From Lima to Paris,Part 1: The Lima Hangover

A growing body of literature suggests that an economic case may exist for investment in large-scale climate change mitigation. At the same time, however, investment is persistently falling well short of the levels required to prevent dangerous climate change, suggesting that economically attractive mitigation opportunities are being missed. To understand whether and where these opportunities exist, this article contrasts macro-level analyses of climate finance with micro-level bottom-up analyses of the scale and composition of low-carbon investment opportunities in four case study developing world cities. This analysis finds that there are significant opportunities to redirect existing finance streams towards more cost-effective, lower-carbon options. This would mobilize substantial new investment in climate mitigation. Two key explanations are proposed for the failure to exploit these opportunities. First, the composition of cost-effective measures is highly context-specific, varying from place to place and sector to sector. Macro-level analyses of climate finance flows are therefore poor indicators of the micro-level landscape for low-carbon investment. Specific local research is therefore needed to understand the opportunities for cost-effective mitigation at that level. Second, many opportunities require enabling governance arrangements that are not currently in place. Mobilizing new low-carbon investment and closing the ‘climate finance gap' therefore requires attention to policy frameworks and financing mechanisms that can facilitate the exploitation of cost-effective low-carbon options.

Policy relevance

The importance of increasing investment in climate mitigation, especially in developing nations, is well established. This article scrutinizes four city-level studies of the scope for cost-effective low-carbon investment, and finds that significant opportunities are not being exploited in developing world cities. Enabling governance structures may help to mainstream climate considerations into investments by local actors (households, businesses and government agencies). While climate finance distributed through international bodies such as the Green Climate Fund may not always be a suitable vehicle to invest directly in disaggregated, local-level measures, it can provide the incentives to develop these governance arrangements.     

从巴黎到卡托维兹：全球气候治理中的统一和分裂

《巴黎协定》达成之后的实施细则谈判从一开始就面临各种挑战。尽管如此,卡托维兹气候大会基本完成了实施细则的磋商,通过统一规则的制定夯实了基于规则的气候治理框架,为“自下而上”的松散协定注入了更多规则绑定强制性色彩,提升了协定的法律地位。会议也见证了气候世界的分裂,包括主要缔约方立场的退化、谈判集团的分化重组、利益集团的博弈、对科学报告的分歧等,从而使关于力度的磋商没有实质进展。从巴黎到卡托维兹的谈判路程表明治理全球化、治理效率以及国家主权之间暂时存在“不可能三角”。未来的谈判应促进从规则到行动的转变。     

Rainfall Variations of Sri Lanka, Part 2: regional gluctuations

Summary Based on the regional division of another paper [39], the rainfall variations of Sri Lanka have been investigated for the respective regions by power spectrum analysis and filtering methods, making use of data for the period from 1881 to 1980. The 3–4 year periodicity was observed over the entire island, but other cycles differ from region to region. The 13–16 months oscillation arises in Regions A, D and E, which roughly correspond to the Wet Zone and Dry Zone. The 10 and 2 year oscillations emerge in Regions A, B and C, where the southwest monsoon dominates the fluctuation patterns. In particular, it was confirmed that the quasi-biennial oscillation is not only in Sri Lanka, but also in other low latitude countries. The quasi-five year oscillation is noticed in Regions D and E, where the northeast monsoon influences on the fluctuation patterns. Irregularities in amplitude and in phase changes were noticed in their longer period fluctuation.

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Variationen des Niederschlags in Sri Lanka. Teil 2: Regionale Fluktuationen

