Ice Sheet and Climate Processes Driving the Uncertainty in Projections of Future Sea Level Rise: Findings From a Structured Expert Judgement Approach.

The ice sheets covering Antarctica and Greenland present the greatest uncertainty in, and largest potential contribution to, future sea level rise. The uncertainty arises from a paucity of suitable observations covering the full range of ice sheet behaviors, incomplete understanding of the influences of diverse processes, and limitations in defining key boundary conditions for the numerical models. To investigate the impact of these uncertainties on ice sheet projections we undertook a structured expert judgement study. Here, we interrogate the findings of that study to identify the dominant drivers of uncertainty in projections and their relative importance as a function of ice sheet and time. We find that for the 21st century, Greenland surface melting, in particular the role of surface albedo effects, and West Antarctic ice dynamics, specifically the role of ice shelf buttressing, dominate the uncertainty. The importance of these effects holds under both a high-end 5°C global warming scenario and another that limits global warming to 2°C. During the 22nd century the dominant drivers of uncertainty shift. Under the 5°C scenario, East Antarctic ice dynamics dominate the uncertainty in projections, driven by the possible role of ice flow instabilities. These dynamic effects only become dominant, however, for a temperature scenario above the Paris Agreement 2°C target and beyond 2100. Our findings identify key processes and factors that need to be addressed in future modeling and observational studies in order to reduce uncertainties in ice sheet projections.

Migration towards Bangladesh coastlines projected to increase with sea-level rise through 2100.

To date, projections of human migration induced by sea-level change (SLC) largely suggest large-scale displacement away from vulnerable coastlines. However, results from our model of Bangladesh suggest counterintuitively that people will continue to migrate toward the vulnerable coastline irrespective of the flooding amplified by future SLC under all emissions scenarios until the end of this century. We developed an empirically calibrated agent-based model of household migration decision-making that captures the multi-faceted push, pull and mooring influences on migration at a household scale. We then exposed ~4800 000 simulated migrants to 871 scenarios of projected 21st-century coastal flooding under future emissions pathways. Our model does not predict flooding impacts great enough to drive populations away from coastlines in any of the scenarios. One reason is that while flooding does accelerate a transition from agricultural to non-agricultural income opportunities, livelihood alternatives are most abundant in coastal cities. At the same time, some coastal populations are unable to migrate, as flood losses accumulate and reduce the set of livelihood alternatives (so-called 'trapped' populations). However, even when we increased access to credit, a commonly-proposed policy lever for incentivizing migration in the face of climate risk, we found that the number of immobile agents actually rose. These findings imply that instead of a straightforward relationship between displacement and migration, projections need to consider the multiple constraints on, and preferences for, mobility. Our model demonstrates that decision-makers seeking to affect migration outcomes around SLC would do well to consider individual-level adaptive behaviors and motivations that evolve through time, as well as the potential for unintended behavioral responses.

Acid deposition, smelter emissions, and the linearity issue in the Western United States.

The variation in sulfur dioxide emissions from nonferrous metal smelters in the western United States over a 4-year period is compared with the variation in sulfate concentrations in precipitation in the Rocky Mountain states. The data support a linear relation between emissions and sulfate concentration. The geographic separation of emissions sources and precipitation monitors indicates a sulfur transport scale exceeding 1000 kilometers.

Environmental policy. Counting the cost of deforestation.

To halt the dramatic alteration in our climate, there must be a reduction in the emission of greenhouse gases. As Bonnie and colleagues discuss in their Perspective, conservation of forests will increase carbon sequestration and decrease greenhouse gas emissions. In this issue, a cost-benefit analysis by Kremen et al. demonstrates the benefits of forest conservation on a local and global scale.

Downregulation of high-density lipoprotein receptor in human fibroblasts by insulin and IGF-I.

High-density lipoprotein (HDL3) particles bind to a cell surface receptor, thereby promoting the efflux of cholesterol from extrahepatic nonsteroidogenic cells. This receptor appears to be upregulated by increased cell cholesterol content and also may be responsive to the growth state of cells. Because insulin can be mitogenic, the effect of insulin on HDL-receptor function was tested. HDL-receptor activity of cholesterol-loaded fibroblasts was inhibited by insulin treatment. Insulin decreased HDL binding in a log-dose fashion (-25% at 67 nM insulin) in association with increases in [3H]thymidine incorporation into DNA. HDL-mediated cholesterol efflux from cholesterol-loaded cells was diminished by insulin treatment of cells in parallel with decreased HDL binding. Insulin induced reciprocal changes in HDL- and low-density lipoprotein (LDL)-receptor activity. In cells in which these receptors were upregulated by varying cell cholesterol content, insulin increased LDL binding (+88%) and decreased HDL binding (-24%). Insulin-like growth factor I (IGF-I, 100 ng/ml) also significantly decreased HDL binding and HDL-mediated cholesterol efflux to a comparable degree. Pooled human serum similarly induced a reduction in HDL binding to its receptor. These results are consistent with the hypothesis that growth factors in general, and insulin and IGF-I in particular, decrease HDL-receptor activity, possibly to promote retention of cholesterol needed for new membrane synthesis during cell proliferation. Such a mechanism could be partly responsible for accumulation of cholesteryl esters in arterial wall cells during atherogenesis in diabetes mellitus.

