May we engineer the climate?

Not only is the science of climate engineering uncertain; the legal issues are also highly uncertain. Although existing international law does not specifically limit the freedom of states to undertake climate engineering, the international community would likely demand a say should climate engineering move from the realm of speculation to concrete proposals. The experience of other environmental regimes, however, suggests that developing an international decision-making mechanism would be difficult, and that the international community might opt for a simple prohibition on climate engineering on grounds of precaution.     

Distributive justice in global climate finance – Recipients’ climate vulnerability and the allocation of climate funds

The ‘climate justice’ lens is increasingly being used in framing discussions and debates on global climate finance. A variant of such justice – distributive justice – emphasises recipient countries’ vulnerability to be an important consideration in funding allocation. The extent to which this principle is pursued in practice has been of widespread and ongoing concerns. Empirical evidence in this regard however remains inadequate and methodologically weak. This research examined the effect of recipients’ climate vulnerability on the allocation of climate funds by controlling for other commonly-identified determinants. A dynamic panel regression method based on Generalised Method of Moments (GMM) was used on a longitudinal dataset, containing approved funds for more than 100,000 projects covering three areas of climate action (mitigation, adaptation, and overlap) in 133 countries over two decades (2000–2018). Findings indicated a non-significant effect of recipients’ vulnerability on mitigation funding, but significant positive effects on adaptation and overlap fundings. ‘Most vulnerable’ countries were likely to receive higher amounts of these two types of funding than the ‘least vulnerable’ countries. All these provided evidence of distributive justice. However, the relationship between vulnerability and funding was parabolic, suggesting ‘moderately vulnerable’ countries likely to receive more funding than the ‘most vulnerable’ countries. Whilst, for mitigation funding, this observation was not a reason for concern, for adaptation and overlap fundings this was not in complete harmony with distributive justice. Paradoxically, countries with better investment readiness were likely to receive more adaptation and overlap funds. In discordance with distributive justice, countries within the Sub-Saharan Africa and South Asia regions, despite their higher climatic vulnerabilities, were likely to receive significantly less adaptation and overlap fundings. Effects of vulnerability were persistent, and past funding had significant effects on current funding. These, coupled with the impact of readiness, suggested a probable Low Funding Trap for the world’s most vulnerable countries. The overarching conclusion is that, although positive changes have occurred since the 2015 Paris Agreement, considerable challenges to distributive justice remain. Significant data and methodological challenges encountered in the research and their implications are also discussed.     

Who feels the impacts of climate change?

Feeling affected by climate change related disasters has the potential to mobilize belief in climate change, concern about the issue, and support for mitigation policies – even when accounting for the effects of physically living through a disaster. In this study we use a two-wave survey design where respondents in the United States were interviewed before and after Hurricane Florence to better understand who feels affected by such disasters. First, we find that being worried about climate change increases the feeling of being affected by the hurricane among those who regularly discuss climate change. Second, we find that those who are high in perspective taking are more likely to feel affected. However, those who are high in empathic concern, but feel obligated to help victims of disasters, are less likely to feel affected. This suggests that hurricanes may cause a collapse of compassion, where those who are especially sensitive to the suffering of others down-regulate their emotional response to costly disasters.     

Uncertainty in the 2°C warming threshold related to climate sensitivity and climate feedback

Climate sensitivity is an important index that measures the relationship between the increase in greenhouse gases and the magnitude of global warming. Uncertainties in climate change projection and climate modeling are mostly related to the climate sensitivity. The climate sensitivities of coupled climate models determine the magnitudes of the projected global warming. In this paper, the authors thoroughly review the literature on climate sensitivity, and discuss issues related to climate feedback processes and the methods used in estimating the equilibrium climate sensitivity and transient climate response (TCR), including the TCR to cumulative CO₂ emissions. After presenting a summary of the sources that affect the uncertainty of climate sensitivity, the impact of climate sensitivity on climate change projection is discussed by addressing the uncertainties in 2°C warming. Challenges that call for further investigation in the research community, in particular the Chinese community, are discussed.     

