Climate Science PDFs
Climate Science PDFs Collection
- Rebuilding Soils on Mined Land for Native Forests in Appalachia
- The eastern U.S. Appalachian region supports the world’s most extensive temperate forests, but surface mining for coal has caused forest loss. New reclamation methods are being employed with the intent of restoring native forest on Appalachian mined lands. Mine soil construction is essential to the reforestation process. Here, we review scientific literature concerning selection of mining materials for mine soil construction where forest ecosystem restoration is the reclamation goal. Successful establishment and productive growth of native Appalachian trees has been documented on mine soils with coarse fragment contents as great as 60% but with low soluble salt levels and slightly to moderately acidic pHs, properties characteristic of the region’s native soils. Native tree productivity on some Appalachian mined lands where weathered rock spoils were used to reconstruct soils was found comparable to productivity on native forest sites. Weathered rock spoils, however, are lower in bioavailable N and P than native Appalachian soils and they lack live seed banks which native soils contain. The body of scientific research suggests use of salvaged native soils for mine soil construction when forest ecosystem restoration is the reclamation goal, and that weathered rock spoils are generally superior to unweathered rock spoils when constructing mine soils for this purpose.
- Amazon Basin climate under global warming: the role of the sea surface temperature
- The Hadley Centre coupled climate–carbon cycle model (HadCM3LC) predicts loss of the Amazon rainforest in response to future anthropogenic greenhouse gas emissions. In this study, the atmospheric component of HadCM3LC is used to assess the role of simulated changes in midtwenty-first century sea surface temperature (SST) in Amazon Basin climate change. When the full HadCM3LC SST anomalies (SSTAs) are used, the atmosphere model reproduces the Amazon Basin climate change exhibited by HadCM3LC, including much of the reduction in Amazon Basin rainfall. This rainfall change is shown to be the combined effect of SSTAs in both thetropical Atlantic and the Pacific, with roughly equal contributions from each basin. The greatest rainfall reduction occurs from May to October, outside of the mature South American monsoon (SAM) season. This dry season response is the combined effect of a more rapid warming of the tropical North Atlantic relative to the south, and warm SSTAs in the tropical east Pacific. Conversely, a weak enhancement of mature SAM season rainfall in response to Atlantic SST change is suppressed by the atmospheric response to Pacific SST. This net wet season response is sufficient to prevent dry season soil moisture deficits from being recharged through the SAM season, leading to a perennial soil moisture reduction and an associated 30% reduction in annual Amazon Basin net primary productivity (NPP). A further 23% NPP reduction occurs in response to a 3.58C warmer air temperature associated with a global mean SST warming.
- Allowable carbon emissions lowered by multiple climate targets
- Climate targets are designed to inform policies that would limit the magnitude and impacts of climate change caused by anthropogenic emissions of greenhouse gases and other substances. The target that is currently recognized by most world governments1 places a limit of two degrees Celsius on the global mean warming since preindustrial times. This would require large sustained reductions in carbon dioxide emissions during the twenty-first century and beyond2–4. Such a global temperature target, however, is not sufficient to control many other quantities, such as transient sea level rise5 , ocean acidification6,7 and net primary production on land8,9. Here, using an Earth system model of intermediate complexity (EMIC) in an observation-informed Bayesian approach, we show that allowable carbon emissions are substantially reduced whenmultiple climate targets are set. We take into account uncertainties in physical and carbon cycle model parameters, radiative efficiencies10, climate sensitivity11 and carbon cycle feedbacks12,13 along with a large set of observational constraints. Within this framework, we explore a broad range of economically feasible greenhouse gas scenarios from the integrated assessment community14–17 to determine the likelihood of meeting a combination of specific global and regional targets under various assumptions. For any given likelihood of meeting a set of such targets, the allowable cumulative emissions are greatly reduced from those inferred from the temperature target alone. Therefore, temperature targets alone are unable to comprehensively limit the risks from anthropogenic emissions.