Reservoir timescales for anthropogenic CO2 in the atmosphere

Non-steady state timescales are complicated and their application to specific geophysical systems requires a common theoretical foundation. We first extend reservoir theory by quantifying the difference between turnover time and transit time (or residence time) for time-dependent systems under any mixing conditions. We explicitly demonstrate the errors which result from assuming these timescales are equal, which is only true at steady state. We also derive a new response function which allows the calculation of age distributions and timescales for well-mixed reservoirs away from steady state, and differentiate between timescales based on gross and net fluxes. These theoretical results are particularly important to tracer-calibrated "box models" currently used to study the carbon cycle, which usually approximate reservoirs as well-mixed. We then apply the results to the important case of anthropogenic CO2 in the atmosphere, since timescales describing its behavior are commonly used but ambiguously defined. All relevant timescales, including lifetime, transit time, and adjustment time, are precisely defined and calculated from data and models. Apparent discrepancies between the current, empirically determined turnover time of 30-60 years and longer model-derived estimates of expected lifetime and adjustment time are explained within this theoretical framework. We also discuss the results in light of policy issues related to global warming, in particular since any comparisons of the "lifetimes" of different greenhouse gases (CO2, CH4, N2O, CFC's etc.) must use a consistent definition to be meaningful.

Continuous ambulatory peritoneal dialysis. Technique of catheter insertion and management of associated surgical complications.

Fifty-seven patients initiated continuous ambulatory peritoneal dialysis. All patients were generally pleased with this form of dialysis and particularly enjoyed the greater mobility and decreased dietary restriction. Complications associated with continuous ambulatory peritoneal dialysis include peritonitis, pericatheter infection, catheter malfunction, dialysate leak, and hernias of the abdominal wall.

Investigating the generality of the delayed-prompt effect.

Two experiments were conducted in an attempt to replicate the findings of Touchette's classic 1971 experiment. The results obtained were more variable than those obtained by Touchette. Four of 34 subjects learned the Horizontal E discrimination without errors. Ten subjects preempted the red prompt stimulus erroneously. Twelve subjects failed to preempt. Among those who failed to preempt, at least six had not learned the target discrimination. There were also five subjects who failed to preempt who, on subsequent tests, demonstrated that they had learned the target discrimination. For these subjects, the onset of the prompt appeared to grant "permission to respond." An attempt is made to account for the differences in the current results and those of Touchette (1971). We also compare our results to the usually successful application of the delayed prompt to education and training problems. We note that the procedures used in these successful applications are often quite different from those in the original Touchette experiment and our own.

[Non-Hodgkin's malignant lymphoma. Therapeutic value of autologous bone marrow transplantation]. / Lymphomes malins non hodgkiniens. Intérêt thérapeutique de l'autogreffe de moelle osseuse.

Twelve patients with non-Hodgkin malignant lymphoma of poor prognosis were treated with heavy chemotherapy of the TACC type (cyclophosphamide 45 mg/kg/day i.v. X 4; cytosine arabinoside 200 mg/m2/12 hours i.v. X 7; 6-thioguanidine 100 mg/m2/12-hourly p.o X 7 and CCNU 200 or 250 mg/m2 p.o. single dose) followed by autologus bone marrow transplantation (853 to 20.000 CFUc/kg). The patients were divided into 2 groups depending on whether they received an induction treatment for large visible tumoral mass (group I: 3 initial presentations, 3 relapses) or a consolidation treatment for small residual tumour (group II: 6 complete and 1 partial remissions). The results show that autologous bone marrow transplantation shortens the duration of the therapeutic aplasia. White cell (greater than 10(9)/l) and platelet (greater than 50.10(9)/l) recovery was observed on days 12 (range 9-19) and 14 (range 8-27) respectively. In group I, 1 patient died of myocardial TACC toxity and acute renal failure on tumoral kidney; there were 2 failures and 3 complete remissions (8, 21, 45 + months). Remissions occurred in patients treated initially; the overall survival since diagnosis was 48+, 48+ and 60+ months. In group II patients there were 1 failure and 5 complete remissions persisting after a 2+ months to 30+ months follow-up; the overall survival was 23+, 24+, 27+, 42+ and 70+ months. The 3 failures in the series occurred in circumstances suggesting contamination of the cryopreserved bone marrow by tumoral cells. The toxicity, largely due to infection, of the TACC-bone marrow transplantation combination was tolerable. It was clearly lower in group II (6 patients, no septicaemia) than in group I (5/6 patients with septicaemia). These preliminary results confirm that there is room for autologous bone marrow transplantation in highly malignant non-Hodgkin lymphomas, particularly during complete remissions to facilitate the use of an aggressive consolidation chemotherapy.