The contribution of global aviation to anthropogenic climate forcing for 2000 to 2018.

Global aviation operations contribute to anthropogenic climate change via a complex set of processes that lead to a net surface warming. Of importance are aviation emissions of carbon dioxide (CO2), nitrogen oxides (NOx), water vapor, soot and sulfate aerosols, and increased cloudiness due to contrail formation. Aviation grew strongly over the past decades (1960-2018) in terms of activity, with revenue passenger kilometers increasing from 109 to 8269 billion km yr-1, and in terms of climate change impacts, with CO2 emissions increasing by a factor of 6.8 to 1034 Tg CO2 yr-1. Over the period 2013-2018, the growth rates in both terms show a marked increase. Here, we present a new comprehensive and quantitative approach for evaluating aviation climate forcing terms. Both radiative forcing (RF) and effective radiative forcing (ERF) terms and their sums are calculated for the years 2000-2018. Contrail cirrus, consisting of linear contrails and the cirrus cloudiness arising from them, yields the largest positive net (warming) ERF term followed by CO2 and NOx emissions. The formation and emission of sulfate aerosol yields a negative (cooling) term. The mean contrail cirrus ERF/RF ratio of 0.42 indicates that contrail cirrus is less effective in surface warming than other terms. For 2018 the net aviation ERF is +100.9 milliwatts (mW) m-2 (5-95% likelihood range of (55, 145)) with major contributions from contrail cirrus (57.4 mW m-2), CO2 (34.3 mW m-2), and NOx (17.5 mW m-2). Non-CO2 terms sum to yield a net positive (warming) ERF that accounts for more than half (66%) of the aviation net ERF in 2018. Using normalization to aviation fuel use, the contribution of global aviation in 2011 was calculated to be 3.5 (4.0, 3.4) % of the net anthropogenic ERF of 2290 (1130, 3330) mW m-2. Uncertainty distributions (5%, 95%) show that non-CO2 forcing terms contribute about 8 times more than CO2 to the uncertainty in the aviation net ERF in 2018. The best estimates of the ERFs from aviation aerosol-cloud interactions for soot and sulfate remain undetermined. CO2-warming-equivalent emissions based on global warming potentials (GWP* method) indicate that aviation emissions are currently warming the climate at approximately three times the rate of that associated with aviation CO2 emissions alone. CO2 and NOx aviation emissions and cloud effects remain a continued focus of anthropogenic climate change research and policy discussions.

Implications of possible interpretations of 'greenhouse gas balance' in the Paris Agreement.

The main goal of the Paris Agreement as stated in Article 2 is 'holding the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C'. Article 4 points to this long-term goal and the need to achieve 'balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases'. This statement on 'greenhouse gas balance' is subject to interpretation, and clarifications are needed to make it operational for national and international climate policies. We study possible interpretations from a scientific perspective and analyse their climatic implications. We clarify how the implications for individual gases depend on the metrics used to relate them. We show that the way in which balance is interpreted, achieved and maintained influences temperature outcomes. Achieving and maintaining net-zero CO2-equivalent emissions conventionally calculated using GWP100 (100-year global warming potential) and including substantial positive contributions from short-lived climate-forcing agents such as methane would result in a sustained decline in global temperature. A modified approach to the use of GWP100 (that equates constant emissions of short-lived climate forcers with zero sustained emission of CO2) results in global temperatures remaining approximately constant once net-zero CO2-equivalent emissions are achieved and maintained. Our paper provides policymakers with an overview of issues and choices that are important to determine which approach is most appropriate in the context of the Paris Agreement.This article is part of the theme issue 'The Paris Agreement: understanding the physical and social challenges for a warming world of 1.5°C above pre-industrial levels'.

Constraints on global temperature target overshoot.

