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In tropical South America there has been substantial progress in atmospheric monitoring capacity, but the region still has a limited number of continental atmospheric stations relative to its large area, hindering net carbon flux estimates using atmospheric inversions. In this study, we use dry-air CO.sub.2 mole fractions measured at the Amazon Tall Tower Observatory (ATTO) and airborne vertical CO.sub.2 profiles in an atmospheric inversion system to estimate net carbon exchange in tropical South America from 2010 to 2018. Given previous knowledge of a bias due to undried samples in the airborne vertical profiles, we calculate the effect of this systematic uncertainty in our inverse estimates and propose a water-vapor correction to the airborne CO.sub.2 profiles. We focus our analysis on the biogeographic Amazon and its neighboring \"Cerrado and Caatinga\" biomes. Including the water-vapor correction changes the posterior ensemble median from -0.33 to -0.04 PgC yr.sup.-1 with a posterior uncertainty of 0.33 PgC yr.sup.-1 for the Amazon and for the Cerrado and Caatinga from 0.31 to 0.50 PgC yr.sup.-1, with an uncertainty of 0.24 PgC yr.sup.-1 . Our estimates of carbon exchange include the contributions from both net vegetation exchange and release from fires. Assuming that the correction brings the observational data closer to the truth implies that the Amazon is a weaker sink of carbon and that the Cerrado and Caatinga is a larger source. We do not find a strong spatial shift of fluxes within the biogeographic Amazon due to the correction, nor do we find a strong impact on the interannual variations. Finally, to further reduce the uncertainty in regional carbon balance estimates in tropical South America, we call for an expansion of the atmospheric monitoring network on the continent, mainly in the Amazon-Andes foothills.

Improved forest management (IFM) has the potential to remove and store large quantities of carbon from the atmosphere. Around the world, 293 IFM offset projects have produced 11% of offset credits by voluntary offset registries to date, channeling substantial climate mitigation funds into forest management projects. This paper summarizes the state of the scientific literature for key carbon offset quality criteria—additionality, baselines, leakage, durability, and forest carbon accounting—and discusses how well currently used IFM protocols align with this literature. Our analysis identifies important areas where the protocols deviate from scientific understanding related to baselines, leakage, risk of reversal, and the accounting of carbon in forests and harvested wood products, risking significant over-estimation of carbon offset credits. We recommend specific improvements to the protocols that would likely result in more accurate estimates of program impact, and identify areas in need of more research. Most importantly, more conservative baselines can substantially reduce, but not resolve, over-crediting risk from multiple factors.

Reducing emissions from deforestation and forest degradation (REDD+) has gained international attention over the past decade, as manifested in both United Nations policy discussions and hundreds of voluntary projects launched to earn carbon-offset credits. There are ongoing discussions about whether and how projects should be integrated into national climate change mitigation efforts under the Paris Agreement. One consideration is whether these projects have generated additional impacts over and above national policies and other measures. To help inform these discussions, we compare the crediting baselines established ex-ante by voluntary REDD+ projects in the Brazilian Amazon to counterfactuals constructed ex-post based on the quasi-experimental synthetic control method. We find that the crediting baselines assume consistently higher deforestation than counterfactual forest loss in synthetic control sites. This gap is partially due to decreased deforestation in the Brazilian Amazon during the early implementation phase of the REDD+ projects considered here. This suggests that forest carbon finance must strike a balance between controlling conservation investment risk and ensuring the environmental integrity of carbon emission offsets. Relatedly, our results point to the need to better align project- and national-level carbon accounting.

Most companies include carbon offsets in their net-zero strategy. However, many offset projects are poor quality and fail to reduce emissions as claimed. Here we focus on the twenty companies retiring the most offsets from the voluntary carbon market over 2020–2023. We examine if their offsets could be considered high quality and likely to benefit the climate. We curate an original company-level dataset to examine quality and climate benefits across four dimensions: (1) use of offsets from low/high-risk project types; (2) age of projects and credits; (3) price of credits; and (4) country of implementation. We find that companies have predominantly sourced low-quality, cheap offsets: 87% carry a high risk of not providing real and additional emissions reductions, with most offsets originating from forest conservation and renewable energy projects. Further, most offsets do not meet industry standards regarding age and country of implementation. These findings provide further evidence that the voluntary carbon market is not supporting effective climate mitigation. Particularly, we show that its persisting quality issues are exacerbated by the demand for low-quality offsets by individual companies. Trencher and colleagues investigate the twenty companies making the largest purchases of offsets from the voluntary carbon market from 2020 to 2023. They find that 87% of the purchased offsets carry a high risk of not providing real and additional emissions reductions. Further, most offsets do not meet industry standards regarding age and country of implementation. The findings reinforce concerns that the voluntary carbon market is failing to support effective climate mitigation.

