Longitudinal predictors of past-year non-suicidal self-injury and motives among college students.

BACKGROUND: Non-suicidal self-injury (NSSI) is the deliberate and direct injuring of body tissue without suicidal intent for purposes not socially sanctioned. Few studies have examined the correlates of NSSI among young adults. This study aimed to identify predictors of lifetime and past-year NSSI, and describe motives for NSSI and disclosure of NSSI to others. METHOD: Interviews were conducted annually with 1081 students enrolled in the College Life Study, a prospective longitudinal study conducted at a large public mid-Atlantic university. NSSI characteristics were assessed at Year 4. Demographic and predictor variables were assessed during Years 1 to 4. Multivariate logistic regression models were used to identify correlates of lifetime NSSI and predictors of past-year NSSI. RESULTS: The prevalence of past-year and lifetime NSSI was 2% and 7% respectively (>70% were female for both lifetime and past-year NSSI). Seven percent of NSSI cases self-injured once, whereas almost half self-injured six or more times. Independent predictors of past-year NSSI were maternal depression, non-heterosexual orientation, affective dysregulation and depression. Independent predictors of lifetime NSSI were depression, non-heterosexual orientation, paternal depression and female sex. One in six participants with NSSI had attempted suicide by young adulthood. The three most commonly reported motives for NSSI were mental distress, coping and situational stressors. Most (89%) told someone about their NSSI, most commonly a friend (68%). CONCLUSIONS: This study identified unique predictors of NSSI, which should help to elucidate its etiology and has implications for early identification and interventions.

Coral reefs under rapid climate change and ocean acidification.

Atmospheric carbon dioxide concentration is expected to exceed 500 parts per million and global temperatures to rise by at least 2 degrees C by 2050 to 2100, values that significantly exceed those of at least the past 420,000 years during which most extant marine organisms evolved. Under conditions expected in the 21st century, global warming and ocean acidification will compromise carbonate accretion, with corals becoming increasingly rare on reef systems. The result will be less diverse reef communities and carbonate reef structures that fail to be maintained. Climate change also exacerbates local stresses from declining water quality and overexploitation of key species, driving reefs increasingly toward the tipping point for functional collapse. This review presents future scenarios for coral reefs that predict increasingly serious consequences for reef-associated fisheries, tourism, coastal protection, and people. As the International Year of the Reef 2008 begins, scaled-up management intervention and decisive action on global emissions are required if the loss of coral-dominated ecosystems is to be avoided.

Combined climate and carbon-cycle effects of large-scale deforestation.

The prevention of deforestation and promotion of afforestation have often been cited as strategies to slow global warming. Deforestation releases CO(2) to the atmosphere, which exerts a warming influence on Earth's climate. However, biophysical effects of deforestation, which include changes in land surface albedo, evapotranspiration, and cloud cover also affect climate. Here we present results from several large-scale deforestation experiments performed with a three-dimensional coupled global carbon-cycle and climate model. These simulations were performed by using a fully three-dimensional model representing physical and biogeochemical interactions among land, atmosphere, and ocean. We find that global-scale deforestation has a net cooling influence on Earth's climate, because the warming carbon-cycle effects of deforestation are overwhelmed by the net cooling associated with changes in albedo and evapotranspiration. Latitude-specific deforestation experiments indicate that afforestation projects in the tropics would be clearly beneficial in mitigating global-scale warming, but would be counterproductive if implemented at high latitudes and would offer only marginal benefits in temperate regions. Although these results question the efficacy of mid- and high-latitude afforestation projects for climate mitigation, forests remain environmentally valuable resources for many reasons unrelated to climate.

The role of the southern ocean in uptake and storage of anthropogenic carbon dioxide

An ocean-climate model that shows high fluxes of anthropogenic carbon dioxide into the Southern Ocean, but very low storage of anthropogenic carbon there, agrees with observation-based estimates of ocean storage of anthropogenic carbon dioxide. This low simulated storage indicates a subordinate role for deep convection in the present-day Southern Ocean. The primary mechanism transporting anthropogenic carbon out of the Southern Ocean is isopycnal transport. These results imply that if global climate change reduces the density of surface waters in the Southern Ocean, isopycnal surfaces that now outcrop may become isolated from the atmosphere, tending to diminish Southern Ocean carbon uptake.

The life span of the biosphere revisited.

A decade ago, Lovelock and Whitfield raised the question of how much longer the biosphere can survive on Earth. They pointed out that, despite the current fossil-fuel induced increase in the atmospheric CO2 concentration, the long-term trend should be in the opposite direction: as increased solar luminosity warms the Earth, silicate rocks should weather more readily, causing atmospheric CO2 to decrease. In their model, atmospheric CO2 falls below the critical level for C3 photosynthesis, 150 parts per million (p.p.m.), in only 100 Myr, and this is assumed to mark the demise of the biosphere as a whole. Here, we re-examine this problem using a more elaborate model that includes a more accurate treatment of the greenhouse effect of CO2, a biologically mediated weathering parameterization, and the realization that C4 photosynthesis can persist to much lower concentrations of atmospheric CO2(<10 p.p.m.). We find that a C4-plant-based biosphere could survive for at least another 0.9 Gyr to 1.5 Gyr after the present time, depending respectively on whether CO2 or temperature is the limiting factor. Within an additional 1 Gyr, Earth may lose its water to space, thereby following the path of its sister planet, Venus.

