The Science of Climate Change

Central to the findings of the Intergovernmental Panel on Climate Change (IPCC) third assessment report, released in Shanghai in January 2001, was the statement: "There is now new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities." This represents a significant strengthening of the analogous statement issued by the IPCC in 1996: "The balance of evidence suggests a discernible human influence on global climate" In this article the scientific evidence leading up to these IPCC statements is reviewed. A historical perspective of the Earth's climate over the last 400,000 years is presented, as is the science of global warming over the last 200 years. The range of projections of climate change over the next century is also summarized giving particular emphasis to projections concerning Canada. The issue of uncertainty in climate change projections is tackled and the public confusion arising from the media portrayal of the science and its entry into the political arena discussed. Finally, The Kyoto Protocol and how it fits within the framework of necessary actions required to reduce greenhouse gas emissions is reviewed. Sommaire Point focal des découvertes décrites dans le troisième rapport du Groupe d'experts intergouvernemental sur l'évolution du climat (GIEC), publié à Shangaï en janvier 2001, on retrouve cette déclaration essentielle : « Il existe maintenant des indications nouvelles et plus convaincantes que la plupart des indices de réchauffement ayant fait l'objet d'observations au cours des derniers 50 ans sont attribuables aux activités humaines ». Cela constitue un renforcement significatif d'une déclaration similaire publiée en 1996 par le GIEC : « Le bilan des preuves considérées porte à penser que le climat planétaire serait influencé par des causes d'origine humaine ». Le présent article porte sur l'ensemble des éléments de preuve scientifique sous-jacent aux déclarations de ces deux déclarations du GIEC. Dans une perspective historique, on y présente les fluctuations climatiques de la planète au cours des derniers 400 000 ans, ainsi que les principales étapes du développement de la science du réchauffement au cours des derniers 200ans. On passe en revue la gamme des projections des changements climatiques pour le prochain siècle, particulièrement en ce qui concerne le Canada. On discute du problème de l'incertitude des projections de changements climatiques, de la confusion du public dans le contexte de l'image de la science dépeint par les médias ainsi que de l'émergence du sujet dans l'arène politique. Finalement, le protocole de Kyoto est revu, surtout en ce qui a trait aux actions requises pour réduire l'émission de gaz à effet de serre

Ice growth in the greenhouse: A seductive paradox but unrealistic scenario

The recent IPCC (2001) assessment stated that "Most models show weakening of the Northern Hemisphere Thermohaline Circulation (THC), which contributes to a reduction of surface warming in the northern North Atlantic. Even in models where the THC weakens, there is still a warming over Europe due to increased greenhouse gases." However, there is still a widespread misunderstanding of the possible consequence of climate change on the Atlantic Ocean Meridional Overturning. In particular, it is often touted, especially in the media, that a possible consequence of anthropogenic greenhouse gas emissions is: "the onset of the next ice age". Here we document the history of this misconception and quantitatively show how it is impossible for an ice age to ensue as a consequence of global warming. Through analysis of the paleoclimate record as well as a number of climate model simulations, we also suggest that it is very unlikely that the Atlantic Meridional Overturning will cease to be active in the near future. We further suggest that a region where intermediate water formation may shut down is in the Labrador Sea, although this has more minor consequences for climate than if deep water formation in the Nordic Seas were to cease. RÉSUMÉ Lors d'une évaluation récente (2001) du GIÉC on a écrit « La plupart des modèles montrent l'existence d'un affaiblissement de la circulation thermohaline (CTH) dans l'hémisphère Nord, ce qui contribue à une réduction du réchauffement de surface de la région nord de l'Atlantique Nord. Et même dans les modèles montrant un affaiblissement de la CTH, il y a quand même réchauffement de la zone européenne à cause de l'augmentation des gaz à effet de serre. » Cependant, beaucoup d'incompréhension subsiste quant aux possibles conséquences d'un changement climatique découlant de ce retournement dans la portion méridionale de l'océan Atlantique. En particulier, on entend souvent, spécialement dans les médias, que l'une des conséquence possible des émissions de gaz à effet de serres anthropogéniques serait « le déclenchement d'un âge glaciaire ». Dans le présent article, nous présentons l'historique de cette méprise et démontrons qu'il est impossible qu'un âge glaciaire soit provoqué par le réchauffement de l'atmosphère de la planète. Aussi, par l'analyse des archives paléoclimatiques et l'étude de nombreux modèles de simulation climatique, nous suggérons qu'il est très improbable quele retournement en cours dans la portion méridionale de l'Atlantique Nord, cesse dans un avenir rapproché. Nous proposons aussi que la mer du Labrador est une région où la formation d'eaux intermédiaires pourrait s'arrêter, bien que les conséquences climatiques soient bien moindres que s'il s'agissait des eaux profondes de la mer du Nord

