Dynamics and circulation regimes of terrestrial planets

By the study of simple analogues, either in the form of simplified numerical models or laboratory experiments, considerable insights may be gained as to the likely roles of planetary size, rotation, thermal stratification and other factors in determining the principal length scales, styles of global circulation and dominant waves and instability processes active in the respective climate systems of Earth, Mars, Venus and Titan. In this review, we explore aspects of these analogues and demonstrate the importance of a number of key dimensionless parameters, most notably thermal Rossby and Rhines numbers and a measure of the dominant frictional or radiative timescale, in defining the type of circulation regime to be expected in a prototype planetary atmosphere subject to axisymmetric driving. These considerations help to place Mars, Venus, Titan and Earth into an appropriate context, and may also lay the foundations for predicting and understanding the climate and circulation regimes of (as yet undiscovered) Earth-like extra-solar planets. However, as recent discoveries of ‘super-Earth’ planets around some nearby stars are beginning to reveal, the parameter space determined from axisymmetrically forced prototype atmospheres may be incomplete and other factors, such as the possibility of tidally locked rotation and tidal forcing, may also need to be taken into account for some classes of extra-solar planet.     

Climate driven changes in subtidal kelp forest communities in NW Spain

Reconstructions suggest a massive decline of nearly 1400 ha of kelp forest in North Western Spain in 2007. In line with global rising temperatures, we hypothesized that Sea Surface Temperature (SST) surpassed a lethal threshold for kelp. We examined whether changes in SST correlated to the proposed decline in kelp forest. All investigated SST characteristics suggested to affect kelp abundance increased significantly during the past thirty years, reaching extreme values during the last decade. In addition over the past two decades, the landscape formerly dominated by both cold and warm temperate canopy forming and understory species changed to one dominated by warm temperate understory species, resulting in a loss of vertical community structure. Fisheries landing data of kelp associated species was used to support the suggested change in kelp abundance. Subsequent recovery of the kelp appears to be occurring in deeper waters.     

Species and plant community reorganization in the Trans-Mexican Volcanic Belt under climate change conditions

This study analyzes six vegetation communities in relation to current climatic parameters and eight climate change scenarios along an elevation gradient extending from 2,710 m to 4,210m in the Trans-Mexican Volcanic Belt. The projected movements of 25 plant species with the current restricted or wide altitudinal distributions were also modeled. To relate climatic parameters to the species and communities, a Precipitation/Temperature(P/T)index was used both for the current and the different climate-change scenarios. The temperatures are expected to increase by 1.1°C to 1.7°C by 2020 and by2°C to 3°C by 2050. A decrease of 4% to 13% in the annual precipitation is expected for the 2020 horizon,and a reduction between 3% and 20% is expected for2050. The reductions in water availability were projected for all altitude levels and plant communities.The most marked reduction was under the HADLEYA2 scenario, in which the lower limit of the altitudinal range increased from 2,710 to 3,310 m(2050 horizon)with reductions in the P/T index between 36% and39% compared to the current climate. Most plant species tended to shift their distribution from 200 to300 m upward in the 2020 temporal horizon scenarios. The Pinus hartwegii, Alnus jorullensis and Pinus montezumae communities would have a shorter altitudinal range as they move upward and merge with the remaining species at the higher altitudinal range. For the 2050 temporal horizon,30% of the species, primarily those from the higher altitudinal range, would disappear because their P/Tindex values would be above the limit of plant survival(4,210 m).     

