While internal climate variability is known to affect climate projections, its influence is often underappreciated and confused with model error. Why? In general, modeling centers contribute a small ...number of realizations to international climate model assessments e.g., phase 5 of the Coupled Model Intercomparison Project (CMIP5). As a result, model error and internal climate variability are difficult, and at times impossible, to disentangle. In response, the Community Earth System Model (CESM) community designed the CESM Large Ensemble (CESM-LE) with the explicit goal of enabling assessment of climate change in the presence of internal climate variability. All CESM-LE simulations use a single CMIP5 model (CESM with the Community Atmosphere Model, version 5). The core simulations replay the twenty to twenty-first century (1920–2100) 30 times under historical and representative concentration pathway 8.5 external forcing with small initial condition differences. Two companion 1000+-yr-long preindustrial control simulations (fully coupled, prognostic atmosphere and land only) allow assessment of internal climate variability in the absence of climate change. Comprehensive outputs, including many daily fields, are available as single-variable time series on the Earth System Grid for anyone to use. Early results demonstrate the substantial influence of internal climate variability on twentieth- to twenty-first-century climate trajectories. Global warming hiatus decades occur, similar to those recently observed. Internal climate variability alone can produce projection spread comparable to that in CMIP5. Scientists and stakeholders can use CESM-LE outputs to help interpret the observational record, to understand projection spread and to plan for a range of possible futures influenced by both internal climate variability and forced climate change.
The Community Earth System Model Version 2 (CESM2) Danabasoglu, G.; Lamarque, J.‐F.; Bacmeister, J. ...
Journal of advances in modeling earth systems,
February 2020, Volume:
12, Issue:
2
Journal Article
Peer reviewed
Open access
An overview of the Community Earth System Model Version 2 (CESM2) is provided, including a discussion of the challenges encountered during its development and how they were addressed. In addition, an ...evaluation of a pair of CESM2 long preindustrial control and historical ensemble simulations is presented. These simulations were performed using the nominal 1° horizontal resolution configuration of the coupled model with both the “low‐top” (40 km, with limited chemistry) and “high‐top” (130 km, with comprehensive chemistry) versions of the atmospheric component. CESM2 contains many substantial science and infrastructure improvements and new capabilities since its previous major release, CESM1, resulting in improved historical simulations in comparison to CESM1 and available observations. These include major reductions in low‐latitude precipitation and shortwave cloud forcing biases; better representation of the Madden‐Julian Oscillation; better El Niño‐Southern Oscillation‐related teleconnections; and a global land carbon accumulation trend that agrees well with observationally based estimates. Most tropospheric and surface features of the low‐ and high‐top simulations are very similar to each other, so these improvements are present in both configurations. CESM2 has an equilibrium climate sensitivity of 5.1–5.3 °C, larger than in CESM1, primarily due to a combination of relatively small changes to cloud microphysics and boundary layer parameters. In contrast, CESM2's transient climate response of 1.9–2.0 °C is comparable to that of CESM1. The model outputs from these and many other simulations are available to the research community, and they represent CESM2's contributions to the Coupled Model Intercomparison Project Phase 6.
Plain Language Summary
The Community Earth System Model (CESM) is an open‐source, comprehensive model used in simulations of the Earth's past, present, and future climates. The newest version, CESM2, has many new technical and scientific capabilities ranging from a more realistic representation of Greenland's evolving ice sheet, to the ability to model in detail how crops interact with the larger Earth system, to improved representation of clouds and rain, and to the addition of wind‐driven waves on the model's ocean surface. The data sets from a large set of simulations that include integrations for the preindustrial conditions (1850s) and for the 1850‐2014 historical period are available to the community, representing CESM2's contributions to the Coupled Model Intercomparison Project Phase 6 (CMIP6).