Evaluating climate change at the Croatian Adriatic from observations and regional climate models’ simulations

The 2m temperature (T2m) and precipitation from five regional climate models (RCMs), which participated in the ENSEMBLES project and were integrated at a 25-km horizontal resolution, are compared with observed climatological data from 13 stations located in the Croatian coastal zone. The twentieth century climate was simulated by forcing RCMs with identical boundary conditions from the ERA-40 reanalysis and the ECHAM5/MPI-OM global climate model (GCM); climate change in the twenty-first century is based on the A1B scenario and assessed from the GCM-forced RCMs’ integrations. When forced by ERA-40, most RCMs exhibit cold bias in winter which contributes to an overestimation of the T2m annual cycle amplitude and the errors in interannual variability are in all RCMs smaller than those in the climatological mean. All models underestimate observed warming trends in the period 1951–2010. The largest precipitation biases coincide with locations/seasons with small observed amounts but large precipitation amounts near high orography are relatively well reproduced. When forced by the same GCM all RCMs exhibit a warming in the cold half-year and a cooling (or weak warming) in the warm period, implying a strong impact of GCM boundary forcing. The future eastern Adriatic climate is characterised by a warming, up to +5 °C towards the end of the twenty-first century; for precipitation, no clear signal is evident in the first half of the twenty-first century, but a reduction in precipitation during summer prevails in the second half. It is argued that land-sea contrast and complex coastal configuration of the Croatian coast, i.e. multitude of island and well indented coastline, have a major impact on small-scale variability. Orography plays important role only at small number of coastal locations. We hypothesise that the parameterisations related to land surface processes and soil hydrology have relatively stronger impact on variability than orography at those locations that include a relatively large fraction of land (most coastal stations), but affecting less strongly locations at the Adriatic islands.     

Climate sensitivity: should the climate tail wag the policy dog?

The small but stubbornly unyielding possibility of a very large long-term response of global temperature to increases in atmospheric carbon dioxide can be termed the fat tail of high climate sensitivity. Recent economic analyses suggest that the fat tail should dominate a rational policy strategy if the damages associated with such high temperatures are large enough. The conclusions of such analyses, however, depend on how economic growth, temperature changes, and climate damages unfold and interact over time. In this paper we focus on the role of two robust physical properties of the climate system: the enormous thermal inertia of the ocean, and the long timescales associated with high climate sensitivity. Economic models that include a climate component, and particularly those that focus on the tails of the probability distributions, should properly represent the physics of this slow response to high climate sensitivity, including the correlated uncertainty between present forcing and climate sensitivity, and the global energetics of the present climate state. If climate sensitivity in fact proves to be high, these considerations prevent the high temperatures in the fat tail from being reached for many centuries. A failure to include these factors risks distorting the resulting economic analyses. For example, we conclude that fat-tail considerations will not strongly influence economic analyses when these analyses follow the common—albeit controversial—practices of assigning large damages only to outcomes with very high temperature changes and of assuming a significant baseline level of economic growth.     

Correlation between climate sensitivity and aerosol forcing and its implication for the “climate trap”

Climate sensitivity and aerosol forcing are dominant uncertain properties of the global climate system. Their estimates based on the inverse approach are interdependent as historical temperature records constrain possible combinations. Nevertheless, many literature projections of future climate are based on the probability density of climate sensitivity and an independent aerosol forcing without considering the interdependency of such estimates. Here we investigate how large such parameter interdependency affects the range of future warming in two distinct settings: one following the A1B emission scenario till the year 2100 and the other assuming a shutdown of all greenhouse gas and aerosol emissions in the year 2020. We demonstrate that the range of projected warming decreases in the former case, but considerably broadens in the latter case, if the correlation between climate sensitivity and aerosol forcing is taken into account. Our conceptual study suggests that, unless the interdependency between the climate sensitivity and aerosol forcing estimates is properly considered, one could underestimate a risk involving the “climate trap”, an unpalatable situation with a high climate sensitivity in which a very drastic mitigation may counter-intuitively accelerate the warming by unmasking the hidden warming due to aerosols.     

Spatiotemporal dynamics of the Urals’ climate in the second half of the 20th century

Dynamics of the surface air temperature and amount of precipitation in the Polar, Northern, and Southern Urals in the 20th century is analyzed. Charts of the temperature distribution in the Urals for the period from 1961 to 2000, taking into account the relief, are plotted in the geographical informational system on the basis of data of instrumental measurements at meteorological stations with the use of the multiple regression analysis and raster modeling. The northeastern direction of the warming gradient and increase of falling precipitations in the period under review is established. Time series of anomalies of the average annual air temperature and amount of precipitation in the 20th century at three meteorological stations, situated in the Polar, Northern, and Southern Urals, are analyzed. The tendency of the growth of anomalies of the average annual temperature and total amount of precipitation is revealed.     