最近60年来气候变化和人类活动对山地河流入海径流、泥沙的影响——以胶东半岛南部五龙河为例

采用Mann-Kendall非参数检验法、累积距平法、有序聚类分析法及线性回归等数学方法,以胶东半岛五龙河流域为例,对最近60年来气候变化和人类活动对山地河流入海径流、泥沙的影响进行了研究。结果表明,20世纪50年代以来五龙河入海径流、泥沙量均呈现出显著的阶段性逐级减少趋势。最近60年来,五龙河年径流量和输沙量主要集中在6—9月;主要受年降水量变化影响,年径流量从1980年开始显著减少,并在1966年出现较大波动;受年降水和径流变化影响,年输沙量也分别在1966和1980年呈减少突变;总体来看,年输沙量减少的趋势性要强于径流量。除气候变化影响外,1966年以来流域内大面积坡耕地改梯田和园地、林地建设等人类活动,也是造成河流径流、泥沙减少的重要原因。整体而言,最近60年来,气候变化和人类活动因素对五龙河入海水沙总量减少的贡献率分别为70%—80%和20%—30%。     

Adoption of the arctic search and rescue agreement: A shift of the arctic regime toward a hard law basis?

This paper examines the Arctic Search and Rescue Agreement—the first legally-binding instrument negotiated and adopted under the auspices of the Arctic Council—and analyzes its implications for the current Arctic regime. Led by the Arctic Council, the Arctic regime was established in a soft law format. However, the soft law nature and restricted mandates of the Arctic Council have limited its capacity to respond to new issues emerging from climate change, particularly those related to the exploitation of oil and gas reserves, commercial shipping through the region, effects on wildlife, and impacts on indigenous peoples' homelands and culture. The adoption of the Agreement represents a new approach for the Arctic States to respond to these new challenges. At the same time, it does not imply that a legally-binding instrument is necessarily preferable for every issue, and importantly, the new Arctic Agreement does not establish new institutional relationships, suggesting satisfaction among the Arctic States with the existing arrangements. Thus, although the Arctic regime is undoubtedly changing, this change should not be treated today as a shift from soft to hard law. What is more certain is that the Arctic Council will continue to function as a cooperative forum where the Arctic States can address these challenges, and its importance will only increase in coming years.     

Impacts of temperature on rice yields of different rice cultivation systems in southern China over the past 40 years

The impact of climate change on rice yield in China remains highly uncertain. We examined the impact of the change of maximum temperature (T_max) and minimum temperature (T_min) on rice yields in southern China from 1967 to 2007. The rice yields were simulated by using the DSSAT3.5 (Decision Support System for Agro-technology Transfer)-Rice model. The change of T_max and T_min in rice growing seasons and simulated rice yields as well as their correlations were analyzed. The simulated yields of middle rice and early rice had a decreasing trend, but late rice yields showed a weak rise trend. There was significant negative correlation between T_max and the early rice yields, as well as the late rice yields in most stations, but non-significant negative correlation for the middle rice yields. An obviously negative relationship was found between T_min and the early and middle rice yields, and a significant positive relationship was found between T_min and the late rice yields. It indicated that under the recent climate warming, the increased T_max brought strong negative impacts on early rice yields and late rice yields, but a weak negative impact on the middle rice yields; the increased T_min had a strong negative impact on the middle rice yields and the early rice yields, but a significant positive impact on the late rice yields. It suggested that it is necessary to adjust rice planting date and adapt to higher T_min.     

Single-grain and multi-grain OSL dating of river terrace sediments in the Tabernas Basin,SE Spain

River terraces represent important records of landscape response to e.g. base-level change and tectonic movement. Both these driving forces are important in the southern Iberian Peninsula. In this study, Optically Stimulated Luminescence (OSL) dating was used to date two principal river terraces in the Tabernas Basin, SE Spain. A total of 23 samples was collected from the fluvial terraces for dating using quartz OSL. Sixteen of the samples could not be dated because of low saturation levels (e.g. typical 2xD₀ < 50 Gy). The remaining seven samples (5 fossil and 2 modern analogues) were investigated using both multi-grain and single-grain analysis. Single grain results show that: (i) measurements from multi-grain aliquots overestimate ages by up to ∼ 4 ka for modern analogues and young samples (<5 ka), presumably because (ii) the presence of many saturated grains has biased the multi-grain results to older ages. Despite the unfavourable luminescence characteristics we are able to present the first numerical ages for two terrace aggradation stages in the Tabernas Basin, one at ∼16 ka and the other within the last 2 ka.     

