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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.

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

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.

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

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.

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.

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

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

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.

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.

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

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

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.

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.

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.

Barking up the Wrong Tree? Forest Sustainability in the wake of Emerging Bioenergy Policies: The spotted owl controversy revealed that federal forest management policies alone could not guarantee functioning forest ecosystems. At the same time as the owl’s listing, agreements made at the 1992 Rio Earth Summit highlighted the mounting pressures on natural systems, thus unofficially marking the advent of sustainable forestry management (SFM).2 While threats to forest ecosystems from traditional logging practices certainly remain,3 developed and developing countries have shifted generally toward more sustainable forest management, at least on paper, including codifying various sustainability indicators in public laws.4 Nevertheless, dark policy clouds are gathering on the forest management horizon. Scientific consensus has grown in recent years around a new and arguably more onerous threat to all of the world’s ecosystems—climate change. Governments’ responses have focused on bioenergy policies aimed at curtailing anthropogenic greenhouse gas (GHG) emissions, and mandatesfor renewables in energy supplies now abound worldwide. [Vol. 37:000

Protected Areas as Frontiers for Human Migration: Causes of human population growth near protected areas have been much debated. We conducted 821 interviews in 16 villages around Budongo Forest Reserve, Masindi district, Uganda, to explore the causes of human migration to protected areas and to identify differences in forest use between migrant and nonmigrant communities. We asked subjects for information about birthplace, migration, household assets, household activities, and forest use. Interview subjects were categorized as nonmigrants (born in one of the interview villages), socioeconomic migrants (chose to emigrate for economic or social reasons) from within Masindi district (i.e., local migrants) and from outside the Masindi district (i.e., regional migrants), or forced migrants (i.e., refugees or internally displaced individuals who emigrated as a result of conflict, human rights abuses, or natural disaster). Only 198 respondents were born in interview villages, indicating high rates of migration between 1998 and 2008. Migrants were drawn to Budongo Forest because they thought land was available (268 individuals) or had family in the area (161 individuals). A greater number of regional migrants settled in villages near Lake Albert than did forced and local migrants. Migration category was also associated with differences in sources of livelihood. Of forced migrants 40.5% earned wages through labor, whereas 25.5% of local and 14.5% of regional migrants engaged in wage labor. Migrant groups appeared to have different effects on the environment. Of respondents that hunted, 72.7% were regional migrants. Principal component analyses indicated households of regional migrants were more likely to be associated with deforestation. Our results revealed gaps in current models of human population growth around protected areas. By highlighting the importance of social networks and livelihood choices, our results contribute to a more nuanced understanding of causes of migration and of the environmental effects of different migrant groups. Conservation Biology, Volume 26, No. 3, 547–556

Emerging Techniques for Soil Carbon measurements: Soil carbon sequestration is one approach to mitigate greenhouse gases. However, to reliably assess the quantities sequestered as well as the chemical structure of the soil carbon, new methods and equipment are needed. These methods and equipment must allow large scale measurements and the construction of dynamic maps. This paper presents results from some emerging techniques to measure carbon quantity and stability. Each methodology has specific capabilities and their combined use along with other analytical tools will improve soil organic matter research. New opportunities arise with the development and application of portable equipment, based on spectroscopic methods, as laser-induced fluorescence, laser-induced breakdown spectroscopy and near infrared, for in situ carbon measurements in different ecosystems. These apparatus could provide faster and lower cost field analyses thus improving soil carbon contents and quality databases. Improved databases are essential to model carbon balance, thus reducing the uncertainties generated through the extrapolation of limited data.

Impact of terrestrial biosphere carbon exchanges on the anomalous CO2 increase in 2002–2003: Understanding the carbon dynamics of the terrestrial biosphere during climate fluctuations is a prerequisite for any reliable modeling of the climate-carbon cycle feedback. We drive a terrestrial vegetation model with observed climate data to show that most of the fluctuations in atmospheric CO2 are consistent with the modeled shift in the balance between carbon uptake by terrestrial plants and carbon loss through soil and plant respiration. Simulated anomalies of the Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) during the last two El Nin˜o events also agree well with satellite observations. Our model results suggest that changes in net primary productivity (NPP) are mainly responsible for the observed anomalies in the atmospheric CO2 growth rate. Changes in heterotrophic respiration (Rh) mostly happen in the same direction, but with smaller amplitude. We attribute the unusual acceleration of the atmospheric CO2 growth rate during 2002–2003 to a coincidence of moderate El Nin˜o conditions in the tropics with a strong NPP decrease at northern mid latitudes, only partially compensated by decreased

An Uncertain Future for Soil Carbon: Predictions of how rapidly the large amounts of carbon stored as soil organic matter will respond to warming are highly uncertain (1). Organic matter plays a key role in determining the physical and chemical properties of soils and is a major reservoir for plant nutrients. Understanding how fast organic matter in soils can be built up and lost is thus critical not just for its net effect on the atmospheric CO2 concentration but for sustaining other soil functions, such as soil fertility, on which societies and ecosystems rely. Recent analytic advances are rapidly improving our understanding of the complex and interacting factors that control the age and form of organic matter in soils, but the processes that destabilize organic matter in response to disturbances (such as warming or land use change) are poorly understood

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