Short-lived climate pollutants (SLCPs) including methane, tropospheric ozone, and black carbon in this work, is a set of compounds with shorter lifetimes than carbon dioxide (CO2) and can cause warming effect on climate. Here, the effective radiative forcing (ERF) is estimated by using an online aerosol-climate model (BCC_AGCM2.0_CUACE/Aero); then the climate responses to SLCPs concentration changes from the pre-industrial era to the present (1850-2010) are estimated. The global annual mean ERF of SLCPs was estimated to be 0.99 [0.79-1.20] W m(-2), and led to warming effects over most parts of the globe, with the warming center (about 1.0 K increase) being located in the mid-high latitudes of the Northern Hemisphere (NH) and the ocean around Antarctica. The changes in annual mean surface air temperature (SAT) caused by SLCPs changes were more prominent in the NH [0.78 (0.62-0.94) K] than in the Southern Hemisphere [0.62 (0.45-0.74) K], and the global annual mean value is 0.70 K. By looking at other variable responses, we found that precipitation had been increased by about 0.10 mm d(-1) in mid- and high-latitudes and decreased by about 0.20 mm d(-1) in subtropical regions, with the global annual mean value of 0.02 mm d(-1). Changes in SLCPs also influenced atmospheric circulation change, a northward shift in the Intertropical Convergence Zone was induced due to the interhemispheric asymmetry in SAT. However, it is found in this work that SLCPs changes had little effect on global average cloud cover, whereas the local cloud cover changes could not be ignored, low cloud cover increase by about 2.5% over high latitudes in the NH and the ribbon area near 60 degrees S, and high cloud cover increased by more than 2.0% over northern Africa and the Indian Ocean. Finally, we compared the ERFs and global and regional warming effects of SLCPs with those induced by CO2 changes. From 1850 to the present, the ERF of SLCPs was equivalent to 66%, 83%, and 50% of that of CO2 in global, NH, and SH mean, respectively. The increases in SAT caused by SLCPs were 43% and 55% of those by CO2 over the globe and China, respectively.

Short-lived climate pollutants (SLCPs) including black carbon (BC), methane (CH4), and tropospheric ozone (O-3) are major climate forcers after carbon dioxide (CO2). These SLCPs also have detrimental impacts on human health and agriculture. Studies show that the Hindu Kush Himalayan (HKH) region, which includes Nepal, has been experiencing the impacts of these pollutants in addition to greenhouse gases. In this study, we derive a national-level emission inventory for SLCPs, CO2, and air pollutants for Nepal and project their impacts under reference (REF) and mitigation policy (POL) scenarios. The impacts on human health, agriculture, and climate were then estimated by applying the following: (1) adjoint coefficients from the Goddard Earth Observing System (GEOS)-chemical transport model that quantify the sensitivity of fine particulate matter (PM2.5) and surface O-3 concentrations in Nepal, and radiative forcing in four latitudinal bands, to emissions in 2 x 2.5 degrees grids, and (2) concentration-response functions to estimate health and crop loss impacts in Nepal. With the mitigating measures undertaken, emission reductions of about 78% each of BC and CH4 and 87% of PM2.5 could be achieved in 2050 compared with the REF scenario. This would lead to an estimated avoidance of 29,000 lives lost and 1.7 million tonnes of crop loss while bringing an economic benefit in present value of 2.7 times more than the total cost incurred in its implementation during the whole period 2010-2050. The results provide useful policy insights and pathways for evidence-based decision-making in the design and effective implementation of SLCP mitigation measures in Nepal.

Global efforts to mitigate climate change have largely focused on reducing emissions of carbon dioxide (CO2), which is responsible for 55-60% of current anthropogenic radiative forcing on warming impact. Because of its long lifetime (similar to 130 years [1]) in the atmosphere, long-lasting CO2 will remain the primary driver of long-term temperature rise even if new CO2 emissions dropped to zero. A fast-action climate mitigation strategies is therefore strongly needed to provide more sizeable short-term benefits than CO2 reductions by reducing emission of short-lived climate pollutants (SLCPs), having atmospheric lifetimes of less than 20 years [2], which would allow for short-term drops in atmospheric concentrations and hence slow climate change over the next several decades. Monitoring of climatically and environmentally active SLCPs is important not only for policy-based reporting, but also for basic process-based understanding of climate related processes in the atmosphere. In this talk, we will overview our recent progress in the developments and applications of laserbased optical instruments for the measurements of environmental and livestock emitted methane (CH4), as well as the measurement of black carbon (BC) absorption. The experimental detail, the preliminary measurement results, the corresponding data processing and analysis will be presented.