Susceptibility of the early Earth to irreversible glaciation caused by carbon dioxide clouds.

Simple energy-balance climate models of the Budyko/Sellers type predict that a small (2-5%) decrease in solar output could result in runaway glaciation on the Earth. But solar fluxes 25-30% lower early in the Earth's history apparently did not lead to this result. One currently favoured explanation is that high partial pressures of carbon dioxide, caused by higher volcanic outgassing rates and/or slower rates of silicate weathering, created a large enough greenhouse effect to keep the planet warm. This does not resolve the problem of climate stability, however, because as we argue here, the oceans can freeze much more quickly than CO2 can accumulate in the atmosphere. Had such a transient global glaciation occurred in the distant past when solar luminosity was low, it might have been irreversible because of the formation of highly reflective CO2 clouds, similar to those encountered in climate simulations of early Mars. Our simulations of the early Earth, incorporating the possible formation of such clouds, suggest that the Earth might not be habitable today had it not been warm during the first part of its history.

The mid-Cretaceous super plume, carbon dioxide, and global warming.

Carbon-dioxide releases associated with a mid-Cretaceous super plume and the emplacement of the Ontong-Java Plateau have been suggested as a principal cause of the mid-Cretaceous global warming. We developed a carbonate-silicate cycle model to quantify the possible climatic effects of these CO2 releases, utilizing four different formulations for the rate of silicate-rock weathering as a function of atmospheric CO2. We find that CO2 emissions resulting from super-plume tectonics could have produced atmospheric CO2 levels from 3.7 to 14.7 times the modern pre-industrial value of 285 ppm. Based on the temperature sensitivity to CO2 increases used in the weathering-rate formulations, this would cause a global warming of from 2.8 to 7.7 degrees C over today's global mean temperature. Altered continental positions and higher sea level may have been contributed about 4.8 degrees C to mid-Cretaceous warming. Thus, the combined effects of paleogeographic changes and super-plume related CO2 emissions could be in the range of 7.6 to 12.5 degrees C, within the 6 to 14 degrees C range previously estimated for mid-Cretaceous warming. CO2 releases from oceanic plateaus alone are unlikely to have been directly responsible for more than 20% of the mid-Cretaceous increase in atmospheric CO2.

Continental-pelagic carbonate partitioning and the global carbonate-silicate cycle.

A carbonate-silicate geochemical cycle model is developed and used to explore dynamic and climatic consequences of constraints on shallow-water carbonate burial and possible carbon loss to the mantle associated with sea-floor subduction. The model partitions carbonate deposition between shallow-water and deep-water environments and includes carbon fluxes between the mantle and lithosphere. When total lithospheric carbonate mass is constant, there are two stable steady states, one in which the carbonate burial flux is mostly continental and another in which it is mostly pelagic. The continental steady state is characterized by a low metamorphic CO2 flux to the atmosphere and predominantly shallow-water carbonate burial. The pelagic steady state is characterized by a high metamorphic CO2 flux and predominantly deep-water carbonate burial. For reasonable parameter values, when total lithospheric carbonate mass is allowed to vary, the model oscillates between predominantly continental and predominantly pelagic modes. Model results suggest that carbonate deposition patterns established during the Cenozoic may be pushing the Earth system from the continental to the pelagic mode on a time scale of 10(8) yr, with a possible consequent order-of-magnitude increase in the metamorphic CO2 flux to the atmosphere.

Carbon dioxide emissions from Deccan volcanism and a K/T boundary greenhouse effect.

A greenhouse warming caused by increased emissions of carbon dioxide from the Deccan Traps volcanism has been suggested as the cause of the terminal Cretaceous extinctions on land and in the sea. We estimate total eruptive and noneruptive CO2 output by the Deccan eruptions (from 6 to 20 x 10(16) moles) over a period of several hundred thousand years based on best estimates of the CO2 weight fraction of the original basalts and basaltic melts, the fraction of CO2 degassed, and the volume of the Deccan Traps eruptions. Results of a model designed to estimate the effects of increased CO2 on climate and ocean chemistry suggest that increases in atmospheric pCO2 due to Deccan Traps CO2 emissions would have been less than 75 ppm, leading to a predicted global warming of less than 1 degree C over several hundred thousand years. We conclude that the direct climate effects of CO2 emissions from the Deccan eruptions would have been too weak to be an important factor in the end-Cretaceous mass extinctions.