mean potential vorticity field is found to be negligible for the most part. However, relative vorticity contribution to the source/sink of potential vorticity and eddy potential enstrophy is not negligible. We also find that eddies are not necessarily diffusive even on a basin-scale.     

Multi-model assessment of global hydropower and cooling water discharge potential under climate change

Worldwide, 98% of total electricity is currently produced by thermoelectric power and hydropower. Climate change is expected to directly impact electricity supply, in terms of both water availability for hydropower generation and cooling water usage for thermoelectric power. Improved understanding of how climate change may impact the availability and temperature of water resources is therefore of major importance. Here we use a multi-model ensemble to show the potential impacts of climate change on global hydropower and cooling water discharge potential. For the first time, combined projections of streamflow and water temperature were produced with three global hydrological models (GHMs) to account for uncertainties in the structure and parametrization of these GHMs in both water availability and water temperature. The GHMs were forced with bias-corrected output of five general circulation models (GCMs) for both the lowest and highest representative concentration pathways (RCP2.6 and RCP8.5). The ensemble projections of streamflow and water temperature were then used to quantify impacts on gross hydropower potential and cooling water discharge capacity of rivers worldwide. We show that global gross hydropower potential is expected to increase between +2.4% (GCM-GHM ensemble mean for RCP 2.6) and +6.3% (RCP 8.5) for the 2080s compared to 1971–2000. The strongest increases in hydropower potential are expected for Central Africa, India, central Asia and the northern high-latitudes, with 18–33% of the world population living in these areas by the 2080s. Global mean cooling water discharge capacity is projected to decrease by 4.5-15% (2080s). The largest reductions are found for the United States, Europe, eastern Asia, and southern parts of South America, Africa and Australia, where strong water temperature increases are projected combined with reductions in mean annual streamflow. These regions are expected to affect 11–14% (for RCP2.6 and the shared socio-economic pathway (SSP)1, SSP2, SSP4) and 41–51% (RCP8.5–SSP3, SSP5) of the world population by the 2080s.     

The thermodynamic influence of subgrid orography in a global climate model

Assessments of the impacts of climate change typically require information at scales of 10 km or less. Such a resolution in global climate simulations is unlikely for at least two decades. We have developed an alternative to explicit resolution that provides a framework for meeting the needs of climate change impact assessment much sooner. We have applied to a global climate model a physically based subgrid-scale treatment of the influence of orography on temperature, clouds, precipitation, and land surface hydrology. The treatment represents subgrid variations in surface elevation in terms of fractional area distributions of discrete elevation classes. For each class it calculates the height rise/descent of air parcels traveling through the grid cell, and applies the influence of the rise/descent to the temperature and humidity profiles of the elevation class. Cloud, radiative, and surface processes are calculated separately for each elevation class using the same physical parametrizations used by the model without the subgrid orography parametrization. The simulated climate fields for each elevation class can then be distributed in post-processing according to the spatial distribution of surface elevation within each grid cell. Parallel 10-year simulations with and without the subgrid treatment have been performed. The simulated temperature, precipitation and snow water are mapped to 2.5-minute (~5 km) resolution and compared with gridded analyses of station measurements. The simulation with the subgrid scheme produces a much more realistic distribution of snow water and significantly more realistic distributions of temperature and precipitation than the simulation without the subgrid scheme. Moreover, the 250-km grid cell means of most other fields are virtually unchanged by the subgrid scheme. This suggests that the tuning of the climate model without the subgrid scheme is also applicable to the model with the scheme.