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Warming caused by cumulative carbon emissions towards the trillionth tonne
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Global efforts to mitigate climate change are guided by projections of future temperatures1. But the eventual equilibrium global mean temperature associated with a given stabilization level of atmospheric greenhouse gas concentrations remains uncertain1–3, complicating the setting of stabilization targets to avoid poten- tially dangerous levels of global warming4–8. Similar problems apply to the carbon cycle: observations currently provide only a weak constraint on the response to future emissions9–11. Here we use ensemble simulations of simple climate-carbon-cycle models constrained by observations and projections from more compre- hensive models to simulate the temperature response to a broad range of carbon dioxide emission pathways. We find that the peak warming caused by a given cumulative carbon dioxide emission is better constrained than the warming response to a stabilization scenario. Furthermore, the relationship between cumulative emissions and peak warming is remarkably insensitive to the emis- sion pathway (timing of emissions or peak emission rate). Hence policy targets based on limiting cumulative emissions of carbon dioxide are likely to be more robust to scientific uncertainty than emission-rate or concentration targets. Total anthropogenic emissions of one trillion tonnes of carbon (3.67 trillion tonnes of CO2), about half of which has already been emitted since industrialization began, results in a most likely peak carbon-dioxide- induced warming of 2 6C above pre-industrial temperatures, with a 5–95% confidence interval of 1.3–3.9 6C.
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Greenhouse-gas emission targets for limiting global warming to 2 C
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More than 100 countries have adopted a global warming limit of 2 6C or below (relative to pre-industrial levels) as a guiding principle for mitigation efforts to reduce climate change risks, impacts and damages1,2. However, the greenhouse gas (GHG) emissions corresponding to a specified maximum warming are poorly known owing to uncertainties in the carbon cycle and the climate response. Here we provide a comprehensive probabilistic analysis aimed at quantifying GHG emission budgets for the 2000–50 period that would limit warming throughout the twenty-first century to below 2 6C, based on a combination of published distributions of climate system properties and observational con- straints. We show that, for the chosen class of emission scenarios, both cumulative emissions up to 2050 and emission levels in 2050 are robust indicators of the probability that twenty-first century warming will not exceed 26C relative to pre-industrial temperatures. Limiting cumulative CO2 emissions over 2000–50 to 1,000Gt CO2 yields a 25% probability of warming exceeding 2 6C—and a limit of 1,440 Gt CO2 yields a 50% probability—given a representative estimate of the distri- bution of climate system properties. As known 2000–06 CO2 emissions3 were234 Gt CO2, less than half the proven economi-cally recoverable oil, gas and coal reserves 4–6 can still be emitted up to 2050 to achieve such a goal. Recent G8 Communique ́s7 envisage halved global GHG emissions by 2050, for which we estimate a 12– 45% probability of exceeding 2 6C—assuming 1990 as emission base year and a range of published climate sensitivity distributions. Emissions levels in 2020 are a less robust indicator, but for the scenarios considered, the probability of exceeding 26C rises to 53–87% if global GHG emissions are still more than 25% above 2000 levels in 2020.
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Working Lands for Wildlife (WLFW)
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Grasslands and Savannas Lead Image
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Grasslands and Savannas Lead Image
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Western WLFW Lead Image
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Senators Reintroduce Landmark Wildlife Conservation Bill
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The bipartisan legislation would invest billions in state, Tribal conservation efforts
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Assessing Road Stream Crossing Barriers in the United States
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This is an instant app to view field survey data collected by SARP and partners using the North Atlantic Aquatic Connectivity Collaborative aquatic organism passage survey protocol
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Southeast Climate Adaptation Science Center-Science Seminar – Southeast Regional Invasive Species and Climate Change
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Join us for our Fall/Winter virtual science seminar series highlighting SE CASC funded projects supporting resource management actions across the Southeast. Each month a SE CASC researcher will provide an overview of their work and the management implications of their research findings.
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Increasing carbon storage in intact African tropical forests
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The response of terrestrial vegetation to a globally changing environment is central to predictions of future levels of atmospheric carbon dioxide1,2. The role of tropical forests is critical because they are carbon-dense and highly productive3,4. Inventory plots across Amazonia show that old-growth forests have increased in carbon storage over recent decades5–7, but the response of one-third of the world’s tropical forests in Africa8 is largely unknown owing to an absence of spatially extensive observation networks9,10. Here we report data from a ten-country network of long-term monitoring plots in African tropical forests. We find that across 79 plots (163ha) above-ground carbon storage in live trees increased by 0.63 Mg C ha21 yr21 between 1968 and 2007 (95% confidence inter- val (CI), 0.22–0.94; mean interval, 1987–96). Extrapolation to unmeasured forest components (live roots, small trees, necromass) and scaling to the continent implies a total increase in carbon storage in African tropical forest trees of 0.34 Pg C yr21 (CI, 0.15–0.43). These reported changes in carbon storage are similar to those reported for Amazonian forests per unit area6,7, providing evidence that increasing carbon storage in old-growth forests is a pan-tropical phenomenon. Indeed, combining all standardized inventory data from this study and from tropical America and Asia5,6,11 together yields a comparable figure of 0.49 Mg C ha21 yr21 (n 5 156; 562 ha; CI, 0.29–0.66; mean interval, 1987–97). This indicates a carbon sink of 1.3 Pg C yr21 (CI, 0.8–1.6) across all tropical forests during recent decades. Taxon-specific analyses of African inventory and other data12 suggest that widespread changes in resource availability, such as increasing atmospheric carbon dioxide concentrations, may be the cause of the increase in carbon stocks13, as some theory14 and models2,10,15 predict.
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