Strong regional differences exist in how hot temperature extremes increase under global warming. Using an ensemble of coupled climate models, we examine the regional warming rates of hot extremes ...relative to annual average warming rates in the same regions. We identify hot spots of accelerated warming of model‐simulated hot extremes in Europe, North America, South America, and Southeast China. These hot spots indicate where the warm tail of a distribution of temperatures increases faster than the average and are robust across most Coupled Model Intercomparison Project Phase 5 models. Exploring the conditions on the specific day when the hot extreme occurs demonstrates that the hot spots are explained by changes in the surface energy fluxes consistent with drying soils. However, the model‐simulated accelerated warming of hot extremes appears inconsistent with observations, except over Europe. The simulated acceleration of hot extremes may therefore be unreliable, a result that necessitates a reevaluation of how climate models resolve the relevant terrestrial processes.
Key Points
Climate model simulations show distinct hot spots, robust across most CMIP5 models, where daily hot extremes warm faster than mean temperatures
Changes in surface energy fluxes, consistent with drying soils, accelerate warming on the day hot extremes occur
The spatial patterns of accelerated warming of hot extremes in the CMIP5 models are inconsistent with observations, except over Europe
Open radical cystectomy (ORC) has proven to be an important component in the treatment of high-risk bladder cancer (BCa). ORC surgical morbidity remains high; therefore, minimally invasive surgical ...techniques have been introduced in an attempt to improve patient outcomes.
To compare cancer outcomes in BCa patients managed with ORC or robotic-assisted radical cystectomy (RARC).
A prospective, randomized trial was completed between 2010 and 2013. Patients were randomized to ORC/pelvic lymphadenectomy (PLND) or RARC/PLND, with all undergoing open/extracorporeal urinary diversion. Median follow-up was 4.9 (IQR: 3.9–5.9) yr after surgery among surviving patients.
Secondary outcomes to the trial included recurrence-free, cancer-specific, and overall survival.
The trial randomized 118 patients who underwent RC/PLND and urinary diversion. Sixty were randomized to RARC and 58 to ORC. Four RARC-assigned patients refused randomization and received ORC; however, an intention to treat analysis was performed. No differences were observed in recurrence (hazard ratio HR: 1.27; 95% confidence interval CI: 0.69–2.36; p=0.4) or cancer-specific survival (p=0.4). No difference in overall survival was observed (p=0.8). However, the pattern of first recurrence demonstrated a nonstatistically significant increase in metastatic sites for those undergoing ORC (sub-HR sHR: 2.21; 95% CI: 0.96–5.12; p=0.064) and a greater number of local/abdominal sites in the RARC-treated patients (sHR: 0.34; 95% CI: 0.12–0.93; p=0.035). The major limitation to this study is that the trial was not powered to determine differences in cancer recurrences, survival outcomes, or patterns of recurrence.
The secondary outcomes from our randomized trial did not definitively demonstrate differences in cancer outcomes in patients treated with ORC or RARC. However, differences in observed patterns of first recurrence highlight the need for future studies.
Of 118 patients randomly assigned to undergo radical cystectomy/pelvic lymphadenectomy and urinary diversion, half were assigned to open surgery and half to robot-assisted techniques. We found no difference in risk of recurring or dying of bladder cancer between the two groups.
In this secondary analysis of cancer outcomes from our randomized controlled trial, we did not find a difference in overall recurrence rates and cancer-specific survival between open radical cystectomy and robot-assisted radical cystectomy for high-risk bladder cancer. Variations in patterns of recurrence require further study.
For more than a decade, the World Meteorological Organization (WMO) Commission for Climatol- ogy (CCl)/CLIVAR/JCOMM Expert Team on Climate Change Detection and Indices (ETCCDI) has been facilitating ...the international coordination of a suite of indices that primarily represent the more extreme aspects of climate. To create gridded values, spatial in- terpolation of the station-based indices is performed using an algorithm that considers the underlying spatial correlation structure of the data, a modified version of Shepard's angular distance weighting (Shepard 1968; see Alexander et al. 2006 for details).