Emission metrics under the 2 °C climate stabilization target

In multi-gas climate policies such as the Kyoto Protocol one has to decide how to compare the emissions of different greenhouse gases. The choice of metric could have significant implications for mitigation priorities considered under the prospective negotiations for climate mitigation agreements. Several metrics have been proposed for this task with the Global Warming Potential (GWP) being the most common. However, these metrics have not been systematically compared to each other in the context of the 2 °C climate stabilization target. Based on a single unified modeling framework, we demonstrate that metric values span a wide range, depending on the metric structure and the treatment of the time dimension. Our finding confirms the basic salient point that metrics designed to represent different aspects of the climate and socio-economic system behave differently. Our result also reflects a complex interface between science and policy surrounding metrics. Thus, it is important to select or design a metric suitable for climate stabilization based on an interaction among practitioners, policymakers, and scientists.     

Might climate change the “healthy migrant” effect?

Migrants from Mexico to the U.S. tend to be healthier than non-migrants in their origin – part of a pattern termed the “healthy migrant effect”. With climate change altering livelihoods across the globe, we ask how the migration-health connection may be altered by environmental strain. On the one hand, positive health selectivity may be intensified if migration becomes more challenging – and therefore increasingly likely to be undertaken by only the healthiest. On the other hand, positive health selectivity may decline if the “push” associated with environmental strain acts upon individuals regardless of health. We use Mexican Migration Project data to model Mexico-US migration by male household heads with consideration of migrant health as well as recent rainfall conditions in communities of origin. Results reveal intriguing interactions such that when moderately dry regions experience rainfall shortage, health selectivity is lower – meaning that less healthy household heads also engage in international migration. We posit that social networks may underlie this association. We further argue that since environmental context may alter the relationship between migration and health, future research on the “healthy migrant effect” should consider environmental conditions. As to implications, if climate change yields pressure on less healthy individuals to migrate, the need for migrant-sensitive health systems and services may be intensified in destination regions.     

Why does the Antarctic Peninsula Warm in climate simulations?

The Antarctic Peninsula has warmed significantly since the 1950s. This pronounced and isolated warming trend is collectively captured by 29 twentieth-century climate hindcasts participating in the version 3 Coupled Model Intercomparison Project. To understand the factors driving warming trends in the hindcasts, we examine trends in Peninsula region’s atmospheric heat budget in every simulation. We find that atmospheric latent heat release increases in nearly all hindcasts. These increases are generally anthropogenic in origin, and account for about 60% of the ensemble-mean warming trend in the Peninsula. They are driven primarily by well-understood features of the anthropogenic intensification of global hydrological cycle. As sea surface temperature increases, moisture contained in atmospheric flows increases. When such flows are forced to ascend the Peninsula’s topography, enhanced local latent heat release results. The mechanism driving the warming of the Antarctic Peninsula is therefore clear in the models. Evidence for a similar mechanism operating in the real world is seen in the increasing snow accumulation rates inferred from ice cores drilled in the Peninsula. However, the relative importance of this mechanism and other processes previously identified as potentially causing the observed warming, such as the recent sea ice retreat in the Bellingshausen Sea, is difficult to assess. Thus the relevance of the simulated warming mechanism to the observed warming is unclear, in spite of its robustness in the models.     

The new national climate change documents of Mexico: what do the regional climate change scenarios represent?

This paper presents a review of the methodology applied for generating the regional climate change scenarios utilized in important National Documents of Mexico, such as the Fourth National Communication to the United Nations Framework Convention on Climate Change, the Fourth National Report to the Convention on Biological Diversity and The Economics of Climate Change in Mexico. It is shown that these regional climate change scenarios, which are one of the main inputs to support the assessments presented in these documents, are an example of the erroneous use of statistical downscaling techniques. The arguments presented here imply that the work based on such scenarios should be revised and therefore, these documents are inadequate for supporting national decision- making.     

Indian summer monsoon influence on the climate in the North Atlantic–European region

Previous studies have shown that climate anomalies over the North Atlantic–Europe (NAE) can influence the Indian summer monsoon (ISM) variability. It is, however, still an outstanding question whether the latter has a significant impact on the former. In this study, observational evidences indicate that the interannual variability of ISM is closely linked to the climate anomalies over NAE. A strong ISM is often associated with significant above normal precipitation over most of western Europe. Meanwhile, positive surface air temperature (SAT) anomalies are usually observed over the Mediterranean, accompanied by below normal SAT in Western Europe during a strong ISM summer. The situation is just opposite during a weak ISM summer. A global primitive equation model is utilized to assess the mechanism of the above observed connection.     

