An investigation into linearity with cumulative emissions of the climate and carbon cycle response in HadCM3LC

We investigate the extent to which global mean temperature, precipitation, and the carbon cycle are constrained by cumulative carbon emissions throughout four experiments with a fully coupled climate-carbon cycle model. The two paired experiments adopt contrasting, idealised approaches to climate change mitigation at different action points this century, with total emissions exceeding two trillion tonnes of carbon in the later pair. Their initially diverging cumulative emissions trajectories cross after several decades, before diverging again. We find that their global mean temperatures are, to first order, linear with cumulative emissions, though regional differences in temperature of up to 1.5K exist when cumulative emissions of each pair coincide. Interestingly, although the oceanic precipitation response scales with cumulative emissions, the global precipitation response does not, due to a decrease in precipitation over land above cumulative emissions of around one trillion tonnes of carbon (TtC). Most carbon fluxes and stores are less well constrained by cumulative emissions as they reach two trillion tonnes. The opposing mitigation approaches have different consequences for the Amazon rainforest, which affects the linearity with which the carbon cycle responds to cumulative emissions. Averaged over the two fixed-emissions experiments, the transient response to cumulative carbon emissions (TCRE) is 1.95 K TtC-1, at the upper end of the IPCC’s range of 0.8-2.5 K TtC-1

Holocene carbon-cycle dynamics based on CO2 trapped in ice at Taylor Dome, Antarctica

A high-resolution ice-core record of atmospheric CO2 concentration over the Holocene epoch shows that the global carbon cycle has not been in steady state during the past 11,000 years. Analysis of the CO2 concentration and carbon stable-isotope records, using a one-dimensional carbon-cycle model,uggests that changes in terrestrial biomass and sea surface temperature were largely responsible for the observed millennial-scale changes of atmospheric CO2 concentrations

Carbon Isotope Constraints on the Deglacial CO2 Rise from Ice Cores

The stable carbon isotope ratio of atmospheric CO2 (d13Catm) is a key parameter in deciphering past carbon cycle changes. Here we present d13Catm data for the past 24,000 years derived from three independent records from two Antarctic ice cores. We conclude that a pronounced 0.3 per mil decrease in d13Catm during the early deglaciation can be best explained by upwelling of old, carbon-enriched waters in the Southern Ocean. Later in the deglaciation, regrowth of the terrestrial biosphere, changes in sea surface temperature, and ocean circulation governed the d13Catm evolution. During the Last Glacial Maximum, d13Catm and atmospheric CO2 concentration were essentially constant, which suggests that the carbon cycle was in dynamic equilibrium and that the net transfer of carbon to the deep ocean had occurred before then

Global warming will affect the maximum potential abundance of boreal plant species

Forecasting the impact of future global warming on biodiversity requires understanding how temperature limits the distribution of species. Here we rely on Liebig's Law of Minimum to estimate the effect of temperature on the maximum potential abundance that a species can attain at a certain location. We develop 95%‐quantile regressions to model the influence of effective temperature sum on the maximum potential abundance of 25 common understory plant species of Finland, along 868 nationwide plots sampled in 1985. Fifteen of these species showed a significant response to temperature sum that was consistent in temperature‐only models and in all‐predictors models, which also included cumulative precipitation, soil texture, soil fertility, tree species and stand maturity as predictors. For species with significant and consistent responses to temperature, we forecasted potential shifts in abundance for the period 2041–2070 under the IPCC A1B emission scenario using temperature‐only models. We predict major potential changes in abundance and average northward distribution shifts of 6–8 km yr−1. Our results emphasize inter‐specific differences in the impact of global warming on the understory layer of boreal forests. Species in all functional groups from dwarf shrubs, herbs and grasses to bryophytes and lichens showed significant responses to temperature, while temperature did not limit the abundance of 10 species. We discuss the interest of modelling the ‘maximum potential abundance’ to deal with the uncertainty in the predictions of realized abundances associated to the effect of environmental factors not accounted for and to dispersal limitations of species, among others. We believe this concept has a promising and unexplored potential to forecast the impact of specific drivers of global change under future scenarios.202