- Managing Forests and Fire in Changing Climates
- With projected climate change, we expect to face much more forest fi re in the coming decades. Policymakers are challenged not to categorize all fires as destructive to ecosystems simply because they have long fl ame lengths and kill most of the trees within the fi re boundary. Ecological context matters: In some ecosystems, high-severity regimes are appropriate, but climate change may modify these fi re regimes and ecosystems as well. Some undesirable impacts may be avoided or reduced through global strategies, as well as distinct strategies based on a forest’s historical fi re regime. SCIENCE VOL 342 4 OCTOBER 2013
- Rate of tree carbon accumulation increases continuously with tree size
- Forests are major components of the global carbon cycle, providing substantial feedback to atmospheric greenhouse gas concentrations1 . Our ability to understand and predict changes in the forest carbon cycle—particularly net primary productivity and carbon storage— increasingly relies on models that represent biological processes across several scales of biological organization, from tree leaves to forest stands2,3. Yet, despite advances in our understanding of productivity at the scales of leaves and stands, no consensus exists about the nature of productivity at the scale of the individual tree4–7, in part because we lack a broad empirical assessment of whether rates of absolute treemass growth (and thus carbon accumulation) decrease, remain constant, or increase as trees increase in size and age. Here we present a global analysis of 403 tropical and temperate tree species, showing that for most species mass growth rate increases continuously with tree size. Thus, large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree. The apparent paradoxes of individual tree growth increasing with tree size despite declining leaf-level8–10 and stand-level10 productivity can be explained, respectively, by increases in a tree’s total leaf area that outpace declines in productivity per unit of leaf area and, among other factors, age-related reductions in population density. Our results resolve conflicting assumptions about the nature of tree growth,inform efforts to undertand and model forest carbon dynamics, and have additional implications for theories of resource allocation11 and plant senescence1
- Risk Communication on Climate: Mental Models and Mass Balance
- Public confusion about the urgency of reductions in greenhouse gas emissions results from a basic misconception.
- When the river runs dry: human and ecological values of dry riverbeds
- Temporary rivers and streams that naturally cease to flow and dry up can be found on every continent. Many other water courses that were once perennial now also have temporary flow regimes due to the effects of water extraction for human use or as a result of changes in land use and climate. The dry beds of these temporary rivers are an integral part of river landscapes. We discuss their importance in human culture and their unique diversity of aquatic, amphibious, and terrestrial biota. We also describe their role as seed and egg banks for aquatic biota, as dispersal corridors and temporal ecotones linking wet and dry phases, and as sites for the storage and processing of organic matter and nutrients. In light of these valuable functions, dry riverbeds need to be fully integrated into river management policies and monitoring programs. We also identify key knowledge gaps and suggest research questions concerning the values of dry riverbeds.
- The energetic implications of curtailing versus storing solar- and wind-generated electricity
- We present a theoretical framework to calculate how storage affects the energy return on energy investment (EROI) ratios of wind and solar resources. Our methods identify conditions under which it is more energetically favorable to store energy than it is to simply curtail electricity production. Electrochemically based storage technologies result in much smaller EROI ratios than large-scale geologically based storage technologies like compressed air energy storage (CAES) and pumped hydroelectric storage (PHS). All storage technologies paired with solar photovoltaic (PV) generation yield EROI ratios that are greater than curtailment. Due to their low energy stored on electrical energy invested (ESOIe) ratios, conventional battery technologies reduce the EROI ratios of wind generation below curtailment EROI ratios. To yield a greater net energy return than curtailment, battery storage technologies paired with wind generation need an ESOIe > 80. We identify improvements in cycle life as the most feasible way to increase battery ESOIe. Depending upon the battery's embodied energy requirement, an increase of cycle life to 10 000–18 000 (2–20 times present values) is required for pairing with wind (assuming liberal round-trip efficiency [90%] and liberal depth-of-discharge [80%] values). Reducing embodied energy costs, increasing efficiency and increasing depth of discharge will also further improve the energetic performance of batteries. While this paper focuses on only one benefit of energy storage, the value of not curtailing electricity generation during periods of excess production, similar analyses could be used to draw conclusions about other benefits as well
- Ecologists Report Huge Storm Losses in China’s Forests
- From delicate orchids and magnolias to rare Chinese yews and Kwangtung pines, the flora of Guangdong Nanling National Nature Reserve is considered so precious that ecologists call the reserve “a treasure trove of species.” But winter storms have reduced the biological hot spot to a splintered ruin. Snow, sleet, and ice laid waste to 90% of the 58,000- hectare reserve’s forests, says He Kejun, director of Guangdong Forestry
- Challenges in the conservation, rehabilitation and recovery of native stream salmonid populations: beyond the 2010 Luarca symposium
