Brazilian Mangroves: Blue Carbon Hotspots of National and Global Relevance to Natural Climate Solutions

Mangroves are known for large carbon stocks and high sequestration rates in biomass and soils, making these intertidal wetlands a cost-effective strategy for some nations to compensate for a portion of their carbon dioxide (CO2) emissions. However, few countries have the national-level inventories required to support the inclusion of mangroves into national carbon credit markets. This is the case for Brazil, home of the second largest mangrove area in the world but lacking an integrated mangrove carbon inventory that captures the diversity of coastline types and climatic zones in which mangroves are present. Here we reviewed published datasets to derive the first integrated assessment of carbon stocks, carbon sequestration rates and potential CO2eq emissions across Brazilian mangroves. We found that Brazilian mangroves hold 8.5% of the global mangrove carbon stocks (biomass and soils combined). When compared to other Brazilian vegetated biomes, mangroves store up to 4.3 times more carbon in the top meter of soil and are second in biomass carbon stocks only to the Amazon forest. Moreover, organic carbon sequestration rates in Brazilian mangroves soils are 15–30% higher than recent global estimates; and integrated over the country’s area, they account for 13.5% of the carbon buried in world’s mangroves annually. Carbon sequestration in Brazilian mangroves woody biomass is 10% of carbon accumulation in mangrove woody biomass globally. Our study identifies Brazilian mangroves as a major global blue carbon hotspot and suggest that their loss could potentially release substantial amounts of CO2. This research provides a robust baseline for the consideration of mangroves into strategies to meet Brazil’s intended Nationally Determined Contributions.

Analysis of the BRICS countries’ pathways towards a low-carbon environment

Global climate change has emerged as humanity’s greatest challenge, affecting both the natural security of the earth and the long-term growth of human society. Protecting the environment and fostering long-term growth while reducing carbon emissions has become a global concern. The BRICS countries (Brazil, Russia, India, China, and South Africa) are participating in the fight against climate change through the promotion of low-carbon environment (LCE). In this study, we use content analysis to discuss some of the policies, plans, and programs outlined by the various governments in the BRICS that can help them implement an LCE. The study indicates that currently Brazil, Russia, India, China, and South Africa are rated as “insufficient,” “critically insufficient,” “compatible,” “incompatible,” and “highly insufficient” respectively in their commitment to nationally determined contributions (NDC) to the Paris Agreement. The paper recommends that the BRICS countries achieve an LCE through expanding low-carbon investments and financing, focusing on taxation that goes beyond energy, investing in low-carbon cities, adapting to a circular economy and low-carbon technologies, expanding electricity markets, and promoting climate-friendly international trade among the BRICS countries.

Relationship Between Emissions Trading System and the 2030 Agenda for Sustainable Development

With the Paris Agreement and through Nationally Determined Contributions, nation-states have agreed to reduce their emissions of greenhouse gases. Some of them have approached this aspect by setting emission trading systems. In some cases, it is in the regional and sub-national levels where these types of developments are taking place. The relevance of this market-based instrument is increasing over time, to the point of being regarded as a cornerstone of climate change mitigation strategies, despite the lack of global agreement on the matter. The importance of emission trading systems, however, can be observed when assessing their relevance for achieving the 2030 Agenda for Sustainable Development. Implementing them can, and should, assist in reaching diverse targets of different Sustainable Development Goals. This is the case of the goals related to energy, economic growth, inclusive industrialization, sustainable cities, sustainable production and consumption patterns, marine and land life, as well as the climate itself. Then, the relevance of emission trading systems can be observed throughout the whole 2030 Agenda. It is thus in this context that this contribution aims to assess the manner in which this relationship takes place in the global fora and in Mexico. A key argument is that there should be the participation of a wider set of sectors and actors.

