Accounting for Skill in Trend, Variability, and Autocorrelation Facilitates Better Multi-Model Projections: Application to the AMOC and Temperature Time Series

We present a novel quasi-Bayesian method to weight multiple dynamical models by their skill at capturing both potentially non-linear trends and first-order autocorrelated variability of the underlying process, and to make weighted probabilistic projections. We validate the method using a suite of one-at-a-time cross-validation experiments involving Atlantic meridional overturning circulation (AMOC), its temperature-based index, as well as Korean summer mean maximum temperature. In these experiments the method tends to exhibit superior skill over a trend-only Bayesian model averaging weighting method in terms of weight assignment and probabilistic forecasts. Specifically, mean credible interval width, and mean absolute error of the projections tend to improve. We apply the method to a problem of projecting summer mean maximum temperature change over Korea by the end of the 21st century using a multi-model ensemble. Compared to the trend-only method, the new method appreciably sharpens the probability distribution function (pdf) and increases future most likely, median, and mean warming in Korea. The method is flexible, with a potential to improve forecasts in geosciences and other fields

Slow and soft passage through tipping point of the Atlantic Meridional Overturning Circulation in a changing climate

Paleo-proxy records suggest that the Atlantic Meridional Overturning Circulation (AMOC) exhibits a threshold for an abrupt change, a so-called tipping point. A classical bifurcation theory, a basis of the tipping dynamics of AMOC implicitly assumes that the tipping point is fixed. However, when a system is subjected to time-varying forcing (e.g., AMOC exposed to ice meltwater) an actual tipping point can be overshot due to delayed tipping, referred to as the slow passage effect. Here, using an Earth system model of intermediate complexity and a low-order model with freshwater forcing, we show that the tipping point of AMOC is largely delayed by the slow passage effect. It causes a large tipping lag of up to 1300 years, and strongly relaxes the abruptness of tipping as well. We further demonstrate that the tipping modulation can actively occur in past, present, and future climates by quantifying the effect during Dansgaard-Oeschger events, meltwater pulse 1A (MWP-1A), and current Greenland ice sheet melting. The suggested slow passage effect may explain the observed lagged AMOC collapse to MWP-1A of about 1000 years and provides implications tipping risk in the future

Exploring the ability of the variable-resolution Community Earth System Model to simulate cryospheric–hydrological variables in High Mountain Asia

Earth system models (ESMs) can help to improve the understanding of climate-induced cryospheric–hydrological impacts in complex mountain regions, such as High Mountain Asia (HMA). Coarse ESM grids, however, have difficulties in representing cryospheric–hydrological processes that vary over short distances in complex mountainous environments. Variable-resolution (VR) ESMs can help to overcome these limitations through targeted grid refinement. This study investigates the ability of the VR Community Earth System Model (VR-CESM) to simulate cryospheric–hydrological variables such as the glacier surface mass balance (SMB) over HMA. To this end, a new VR grid is generated, with a regional grid refinement up to 7 km over HMA. Two coupled atmosphere–land simulations are run for the period 1979–1998. The second simulation is performed with an updated glacier cover dataset and includes snow and glacier model modifications. Comparisons are made to gridded outputs derived from a globally uniform 1∘ CESM grid, observation-, reanalysis-, and satellite-based datasets, and a glacier model forced by a regional climate model (RCM). Climatological biases are generally reduced compared to the coarse-resolution CESM grid, but the glacier SMB is too negative relative to observation-based glaciological and geodetic mass balances, as well as the RCM-forced glacier model output. In the second simulation, the SMB is improved but is still underestimated due to cloud cover and temperature biases, missing model physics, and incomplete land–atmosphere coupling. The outcomes suggest that VR-CESM could be a useful tool to simulate cryospheric–hydrological variables and to study climate change in mountainous environments, but further developments are needed to better simulate the SMB of mountain glaciers

Contrasting response of hydrological cycle over land and ocean to a changing CO2 pathway

The hydrological cycle has a significant impact on human activities and ecosystems, so understanding its mechanisms with respect to a changing climate is essential. In particular, a more detailed understanding of hydrological cycle response to transient climate change is required for successful adaptation and mitigation policies. In this study, we exploit large ensemble model experiments using the Community Earth System Model version 1.2.2 (CESM1) in which CO2 concentrations increase steadily and then decrease along the same path. Our results show that precipitation changes in the CO2 increasing and decreasing phases are nearly symmetrical over land but asymmetric over oceans. After CO2 concentrations peak, the ocean continues to uptake heat from the atmosphere, which is a key process leading the hydrological cycle’s contrasting response over land and ocean. The symmetrical hydrological cycle response over land involves a complex interplay between rapid responses to CO2 and slower responses to ensuing warming. Therefore, the surface energy constraints lead to the contrasting hydrological response over land and ocean to CO2 forcing that needs to be verified and considered in climate change mitigation and adaption actions

Geriatric Nutritional Risk Index as a prognostic marker in patients with extensive-stage disease small cell lung cancer: Results from a randomized controlled trial

Background Clinical impact of the Geriatric Nutritional Risk Index (GNRI) in patients with extensive-stage disease small cell lung cancer (ED-SCLC) have not previously been reported. Methods This study analyzed 352 patients enrolled in a previous randomized phase III trial comparing the efficacy of irinotecan plus cisplatin with that of etoposide plus cisplatin as the first-line therapy for ED-SCLC. GNRI values were calculated using serum albumin levels and actual and ideal bodyweights. Patients with a GNRI > 98, 92-98, and <92 were grouped into no, low, and moderate/major risk groups, respectively. Results The objective response rates were 63.2%, 52.6%, and 49.2% in the no, low, and moderate/major risk groups, respectively (P = 0.024). The median progression-free survival (PFS) was shorter in patients with a lower GNRI than in those with a higher GNRI (no vs. low vs. moderate/major risk group; 6.5 vs. 5.8 vs. 5.9 months, respectively; P = 0.028). There were significant differences in median overall survival (OS) according to GNRI (no vs. low vs. moderate/major risk group; 13.2 vs. 10.3 vs. 8.4 months, respectively; P < 0.001). Multivariate analysis revealed that being in the moderate/major risk group was an independent poor prognostic factor for PFS (hazard ratio [HR]: 1.300, 95% confidence interval [CI]: 1.012-1.670; P = 0.040) and OS (HR: 1.539; 95% CI: 1.069-2.216; P = 0.020). Conclusions This prospective study shows that a low GNRI value was associated with a poor prognosis, and it supports the relationship between systemic inflammation, nutritional status, and clinical outcomes in patients with ED-SCLC.Key points Significant findings of the study The lower GNRI group had a low response rate to chemotherapy for ED-SCLC. The HRs for PFS and OS were 1.300 and 1.539 in the patients with GNRI < 92. What this study adds Low GNRI is associated with poor prognosis in ED-SCLC.

Iatrogenic Left Internal Mammary Artery to Great Cardiac Vein Anastomosis Treated With Coil Embolization

Inadvertent left internal mammary artery (LIMA)-great cardiac vein (GCV) anastomosis is a rare complication of coronary artery bypass graft surgery. Patients with iatrogenic aortocoronary fistula (ACF) were usually treated surgical repair, percutaneous embolic occlusion with coil or balloon. We report a case of iatrogenic LIMA to GCV anastomosis successfully treated with coil embolization and protected left main coronary intervention through the percutaneous transfemoral approach