Taking stock of national climate policies to evaluate implementation of the Paris Agreement

Many countries have implemented national climate policies to accomplish pledged Nationally Determined Contributions and to contribute to the temperature objectives of the Paris Agreement on climate change. In 2023, the global stocktake will assess the combined effort of countries. Here, based on a public policy database and a multi-model scenario analysis, we show that implementation of current policies leaves a median emission gap of 22.4 to 28.2 GtCO2eq by 2030 with the optimal pathways to implement the well below 2 °C and 1.5 °C Paris goals. If Nationally Determined Contributions would be fully implemented, this gap would be reduced by a third. Interestingly, the countries evaluated were found to not achieve their pledged contributions with implemented policies (implementation gap), or to have an ambition gap with optimal pathways towards well below 2 °C. This shows that all countries would need to accelerate the implementation of policies for renewable technologies, while efficiency improvements are especially important in emerging countries and fossil-fuel-dependent countries

Modeling the impacts of major forest disturbances on the Earth\u27s coupled carbon-climate system, and the capacity of forests to meet future demands for wood, fuel, and fiber

The carbon balance of forested ecosystems are fundamentally linked to cycles of disturbance and recovery. Two of the most extreme natural disturbances are tropical cyclones and Amazon forest fires. While an average of more than 80 tropical storms and hurricanes occur per year, the number, severity, and impacts of these storms varies through time and may be increasing, while the committed carbon emissions from a single large storm such as Katrina can be as large as the net annual carbon sequestration of U.S. forest trees. Forest fires are a growing concern too, particularly in the sensitive Amazon region where they potentially compound the risk of forest die-back from climate change. The overall science goal of this project is to understand how altered natural disturbance rates could affect the carbon balance of terrestrial ecosystems, and as a consequence, the development strategies designed to mitigate against future climate change. In particular, we address two major science questions: 1) How could potentially altered disturbance rates from tropical cyclones and Amazonian fires affect vegetation, carbon stocks and fluxes, and the development of climate change mitigation strategies? 2) How does remote sensing data quantity and quality constrain model projections of the effects of altered disturbance rates on vegetation, carbon stocks and fluxes, and the development of climate change mitigation strategies? These science questions are addressed through four linked objectives: 1) remote sensing and modeling forest disturbances (tropical cyclones and Amazonian fires); 2) assess the consequences of forest disturbances in integrated assessments; 3) link ecological and socio-economic models addressing forest disturbance; and 4) quantify the implications of forest disturbances for future satellite missions and Earth System models

Can updated climate pledges limit warming well below 2°C?; Increased ambition and implementation are essential

As part of the 2015 Paris Agreement, countries agreed to regularly revisit and enhance their national climate strategies and, every 5 years, to offer new emissions targets in the form of nationally determined contributions (NDCs) (1). This year’s 26th Conference of Parties provides a waypoint in this updating process as countries have been offering enhanced or completely new NDCs (2, 3) (henceforth, updated pledges) (4). We find that compared with the 2015 pledges, the updated pledges suggest a strengthening of ambition through 2030. By calculating probabilistic temperature outcomes over the 21st century for five emissions scenarios (see the figure and table S1), we find that the updated pledges provide a stronger near-term foundation to deliver on the long-term goals of the Paris Agreement of reducing the probability of the worst levels of temperature change this century and increasing the likelihood of limiting temperature change to well below 2°C