RESUMO
Estimates of 21st Century global-mean surface temperature increase have generally been based on scenarios that do not include climate policies. Newly developed multigas mitigation scenarios, based on a wide range of modeling approaches and socioeconomic assumptions, now allow the assessment of possible impacts of climate policies on projected warming ranges. This article assesses the atmospheric CO(2) concentrations, radiative forcing, and temperature increase for these new scenarios using two reduced-complexity climate models. These scenarios result in temperature increase of 0.5-4.4 degrees C over 1990 levels or 0.3-3.4 degrees C less than the no-policy cases. The range results from differences in the assumed stringency of climate policy and uncertainty in our understanding of the climate system. Notably, an average minimum warming of approximately 1.4 degrees C (with a full range of 0.5-2.8 degrees C) remains for even the most stringent stabilization scenarios analyzed here. This value is substantially above previously estimated committed warming based on climate system inertia alone. The results show that, although ambitious mitigation efforts can significantly reduce global warming, adaptation measures will be needed in addition to mitigation to reduce the impact of the residual warming.
Assuntos
Efeito Estufa , Temperatura , Dióxido de Carbono/metabolismo , Clima , Ecossistema , Modelos TeóricosRESUMO
Pulse-like carbon dioxide release to the atmosphere on centennial time scales has only been identified for the most recent glacial and deglacial periods and is thought to be absent during warmer climate conditions. Here, we present a high-resolution carbon dioxide record from 330,000 to 450,000 years before present, revealing pronounced carbon dioxide jumps (CDJ) under cold and warm climate conditions. CDJ come in two varieties that we attribute to invigoration or weakening of the Atlantic meridional overturning circulation (AMOC) and associated northward and southward shifts of the intertropical convergence zone, respectively. We find that CDJ are pervasive features of the carbon cycle that can occur during interglacial climate conditions if land ice masses are sufficiently extended to be able to disturb the AMOC by freshwater input.
RESUMO
The ocean moderates anthropogenic climate change at the cost of profound alterations of its physics, chemistry, ecology, and services. Here, we evaluate and compare the risks of impacts on marine and coastal ecosystemsand the goods and services they providefor growing cumulative carbon emissions under two contrasting emissions scenarios. The current emissions trajectory would rapidly and significantly alter many ecosystems and the associated services on which humans heavily depend. A reduced emissions scenarioconsistent with the Copenhagen Accord's goal of a global temperature increase of less than 2°Cis much more favorable to the ocean but still substantially alters important marine ecosystems and associated goods and services. The management options to address ocean impacts narrow as the ocean warms and acidifies. Consequently, any new climate regime that fails to minimize ocean impacts would be incomplete and inadequate.
Assuntos
Organismos Aquáticos , Dióxido de Carbono , Ecossistema , Aquecimento Global , Efeito Estufa , Animais , Aquicultura , Saúde , Humanos , Oceanos e Mares , Risco , ViagemRESUMO
Lumbar sympathectomy is a good procedure for occlusion of the superficial femoral artery provided collateral circulation be stimulated by walking, and of course provided this circulation be intact. This requires an aortography which is necessary to arrive at a good prognosis. Lumbar sympathectomy without a previous aortogram is meaningless: it would lead to the ignorance of short stenoses of the internal iliac or deep femoral arteries and misinterpretation of the efficiency of lumbar sympathectomy.
Assuntos
Arteriopatias Oclusivas/terapia , Artéria Femoral , Perna (Membro)/irrigação sanguínea , Simpatectomia , Arteriopatias Oclusivas/fisiopatologia , Arteriosclerose/fisiopatologia , Arteriosclerose/terapia , Seguimentos , Humanos , Fluxo Sanguíneo RegionalAssuntos
Fístula Arteriovenosa/etiologia , Artéria Femoral , Veia Femoral , Sarcoma/complicações , Idoso , Aorta Abdominal/diagnóstico por imagem , Fístula Arteriovenosa/patologia , Fístula Arteriovenosa/cirurgia , Artéria Femoral/patologia , Artéria Femoral/cirurgia , Veia Femoral/patologia , Veia Femoral/cirurgia , Humanos , Masculino , Radiografia , Sarcoma/patologia , Sarcoma/cirurgiaRESUMO
A case is reported of an 18-year-old man with a syndrome of multiple aneurysms of unknown origin. Several interventions were necessary over a 30-year-period, mainly for haemodynamic reasons or compression. A review of the literature revealed seven similar cases, two of which had Ehlers-Danlos Syndrome.
Assuntos
Aneurisma/complicações , Artéria Braquial , Artéria Carótida Interna , Artéria Ilíaca , Artéria Renal , Artéria Esplênica , Adolescente , Adulto , Fatores Etários , Aneurisma/congênito , Aneurisma/etiologia , Aneurisma/cirurgia , Humanos , Masculino , Fatores de TempoRESUMO
A low-order physical-biogeochemical climate model was used to project atmospheric carbon dioxide and global warming for scenarios developed by the Intergovernmental Panel on Climate Change. The North Atlantic thermohaline circulation weakens in all global warming simulations and collapses at high levels of carbon dioxide. Projected changes in the marine carbon cycle have a modest impact on atmospheric carbon dioxide. Compared with the control, atmospheric carbon dioxide increased by 4 percent at year 2100 and 20 percent at year 2500. The reduction in ocean carbon uptake can be mainly explained by sea surface warming. The projected changes of the marine biological cycle compensate the reduction in downward mixing of anthropogenic carbon, except when the North Atlantic thermohaline circulation collapses.