Brown carbon (BrC) is the ubiquitous part of the atmospheric organic carbon. It absorbs solar lights and greatly impacts the Earth's radiative balance. This study examines the spectral characteristics of BrC and its radiative effect in the Dhaka South (DS) site and Dhaka North (DN) site from July 2023 to January 2024 with a high-volume particulate matter sampler on quartz filters. Spectral characteristics such as absorption coefficient (babe,), mass absorption efficiency (MAE), absorption angstrom exponent (AAE), and refractive index (Kabs-x) were determined by using a UV -visible spectrophotometer, and fluorescence emission spectra were analyzed in different pH by the fluorescent spectrophotometer. The concentrations of BrC and black carbon (BC) were determined by an aethalometer. The mean concentrations of BrC and BC in Dhaka city were 18.63 +/- 3.84 mu g 111-3 and 17.93 +/- 3.82 pg M-3, respectively. The AAE values lie in the range of 3.20-4.01 (DN) and 3.27-4.53 (DS), and the radiative forcing efficiency of BrC was obtained at 4.43 +/- 1.02 W g-1 in DN and 3.93 +/- 0.74 W g-1 in DS, indicating the presence of highly light-absorbing BrC in these locations. Average MAE and Kabs_k values were 1.55 +/- 0.45 m2g1 and 0.044 + 0.013, respectively, in DS, alternatively 1.84 +/- 0.59 m2g1 and 0.052 +/- 0.016 in DN. The fluorescence excitation-emission spectra confirmed the presence of a polyconjugate cyclic ring with multifunctional groups in the structure of BrC. Light absorption properties and fluorescence emission spectra were varied with the change of pH. As the pH increased (2-8), the AAE value decreased and MAEB,c_365 increased due to protonation or deprotonation. This study highlights that the BrC has a significant impact on the air quality as well as the Earth's radiative balance, emphasizing its strong light-absorbing properties and variability with environmental factors.

Vulnerability of peat plateaus to global warming was analyzed in northeastern European Russia. A laboratory experiment on artificial incubation of peat was carried out to analyze the resilience of organic matter of frozen peat bogs (palsas) to decomposition. The rate of mineralization of peat organic matter was calculated from data on the CO2 and CH4 emissions from the peat incubated at a temperature of +4 degrees C under artificial aerobic and anaerobic conditions during 1300 days. Peat samples were taken from the active layer (AL), transitional layer (TL), and permafrost layer (PL). The delta 13C and delta 15N isotopes and the C/N, O/C, and H/C ratios were determined as indicators of change in the decomposition rate of organic matter. By the 1300th day of the experiment under aerobic conditions, the total CO2 amount released from the analyzed samples (per 1 g of carbon) was 10.24-37.4 mg C g-1 (on average, 25.76 mg C g-1), while under anaerobic conditions, it was only 2.1-3.38 mg C g-1 (on average, 3.15 mg C g-1). The CH4 emission was detected only in the peat from the transitional layer in very small quantities. The incubation experiment results support the hypothesis that peat plateaus are resilient, especially under anaerobic conditions, regardless the ongoing climate warming.

Precipitation comes in various phases, including rainfall, snowfall, sleet, and hail. Shifts of precipitation phases, as well as changes in precipitation amount, intensity, and frequency, have significant impacts on regional climate, hydrology, ecology, and the energy balance of the land-atmosphere system. Over the past century, certain progress has been achieved in aspects such as the observation, discrimination, transformation, and impact of precipitation phases. Mainly including: since the 1980s, studies on the observation, formation mechanism, and prediction of precipitation phases have gradually received greater attention and reached a certain scale. The estimation of different precipitation phases using new detection theories and methods has become a research focus. A variety of discrimination methods or schemes, such as the potential thickness threshold method of the air layer, the temperature threshold method of the characteristic layer, and the near-surface air temperature threshold method, have emerged one after another. Meanwhile, comparative studies on the discrimination accuracy and applicability assessment of multiple methods or schemes have also been carried out simultaneously. In recent years, the shift of precipitation from solid to liquid (SPSL) in the mid-to-high latitudes of the Northern Hemisphere has become more pronounced due to global warming and human activities. It leads to an increase in rain-on-snow (ROS) events and avalanche disasters, affecting the speed, intensity, and duration of spring snow-melting, accelerating sea ice and glacier melting, releasing carbon from permafrost, altering soil moisture, productivity, and phenological characteristics of ecosystems, and thereby affecting their structures, processes, qualities, and service functions. Although some progress has been made in the study of precipitation phases, there remains considerable research potential in terms of completeness of basic data, reliability of discrimination schemes, and the mechanistic understanding of the interaction between SPSL and other elements or systems. The study on shifts of precipitation phases and their impacts will play an increasingly important role in assessing the impacts of global climate change, water cycle processes, water resources management, snow and ice processes, snow and ice-related disasters, carbon emissions from permafrost, and ecosystem safety.

