The Arctic experiences rapid climate change, but our ability to predict how this will influence plant communities is hampered by a lack of data on the extent to which different species are associated with particular environmental conditions, how these conditions are interlinked, and how they will change in coming years. Increasing temperatures may negatively affect plants associated with cold areas due to increased competition with warm-adapted species, but less so if local temperature variability is larger than the expected increase. Here we studied the potential drivers of vegetation composition and species richness along coast to inland and altitudinal gradients by the Nuuk fjord in western Greenland using hierarchical modelling of species communities (HMSC) and linear mixed models. Community composition was more strongly associated with random variability at intermediate spatial scales (among plot groups 500 m apart) than with large-scale variability in summer temperature, altitude or soil moisture, and the variation in community composition along the fjord was small. Species richness was related to plant cover, altitude and slope steepness, which explained 42% of the variation, but not to summer temperature. Jointly, this suggests that the direct effect of climate change will be weak, and that many species are associated with microhabitat variability. However, species richness peaked at intermediate cover, suggesting that an increase in plant cover under warming climatic conditions may lead to decreasing plant diversity.

The transition to cleaner cooking fuels currently ongoing in many low- and middle-income countries may have benefits for health, but also climate. We have studied the climate implications of the SE4ALL policy goal in Tanzania of 75 percent access to modern cooking solutions by 2030 in which mainly firewood and charcoal are replaced by LPG and electricity. To see the long-term climate benefit, we have estimated the reduction in CO2equivalent emissions (GWP100) and effect on global temperature until 2100 relative to the baseline for three explorative scenarios with different levels of ambition: baseline growth to nearly complete transition to modern cooking. Due to population growth the energy demand and CO2-eq. emissions increase even in the most ambitious energy transition scenario. We model reduction in global temperature in 2100 relative to the baseline to be between -0.63 and -2.9 milli degrees C. While we confirm the climate benefit of a transition to cleaner cooking fuels in households, the benefit is smaller than previously thought. This is mainly due to a much weaker radiative forcing of black carbon and somewhat stronger radiative forcing for organic carbon, in the climate parameters from IPCC Sixth Assessment Report.

The navigability of Arctic maritime passages has improved with the rapid retreat of sea ice in recent decades, and it is projected that the Northern Sea Route (NSR) will support further increases in shipping in the future. However, the opening of the NSR may bring potential environmental and climate risks to the Arctic and the rest of the world. This investigation assessed shipping emissions along the NSR and the climate impacts under global warming of 2 degrees C and 3 degrees C to support coordinated international decision-making. The results show that the magnitude of annual energy consumption of ships along the NSR is 109 kWh under global warming of 2 degrees C and 3 degrees C. The environmental impacts of the shipping decrease with fuel transition to clean, carbon-neutral fuel sources. Specifically, the maximum emission is CO2 (106 t), followed by NOX (104-5 t), CO (103-4 t), SOX (103 t), CH4 (102-3 t), organic carbon (102-3 t), N2O (101-2 t), and black carbon (BC, 101-2 t), in which CO2 and BC have great difference under high and low loads. Total emission exacerbates Arctic and global warming, and it is more significant in the Arctic in the next twenty years and across the rest of the world in the next one hundred years. The greatest climate impact factor is CO2, followed by NOX and BC which are more important in global and Arctic warming, respectively.

Study RegionThe Naryn River Basin, KyrgyzstanStudy FocusWe investigate the impacts of climate change in the basin based on two families of General Circulation Models (GCMs) using the hydrological model SWAT. The forcing datasets are the widely used ISIMIP2 (I2) and the newly derived ISIMIP3 (I3) data which refer to the 5th and 6th stage of the Coupled Model Intercomparison Project (CMIP). Due to notable differences in the forcing we evaluate their impacts on various hydrological components of the basin, such as discharge, evapotranspiration (ETA) and soil moisture (SM). Besides, a partial correlation (PC) analysis is used to assess the meteorological controls of the basin with special emphasize on the SM-ETA coupling. New Hydrological Insights for the RegionAgreement in the basin's projections is found, such as discharge shifts towards an earlier peak flow of one month, significant SM reductions and ETA increases. I3 temperature projections exceed their previous estimates and show an increase in precipitation, which differs from I2. However, the mitigating effects do not lead to an improvement in the region's susceptibility to soil moisture deficits. The PC study reveals enhanced water-limited conditions expressed as positive SM-ETA feedback under I2 and I3, albeit slightly weaker under I3.