In the aftermath of the Paris Agreement, the climate science and policy communities are beginning to assess the feasibility and potential benefits of limiting global warming to 1.5 °C or 2 °C above preindustrial. Understanding the dependence of the magnitude and duration of possible temporary exceedance (i.e., "overshoot") of temperature targets on sustainable energy decarbonization futures and carbon dioxide (CO2) removal rates will be an important contribution to this policy discussion. Drawing upon results from the mitigation literature and the IPCC Working Group 3 (WG3) scenario database, we examine the global mean temperature implications of differing, independent pathways for the decarbonization of global energy supply and the implementation of negative emissions technologies. We find that within the scope of scenarios broadly-consistent with the WG3 database, the magnitude of temperature overshoot is more sensitive to the rate of decarbonization. However, limiting the duration of overshoot to less than two centuries requires ambitious deployment of both decarbonization and negative emissions technology. The dependencies of temperature target overshoot's properties upon currently untested negative emissions technologies suggests that it will be important to consider how climate impacts depend on both the magnitude and duration of overshoot, not just long term residual warming.

Transplantation of adult and paediatric horseshoe kidneys.

BACKGROUND: The incidence of horseshoe kidneys is between 1 in 300 and 1 in 1600. Horseshoe kidneys may be either transplanted into two recipients after division of the kidney, or used for en bloc transplantation into one recipient. METHODS: We report two cases of adult-to-child and child-to-adult transplantation of horseshoe kidneys. Embryology and associated abnormalities are outlined, and previous case reports reviewed. RESULTS: One transplant was successful and one transplant failed due to an unrecognized C peptide deficiency. CONCLUSIONS: Horseshoe kidneys are acceptable as donor organs in renal transplantation.

Pyeloureterostomy in the management of renal allograft ureteral complications: an alternative technique.

Pyeloureterostomy is the standard procedure for reconstructing renal allograft ureteral complications. Most reports describe an end-to-end technique with or without native nephrectomy. An alternative is an end-to-side anastomosis, leaving the native ureter in continuity. We report our experience with the latter method. Since July 1983, 437 renal transplantations have been performed at our institution. End-to-side pyeloureterostomy has been used in 5 cases for urological reconstruction after renal transplantation following ureteral ischemic necrosis or stenosis. In 1 patient the native kidneys had been removed several years previously but in the remaining 4 the native kidneys were left in situ. There have been no significant complications following this procedure. We believe that by not significantly mobilizing, ligating or dividing the native ureter the chance of anastomotic breakdown due to ischemia may be decreased.

Model of orthotopic renal transplantation in the rabbit.

A microsurgical method of orthotopic renal allotransplantation in the rabbit is described, and the results of 179 consecutive procedures are presented. There were 10 (5.5%) deaths within 1 week of transplantation. Early complications included vascular thrombosis (4.4%), and obstruction (6.7%) and fistula formation (0.6%) at the uretero-ureteric anastomosis. This method of end-to-end vascular and ureteric anastomoses is straightforward and, in contrast to other models, does not require occlusion of the recipient inferior vena cava or aorta, use of a long segment of donor ureter, or operation on the recipient bladder.

Right atrial catheters: reliable, immediate and durable vascular access for haemodialysis and plasma exchange.

This paper prospectively evaluates 33 dual lumen, right atrial catheters inserted into either an external or internal jugular vein by open operation in 29 patients, of whom 15 required haemodialysis and 14 required temporary plasma exchange. The median (range) catheter survival in the haemodialysis and plasma exchange groups was 108 days (7-334 days) and 61 days (10-116 days), respectively. Life table analysis demonstrated that overall catheter survival was 58% at 200 days. The main causes of catheter failure were infection (four cases), poor flow (three cases) and accidental removal (one case). Another nine catheters were removed electively because of maturation of alternative methods of vascular access (five cases), completion of plasma exchange treatment (three cases), or successful renal transplantation (one case). Long-term silastic catheters, inserted into the right atrium via a jugular vein, have distinct advantages over temporary subclavian vein catheters and external arteriovenous (AV) shunts; this form of access is the method of choice for haemodialysis and plasma exchange patients who require immediate and short- to medium-term vascular access.