Key Points
Community Earth System Model Version 2 includes many substantial science and infrastructure improvements since its previous version
Preindustrial control and historical simulations were performed with low‐top and high‐top with comprehensive chemistry atmospheric models
Comparisons to observations are improved relative to previous versions, including major reductions in radiation and precipitation biases
The major evolution of the National Center for Atmospheric Research Community Atmosphere Model (CAM) is used to diagnose climate feedbacks, understand how climate feedbacks change with different ...physical parameterizations, and identify the processes and regions that determine climate sensitivity. In the evolution of CAM from version 4 to version 5, the water vapor, temperature, surface albedo, and lapse rate feedbacks are remarkably stable across changes to the physical parameterization suite. However, the climate sensitivity increases from 3.2 K in CAM4 to 4.0 K in CAM5. The difference is mostly due to (i) more positive cloud feedbacks and (ii) higher CO₂ radiative forcing in CAM5. The intermodel differences in cloud feedbacks are largest in the tropical trade cumulus regime and in the midlatitude storm tracks. The subtropical stratocumulus regions do not contribute strongly to climate feedbacks owing to their small area coverage. A “modified Cess” configuration for atmosphere-only model experiments is shown to reproduce slab ocean model results. Several parameterizations contribute to changes in tropical cloud feedbacks between CAM4 and CAM5, but the new shallow convection scheme causes the largest midlatitude feedback differences and the largest change in climate sensitivity. Simulations with greater cloud forcing in the mean state have lower climate sensitivity. This work provides a methodology for further analysis of climate sensitivity across models and a framework for targeted comparisons with observations that can help constrain climate sensitivity to radiative forcing.
Ground‐based observations show that persistent liquid‐containing Arctic clouds occur frequently and have a dominant influence on Arctic surface radiative fluxes. Yet, without a hemispheric multi‐year ...perspective, the climate relevance of these intriguing Arctic cloud observations was previously unknown. In this study, Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) observations are used to document cloud phase over the Arctic basin (60–82°N) during a five‐year period (2006–2011). Over Arctic ocean‐covered areas, low‐level liquid‐containing clouds are prevalent in all seasons, especially in Fall. These new CALIPSO observations provide a unique and climate‐relevant constraint on Arctic cloud processes. Evaluation of one climate model using a lidar simulator suggests a lack of liquid‐containing Arctic clouds contributes to a lack of “radiatively opaque” states. The surface radiation biases found in this one model are found in multiple models, highlighting the need for improved modeling of Arctic cloud phase.
Key Points
New CALIPSO‐GOCCP observations show ubiquitous liquid‐containing Arctic clouds
Insufficient liquid‐containing Arctic cloud leads to radiation biases in models
Reproducing observed cloud phase is an important target for model improvement
Understanding the influence of clouds on amplified Arctic surface warming remains an important unsolved research problem. Here, this cloud influence is directly quantified by disabling cloud ...radiative feedbacks or “cloud locking” within a state‐of‐the‐art and well‐documented model. Through comparison of idealized greenhouse warming experiments with and without cloud locking, the influence of Arctic and global cloud feedbacks is assessed. Global cloud feedbacks increase both global and Arctic warming by around 25%. In contrast, disabling Arctic cloud feedbacks has a negligible influence on both Arctic and global surface warming. Interestingly, the sum of noncloud radiative feedbacks does not change with either global or Arctic‐only cloud locking. Notably, the influence of Arctic cloud feedbacks is likely underestimated, because, like many models, the model used here underestimates high‐latitude supercooled cloud liquid. More broadly, this work demonstrates the value of regional and global cloud locking in a well‐characterized model.