An atmosphere–ocean regional climate model for the Mediterranean area: assessment of a present climate simulation

We present an atmosphere–ocean regional climate model for the Mediterranean basin, called the PROTHEUS system, composed by the regional climate model RegCM3 as the atmospheric component and by a regional configuration of the MITgcm model as the oceanic component. The model is applied to an area encompassing the Mediterranean Sea and compared to a stand-alone version of its atmospheric component. An assessment of the model performances is done by using available observational datasets. Despite a persistent bias, the PROTHEUS system is able to capture the inter-annual variability of seasonal sea surface temperature (SST) and also the fine scale spatio-temporal evolution of observed SST anomalies, with spatial correlation as high as 0.7 during summer. The close inspection of a 10-day strong wind event during the summer of 2000 proves the capability of the PROTHEUS system to correctly describe the daily evolution of SST under strong air–sea interaction conditions. As a consequence of the model’s skill in reproducing observed SST and wind fields, we expect a reliable estimation of air–sea fluxes. The model skill in reproducing climatological land surface fields is in line with that of state of the art regional climate models.     

Assessing the potential impact of climate change on the UK’s electricity network

We investigate how weather affects the UK’s electricity network, by examining past data of weather-related faults on the transmission and distribution networks. By formalising the current relationship between weather-related faults and weather, we use climate projections from a regional climate model (RCM) to quantitatively assess how the frequency of these faults may change in the future. This study found that the incidences of both lightning and solar heat faults are projected to increase in the future. There is evidence that the conditions that cause flooding faults may increase in the future, but a reduction cannot be ruled out. Due to the uncertainty associated with future wind projections, there is no clear signal associated with the future frequency of wind and gale faults, however snow, sleet and blizzard faults are projected to decrease due to a reduction in the number of snow days.     

Will the tropical land biosphere dominate the climate–carbon cycle feedback during the twenty-first century?

Global warming caused by anthropogenic CO₂ emissions is expected to reduce the capability of the ocean and the land biosphere to take up carbon. This will enlarge the fraction of the CO₂ emissions remaining in the atmosphere, which in turn will reinforce future climate change. Recent model studies agree in the existence of such a positive climate–carbon cycle feedback, but the estimates of its amplitude differ by an order of magnitude, which considerably increases the uncertainty in future climate projections. Therefore we discuss, in how far a particular process or component of the carbon cycle can be identified, that potentially contributes most to the positive feedback. The discussion is based on simulations with a carbon cycle model, which is embedded in the atmosphere/ocean general circulation model ECHAM5/MPI-OM. Two simulations covering the period 1860–2100 are conducted to determine the impact of global warming on the carbon cycle. Forced by historical and future carbon dioxide emissions (following the scenario A2 of the Intergovernmental Panel on Climate Change), they reveal a noticeable positive climate–carbon cycle feedback, which is mainly driven by the tropical land biosphere. The oceans contribute much less to the positive feedback and the temperate/boreal terrestrial biosphere induces a minor negative feedback. The contrasting behavior of the tropical and temperate/boreal land biosphere is mostly attributed to opposite trends in their net primary productivity (NPP) under global warming conditions. As these findings depend on the model employed they are compared with results derived from other climate–carbon cycle models, which participated in the Coupled Climate–Carbon Cycle Model Intercomparison Project (C4MIP).

Institutions in conflict? the climate change flexibility mechanisms and the multinational trading system

In an attempt to combat climate change on a global scale, the Kyoto Protocol to the United Nations Framework Convention on Climate Change (UNFCCC) was adopted in conjunction with a wide range of policies both at national and international level. In particular, flexibility mechanisms-emissions trading system, joint implementation (JI) and clean development mechanism (CDM)-were incorporated in the Protocol to fulfil the commitment of the Parties by utilising a market system. Under the flexibility mechanisms, an artificial market is created in which the emission allowances or emission reduction units are traded. Not surprisingly, such measures might result in significant impacts on the trade of both goods and services, presumably creating the most complex and dynamic interaction with the Multilateral Trading System (MTS) which is overseen by the World Trade Organisation (WTO). If the implementation of flexibility mechanisms is identified as inconsistent with the requirements of the MTS, enforcement of such policies may prove difficult due to constraints imposed by GATT/WTO provisions.The purpose of this article is to scrutinise potential incompatibility between the implementation of flexibility mechanisms and GATT/WTO provisions. The rules governing the implementation of flexibility mechanisms have yet to be decided due to the divergent views of States regarding the design of the mechanisms. Thus, the analysis of the interaction will be undertaken based on hypothetical scenarios of each mechanism to account for all possible consequences of their implementation. Such an analysis will facilitate detection of any potential conflicts between the implementation of flexibility mechanisms and the trade regimes in advance, thus encompassing the potential incompatibility in designing the mechanisms and helping achieve increasingly effective implementation of flexibility mechanisms.