Recent studies examine the potential for large urban fires ignited in a hypothetical nuclear exchange of one hundred 15 kt weapons between India and Pakistan to alter the climate (e.g., Mills et al., 2014, , and Reisner et al., 2018, ). In this study, the global climate forcing and response is predicted by combining two atmospheric models, which together span the micro-scale to global scale processes involved. Individual fire plumes are modeled using the Weather Research and Forecasting (WRF) model, and the climate response is predicted by injecting the WRF-simulated black carbon (BC) emissions into the Energy Exascale Earth System Model (E3SM) atmosphere model Version 1 (EAMv1). Consistent with previous studies, the radiative forcing depends on smoke quantity and injection height, examined here as functions of fuel loading and atmospheric conditions. If the fuel burned is 1 g cm(-2), BC is quickly removed from the troposphere, causing no global mean climate forcing. If the fuel burned is 16 g cm(-2) and 100 such fires occurred simultaneously with characteristics similar to historical large urban firestorms, BC reaches the stratosphere, reducing solar radiation and causing cooling at the Earth's surface. Uncertainties in smoke composition and aerosol representation cause large uncertainties in the magnitude of the radiative forcing and cooling. The approximately 4 yr duration of the radiative forcing is shorter than the 8 to 15 yr that has previously been simulated. Uncertainties point to the need for further development of potential nuclear exchange scenarios, quantification of fuel loading, and improved understanding of fire propagation and aerosol modeling.

Larch-dominant communities are the most extensive high-latitude forests in Eurasia and are experiencing the strongest impacts from warming temperatures. We analyzed larch (Larix dahurica Turcz) growth index (GI) response to climate change. The studied larch-dominant communities are located within the permafrost zone of Northern Siberia at the northern tree limit (ca. N 67A degrees 38', E 99A degrees 07'). Methods included dendrochronology, analysis of climate variables, root zone moisture content, and satellite-derived gross (GPP) and net (NPP) primary productivity. It was found that larch response to warming included a period of increased annual growth increment (GI) (from the 1970s to ca. 1995) with a follow on GI decline. Increase in GI correlated with summer air temperature, whereas an observed decrease in GI was caused by water stress (vapor pressure deficit and drought increase). Water stress impact on larch growth in permafrost was not observed before the onset of warming (ca. 1970). Water limitation was also indicated by GI dependence on soil moisture stored during the previous year. Water stress was especially pronounced for stands growing on rocky soils with low water-holding capacity. GPP of larch communities showed an increasing trend, whereas NPP stagnated. A similar pattern of GI response to climate warming has also been observed for Larix sibirica Ledeb, Pinus sibirica Du Tour, and Abies sibirica Ledeb in the forests of southern Siberia. Thus, warming in northern Siberia permafrost zone resulted in an initial increase in larch growth from the 1970s to the mid-1990s. After that time, larch growth increment has decreased. Since ca. 1990, water stress at the beginning of the vegetative period became, along with air temperature, a main factor affecting larch growth within the permafrost zone.

Part 1 of this review synthesizes recent research on status and climate vulnerability of freshwater and saltwater wetlands, and their contribution to addressing climate change (carbon cycle, adaptation, resilience). Peatlands and vegetated coastal wetlands are among the most carbon rich sinks on the planet sequestering approximately as much carbon as do global forest ecosystems. Estimates of the consequences of rising temperature on current wetland carbon storage and future carbon sequestration potential are summarized. We also demonstrate the need to prevent drying of wetlands and thawing of permafrost by disturbances and rising temperatures to protect wetland carbon stores and climate adaptation/resiliency ecosystem services. Preventing further wetland loss is found to be important in limiting future emissions to meet climate goals, but is seldom considered. In Part 2, the paper explores the policy and management realm from international to national, subnational and local levels to identify strategies and policies reflecting an integrated understanding of both wetland and climate change science. Specific recommendations are made to capture synergies between wetlands and carbon cycle management, adaptation and resiliency to further enable researchers, policy makers and practitioners to protect wetland carbon and climate adaptation/resiliency ecosystem services.

The transportation system is one of the main sectors with significant climate impact. In the U.S. it is the second main emitter of carbon dioxide. Its impact in terms of emission of carbon dioxide is well recognized. But a number of aerosol species have a non-negligible impact. The radiative forcing due to these species needs to be quantified. A radiative transfer code is used. Remote sensing data is retrieved to characterize different regions. The radiative forcing efficiency for black carbon are 396 200 W/m(2)/AOD for the ground mode and 531 +/- 190 W/m(2)/AOD for the air transportation, under clear sky conditions. The radiative forcing due to contrail is 0.14 +/- 0.06 W/m(2) per percent coverage. Based on the forcing from the different species emitted by each mode of transportation, policies may be envisioned. These policies may affect demand and emissions of different modes of transportation. Demand and fleet models are used to quantify these interdependencies. Depending on the fuel price of each mode, mode shifts and overall demand reduction occur, and more fuel efficient vehicles are introduced in the fleet at a faster rate. With the introduction of more fuel efficient vehicles, the effect of fuel price on demand is attenuated. An increase in fuel price of 50 cents per gallon, scaled based on the radiative forcing of each mode, results in up to 5% reduction in emissions and 6% reduction in radiative forcing. With technologies, significant reduction in climate impact may be achieved. (C) 2015 Elsevier Ltd. All rights reserved.