Hidden attractors have received considerable interest in physics, mechanics and other dynamical areas recently. This paper introduces a novel autonomous system with hidden attractor. In particular, there exists no-equilibrium point in this system. Although the new system is simple with six terms, it exhibits complex behavior such as chaos and multistability. In addition, the offset boosting of a variable is achieved by adding a single controlled constant. Dynamical properties of the no-equilibrium system have been discovered by using nonlinear dynamical tools as well as an electronic implementation.

Offsetting is emerging as an important but controversial approach for managing environment–development conflicts. Biodiversity offsets are designed to compensate for damage to biodiversity from development by providing biodiversity gains elsewhere. Here, we suggest how biodiversity offset policies can generate behaviours that exacerbate biodiversity decline, and identify four perverse incentives that could arise even from soundly designed policies. These include incentives for (i) entrenching or exacerbating baseline biodiversity declines, (ii) winding back non‐offset conservation actions, (iii) crowding out of conservation volunteerism and (iv) false public confidence in environmental outcomes due to marketing offset actions as gains. Synthesis and applications. Despite its goal of improving biodiversity outcomes, there is potential for best‐practice offsetting to achieve the opposite result. Reducing this risk requires coupling offset crediting baselines to measured trajectories of biodiversity change and understanding the potential interaction between offsetting and other environmental policies.

Biodiversity offsets are applied in many countries to compensate for impacts on the environment, but research on regulatory frameworks and implementation enabling effective offsets is lacking. This paper reviews research on biodiversity offsets, providing a framework for the analysis of program design (no net loss goal, uncertainty and ratios, equivalence and accounting, site selection, landscape-scale mitigation planning, timing) and implementation (compliance, adherence to the mitigation hierarchy, leakage and trade-offs, oversight, transparency and monitoring). Some more challenging aspects concern the proper metrics and accounting allowing for program evaluation, as well as the consideration of trade-offs when regulations focus only on the biodiversity aspect of ecosystems. Results can be used to assess offsets anywhere and support the creation of programs that balance development and conservation.

A consistent analysis of signal-in-space ranging errors (SISREs) is presented for all current satellite navigation systems, considering both global average values and worst-user-location statistics. The analysis is based on 1 year of broadcast ephemeris messages of the Global Positioning System (GPS), GLONASS, Galileo, BeiDou and QZSS collected with a near-global receiver network. Position and clock values derived from the navigation data are compared against precise orbit and clock products provided by the International GNSS Service and its multi-GNSS experiment. Satellite laser ranging measurements are used for a complementary and independent assessment of the orbit-only SISRE contribution. The need for proper consideration of antenna offsets is highlighted and block-/constellation-specific radial antenna offset values for the center-of-mass correction of broadcast orbits are derived. Likewise, the need for application of differential code biases in the comparison of broadcast and precise clock products is emphasized. For GPS, the analysis of the legacy navigation message is complemented by a discussion of the CNAV message performance based on the first CNAV test campaign in June 2013. Global average SISRE values for the individual constellations amount to 0.7 ± 0.02 m (GPS), 1.5 ± 0.1 m (BeiDou), 1.6 ± 0.3 m (Galileo), 1.9 ± 0.1 m (GLONASS), and 0.6 ± 0.2 m (QZSS) over a 12-month period in 2013/2014.

Biodiversity offsets have become a widely accepted means of attempting to compensate for biodiversity loss from development, and are applied in planning and decision-making processes at many levels. Yet their use is contentious, and numerous problems with both the concept and the practice have been identified in the literature. Our starting point is the understanding that offsets are a kind of biodiversity compensation measure through which the goal of no net loss (or net gain) of biodiversity can be at least theoretically achieved. Based on a typology of compensation measures distinguishing between habitat protection, improvement (including restoration, habitat creation and improved management practices) and other compensation, we review the literature to develop a framework of conditions that must be met if habitat protection and improvement initiatives can be truly considered offsets and not merely a lesser form of compensation. It is important that such conceptual clarity is reflected in offset policy and guidance, if offsets are to be appropriately applied and to have any chance of fully compensating for biodiversity loss. Our framework can be used to support the review and ongoing development of biodiversity offset policy and guidance, with the aim of improving clarity, rigour and therefore the chances that good biodiversity outcomes can be achieved.