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For short lived climate forcers (SLCFs), the impact of emissions depends on where and when the emissions take place. Comprehensive new calculations of various emission metrics for SLCFs are presented based on radiative forcing (RF) values calculated in four different (chemistry-transport or coupled-chemistry climate) models. We distinguish between emissions during summer (May-October) and winter season (November-April) for emissions from Europe, East Asia, as well as the global shipping sector. The species included in this study are aerosols and aerosols precursors (BC, OC, SO2, NH3), and ozone precursors (NOx, CO, VOC), which also influence aerosols, to a lesser degree. Emission metrics for global climate responses of these emissions, as well as for CH4, have been calculated relative to CO2, using Global Warming Potential (GWP) and Global Temperature change Potential (GTP), based on dedicated RF simulations by four global models. The emission metrics include indirect cloud effects of aerosols and the semi-direct forcing for BC. In addition to the standard emission metrics for pulse and sustained emissions, we have also calculated a new emission metric designed for an emission profile consisting of a ramp up period of 15 years followed by sustained emissions, which is more appropriate for a gradual implementation of mitigation policies. For the aerosols, the emission metric values are larger in magnitude for Europe than East Asia and for summer than winter. A variation is also observed for the ozone precursors, with largest values in East Asia and winter for CO and in Europe and summer for VOC. In general, the variations between the emission metrics derived from different models are larger than the variations between regions and seasons, but the regional and seasonal variations for the best estimate also hold for most of the models individually. Further, the estimated climate impact of a mitigation policy package is robust even when accounting for correlations. For the ramp up emission metrics, the values are generally larger than for pulse or sustained emissions, which holds for all SLCFs. For a potential SLCFs mitigation policy, the dependency of metric values on the region and season of emission should be considered. [ABSTRACT FROM AUTHOR]

We quantify the concentrations change of atmospheric pollutants and Radiative Forcing (RF) of short-lived components due to shipping emissions of NOx, SOx, CO, NMVOCs, BC and OC. A set of models is used to evaluate the period 2004-2030. This time period reflects expected increasing traffic in the Arctic region. Two datasets for ship emissions are used that may characterize the potential impact from shipping and the degree to which shipping controls may mitigate impacts: A high (HIGH) scenario and a low scenario with Maximum Feasible Reduction (MFR) of black carbon in the Arctic. In MFR, BC emissions in the Arctic are reduced with 70% representing a combination technology performance and/or reasonable advances in single-technology performance. Both scenarios result in moderate to substantial increases in concentrations of pollutants both globally and in the Arctic. Exceptions are black carbon in the MFR scenario, and sulfur species and organic carbon in both scenarios due to the future phase-in of current regulation that reduces fuel sulfur content. In the season with potential transit traffic through the Arctic in 2030 significant increases occur for all pollutants in large parts of the Arctic. Net global RFs from 2004-2030 of 53mWm-2 (HIGH) and 73mWm-2 (MFR) are similar to those found for preindustrial to present net global aircraft RF. The found warming contrasts the cooling from historical ship emissions. The reason for this difference and the higher global forcing for the MFR scenario is mainly the reduced future fuel sulfur content resulting in less cooling from sulfate aerosols. Arctic regional forcing is largest in the HIGH scenario because other components become locally more important in polar latitudes. In the HIGH scenario ozone dominates the RF during Arctic summer and the transit season. RF due to BC in air, and snow and ice becomes of significance in Arctic spring. For the HIGH scenario the net Arctic RF during spring is 5 times higher than in winter. [ABSTRACT FROM AUTHOR]

We examine the climate effects of the emissions of near-term climate forcers (NTCFs) from 4 continental regions (East Asia, Europe, North America and South Asia) using radiative forcing from the task force on hemispheric transport of air pollution sourcereceptor global chemical transport model simulations. These simulations model the transport of 3 aerosol species (sulphate, particulate organic matter and black carbon) and 4 ozone precursors (methane, nitric oxides (NOx), volatile organic compounds and carbon monoxide). From the equilibrium radiative forcing results we calculate global climate metrics, global warming potentials (GWPs) and global temperature change potentials (GTPs) and show how these depend on emission region, and can vary as functions of time. For the aerosol species, the GWP(100) values are -37±12, -46± 20, and 350±200 for SO2, POM and BC respectively for the direct effects only. The corresponding GTP(100) values are -5.2±2.4, -6.5±3.5, and 50±33. This analysis is further extended by examining the temperature-change impacts in 4 latitude bands. This shows that the latitudinal pattern of the temperature response to emissions of the NTCFs does not directly follow the pattern of the diagnosed radiative forcing. For instance temperatures in the Arctic latitudes are particularly sensitive to NTCF emissions in the northern mid-latitudes. At the 100-yr time horizon the ARTPs show NOx emissions can have a warming effect in the northern mid and high latitudes, but cooling in the tropics and Southern Hemisphere. The northern mid-latitude temperature response to northern mid-latitude emissions of most NTCFs is approximately twice as large as would be implied by the global average. [ABSTRACT FROM AUTHOR]