Key Points
Disabling cloud radiative feedbacks in a climate model can separate the influence of Arctic and global cloud feedbacks on greenhouse warming
Arctic surface greenhouse warming increases due to global cloud feedbacks but is insensitive to Arctic cloud feedbacks
The sum of noncloud feedbacks (water vapor, lapse rate, and surface albedo) is unaffected by disabling cloud feedbacks both globally and in the Arctic alone
Whilst initial rates of insulin independence following islet transplantation are encouraging, long‐term function using the Edmonton Protocol remains a concern. The aim of this single‐arm, multicenter ...study was to evaluate an immunosuppressive protocol of initial antithymocyte globulin (ATG), tacrolimus and mycophenolate mofetil (MMF) followed by switching to sirolimus and MMF. Islets were cultured for 24 h prior to transplantation. The primary end‐point was an HbA1c of <7% and cessation of severe hypoglycemia. Seventeen recipients were followed for ≥12 months. Nine islet preparations were transported interstate for transplantation. Similar outcomes were achieved at all three centers. Fourteen of the 17 (82%) recipients achieved the primary end‐point. Nine (53%) recipients achieved insulin independence for a median of 26 months (range 7–39 months) and 6 (35%) remain insulin independent. All recipients were C‐peptide positive for at least 3 months. All subjects with unstimulated C‐peptide >0.2 nmol/L had cessation of severe hypoglycemia. Nine of the 17 recipients tolerated switching from tacrolimus to sirolimus with similar graft outcomes. There was a small but significant reduction in renal function in the first 12 months. The combination of islet culture, ATG, tacrolimus and MMF is a viable alternative for islet transplantation.
This multicenter Australian trial of islet transplantation alone, using antithymocyte globulin, tacrolimus, and mycophenolate mofetil, confi rms improving outcomes for the procedure and demonstrates that it is possible to develop new islet centers, thereby improving accessibility for patients.
Satellite observations and their corresponding instrument simulators are used to document global cloud biases in the Community Atmosphere Model (CAM) versions 4 and 5. The model–observation ...comparisons show that, despite having nearly identical cloud radiative forcing, CAM5 has a much more realistic representation of cloud properties than CAM4. In particular, CAM5 exhibits substantial improvement in three long-standing climate model cloud biases: 1) the underestimation of total cloud, 2) the overestimation of optically thick cloud, and 3) the underestimation of midlevel cloud. While the increased total cloud and decreased optically thick cloud in CAM5 result from improved physical process representation, the increased midlevel cloud in CAM5 results from the addition of radiatively active snow. Despite these improvements, both CAM versions have cloud deficiencies. Of particular concern, both models exhibit large but differing biases in the subtropical marine boundary layer cloud regimes that are known to explain intermodel differences in cloud feedbacks and climate sensitivity. More generally, this study demonstrates that simulator-facilitated evaluation of cloud properties, such as amount by vertical level and optical depth, can robustly expose large and at times radiatively compensating climate model cloud biases.
We set forth to assess the quality of an herbal medicine sold in Hong Kong called Qianliguang by employing a multi-methodological approach. The quality is set by its identity, chemical composition, ...and bioactivities, among others. Qianliguang (Senecionis scandentis Herba, Senecio scandens Buch.-Ham. ex D.Don) has known antibacterial properties. However, it is poisonous and overconsumption can result in liver damage. Eighteen Qianliguang samples were purchased from herbal shops at various districts in Hong Kong. Samples were first authenticated organoleptically. DNA barcoding at the psbA-trnH, ITS2, and rbcL loci was then conducted to confirm the species. HPLC-UV was performed to screen for the presence of the chemical compounds and to quantify the flavonoid hyperoside. UPLC-MS was used to quantify the amount of the toxic pyrrolizidine alkaloid (PA) adonifoline. Microdilution assay was performed to show the antibacterial effect on Streptococcus aureus and S. pneumoniae. Results showed that five samples were found to be substituted by species belonging to the genus Lespedeza; four samples were mixtures containing not only Qianliguang but also Achyranthes aspera L., Lonicera confusa DC., or Solanum nigrum L. HPLC-UV showed that only ten contained enough hyperoside to meet the standard requirement. In addition, nine samples had adonifoline that exceeded the toxicity standard requirement. In the microdilution assay, samples containing Qianliguang showed inhibition on S. aureus and S. pneumoniae, while among the five Lespedeza sp. samples the antibacterial effects on S. aureus were not detectable; only one sample showed inhibition to S. pneumoniae. Our study illustrated the necessity of using a multi-methodological approach for herbal medicine quality assessment. We also showed that Qianliguang samples in the Hong Kong market were either toxic or adulterated. It is therefore essential to improve the quality control of Qianliguang and probably other herbs in the herbal market.
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