Zusammenfassung Aufgrund einer früher vorgenommenen regionalen Einteilung [39] wurden die Niederschlagsvariationen in Sri Lanka für die einzelnen Regionen mit Spektralanalyse und Filterungsmethoden unter Verwendung von Beobachtungsdaten aus der Periode 1881–1980 untersucht. Die 3- bis 4jährige Periodizität wurde auf der ganzen Insel festgestellt; aber andere Zyklen unterscheiden sich von Region zu Region. Eine 13- bis 16monatige Oszillation zeigt sich in den Regionen A, D und E, die ungefähr der Feuchtzone und der Trockenzone entsprechen. 10- bis 2jährige Oszillationen treten in den Regionen A, B und C auf, wo der Südwestmonsun die Fluktuationsformen beherrscht. Im besonderen wurde festgestellt, daß die quasi-zweijährige Oszillation nicht nur in Sri Lanka, sondern auch in anderen Ländern niedriger Breiten vorkommt. Eine quasifünfjährige Oszillation wurde in den Regionen D und E festgestellt, wo der Nordostmonsun die Fluktuationsformen beeinflußt. Unregelmäßigkeiten in der Amplitude und in Phasenänderungen wurden in ihrer längerperiodischen Fluktuation festgestellt.

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With 4 Figures     

A coupled climate model simulation of the Last Glacial Maximum,Part 2: approach to equilibrium

The climate of the last glacial maximum (LGM) is simulated with a coupled climate model. The simulated climate undergoes a rapid adjustment during the first several decades after imposition of LGM boundary conditions, as described in Part 1, and then evolves toward equilibrium over 900 model years. The climate simulated by the coupled model at this period is compared with observationally-based LGM reconstructions and with LGM results obtained with an atmosphere-mixed layer (slab) ocean version of the model in order to investigate the role of ocean dynamics in the LGM climate. Global mean surface air temperature and sea surface temperature (SST) decrease by about 10 °C and 5.6 °C in the coupled model which includes ocean dynamics, compared to decreases of 6.3 and 3.8 °C in slab ocean case. The coupled model simulates a cooling of about 6.5 °C over the tropics, which is larger than that of the CLIMAP reconstruction (1.7 °C) and larger than that of the slab ocean simulation (3.3 °C), but which is in reasonable agreement with some recent proxy estimates. The ocean dynamics of the coupled model captures features found in the CLIMAP reconstructions such as a relative maximum of ocean cooling over the tropical Pacific associated with a mean La Niña-like response and lead to a more realistic SST pattern than in the slab model case. The reduction in global mean precipitation simulated in the coupled model is larger (15%) than that simulated with the slab ocean model (~10%) in conjunction with the enhanced cooling. Some regions, such as the USA and the Mediterranean region, experience increased precipitation in accord with proxy paleoclimate evidence. The overall much drier climate over the ocean leads to higher sea surface salinity (SSS) in most ocean basins except for the North Atlantic where SSS is considerably lower due to an increase in the supply of fresh water from the Mississippi and Amazon rivers and presumably a decrease in salt transport by the weakened North Atlantic overturning circulation. The North Atlantic overturning stream function weakens to less than half of the control run value. The overturning is limited to a shallower depth (less than 1000 m) and its outflow is confined to the Northern Hemisphere. In the Southern Ocean, convection is much stronger than in the control run leading to a stronger overturning stream function associated with enhanced Antarctic Bottom Water formation. As a result, Southern Ocean water masses fill the entire deep ocean. The Antarctic Circumpolar Current (ACC) transport through the Drake Passage increases by about 25%. The ACC transport, despite weaker zonal winds, is enhanced due to changes in bottom pressure torque. The weakening of the overturning circulation in the North Atlantic and the accompanying 30% decrease in the poleward ocean heat transport contrasts with the strengthening of the overturning circulation in the Southern Ocean and a 40% increase in heat transport. As a result, sea ice coverage and thickness are affected in opposite senses in the two hemispheres. The LGM climate simulated by the coupled model is in reasonable agreement with paleoclimate proxy evidence. The dynamical response of the ocean in the coupled model plays an important role in determining the simulated, and undoubtedly, the actual, LGM climate.     