Subocclusive transvenous approach of dural arteriovenous fistula

Introdução: As fístulas arteriovenosas durais (FAVd) são usualmente adquiridas e quando apresentam drenagem venosa cortical estão associadas a um risco elevado de hemorragia. Podem ser tratadas por embolização (transarterial ou transvenosa), cirurgicamente ou pela combinação das duas técnicas. A embolização por via transvenosa induz uma trombose iatrogénica do seio venoso, acarretando risco de enfarte venoso e/ou hemorragia. Objectivo: Rever os casos de FAVd do seio lateral submetidas a embolização transvenosa. O nosso principal objectivo é avaliar a eficácia e a morbilidade deste tipo de tratamento e o segundo é discutir as possíveis vantagens de uma abordagem suboclusiva na primeira sessão de tratamento. Resultados: Os autores apresentam seis casos clínicos de FAVd, cujas formas de apresentação foram: diminuição da acuidade visual (3); sopro pulsátil no ouvido (3); cefaleias (2); hemorragia subaracnoideia (1); hipoacusia subjectiva (1); edema da papila (1); défice motor (1). Angiograficamente: Cognard IIa (3), IIab (2) e IV (1), todas com envolvimento dos seios laterais. As principais aferências eram: ACE ipsilateral (6); ACI ipsilateral (6); AV ipsilateral (6); ACE contralateral (5); AV contralateral (5); ACI contralateral (3); ACP ipsilateral (1). O tratamento inicial foi sempre a abordagem transarterial, com resultados angiográficos aceitáveis, embora transitórios. Posteriormente optou-se pela via transvenosa com preenchimento do seio lateral com GDC coils. Em cinco dos doentes decidiu-se pela suboclusão, com persistência de algumas aferências. Em quatro, a angiografia subsequente demonstrou trombose “espontânea” do seio lateral com resolução clínica e angiográfica da doença. Num deles a trombose ocorreu ainda durante a sessão inicial. Todos os procedimentos decorreram sem complicações e nenhum dos doentes desenvolveu novos défices neurológicos focais. Conclusões: A abordagem transvenosa das FAVd obteve um sucesso técnico e clínico assinalável, sem presença de complicações. Pensamos que a suboclusão do seio venoso com coils poderá induzir menor alteração hemodinâmica aguda, possibilitando uma trombose mais lenta, diminuindo o risco de complicações, mas com resolução angiográfica ulterior da FAVd

Enhanced Australian carbon sink despite increased wildfire during the 21st century

Climate projections show Australia becoming significantly warmer during the 21st century, and precipitation decreasing over much of the continent. Such changes are conventionally considered to increase wildfire risk. Nevertheless, we show that burnt area increases in southern Australia, but decreases in northern Australia. Overall the projected increase in fire is small (0.72–1.31% of land area, depending on the climate scenario used), and does not cause a decrease in carbon storage. In fact, carbon storage increases by 3.7–5.6 Pg C (depending on the climate scenario used). Using a process-based model of vegetation dynamics, vegetation–fire interactions and carbon cycling, we show increased fire promotes a shift to more fire-adapted trees in wooded areas and their encroachment into grasslands, with an overall increase in forested area of 3.9–11.9%. Both changes increase carbon uptake and storage. The increase in woody vegetation increases the amount of coarse litter, which decays more slowly than fine litter hence leading to a relative reduction in overall heterotrophic respiration, further reducing carbon losses. Direct CO2 effects increase woody cover, water-use efficiency and productivity, such that carbon storage is increased by 8.5–14.8 Pg C compared to simulations in which CO2 is held constant at modern values. CO2 effects tend to increase burnt area, fire fluxes and therefore carbon losses in arid areas, but increase vegetation density and reduce burnt area in wooded areas

Corrigendum to "High-resolution interpolar difference of atmospheric methane around the Last Glacial Maximum" published in Biogeosciences, 9, 3961–3977, 2012

No abstract available