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A multidecadal decrease in downward surface solar radiation (solar “dimming”) followed by a multidecadal increase in surface radiation (solar “brightening”) have been reported over Europe. The trends mainly occur under cloud‐free skies, and they are primarily caused by the direct aerosol radiative effect. The present study compares observed cloud‐free solar “dimming” and “brightening” trends with corresponding output from IPCC‐AR4 20th century simulations and furthermore examines how sulfate and black carbon aerosol histories, used as model input, affect simulated surface radiation trends. Outputs from 14 models are compared to observed cloud‐free surface radiation fluxes derived from a combination of (1) satellite cloud observations, synoptic cloud reports, and surface solar irradiance measurements and (2) sunshine duration measurements and variability of the atmospheric transmittance derived from solar irradiance measurements. Most models display a transition from decreasing to increasing solar irradiance, but the timing of the reversal varies by about 25 years. Consequently, large discrepancies in sign and magnitude occur between modeled and observed “dimming” and “brightening” trends (up to 4.5 Wm−2 per decade for Europe). Considering all models with identical aerosol histories, differences in cloud‐free radiation trends are in all but one case less than 0.7 Wm−2 per decade. Thirteen of the fourteen models produce a transition from “dimming” to “brightening” that is consistent with the timing of the reversal from increasing to decreasing aerosol emissions in the input aerosol history. Consequently, the poor agreement between modeled and observed “dimming” and “brightening” is due to incorrect aerosol emission histories rather than other factors.

Observations indicate that greenhouse induced twentieth‐century warming has been strongly modulated by variations in surface solar radiation. Between the 1950s and 1980s, declining surface solar radiation (“global dimming”) likely caused a dampening of global warming, whereas increasing surface solar radiation (“brightening”) may have contributed to the rapid warming in the last 2 decades, and possibly also in the first half of the twentieth century. This is also reflected in the decadal evolution of diurnal temperature range, which is highly correlated with surface solar radiation, and which shows a distinct transition from a strong decrease between the 1950s and 1980s, toward a leveling off thereafter. The present study investigates to what extent these effects are simulated in the latest generation of global climate models used in the fourth Intergovernmental Panel on Climate Change (IPCC) assessment report (AR4) (phase 3 of the Coupled Model Intercomparison Project (CMIP3) models). While these models reproduce the overall twentieth century warming over global land surfaces well, they underestimate the decadal variations in the warming and particularly also in diurnal temperature range, indicative of a lack of decadal variations in surface solar radiation in the models.

Previous research indicates that clear‐sky downward solar radiation measured at the surface over China significantly decreased by about −8.6 W m−2 per decade during 1961–1989 and insignificantly increased during 1990–1999. Furthermore, solar radiation over Japan remained relatively constant during 1971–1989 and significantly increased by +5.3 W m−2 per decade during 1990–1999. The present study compares observed trends with those from twentieth century simulations by 14 global climate models in the CMIP3/IPCC‐AR4. Since radiative forcing by aerosols is the primary contributor to long‐term variations in surface solar radiation, the simulations are expected to resemble the observed trends if the input aerosol histories are realistic. To minimize the confounding impact of different cloud realizations in the observations and models, the radiative effects of cloud cover anomalies are removed from the surface solar radiation anomalies via linear regression. Although all of the models exhibit significant dimming trends over China before 1990, the largest model trend is −3.4 W m−2 per decade, less than half the magnitude and significantly different from the observed trend. Models including black carbon aerosol produce stronger decreasing trends than those that do not. The models also fail to reproduce the trend during 1990–1999 over Japan, and the largest model trend is +2.3 W m−2 per decade, only about half of the observed trend. These results suggest that global climate models uniformly underestimate the increase in aerosol radiative forcing over China prior to 1990 and uniformly underestimate the decrease in aerosol radiative forcing over Japan after 1990.

The Earth has warmed at an unprecedented pace in the decades of the 1980s and 1990s (IPCC in Climate change 2007: the scientific basis, Cambridge University Press, Cambridge, 2007 ). In Wu et al. (Proc Natl Acad Sci USA 104:14889–14894, 2007 ) we showed that the rapidity of the warming in the late twentieth century was a result of concurrence of a secular warming trend and the warming phase of a multidecadal (~65-year period) oscillatory variation and we estimated the contribution of the former to be about 0.08°C per decade since ~1980. Here we demonstrate the robustness of those results and discuss their physical links, considering in particular the shape of the secular trend and the spatial patterns associated with the secular trend and the multidecadal variability. The shape of the secular trend and rather globally-uniform spatial pattern associated with it are both suggestive of a response to the buildup of well-mixed greenhouse gases. In contrast, the multidecadal variability tends to be concentrated over the extratropical Northern Hemisphere and particularly over the North Atlantic, suggestive of a possible link to low frequency variations in the strength of the thermohaline circulation. Depending upon the assumed importance of the contributions of ocean dynamics and the time-varying aerosol emissions to the observed trends in global-mean surface temperature, we estimate that up to one third of the late twentieth century warming could have been a consequence of natural variability.

Quantification of global land evapotranspiration (ET) has long been associated with large uncertainties due to the lack of reference observations. Several recently developed products now provide the capacity to estimate ET at global scales. These products, partly based on observational data, include satellite ]based products, land surface model (LSM) simulations, atmospheric reanalysis output, estimates based on empirical upscaling of eddycovariance flux measurements, and atmospheric water balance datasets. The LandFlux-EVAL project aims to evaluate and compare these newly developed datasets. Additionally, an evaluation of IPCC AR4 global climate model (GCM) simulations is presented, providing an assessment of their capacity to reproduce flux behavior relative to the observations ]based products. Though differently constrained with observations, the analyzed reference datasets display similar large-scale ET patterns. ET from the IPCC AR4 simulations was significantly smaller than that from the other products for India (up to 1 mm/d) and parts of eastern South America, and larger in the western USA, Australia and China. The inter-product variance is lower across the IPCC AR4 simulations than across the reference datasets in several regions, which indicates that uncertainties may be underestimated in the IPCC AR4 models due to shared biases of these simulations.