Pyloric Stenosis Leading to Sinus Venous Thrombosis; A Case Report

Pyloric stenosis is typically diagnosed early and repaired after resuscitation and electrolyte correction in a timely manner. Delay in diagnosis or presentation of patient can lead to significant morbidity and even mortality. Here we present a case of pyloric stenosis leading to dehydration severe enough to lead to venous sinus thrombosis. This case highlights the importance of early detection of pyloric stenosis with timely correction of fluid status and electrolytes. Venous sinus thrombosis is a serious complication associated with our patient’s pyloric stenosis that has not yet been reported in literature

Recurrent Spontaneous Pneumothorax During Pregnancy; A Case Report

Spontaneous pneumothorax is a rare but potentially life-threatening condition during pregnancy. We discuss a case of recurrent spontaneous pneumothorax during a single pregnancy. The pneumothorax occurred twice during the pregnancy, first in the second trimester and again in the third trimester with both times being managed conservatively. Due to the low prevalence of this condition management guidelines are few. We report our management of recurrent spontaneous pneumothorax during pregnancy to support the literature and current guidelines

Secondary Scoliosis from a Retroperitoneal Ganglioneuroma in a 9-year-old Female: Case Report

Ganglioneuromas are rare benign tumors that tend to be asymptomatic until large enough to compress adjacent structures. These tumors are often found during childhood during evaluations for other pathologies. Retroperitoneal ganglioneuromas may be a secondary cause of scoliosis. Here, we present a case of a child who was found to have a retroperitoneal ganglioneuroma during an evaluation for scoliosis.

A Case of Metastatic Melanoma Presenting as a Small Bowel Obstruction

Small bowel obstructions are most commonly caused by adhesion. Less common causes arise from malignant pathology. Here we present a relatively rare case of a small bowel obstruction due to malignant melanoma. Melanoma involving the gastrointestinal tract is relatively rare with most cases occurring as metastatic spread from a cutaneous primary. The treatment typically requires a surgical resection or palliative bypass. When a patient presents with a small bowel obstruction but without prior abdominal surgeries or hernias a malignant obstruction must be on the differential

Can Regulation of Freshwater Runoff in Hudson Bay Affect the Climate of the North Atlantic?