Typhoon Track,Intensity, and Structure: From Theory to Prediction

To improve understanding of essential aspects that influence forecasting of tropical cyclones (TCs), the National Key Research and Development Program, Ministry of Science and Technology of the People’s Republic of China conducted a five-year project titled “Key Dynamic and Thermodynamic Processes and Prediction for the Evolution of Typhoon Intensity and Structure” (KPPT). Through this project, new understandings of TC intensification, including outer rainband-driven secondary eyewall formation and the roles of boundary layer dynamics and vertical wind shear, and improvements to TC data assimilation with integrated algorithms and adaptive localizations are achieved. To promote a breakthrough in TC intensity and structure forecasting, a new paradigm for TC evolution dynamics (i.e., the correlations, interactions, and error propagation among the triangle of TC track, intensity, and structure) is proposed; and an era of dynamic-constrained, big-data driven, and strongly coupled data assimilation at the subkilometer scale and seamless prediction is expected.     

Local foehn effects in the upper Isar Valley, Part 2: numerical simulations

Summary The local wind system in the upper Isar Valley (Bavarian Alps) near Mittenwald has the peculiarity that regularly strong foehn-like nocturnal flows occur, mainly during clear nights in autumn and winter. We will refer to this phenomenon as “Minifoehn”, as its properties are similar to the classical deep foehn in the sense that its breakthrough into the Isar Valley usually brings a striking increase in temperature and a concomitant decrease in relative humidity. Numerical simulations with the MM5 model reveal that this phenomenon is related to a nocturnal drainage flow originating from a plateau south of Mittenwald. This flow is driven by the temperature difference between this plateau (1180 m) and the free atmosphere above Mittenwald (920 m, 15 km north of the plateau) at the same level. The air masses flow through two different valleys that merge again further downstream. The upper part of one of the two drainage currents goes over a small mountain ridge (1180 m) south-west of Mittenwald and then descends into the Isar Valley, leading to an advection of potentially warm air towards Mittenwald. This branch of the drainage current constitutes the Minifoehn. The remaining part of the drainage current flows through a narrow gap towards the Isar Valley and then joins the drainage flow of this valley. As these air masses are significantly cooler than the Minifoehn branch, large horizontal temperature gradients can be found around Mittenwald. The dynamical behaviour of the cold air flow turns out to be qualitatively consistent with shallow-water theory only in the absence of a forcing by large-scale winds. Otherwise, gravity-wave induced pressure perturbations interact with the drainage flow and modify the low-level flow field. The simulations show that the gravity waves are excited by the mountain range that separates the two valleys mentioned above. Moreover, the simulations indicate that the structure of this nocturnal wind system is not very sensitive to the direction of synoptic-scale winds as long as they come from the southern sector. On the other hand, ambient northerly winds are able to prevent the drainage flow and therefore the local foehn effects in the Isar Valley provided that synoptic winds are strong enough. The results of the MM5 simulations are in good agreement with the measurements and observations described in part 1 of this study.     

Many roads to Paris: Explaining urban climate action in 885 European cities

Research on urban climate action has identified a broad range of potential factors explaining why and how local governments decide to tackle climate change. However, empirical evidence linking such factors in order to explain actual urban climate action has so far been mixed. To address this roadblock, our paper relies on a novel approach, postulating that different configurations of factors may lead to the same outcome (“equifinality”), through a qualitative comparative analysis (QCA). It is based on an available data set of local climate mitigation plans in 885 European cities. We find that urban climate action is systematically associated with four qualitatively different configurations of factors, each with its own consistent narrative (“networker cities”, “green cities”, “lighthouse cities”, “fundraising cities”). Crucially, some factors play a positive role in some configurations, a negative in others, and no role in further configurations (e.g., whether a city is located in a country with supportive national climate policies). This confirms that there is no single explanation for urban climate action. Achieving greater robustness in empirical research about urban climate action may thus require a shift, both conceptual and methodological, to the interactions between factors, allowing for different explanations in different contexts.     

Automated mechanism generation. Part 2: application to atmospheric chemistry of alkanes and oxygenates

In this study, an automated mechanism generation framework was applied to atmospheric chemistry of volatile organic compounds (VOCs) and nitrogen oxides (NO _x ). The framework generates reactions with minimal input based on a small set of reaction operators and includes a hierarchy for specifying rate constants for every reaction created. Mechanisms were generated for formaldehyde-air-NO _x , acetaldehyde-formaldehyde-n-octane-air-NO _x , and acetone-air-NO _x , and the model results were compared to experimental data obtained from smog chambers and to the SAPRC-99 lumped models. The models generated captured the experimental data very well, and their mechanistic formulation provided new insights into the controlling reaction pathways to pollutant formation. The approach applied here is sufficiently general that it can be applied to a wide range of alkane and oxygenate mixtures.     