Methane and the Paris Agreement temperature goals

Meeting the Paris Agreement temperature goal necessitates limiting methane (CH 4 )-induced warming, in addition to achieving net-zero or (net-negative) carbon dioxide (CO 2 ) emissions. In our model, for the median 1.5°C scenario between 2020 and 2050, CH 4 mitigation lowers temperatures by 0.1°C; CO 2 increases it by 0.2°C. CO 2 emissions continue increasing global mean temperature until net-zero emissions are reached, with potential for lowering temperatures with net-negative emissions. By contrast, reducing CH 4 emissions starts to reverse CH 4 -induced warming within a few decades. These differences are hidden when framing climate mitigation using annual ‘CO 2 -equivalent’ emissions, including targets based on aggregated annual emission rates. We show how the different warming responses to CO 2 and CH 4 emissions can be accurately aggregated to estimate warming by using ‘warming-equivalent emissions', which provide a transparent and convenient method to inform policies and measures for mitigation, or demonstrate progress towards a temperature goal. The method presented (GWP*) uses well-established climate science concepts to relate GWP100 to temperature, as a simple proxy for a climate model. The use of warming-equivalent emissions for nationally determined contributions and long-term strategies would enhance the transparency of stocktakes of progress towards a long-term temperature goal, compared to the use of standard equivalence methods. This article is part of a discussion meeting issue ‘Rising methane: is warming feeding warming? (part 2)’.

Path to net zero is critical to climate outcome

Net zero greenhouse gas targets have become a central element for climate action. However, most company and government pledges focus on the year that net zero is reached, with limited awareness of how critical the emissions pathway is in determining the climate outcome in both the near- and long-term. Here we show that different pathways of carbon dioxide and methane—the most prominent long-lived and short-lived greenhouse gases, respectively—can lead to nearly 0.4 °C of warming difference in midcentury and potential overshoot of the 2 °C target, even if they technically reach global net zero greenhouse gas emissions in 2050. While all paths achieve the Paris Agreement temperature goals in the long-term, there is still a 0.2 °C difference by end-of-century. We find that early action to reduce both emissions of carbon dioxide and methane simultaneously leads to the best climate outcomes over all timescales. We therefore recommend that companies and countries supplement net zero targets with a two-basket set of interim milestones to ensure that early action is taken for both carbon dioxide and methane. A one-basket approach, such as the standard format for Nationally Determined Contributions, is not sufficient because it can lead to a delay in methane mitigation.

Global roll-out of comprehensive policy measures may aid in bridging emissions gap

Closing the emissions gap between Nationally Determined Contributions (NDCs) and the global emissions levels needed to achieve the Paris Agreement’s climate goals will require a comprehensive package of policy measures. National and sectoral policies can help fill the gap, but success stories in one country cannot be automatically replicated in other countries. They need to be adapted to the local context. Here, we develop a new Bridge scenario based on nationally relevant, short-term measures informed by interactions with country experts. These good practice policies are rolled out globally between now and 2030 and combined with carbon pricing thereafter. We implement this scenario with an ensemble of global integrated assessment models. We show that the Bridge scenario closes two-thirds of the emissions gap between NDC and 2 °C scenarios by 2030 and enables a pathway in line with the 2 °C goal when combined with the necessary long-term changes, i.e. more comprehensive pricing measures after 2030. The Bridge scenario leads to a scale-up of renewable energy (reaching 52%–88% of global electricity supply by 2050), electrification of end-uses, efficiency improvements in energy demand sectors, and enhanced afforestation and reforestation. Our analysis suggests that early action via good-practice policies is less costly than a delay in global climate cooperation.

Updated nationally determined contributions collectively raise ambition levels but need strengthening further to keep Paris goals within reach

By September 2021, 120 countries had submitted new or updated Nationally Determined Contributions (NDCs) to the UNFCCC in the context of the Paris Agreement. This study analyses the greenhouse gas (GHG) emissions and macroeconomic impacts of the new NDCs. The total impact of the updated NDCs of these countries on global emission levels by 2030 is an additional reduction of about 3.7 GtCO2e, compared to the previously submitted NDCs. This increases to about 4.1 GtCO2e, if also the lower projected emissions of the other countries are included. However, this total reduction needs to be four times greater to be consistent with keeping global temperature increase to well below 2 °C, and even eight times greater for 1.5 °C. Seven G20 economies have pledged stronger emission reduction targets for 2030 in their updated NDCs, leading to additional aggregated GHG emission reductions of about 3.1 GtCO2e, compared to those in the previous NDCs. The socio-economic impacts of the updated NDCs are limited in major economies, while structural shifts occur away from fossil fuel supply sectors and towards renewable electricity. However, two G20 economies have submitted new targets that will lead to an increase in emissions of about 0.3 GtCO2e, compared to their previous NDCs. The updated NDCs of non-G20 economies contain further net reductions. We conclude that countries should strongly increase the ambition levels of their updated NDC submissions to keep the climate goals of the Paris Agreement within reach.