A sequence of phenomena links anthropogenic changes in the timing of freshwater runoff in Hudson Bay to a possible impact on the North Atlantic thermohaline circulation. The chain of events starts with the spreading of estuarine plumes under ice and continues with the effect of lowered salinity on the rate of ice formation, regional effects on the scale of Hudson Bay, the export of freshwater to the Labrador Sea, its impact on deep convection in that area, and the relative importance of such changes to the North Atlantic circulation. At each step we compare anthropogenic effects with other factors and place them within the perspective of natural variability. Our conclusion does not support the contention that freshwater runoff regulation, even of all rivers in the basins of Hudson and James Bays, could have a significant or even a detectable effect on the climate of the North Atlantic.Une séquence de phénomènes relie des changements anthropiques dans le moment où les eaux douces commencent à s'écouler dans la baie d'Hudson à leur répercussion possible sur les courants thermiques des eaux marines. La séquence débute par la formation d'un panache estuarien sous la glace et se poursuit avec l'effet de la baisse de salinité sur la vitesse de formation de la glace, des répercussions régionales affectant toute la baie d'Hudson, l'exportation d'eau douce vers la mer du Labrador et ses retombées sur la convection profonde dans cette zone, ainsi qu'avec l'importance relative de tels changements sur les courants nord-atlantiques. À chaque étape, on compare les influences anthropiques avec d'autres facteurs pour les situer dans un contexte de variabilité. Notre conclusion n'appuie pas la thèse que la régulation de l'écoulement des eaux douces, même si elle s'étendait à tous les cours d'eau des bassins de la baie d'Hudson et de la baie James, pourrait avoir des répercussions notables ou même détectables sur le climat nord-atlantique

A Rare Case of Right Lower Lobe Intralobar Pulmonary Sequestration in an Adult

Pulmonary sequestration is a rare congenital abnormality which is often diagnosed in childhood. There are two types of sequestration which are differentiated by the presence, or lack of pleural lining dividing the aberrant lung tissue from functional lung. Data for the management of this pathology in adults remains scarce. Here we present a case of intralobar pulmonary sequestration in an adult. The management of this patient comprised of surgical treatment involving lobectomy and ligation of the feeding vessel. The patient had an uneventful recovery and final pathology revealed a chronic infection in the sequestration

A Case of Recurrent Breast Cancer Diagnosed from Symptomatic Metastasis to Bladder

Abstract: Women in the United States have an approximate 1 in 8 chance of developing breast cancer in their lifetime. The main cause of death from breast cancer is from metastatic spread of the disease; with the most frequent sites of spread being to the bone, brain, and lungs. The urinary bladder is a rare site of metastasis that has been rarely reported on in the literature. Here we present a case of recurrent metastatic breast cancer found in the urinary bladder without findings of any other sites of metastasis

Old and Young X-ray Point Source Populations in Nearby Galaxies

We analyzed 1441 Chandra X-ray point sources in 32 nearby galaxies. The total point-source X-ray luminosity L_XP is well correlated with B, K, and FIR+UV luminosities of spiral host galaxies, and with the B and K luminosities for ellipticals. This suggests an intimate connection between L_XP and both the old and young stellar populations, for which K and FIR+UV luminosities are proxies for the galaxy mass M and star-formation rate SFR. We derive proportionality constants 1.3E29 erg/s/Msol and 0.7E39 erg/s/(Msol/yr), which can be used to estimate the old and young components from M and SFR, respectively. The cumulative X-ray luminosity functions for the point sources have quite different slopes for the spirals (gamma ~= 0.5-0.8) and ellipticals (gamma ~= 1.4), implying *the most luminous point sources dominate L_XP* for the spirals. Most of the point sources have X-ray colors that are consistent with either LMXBs or Ultraluminous X-ray sources (ULXs a.k.a. IXOs) and we rule out classical HMXBs (e.g. neutron-star X-ray pulsars) as contributing much to L_XP. Thus, for spirals, the ULXs dominate L_XP. We estimate that >~20% of all ULXs found in spirals originate from the older (pop II) stellar populations, indicating that many of the ULXs that have been found in spiral galaxies are in fact pop II ULXs, like those in elliptical galaxies. The linear dependence of L_XP on the SFR argues for either a steepening in the X-ray luminosity function of the young (pop I) X-ray source population at L_X >~10^(38.5-39) erg/s, or a decreasing efficiency for producing all types of young X-ray point sources as the galaxy SFR increases.Comment: 33 pages AASTEX, ApJ accepted. Please download full version with figures from http://www.pha.jhu.edu/~colbert/chps_accepted.p