One-dimensional turbulence: Part 2. Staircases in double-diffusive convection

One-Dimensional Turbulence (ODT), a turbulence model implemented as an unsteady simulation, is applied to the diffusive regime of double-diffusive convection. For this application, no parameter adjustment or other empiricism is required. Computed component fluxes across heat–salt and salt–sugar interfaces are consistent with the Linden–Shirtcliffe picture, applicable at intermediate density ratios, and Newell's model of interface evolution at high density ratios. The experimentally observed onset of a variable regime at density ratios below 2 is reproduced. Simulations of interface formation in a bottom-heated salt-stabilized medium indicate that Fernando's scaling for interface stabilization height may also apply to the height of initial interface formation. The simulations generate staircases resembling those seen in laboratory experiments, and suggest a refinement of a scaling inferred from experiments. Computed results for a thermally forced configuration and an unforced, vertically homogeneous configuration are compared.     

Meteorology and haze structure during AGASP-II,Part 2: Canadian Arctic flights, 13–16 April 1986

In April 1986, a well-instrumented NOAA WP-3D research aircraft conducted three flights in the Canadian Arctic tied to the Canadian Atmospheric Environment Service baseline station in Alert, Northwest Territories. Two of the flights were coordinated with the National Aeronautical Establishment of Canada Twin Otter and the University of Washington C-131 research aircraft. The haze observed in the Canadian Arctic was well-aged and mixed throughout the troposphere in concentrations well below those observed during the previous weeks in the Alaskan Arctic. Over the ice, beneath the surface temperature inversion, ozone was generally depleted to near zero. Over the coast at Alert, there is evidence that topography and downslope winds reduce the strength of the inversion, thus allowing lower tropospheric gases and aerosols to mix down to the surface. At the top of the troposphere, an aerosol-depleted region was observed. In the lower stratosphere, aerosol concentrations were elevated above those observed in the troposphere.     

Meteorology and haze structure during AGASP-II,Part 1: Alaskan Arctic flights, 2–10 April 1986

The second Arctic Gas and Aerosol Sampling Program (AGASP-II) was conducted across the Alaskan and Canadian Arctic in April 1986, to study the in situ aerosol, and the chemical and optical properties of Arctic haze. The NOAA WP-3D aircraft, with special instrumentation added, made six flights during AGASP-II. Measurements of wind, pressure, temperature, ozone, water vapor, condensation nuclei (CN) concentration, and aerosol scattering extinction (b_sp) were used to determine the location of significant haze layers. The measurements made on the first three flights, over the Arctic Ocean north of Barrow and over the Beaufort Sea north of Barter Island, Alaska are discussed in detail in this report of the first phase of AGASP II. In the Alaskan Arctic the WP-3D detected a large and persistent region of haze between 960 and 750 mb, in a thermally stable layer, on 2, 8, and 9 April 1986. At its most dense, the haze contained CN concentrations >10,000 cm^–3 and b_sp of 80×10^–6 m^–1 suggesting active SO₂ to H₂SO₄ gas-to-particle conversion. Calculations based upon observed SO₂ concentrations and ambient relative humidities suggest that 10⁴–10⁵ small H₂SO₄ droplets could have been produced in the haze layers. High concentrations of sub-micron H₂SO₄ droplets were collected in haze. Ozone concentrations were 5–10 ppb higher in the haze layers than in the surrounding troposphere. Outside the regions of haze, CN concentrations ranged from 100 to 400 cm^–3 and b_sp values were about (20–40)×10^–6 m^–1. Air mass trajectories were computed to depict the air flow upwind of regions in which haze was observed. In two cases the back trajectories and ground measurements suggested the source to be in central Europe.     