Land‐atmosphere coupling can amplify heat extremes under declining soil moisture. Here we evaluate this coupling in 25 Coupled Model Intercomparison Project Phase 5 models using flux tower ...observations over Europe and North America. We compared heat extremes (2.5% of the hottest days of the year) and the evaporative fraction (EF; a measure of land surface dryness) on the day the heat extremes occurred. We found a negative relationship between the magnitude of heat extremes and EF in both models and observations in transitional regions, with the hottest temperatures occurring during the driest days, with a similar but less certain relationship in dry regions. Surprisingly, many models also showed an amplification of heat extremes by low EF in wet regions, a finding not supported by observations. Many models may therefore overamplify heat extremes over wet regions by overestimating the strength of land‐atmosphere coupling, with consequences for future projections of heat extremes.
Plain Language Summary
Hot days are expected to become more frequent with climate change. Heat extremes can be exacerbated by dry conditions due to a lack of evaporative cooling. This has been shown to be an important mechanism for future amplification of heat extremes in several regions. We evaluated how well global climate models can simulate these interactions between hot and dry conditions under current climate conditions. We showed that many models overestimate this interaction in wet regions and consequently overamplify heat extremes. Our study points to an area of necessary model improvement to increase confidence in future projections of heat extremes.
Key Points
Land‐atmosphere coupling can amplify heat extremes under drying soil moisture
We evaluate this coupling in CMIP5 models against flux tower observations
We show many CMIP5 models overamplify heat extremes in wet regions by overestimating the strength of land surface coupling
How much does it rain over land? Herold, N.; Alexander, L. V.; Donat, M. G. ...
Geophysical research letters,
16 January 2016, Letnik:
43, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Despite the availability of several observationally constrained data sets of daily precipitation based on rain gauge measurements, remote sensing, and/or reanalyses, we demonstrate a large disparity ...in the quasi‐global land mean of daily precipitation intensity. Surprisingly, the magnitude of this spread is similar to that found in the Coupled Model Intercomparison Project Phase 5 (CMIP5). A weakness of reanalyses and CMIP5 models is their tendency to over simulate wet days, consistent with previous studies. However, there is no clear agreement within and between rain gauge and remotely sensed data sets either. This large discrepancy highlights a shortcoming in our ability to characterize not only modeled daily precipitation intensities but even observed precipitation intensities. This shortcoming is partially reconciled by an appreciation of the different spatial scales represented in gridded data sets of in situ precipitation intensities and intensities calculated from gridded precipitation. Unfortunately, the spread in intensities remains large enough to prevent us from satisfactorily determining how much it rains over land.
Key Points
Many observationally constrained data sets of daily precipitation exist
We highlight a large discrepancy in mean daily precipitation intensity between these data sets
Thus, users should not treat all observational data sets of precipitation equally
A climate model, coupled to a sophisticated land surface scheme, is used to explore the impact of land use induced land cover change (LULCC) on climate extremes indices recommended by the Expert Team ...on Climate Change Detection and Indices (ETCCDI). The impact from LULCC is contrasted with the impact of doubling atmospheric carbon dioxide (CO2). Many of the extremes indices related to temperature are affected by LULCC and the resulting changes are locally and field significant. Some indices are systematically affected by LULCC in the same direction as increasing CO2 while for others LULCC opposes the impact of increasing CO2. We suggest that assumptions that anthropogenically induced changes in temperature extremes can be approximated just by increasing greenhouse gases are flawed, as LULCC may regionally mask or amplify the impact of increasing CO2 on climate extremes. In some regions, the scale of the LULCC forcing is of a magnitude similar to the impact of CO2 alone. We conclude that our results complicate detection and attribution studies, but also offer a way forward to a clearer and an even more robust attribution of the impact of increasing CO2 at regional scales.