Cookstove use is globally one of the largest unregulated anthropogenic sources of primary carbonaceous aerosol. While reducing cookstove emissions through national-scale mitigation efforts has clear benefits for improving indoor and ambient air quality, and significant climate benefits from reduced green-house gas emissions, climate impacts associated with reductions to co-emitted black (BC) and organic carbonaceous aerosol are not well characterized. Here we attribute direct, indirect, semi-direct, and snow/ice albedo radiative forcing (RF) and associated global surface temperature changes to national-scale carbonaceous aerosol cookstove emissions. These results are made possible through the use of adjoint sensitivity modeling to relate direct RF and BC deposition to emissions. Semi-and indirect effects are included via global scaling factors, and bounds on these estimates are drawn from current literature ranges for aerosol RF along with a range of solid fuel emissions characterizations. Absolute regional temperature potentials are used to estimate global surface temperature changes. Bounds are placed on these estimates, drawing from current literature ranges for aerosol RF along with a range of solid fuel emissions characterizations. We estimate a range of 0.16 K warming to 0.28 K cooling with a central estimate of 0.06 K cooling from the removal of cookstove aerosol emissions. At the national emissions scale, countries' impacts on global climate range from net warming (e.g., Mexico and Brazil) to net cooling, although the range of estimated impacts for all countries span zero given uncertainties in RF estimates and fuel characterization. We identify similarities and differences in the sets of countries with the highest emissions and largest cookstove temperature impacts (China, India, Nigeria, Pakistan, Bangladesh and Nepal), those with the largest temperature impact per carbon emitted (Kazakhstan, Estonia, and Mongolia), and those that would provide the most efficient cooling from a switch to fuel with a lower BC emission factor (Kazakhstan, Estonia, and Latvia). The results presented here thus provide valuable information for climate impact assessments across a wide range of cookstove initiatives.

Emissions of greenhouse gases and air pollutants from megacities impact the climate. The long-lived greenhouse gases CO2, CH4 and N2O as well as climate-active pollutants such as NOx, VOC and particulate matter (PM) are all emitted from megacities. NOx and VOC contribute to tropospheric ozone formation and affect the lifetime of long-lived greenhouse gases. Anthropogenic aerosols include sulphate, black carbon (BC) and particulate organic matter (POM). Aerosols impact climate directly (absorption, backscattering) and also have indirect (cloud) effects. We assess the climate impact of megacity emissions with the Met Office Hadley Centre Earth System Model HadGEM2 applying an annihilation'' scenario in which the emissions at megacities are entirely removed. Generally, the contribution of megacities to global pollutant emissions is on the order of 2-5% of the total global annual anthropogenic base emission flux. The impact of megacity climate-active pollutants is assessed via an annual mean top-of-atmosphere direct radiative forcing (AMTOA-DRF) from long-lived GHG as well as ozone, methane and aerosols. In this simulations the long-lived component (CO2, CH4 and N2O) contributes a positive TOA-DRF of + 120.0, + 28.4 and + 3.3mWm(-2), respectively, under present-day conditions. Climate-active pollutants (NOx, VOC) contribute an AMTOA-DRF of + 5.7 +/- 0.02mWm(-2) from an increase in the ozone burden -1.9 +/- 0.04mW m(-2), -6.1 +/- 0.21 mWm(-2) from the aerosol AMTOA-DRF in the short-wave spectrum and + 1.5 +/- 0.01 mWm(-2) from aerosol in the long-wave spectrum. The combined AMTOA-DRF from all climate-active pollutants is slightly negative at -0.8 +/- 0.24 mWm(-2) and the total AMTOA-DRF amounts to + 150.9 +/- 0.24 mWm(-2). Under future conditions (2050s) the total AMTOA-DRF from long-lived GHG is found to profoundly increase to + 322.6mW m(-2) while the total AMTOA-DRF from climate-active pollutants turns positive and decreases slightly to + 0.5 +/- 0.09 mWm(-2) yielding a combined AMTOA-DRF of + 323.1 +/- 0.09 mWm(-2) in the future. It is apparent that under the given emission scenarios the radiative forcing from long-lived GHG, particularly CO2, by far dominates the impact of megacities on climate. (C) Crown Copyright-2012 Published by Elsevier B.V. All rights reserved.