A Coastal Bay Summer Breeze Study,Part 2: High-resolution Numerical Simulation of Sea-breeze Local Influences

We complete the analysis of the data obtained during the experimental campaign around the semi circular bay of Quiberon, France, during two weeks in June 2006 (see Part 1). A reanalysis of numerical simulations performed with the Advanced Regional Prediction System model is presented. Three nested computational domains with increasing horizontal resolution down to 100 m, and a vertical resolution of 10 m at the lowest level, are used to reproduce the local-scale variations of the breeze close to the water surface of the bay. The Weather Research and Forecasting mesoscale model is used to assimilate the meteorological data. Comparisons of the simulations with the experimental data obtained at three sites reveal a good agreement of the flow over the bay and around the Quiberon peninsula during the daytime periods of sea-breeze development and weakening. In conditions of offshore synoptic flow, the simulations demonstrate that the semi-circular shape of the bay induces a corresponding circular shape in the offshore zones of stagnant flow preceding the sea-breeze onset, which move further offshore thereafter. The higher-resolution simulations are successful in reproducing the small-scale impacts of the peninsula and local coasts (breeze deviations, wakes, flow divergences), and in demonstrating the complexity of the breeze fields close to the surface over the bay. Our reanalysis also provides guidance for numerical simulation strategies for analyzing the structure and evolution of the near-surface breeze over a semi-circular bay, and for forecasting important flow details for use in upcoming sailing competitions.     

走向《巴黎协定》温升目标：已经在路上

目前欧盟、中国、日本、韩国、加拿大,以及南非等国家或地区,已经公布了温室气体中和或者碳中和的目标,如果加上很可能很快也会提出碳中和目标的美国,全球有可能近70%的CO₂排放的国家或地区提出碳中和的目标。由于这些国家或地区是全球技术主导和经济主导地,因而全球2050年左右实现碳中和具有可行性。2050年左右实现碳中和,即和《巴黎协定》2℃目标,甚至和其1.5℃温升目标下的减排路径相一致。研究表明实现2050年左右碳中和有其可行性,实现该目标需要更多的技术创新,未来将是各个国家技术竞争和经济竞争阶段。     

Simulation of the Askervein flow. Part 2: Large-eddy simulations

Large-eddy simulations of the neutrally stratified flow over the Askervein Hill were performed, to improve the knowledge of the flow obtained from field measurements and numerical simulations with Reynolds averaged Navier-Stokes (RANS) methods. A Lagrangian dynamic subgrid model was used but, to avoid the underdissipative character near the ground, it was merged with a damped Smagorinsky model. Simulations of a flat boundary-layer flow with this subgrid model showed that the turbulent vertical motions and shear stress were better resolved using grids with a stream to spanwise aspect ratio Δx / Δy = 2 than with an aspect ratio Δx / Δy = 1. Regarding the flow over the Askervein Hill, it was found that large-eddy simulations provide an acceptable solution for the mean-velocity field and better predictions of the turbulent kinetic energy in the upstream side of the hill than the model. However, as with the model, grid convergence was not achieved in the lee side and the size of the zone with reversed flow increased with the grid refinement. Nevertheless, the existence of the intermittent separation predicted with unsteady RANS in part one of this work seems unquestionable, due to the deceleration of the flow. In our opinion, a better modelling of the decelerating boundary layer in the lee side is required to improve the results obtained using equilibrium assumptions and achieve grid convergence.     

North African climate variability. Part 2: Tropical circulation systems

Summary Tropical North African climate variability is investigated using a Sahel rainfall index and streamflow of the Nile River in the 20^th century. The mechanisms that govern tropical North Africa climate are diagnosed from NCEP reanalysis data in the period 1958–1998: spatially – using composite and correlation analysis, and temporally – using wavelet co-spectral analysis. The Sahelian climate is characterised by a decadal rhythm, whilst the mountainous eastern and equatorial regions exhibit interannual cycles. ENSO-modulated zonal circulations over the Atlantic/Pacific sector are important for decadal variations, and create a climatic polarity between South America and tropical North Africa as revealed through upper-level velocity potential and convection patterns. A more localised N–S shift in convection between the Sahel and Guinea coast is associated with the African Easterly Jet.