Understanding the dynamics of soil respiration (Rs) in response to freeze-thaw cycles is crucial due to permafrost degradation on the Qinghai-Tibet Plateau (QTP). We conducted continuous in situ observations of Rs using an Li-8150 automated soil CO2 flux system, categorizing the freeze-thaw cycle into four stages: completely thawed (CT), autumn freeze-thaw (AFT), completely frozen (CF), and spring freeze-thaw (SFT). Our results revealed distinct differences in Rs magnitudes, diurnal patterns, and controlling factors across these stages, attributed to varying thermal regimes. The mean Rs values were as follows: 2.51 (1.10) mu mol center dot m(-2)center dot s(-1) (CT), 0.37 (0.04) mu mol center dot m(-2)center dot s(-1) (AFT), 0.19 (0.06) mu mol center dot m(-2)center dot s(-1) (CF), and 0.68 (0.19) mu mol center dot m(-2)center dot s(-1) (SFT). Cumulatively, the Rs contributions to annual totals were 89.32% (CT), 0.79% (AFT), 5.01% (CF), and 4.88% (SFT). Notably, the temperature sensitivity (Q10) value during SFT was 2.79 times greater than that in CT (4.63), underscoring the significance of CO2 emissions during spring warming. Soil temperature was the primary driver of Rs in the CT stage, while soil moisture at 5 cm depth and solar radiation significantly influenced Rs during SFT. Our findings suggest that global warming will alter seasonal Rs patterns as freeze-thaw phases evolve, emphasizing the need to monitor CO2 emissions from alpine meadow ecosystems during spring.

Pollutant emissions in China have significantly decreased over the past decade and are expected to continue declining in the future. Aerosols, as important pollutants and short-lived climate forcing agents, have significant but currently unclear climate impacts in East Asia as their concentrations decrease until mid-century. Here, we employ a well-developed regional climate model RegCM4 combined with future pollutant emission inventories, which are more representative of China to investigate changes in the concentrations and climate effects of major anthropogenic aerosols in East Asia under six different emission reduction scenarios (1.5 degrees C goals, Neutral-goals, 2 degrees C -goals, NDC-goals, Current-goals, and Baseline). By the 2060s, aerosol surface concentrations under these scenarios are projected to decrease by 89%, 87%, 84%, 73%, 65%, and 21%, respectively, compared with those in 2010-2020. Aerosol climate effect changes are associated with its loadings but not in a linear manner. The average effective radiative forcing at the surface in East Asia induced by aerosol-radiation-cloud interactions will diminish by 24% +/- 13% by the 2030s and 35% +/- 13% by the 2060s. These alternations caused by aerosol reductions lead to increases in near-surface temperatures and precipitations. Specifically, aerosol-induced temperature and precipitation responses in East Asia are estimated to change by -78% to -20% and -69% to 77%, respectively, under goals with different emission scenarios in the 2060s compared to 2010-2020. Therefore, the significant climate effects resulting from substantial reductions in anthropogenic aerosols need to be fully considered in the pathway toward carbon neutrality.

Rationale. Glaciers in the Tibetan Plateau (TP), especially in the Himalayas, are retreating rapidly due to rising air temperature and increasing anthropogenic emissions from nearby regions. Traditionally, pollutants deposited on the glaciers have been assumed to originate from long-range transport from its outside. Methodology. This study investigated the concentrations of black carbon (BC) and major ions in snowpit samples collected from two glaciers in the south-eastern TP (Demula and Palongzangbu) and one glacier in the west Himalayas (Jiemayangzong). The radiative forcing of BC was calculated based on BC concentration and glacier characteristics. Results. The results revealed that the BC/Ca2+ concentration ratio in snowpit samples from Palongzangbu, located near residential villages, is similar to 2.05 times higher than that of Demula, which is mainly influenced by long-range transported pollutants. Furthermore, on Jiemayangzong glacier, snowpit samples collected with 100-m vertical resolution exhibited that BC-induced radiative forcings at low altitude are similar to 2.37 +/- 0.16 times greater than those at high altitude. Discussion. These findings demonstrated that in addition to long-range transport, emissions from local residents also make substantial contributions to BC and certain major ions (e.g. SO42-). To accurately assess the sources and radiative forcing of BC and other light-absorbing impurities on glaciers of the TP, it is necessary to consider the impact of local populations and altitude-dependent variations.