Key Points
Temperature extremes indices are affected by LULCC
LULCC may locally mask or amplify impact of increasing CO2 on extreme indices
Results offer way towards clearer, more robust attribution of CO2 impact
Purpose The purpose of this guideline is to provide a clinical framework for follow-up of clinically localized renal neoplasms undergoing active surveillance, or following definitive therapy. ...Materials and Methods A systematic literature review identified published articles in the English literature between January 1999 and 2011 relevant to key questions specified by the Panel related to kidney neoplasms and their follow-up (imaging, renal function, markers, biopsy, prognosis). Study designs consisting of clinical trials (randomized or not), observational studies (cohort, case-control, case series) and systematic reviews were included. Results Guideline statements provided guidance for ongoing evaluation of renal function, usefulness of renal biopsy, timing/type of radiographic imaging and formulation of future research initiatives. A lack of studies precluded risk stratification beyond tumor staging; therefore, for the purposes of postoperative surveillance guidelines, patients with localized renal cancers were grouped into strata of low- and moderate- to high-risk for disease recurrence based on pathological tumor stage. Conclusions Evaluation for patients on active surveillance and following definitive therapy for renal neoplasms should include physical examination, renal function, serum studies and imaging and should be tailored according to recurrence risk, comorbidities and monitoring for treatment sequelae. Expert opinion determined a judicious course of monitoring/surveillance that may change in intensity as surgical/ablative therapies evolve, renal biopsy accuracy improves and more long-term follow-up data are collected. The beneficial impact of careful follow-up will also need critical evaluation as further study is completed.
In this study, we present the collation and analysis of the gridded land‐based dataset of indices of temperature and precipitation extremes: HadEX2. Indices were calculated based on station data ...using a consistent approach recommended by the World Meteorological Organization (WMO) Expert Team on Climate Change Detection and Indices, resulting in the production of 17 temperature and 12 precipitation indices derived from daily maximum and minimum temperature and precipitation observations. High‐quality in situ observations from over 7000 temperature and 11,000 precipitation meteorological stations across the globe were obtained to calculate the indices over the period of record available for each station. Monthly and annual indices were then interpolated onto a 3.75° × 2.5° longitude‐latitude grid over the period 1901–2010. Linear trends in the gridded fields were computed and tested for statistical significance. Overall there was very good agreement with the previous HadEX dataset during the overlapping data period. Results showed widespread significant changes in temperature extremes consistent with warming, especially for those indices derived from daily minimum temperature over the whole 110 years of record but with stronger trends in more recent decades. Seasonal results showed significant warming in all seasons but more so in the colder months. Precipitation indices also showed widespread and significant trends, but the changes were much more spatially heterogeneous compared with temperature changes. However, results indicated more areas with significant increasing trends in extreme precipitation amounts, intensity, and frequency than areas with decreasing trends.
Key Points
We present the most comprehensive land‐based gridded dataset of climate extremes
Temperature extremes show consistent warming trends over the past century
Precipitation extremes are increasing in more areas than they are decreasing
ABSTRACT
This article investigates extratropical winter cyclone activity in the Southern Hemisphere (SH) in a multi‐model ensemble (MME) of coupled atmosphere–ocean general circulation model (AOGCM) ...simulations of recent and potential future climate conditions. Most individual models and also the ensemble mean yield good reproductions of the typical cyclone characteristics found in reanalysis data, although some individual models show peculiarities, and a large inter‐model spread in terms of quantity of identified cyclone tracks is found. We use a scaling approach to combine the cyclone statistics from different models into a MME. In the future climate simulations, the total number of SH cyclones is reduced, whereas an increased number of strong cyclones is found in most models and in the ensemble mean. The long term trend with respect to all cyclones is a robust feature throughout the simulations. It is associated with a general poleward shift, shown to be related to both tropical upper tropospheric warming and shifting meridional sea surface temperature gradients in the Southern Ocean. The magnitude of increased strong cyclone activity has a focus on the Eastern Hemisphere. It is clearly influenced by natural variability and thus depends on specific time periods considered.
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