Model and parameter uncertainty in IDF relationships under climate change

Quantifying distributional behavior of extreme events is crucial in hydrologic designs. Intensity Duration Frequency (IDF) relationships are used extensively in engineering especially in urban hydrology, to obtain return level of extreme rainfall event for a specified return period and duration. Major sources of uncertainty in the IDF relationships are due to insufficient quantity and quality of data leading to parameter uncertainty due to the distribution fitted to the data and uncertainty as a result of using multiple GCMs. It is important to study these uncertainties and propagate them to future for accurate assessment of return levels for future. The objective of this study is to quantify the uncertainties arising from parameters of the distribution fitted to data and the multiple GCM models using Bayesian approach. Posterior distribution of parameters is obtained from Bayes rule and the parameters are transformed to obtain return levels for a specified return period. Markov Chain Monte Carlo (MCMC) method using Metropolis Hastings algorithm is used to obtain the posterior distribution of parameters. Twenty six CMIP5 GCMs along with four RCP scenarios are considered for studying the effects of climate change and to obtain projected IDF relationships for the case study of Bangalore city in India. GCM uncertainty due to the use of multiple GCMs is treated using Reliability Ensemble Averaging (REA) technique along with the parameter uncertainty. Scale invariance theory is employed for obtaining short duration return levels from daily data. It is observed that the uncertainty in short duration rainfall return levels is high when compared to the longer durations. Further it is observed that parameter uncertainty is large compared to the model uncertainty.     

Ambivalent climate of opinions: Tensions and dilemmas in understanding geoengineering experimentation

Due to the fear of the consequences of climate change, many scientists today advocate the research into—but not deployment of—geoengineering, large-scale technological control of the global climate, to reduce the uncertainty around its efficacy and harms. Scientists propose in particular initiating field trials of stratospheric aerosol injection (SAI). This paper examines how the meanings of geoengineering experimentation, specifically SAI field trials, are reconfigured in the deliberation of the lay public. To this end, we conducted focus groups with Japanese citizens in June 2015 on the geoengineering concept and SAI field trials. Our main findings are as follows: the ‘climate emergency’ framing compelled the lay public to accept, either willingly or reluctantly, the need for ‘geoengineering research’; however, public discourse on SAI field trials was ambiguous and ambivalent, involving both tensions and dilemmas in understanding what the SAI field trial is for and about. Our results exhibit how the lay public wrestles with understanding the social, political, and ethical implications of SAI field trials in multiple dimensions, namely, accountability, controllability, predictability, and desirability. The paper argues that more clarity in the term ‘geoengineering research’ is needed to facilitate inclusive and pluralistic debates on geoengineering experimentation and not to preemptively arrive at a consensus that ‘we need more research.’ We conclude that ambivalence about both the pros and cons of geoengineering experimentation seems to be enduring; thus, instead of ignoring or repressing it, embracing ambivalence is required to keep the geoengineering debate democratic and inclusive.     

Power and politics in climate change adaptation efforts: Struggles over authority and recognition in the context of political instability

Throughout the world, climate change adaptation policies supported by the United Nations Framework Convention on Climate Change (UNFCCC) have provided significant sources of funding and technical support to developing countries. Yet often the adaptation responses proposed belie complex political realities, particularly in politically unstable contexts, where power and politics shape adaptation outcomes. In this paper, the concepts of authority and recognition are used to capture power and politics as they play out in struggles over governing changing resources. The case study in Nepal shows how adaptation policy formation and implementation becomes a platform in which actors seek to claim authority and assert more generic rights as political and cultural citizens. Focusing on authority and recognition helps illuminate how resource governance struggles often have very little to do with the resources themselves. Foundational to the argument is how projects which seek to empower actors to manage their resources, produce realignments of power and knowledge that then shape who is invested in what manner in adaptation. The analysis adds to calls for reframing ‘adaptation’ to encompass the socionatural processes that shape vulnerability by contributing theoretical depth to questions of power and politics.