The responses of carbon dioxide (CO2) and other climate variables to an emission pulse of CO2 into the atmosphere are often used to compute the Global Warming Potential (GWP) and Global Temperature change Potential (GTP), to characterize the response time scales of Earth System models, and to build reduced-form models. In this carbon cycle-climate model intercomparison project, which spans the full model hierarchy, we quantify responses to emission pulses of different magnitudes injected under different conditions. The CO2 response shows the known rapid decline in the first few decades followed by a millennium-scale tail. For a 100GtC emission pulse, 24±10% is still found in the atmosphere after 1000 yr; the ocean has absorbed 60±18% and the land the remainder. The response in global mean surface air temperature is an increase by 0.19±0.10 °C within the first twenty years; thereafter and until year 1000, temperature decreases only slightly, whereas ocean heat content and sea level continue to rise. Our best estimate for the Absolute Global Warming Potential, given by the time-integrated response in CO2 at year 100 times its radiative efficiency, is 92.7x 10-15 yrWm-2 per kg CO2. This value very likely (5 to 95% confidence) lies within the range of (70 to 115) x 10-15 yrWm-2 per kg CO2. Estimates for time-integrated response in CO2 published in the IPCC First, Second, and Fourth Assessment and our multi-model best estimate all agree within 15%. The integrated CO2 response is lower for pre-industrial conditions, compared to present day, and lower for smaller pulses than larger pulses. In contrast, the response in temperature, sea level and ocean heat content is less sensitive to these choices. Although, choices in pulse size, background concentration, and model lead to uncertainties, the most important and subjective choice to determine AGWP of CO2 and GWP is the time horizon. [ABSTRACT FROM AUTHOR]

The article discusses the synthesis and calculation of climate-based emission metrics of different species. It integrates radiative forcing (RF) with temperature change to a reference gas. It mentions several methods such as the Life Cycle Assessment (LCA), Impulse Response Function (IRF) and Bern Carbon Cycle. It concludes that the importance of short lived climate forcers (SLCFs) varies depending on the metric used.

Atmospheric concentration changes and the resulting radiative forcing (RF) due to emissions from shipping and petroleum activity in the Arctic have been studied, using three-dimensional chemistry transport (OsloCTM2) and radiative transfer models. The present work focuses on short-lived climate forcers, based on a coherent dataset of present day emissions from petroleum and shipping activities in the Arctic region. We find that the net forcing effect of Arctic shipping emissions of short-lived climate forcers (SLCFs) is negative, while the net effect from Arctic petroleum emissions of SLCFs is positive. The negative RF from Arctic shipping arises mainly from direct aerosol -- and first indirect effects of sulphate. Positive RF from Arctic petroleum is mainly due to black carbon in air and deposited on snow and ice. Normalized forcing (RF per change in atmospheric burden) and global warming potentials (GWP) suggest that Arctic conditions (high solar angle, high surface albedo, summer season with midnight sun and polar night during winter) lead to different sensitivity to emissions here compared to lower latitudes. [ABSTRACT FROM AUTHOR]

The Arctic sea-ice is retreating faster than predicted by climate models and could become ice free during summer this century. The reduced sea-ice extent may effectively "unlock" the Arctic Ocean to increased human activities such as transit shipping and expanded oil and gas production. Travel time between Europe and the north Pacific Region can be reduced by up to 50% with low sea-ice levels and the use of this route could increase substantially as the sea-ice retreats. Oil and gas activities already occur in the Arctic region and given the large undiscovered petroleum resources increased activity could be expected with reduced sea-ice. We use a detailed global energy market model and a bottom-up shipping model with a sea-ice module to construct emission inventories of Arctic shipping and petroleum activities in 2030 and 2050. The emission inventories are on a 1 x 1 degree grid and cover both short-lived pollutants and ozone pre-cursors (SO2, NOx, CO, NMVOC, BC, OC) and the long-lived greenhouse gases (CO2, CH4, N2O). We find rapid growth in transit shipping due to increased profitability with the shorter transit times compensating for increased costs in traversing areas of sea-ice. Oil and gas production remains relatively stable leading to reduced emissions from emission factor improvements. The location of oil and gas production moves into locations requiring more ship transport relative to pipeline transport, leading to rapid emissions growth from oil and gas transport via ship. Our emission inventories for the Arctic region will be used as input into chemical transport, radiative transfer, and climate models to quantify the role of Arctic activities in climate change compared to similar emissions occurring outside of the Arctic region. [ABSTRACT FROM AUTHOR]