- – In May 2010, I chaired a session on challenges to salmonid conservation at the international symposium ‘Advances in the population ecology of stream salmonids’ in Luarca, Spain. I suggested that in addition to scientific challenges, a major challenge will be improving the links between ecologists, conservationists and policy makers. Because the Luarca symposium focused mainly on ecological research, little time was explicitly devoted to conservation. My objective in this paper is to further discuss the role of ecological research in informing salmonid conservation. I begin with a brief overview of research highlights from the symposium. I then use selected examples to show that ecological research has already contributed much towards informing salmonid conservation, but that ecologists will always be faced with limitations in their predictive ability. I suggest that conservation will need to move forward regardless of these limitations, and I call attention to some recent efforts wherein ecological research has played a crucial role. I conclude that ecologists should take urgent action to ensure that their results are availableto inform resource managers, conservation organisations and policy makers regarding past losses and present threats to native, locally-adapted salmonid stocks.
- Climate change impacts on the biophysics and economics of world fisheries
- Global marine fisheries are underperforming economically because of overfishing, pollution and habitat degradation. Added to these threats is the looming challenge of climate change. Observations, experiments and simulation models show that climate change would result in changes in primary productivity, shifts in distribution and changes in the potential yield of exploited marine species, resulting in impacts on the economics of fisheries worldwide. Despite the gaps in understanding climate change effects on fisheries, there is sufficient scientific information that highlights the need to implement climate change mitigation and adaptation policies to minimize impacts on fisheries.
- Dissecting insect responses to climate warming: overwintering and post-diapause performance in the southern green stink bug, Nezara viridula, under simulated climate-change conditions
- The effect of simulated climate change on overwintering and postdiapause reproductive performance is studied in Nezara viridula (L.) (Heteroptera: Pentatomidae) close to the species’ northern range limit in Japan. Insects are reared from October to June under quasi-natural (i.e. ambient outdoor) conditions and in a transparent incubator, in which climate warming is simulated by adding 2.5 ◦ C to the ambient temperatures. Despite the earlier assumption that females of N. viridula overwinter in diapause, whereas males do so in quiescence, regular dissections show that the two sexes overwinter in a state of true diapause. During winter, both sexes are dark-coloured and have undeveloped reproductive organs. Resumption of development does not start until late March. During winter, the effect of simulated warming on the dynamics and timing of physiological processes appears to be limited. However, the warming significantly enhances winter survival (from 27–31% to 47–70%), which is a key factor in range expansion of N. viridula. In spring, the effect of simulated warming is complex. It advances the post-diapause colour change and transition from dormancy to reproduction. The earlier resumption of development is more pronounced in females: in April, significantly more females are already in a reproductive state under the simulated warming than under quasi-natural conditions. In males, the tendency is similar, although the difference is not significant. Warming significantly enhances spring survival and percentage of copulating adults, although not the percentage of ovipositing females and fecundity. The results suggest that, under the expected climate-warming conditions, N. viridula will likely benefit mostly as a result of increased winter and spring survival and advanced post-diapause reproduction. Further warming is likely to allow more adults to survive the critical cold season and contribute (both numerically and by increasing heterogeneity) to the post-overwintering population growth, thus promoting the establishment of this species in newly-colonized area
- The Holocene`
- Combining nine tree growth proxies from four sites, from the west coast of Norway to the Kola Peninsula of NW Russia, provides a well replicated (> 100 annual measurements per year) mean index of tree growth over the last 1200 years that represents the growth of much of the northern pine timberline forests of northern Fennoscandia. The simple mean of the nine series, z-scored over their common period, correlates strongly with mean June to August temperature averaged over this region (r = 0.81), allowing reconstructions of summer temperature based on regression and variance scaling. The reconstructions correlate significantly with gridded summer temperatures across the whole of Fennoscandia, extending north across Svalbard and south into Denmark. Uncertainty in the reconstructions is estimated by combining the uncertainty in mean tree growth with the uncertainty in the regression models. Over the last seven centuries the uncertainty is < 4.5% higher than in the 20th century, and reaches a maximum of 12% above recent levels during the 10th century. The results suggest that the 20th century was the warmest of the last 1200 years, but that it was not significantly different from the 11th century. The coldest century was the 17th. The impact of volcanic eruptions is clear, and a delayed recovery from pairs or multiple eruptions suggests the presence of some positive feedback mechanism. There is no clear and consistent link between northern Fennoscandian summer temperatures and solar forcing.
