Sectoral approach : what is in it for the Chinese economy?

In any international negotiation on climate change close link among science, economics and politics can hardly be ignored. The argument for mitigation in case of long lived stock pollutants can never be rationally based on current growth level. It is a complex situation and any over simplifies approach will further complicate rather than lead to any positive solution. Competitiveness argument, border adjustment, trade barriers on emission intensive goods and services of Annex I countries can hardly be justified even at the current market share in trade, production, consumption. The best way to approach the problem can be to combine domestic and international actions judiciously. Need for transition to globally low carbon economy by the end of the century is least contested today. Common responsibility of attaining decarbonised growth path for global human welfare is uncontested but much contested is the differentiated responsibility design mechanism. Differentiated responsibility is a dynamic notion. So who should do how much and when, in dynamic context, is still an unresolved research question. But what is understood well is a fully functional global carbon market with global carbon price can provide a least cost solution with desired level of autonomy chosen by each country. Past attempts through CDM provide a small short term step towards that for flow of finance in niche investments and new technology, Sectoral Approach (SA) can provide a second level of stepping stone towards fully functional carbon market through financial flow into non niche market such as energy efficiency type of investment. China today is the leader among Non-Annex I countries in CDM and with first layer of capacity building it can be the natural leaders in SA

Searching for gravitational wave optical counterparts with the Zwicky Transient Facility: summary of O4a

International audienceDuring the first half of the fourth observing run (O4a) of the International Gravitational Wave Network (IGWN), the Zwicky Transient Facility (ZTF) conducted a systematic search for kilonova (KN) counterparts to binary neutron star (BNS) and neutron star-black hole (NSBH) merger candidates. Here, we present a comprehensive study of the five high-significance (FAR < 1 per year) BNS and NSBH candidates in O4a. Our follow-up campaigns relied on both target-of-opportunity observations (ToO) and re-weighting of the nominal survey schedule to maximize coverage. We describe the toolkit we have been developing, Fritz, an instance of SkyPortal, instrumental in coordinating and managing our telescope scheduling, candidate vetting, and follow-up observations through a user-friendly interface. ZTF covered a total of 2841 deg$^2$ within the skymaps of the high-significance GW events, reaching a median depth of g~20.2 mag. We circulated 15 candidates, but found no viable KN counterpart to any of the GW events. Based on the ZTF non-detections of the high-significance events in O4a, we used a Bayesian approach, nimbus, to quantify the posterior probability of KN model parameters that are consistent with our non-detections. Our analysis favors KNe with initial absolute magnitude fainter than -16 mag. The joint posterior probability of a GW170817-like KN associated with all our O4a follow-ups was 64%. Additionally, we use a survey simulation software, simsurvey, to determine that our combined filtered efficiency to detect a GW170817-like KN is 36%, when considering the 5 confirmed astrophysical events in O3 (1 BNS and 4 NSBH), along with our O4a follow-ups. Following Kasliwal et al. (2020), we derived joint constraints on the underlying KN luminosity function based on our O3 and O4a follow-ups, determining that no more than 76% of KNe fading at 1 mag/day can peak at a magnitude brighter than -17.5 mag