This systematic literature review critically evaluates the extent to which community-based vulnerability assessments are progressing towards less siloed approaches that address spatial and temporal interactions and multiple exposures. The review focuses on studies that apply the most commonly operationalised frameworks in the livelihoods and climate change disciplines between 2014 and 2023, the Sustainable Livelihoods Framework (SLF) (n = 72) and the IPCC AR4 Framework (AR4) (n = 101). This review found that a minimal number of studies are addressing limitations. This was most significant in relation to the inadequate consideration of spatial scale (SLF 1%; AR4 5%), future temporal scale (SLF 4%; AR4 7%), and exposure to multiple shocks and stressors (AR4 7%; SLF 8%) within studies. Progress was seen with respect to overcoming siloed perspectives, which had previously led to the exclusion of external shock and stressor events (SLF) or socioeconomic factors (AR4) within assessments. Despite this progress, AR4 based studies were found to exclude key components of adaptive capacity, particularly in relation to natural (28%), financial (57%) and components of social capital. Additionally, only 47% of SLF based studies measured exposure to shock and stressor events. To overcome limitations scholars must engage with i) less-siloed frameworks that combine perspectives from the livelihoods and climate change disciplines and ii) non-static approaches that assess vulnerability in the context of social-ecological systems or use ethnographic methods (e.g., scenario planning and participatory mapping) to contextualise outputs. By engaging with these limitations, scholars reduce the potential for assessments to produce ineffective, or maladaptive outcomes.

In the districts of Purulia and Bankura, this study offers a methodology for spatial assessment of vulnerable and risk-prone areas. These districts are adjacent in space and have identical geographic characteristics (other than the eastern portion of Bankura district). Vulnerability and risk assessment could be used to measure the interactions between individuals and their surroundings. This research aims to pinpoint the areas in these two districts that are particularly susceptible to natural, social, and meteorological disasters. The natural and climate-induced factors considered are rainfall distribution and vegetation conditions. The social factors are agricultural dependence, percentage of farmers, female population, labor dependence on agriculture, and literacy rate. The potential impacts of developmental and environmental degradation processes can be examined and assessed by classifying regions according to their vulnerability and risk levels. The fundamental factors impacting susceptibility and risk, which are recognized, and the associated thematic-based outputs are produced in this study based on the persistent phenomenon of drought within these two districts. The elements of vulnerability selected for this study are exposure, sensitivity, and adaptive capacity (IPCC AR4) and risk, which is the combined outcome of hazard, exposure, and vulnerability (IPCC AR5). The aim of this research is to create a simplified, scalable assessment model for evaluating both vulnerabilities and threats, which can help with drought mitigation. It has been observed from the results that the western portion of the study area (Arsha, Purulia-I, Baghmundi blocks of Purulia district) with relatively higher risk and vulnerability needs more attention for reducing the vulnerability and risk than the eastern part. As a result, this research can serve as a platform for district-level prioritizing efforts, emergency response protocols, and policy interventions aimed at reducing disaster susceptibility (mostly drought) in Bankura and Purulia districts.

The purpose of this study was to develop a Korean climate change vulnerability assessment tool, the Vulnerability Assessment Tool to build Climate Change Adaptation Plan (VESTAP). Based on Intergovernmental Panel on Climate Change methodology, VESTAP can be used to evaluate Korea’s vulnerability to major climate impacts (including 32 conditions in 8 categories). VESTAP is based on RCP 4.5/8.5 scenarios and can provide evaluation results in 10-year intervals from the 2010s to 2040s. In addition, this paper presents the results of a case study using VESTAP for targeted assessment of health vulnerability to heat waves under the RCP 8.5 scenario for the 2040s. Through vulnerability assessment at the province level in South Korea, Daegu Metropolitan City was identified as the most vulnerable region. The municipality and submunicipality levels of Daegu were also assessed in separate stages. The results indicated that Pyeongni 3-Dong in Seo-Gu was most vulnerable. Through comprehensive analysis of the results, the climate exposure index was identified as the greatest contributor to health vulnerability in Korea. Regional differences in climate exposure can be moderated by social investment in improving sensitivity and adaptive capacity. This study is significant in presenting a quantitative assessment of vulnerability to climate change by the administrative unit in South Korea. The results of this study are expected to contribute to the efficient development and implementation of climate change adaptation policies in South Korea.

As in the observed record, the termination of El Niño in the coupled IPCC-AR4 climate models involves meridional processes tied to the seasonal cycle. These meridional processes both precondition the termination of El Niño events in general and lead to a peculiar termination of extreme El Niño events (such as those of 1982-83 and 1997-98), in which the eastern equatorial Pacific warm sea surface temperature anomalies (SSTA) persist well into boreal spring/early-summer. The mechanisms controlling the peculiar termination of extreme El Niño events, which involves to the development of an equatorially centred intertropical convergence zone, are consistent across the four models that exhibit extreme El Niños and observational record, suggesting that this peculiar termination represents a general feature of extreme El Niños. Further, due to their unusual termination, extreme El Niños exhibit an apparent eastward propagation of their SSTA, which can strongly influence estimates of the apparent propagation of ENSO over multi-decadal periods. Interpreting these propagation changes as evidence of changes in the underlying dynamical feedbacks behind El Niño could therefore be misleading, given the strong influence of a single extreme event.