- The Wheel of Life Food, Climate, Human Rights, and the Economy
- The links between climate change and industrial agriculture create a nexus of crises—food insecurity, natural resource depletion and degradation, as well as human rights violations and inequities. While it is widely recognized that greenhouse gas (GHG) emissions due to human activity are detrimental to the natural environment, it can be difficult to untangle the cascading effects on other sectors. To unravel some of the effects, this paper focuses on three interrelated issues: 1) What are the critical links between climate change and agriculture? 2) How is the nexus of agriculture and climate change affecting human societies particularly regarding food and water, livelihoods, migration, gender equality, and other basic survival and human rights? 3) What is the interplay between economic and finance systems, on the one hand, and food security, climate change, and fundamental human rights, on the other? In the process of drawing connections among these issues, the report will identify the commonality of drivers, or “push” factors, that lead to adverse impacts. A central theme throughout this report is that policies and practices must begin with the ecological imperative in order to ensure authentic security and stability on all fronts including food, water, livelihoods and jobs, climate, energy, and economic. In turn this engenders equity, social justice, and diverse cultures. This imperative, or ethos of nature, is a foundation that serves as a steady guide when reviewing mitigation and adaptation solutions to climate change. Infused within this theme is the sobering recognition that current consumption and production patterns are at odds with goals of reducing GHGs and attaining global food security. For instance, consumption and production levels, based on the global average, are 25 percent higher than the earth’s ecological capacity.1 As societies address the myriad ecological and social issues at the axis of global warming, a central task will be to re-align consumption and production trends in a manner that can fulfill economic and development requirements. This will require a major shift away from present economic growth paradigms based on massive resource extraction and toward creating prosperous and vital societies and economies that preserve the planet’s environmental capacity
- Missing feedbacks, asymmetric uncertainties, and the underestimation of future warming
- Historical evidence shows that atmospheric greenhouse gas (GhG) concentrations increase during periods of warming, implying a positive feedback to future climate change. We quantified this feedback for CO2 and CH4 by combining the mathematics of feedback with empirical icecore information and general circulation model (GCM) climate sensitivity, finding that the warming of 1.5 –4.5C associated with anthropogenic doubling of CO2 is amplified to 1.6– 6.0C warming, with the uncertainty range deriving from GCM simulations and paleo temperature records. Thus, anthropogenic emissions result in higher final GhG concentrations, and therefore more warming, than would be predicted in the absence of this feedback. Moreover, a symmetrical uncertainty in any component of feedback, whether positive or negative, produces an asymmetrical distribution of expected temperatures skewed toward higher temperature. For both reasons, the omission of key positive feedbacks and asymmetrical uncertainty from feedbacks, it is likely that the future will be hotter than we think. Citation: Torn, M. S., and J. Harte (2006), Missing feedbacks, asymmetric uncertainties, and the underestimation of future warming.