Research in geocryology is currently principally concerned with the effects of climate change on permafrost terrain. The motivations for most of the research are (1) quantification of the anticipated net emissions of CO2 and CH4 from warming and thaw of near-surface permafrost and (2) mitigation of effects on infrastructure of such warming and thaw. Some of the effects, such as increases in ground temperature or active-layer thickness, have been observed for several decades. Landforms that are sensitive to creep deformation are moving more quickly as a result, and Rock Glacier Velocity is now part of the Essential Climate Variable Permafrost of the Global Climate Observing System. Other effects, for example, the occurrence of physical disturbances associated with thawing permafrost, particularly the development of thaw slumps, have noticeably increased since 2010. Still, others, such as erosion of sedimentary permafrost coasts, have accelerated. Geochemical effects in groundwater from trace elements, including contaminants, and those that issue from the release of sediment particles during mass wasting have become evident since 2020. Net release of CO2 and CH4 from thawing permafrost is anticipated within two decades and, worldwide, may reach emissions that are equivalent to a large industrial economy. The most immediate local concerns are for waste disposal pits that were constructed on the premise that permafrost would be an effective and permanent containment medium. This assumption is no longer valid at many contaminated sites. The role of ground ice in conditioning responses to changes in the thermal or hydrological regimes of permafrost has re-emphasized the importance of regional conditions, particularly landscape history, when applying research results to practical problems.

Atmospheric Brown Carbon (BrC) with strong wavelength-dependence light-absorption ability can significantly affect radiative forcing. Highly resolved emission inventories with lower uncertainties are important premise and essential in scientifically evaluating impacts of emissions on air quality, human health and climate change. This study developed a bottom-up inventory of primary BrC from combustion sources in China from 1960 to 2016 with a spatial resolution at 0.1 degrees x 0.1 degrees, based on compiled emission factors and detailed activity data. The primary BrC emission in China was about 593 Gg (500-735 Gg as interquartile range) in 2016, contributing to 7% (5%-8%) of a previously estimated global total BrC emission. Residential fuel combustion was the largest source of primary BrC in China, with the contribution of 67% as the national average but ranging from 25% to 99% among different provincial regions. Significant spatial disparities were also observed in the relative shares of different fuel types. Coal combustion contribution varied from 8% to 99% across different regions. Heilongjiang and North China Plain had high emissions of primary BrC. Generally, on the national scale, spatial distribution of BrC emission density per area was aligned with the population distribution. Primary BrC emission from combustion sources in China have been declined since a peak of similar to 1300 Gg in 1980, but the temporal trends were distinct in different sectors. The high-resolution inventory developed here enables radiative forcing simulations in future atmospheric models so as to promote better understanding of carbonaceous aerosol impacts in the Earth's climate system and to develop strategies achieving co-benefits of human health protection and climate change.

Aviation emissions contribute to climate change and local air pollution, with important contributions from non-CO2 emissions. These exhibit diverse impacts on atmospheric chemistry and radiative forcing (RF), varying with location, altitude, and time. Assessments of local mitigation strategies with global emission metrics may overlook this variability, but detailed studies of aviation emissions in areas smaller than continents are scarce. Integrating the AviTeam emission model and OsloCTM3, we quantify CO2, NOx, BC, OC, and SOx emissions, tropospheric concentration changes, RF, region-specific metrics, and assess alternative fuels for Norwegian domestic aviation. Mitigation potentials fora fuel switch to LH2 differ by up to 3.1 x 108 kgCO2-equivalents (GWP20) when using region-specific compared to global metrics. These differences result from a lower, region- specific contribution of non-CO2 emissions, particularly related to NOx. This study underscores the importance of accounting for non-CO2 variability in regional assessments, whether through region-specific metrics or advanced atmospheric modelling techniques.

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.