Spontaneous renal allograft rupture: a disappearing phenomenon in the cyclosporine era?

Spontaneous renal allograft rupture occurred in six patients in a series of 384 consecutive renal transplants performed between July 1983 and December 1990. All cases occurred in patients treated with Azathioprine and Prednisolone, and none occurred in patients immunosuppressed with Cyclosporine. Acute allograft rejection was the underlying cause of rupture. All patients underwent urgent operation and repair of the ruptured transplant. Four patients had good renal function 74-84 months after repair, while two returned to dialysis 3 and 65 months after repair because of irreversible rejection.

Kidney transplantation from living related donors: a 19-year experience.

OBJECTIVE: To determine the outcome of patients with end-stage chronic renal failure treated by live donor renal transplantation at the Royal Melbourne Hospital and Royal Children's Hospital between 1973 and 1991, during which time two distinct immunosuppressive regimens were used. DESIGN: Data about live donor renal transplant recipients were retrieved from the Australian and New Zealand Dialysis and Transplantation Association Registry, to which we have submitted data on all transplant recipients at six monthly intervals since the commencement of our dialysis and transplant programs. PATIENTS: Seventy-two patients with chronic renal failure who received live donor renal transplants during the 19 years from February 1973 to February 1992 were included. MAIN OUTCOME MEASURES: Patient survival, transplant survival, transplant function, change in prednisolone requirements, and duration of hospital stay. RESULTS: The first 32 patients were treated with immunosuppressive regimens based on combinations of prednisolone and azathioprine ("dual therapy"), while the next 40 patients were treated with combinations of cyclosporin, prednisolone and azathioprine ("triple therapy"). Survival of patients in each group five years after transplantation was 97%. Actuarial graft survival at 5, 10 and 15 years in the dual therapy group was 58%, 52% and 47%, compared with a 5-year actuarial graft survival in the triple therapy group of 96%. There was no statistically significant difference in renal transplant function between the two groups within the first 6 years after transplantation. Twelve of 26 patients (46%) treated initially with triple therapy were able to stop treatment with prednisolone within 12 months of transplantation. Median hospital stay was 12 (range, 6-35) days during the period 1973-1985 and 8 (range, 5-20) days for the 1985-1992 period. CONCLUSION: Live donor renal transplantation has provided a highly satisfactory means of treating patients with end-stage chronic renal failure in the short and long term. Our recent experience indicates that excellent patient and graft survival and adequate renal function can be achieved by treating live donor renal transplant recipients with a triple immunosuppressive regimen of low dose cyclosporin, prednisolone and azathioprine.

Renal transplantation in very young children.

Results of renal transplantation in very young children with end-stage chronic renal failure have been poor compared with those in older children and adults. Consequently small children either may not be treated or may be placed on chronic dialysis programmes. Between 1988 and 1992, six children under the age of 5 years received seven renal transplants at the Royal Children's Hospital, Parkville, Victoria, Australia; five from live donors and two from cadaver donors. All children were treated with peritoneal dialysis before transplantation, and immunosuppressed with a standardized regimen of cyclosporine, azathioprine and prednisolone. An extraperitoneal incision was used, and the donor renal vessels were anastomosed to the lower abdominal aorta and inferior vena cava or the common iliac vein. All children received intensive monitoring and fluid replacement during the peri-operative period. Patient survival was 100%. One cadaver graft failed 1 week after transplantation because of irreversible acute rejection. This child subsequently received a successful second transplant. Two children developed postoperative urinary fistulae which were treated successfully by further operation. Current renal function in all children is excellent. The success of this programme has led us to review our attitude towards renal transplantation in this age group and to advocate live donor renal transplantation as the treatment of choice in very young children with end-stage chronic renal failure whenever possible.