- TRY – a global database of plant traits
- Plant traits – the morphological, anatomical, physiological, biochemical and phenological characteristics of plants and their organs – determine how primary producers respond to environmental factors, affect other trophic levels, influence ecosystem processes and services and provide a link from species richness to ecosystem functional diversity. Trait data thus represent the raw material for a wide range of research from evolutionary biology, community and functional ecology to biogeography. Here we present the global database initiative named TRY, which has united a wide range of the plant trait research community worldwide and gained an unprecedented buy-in of trait data: so far 93 trait databases have been contributed. The data repository currently contains almost three million trait entries for 69 000 out of the world’s 300 000 plant species, with a focus on 52 groups of traits characterizing the vegetative and regeneration stages of the plant life cycle, including growth, dispersal, establishment and persistence. A first data analysis shows that most plant traits are approximately log-normally distributed, with widely differing ranges of variation across traits. Most trait variation is between species (interspecific), but significant intraspecific variation is also documented, up to 40% of the overall variation. Plant functional types (PFTs), as commonly used in vegetation models, capture a substantial fraction of the observed variation – but for several traits most variation occurs within PFTs, up to 75% of the overall variation. In the context of vegetation models these traits would better be represented by state variables rather than fixed parameter values. The improved availability of plant trait data in the unified global database is expected to support a paradigm shift from species to trait-based ecology, offer new opportunities for synthetic plant trait research and enable a more realistic and empirically grounded representation of terrestrial vegetation in Earth system models.
- U.S. Forest Carbon and Climate Change Controversies and Win-Win Policy Approaches
- As consensus grows about the serious impacts of global climate change, the role of forests in carbon storage is increasingly recognized. Terrestrial vegetation worldwide currently removes about 24 percent of the greenhouse gases released by industrial processes. Unfortunately, this contribution is approximately cancelled out by carbon released as a result of global deforestation and other ecosystem changes. Slowing or halting the rate of deforestation is thus one of the prime strategies to mitigate global climate change. The U.S. situation differs from the global one in several ways. Since both forest acres and average biomass per forest acre are currently increasing, as U.S. forests recover from past clearing or heavy harvest, our forest carbon stores are growing larger over time. However, our high rate of industrial emissions means that only about 10 percent of the carbon released from burning fossil fuels in the United States is captured by our forests. Moreover, net U.S. forest carbon sequestration has begun to slow in recent years as reforestation reaches its limits and development sprawls into more rural forested areas. U.S. forests could possibly capture a much higher portion of our industrial emissions, but only if we prevent forest conversion and development and manage our forests to maximize carbon stores.
- Unburnable Carbon – Are the world’s financial markets carrying a carbon bubble?
- The Carbon Tracker initiative is a new way of looking at the carbon emissions problem. It is focused on the fossil fuel reserves held by publically listed companies and the way they are valued and assessed by markets. Currently financial markets have an unlimited capacity to treat fossil fuel reserves as assets. As governments move to control carbon emissions, this market failure is creating systemic risks for institutional investors, notably the threat of fossil fuel assets becoming stranded as the shift to a low-carbon economy accelerates.
- Scenario Planning: a Tool for Conservation in an Uncertain World
- : Conservation decisions about how, when, and where to act are typically based on our expectations for the future. When the world is highly unpredictable and we are working from a limited range of expectations, however, our expectations will frequently be proved wrong. Scenario planning offers a framework for developing more resilient conservation policies when faced with uncontrollable, irreducible uncertainty. A scenario in this context is an account of a plausible future. Scenario planning consists of using a few contrasting scenarios to explore the uncertainty surrounding the future consequences of a decision. Ideally, scenarios should be constructed by a diverse group of people for a single, stated purpose. Scenario planning can incorporate a variety of quantitative and qualitative information in the decision-making process. Often, consideration of this diverse information in a systemic way leads to better decisions. Furthermore, the participation of a diverse group of people in a systemic process of collecting, discussing, and analyzing scenarios builds shared understanding. The robustness provided by the consideration of multiple possible futures has served several groups well; we present examples from business, government, and conservation planning that illustrate the value of scenario planning. For conservation, major benefits of using scenario planning are (1) increased understanding of key uncertainties, (2) incorporation of alternative perspectives into conservation planning, and (3) greater resilience of decisions to surprise.
- Call Off the Quest
- Over the past 30 years, the climate research community has made valiant efforts to answer the “climate sensitivity” question: What is the long-term equilibrium warming response to a doubling of atmospheric carbon dioxide? Earlier this year, the Intergovernmental Panel on Climate Change (1) concluded that this sensitivity is likely to be in the range of 2° to 4.5°C, with a 1-in-3 chance that it is outside that range. The lower bound of 2°C is slightly higher than the 1.6°C proposed in the 1970s (2). 26 OCTOBER 2007 VOL 318 SCIENCE
