Description: Characterizing the variability across timescales is important for understanding the underlying dynamics of the Earth system. It remains challenging to do so from palaeoclimate archives since they are more often than not irregular, and traditional methods for producing timescale-dependent estimates of variability, such as the classical periodogram and the multitaper spectrum, generally require regular time sampling. We have compared those traditional methods using interpolation with interpolation-free methods, namely the Lomb–Scargle periodogram and the first-order Haar structure function. The ability of those methods to produce timescale-dependent estimates of variability when applied to irregular data was evaluated in a comparative framework, using surrogate palaeo-proxy data generated with realistic sampling. The metric we chose to compare them is the scaling exponent, i.e. the linear slope in log-transformed coordinates, since it summarizes the behaviour of the variability across timescales. We found that, for scaling estimates in irregular time series, the interpolation-free methods are to be preferred over the methods requiring interpolation as they allow for the utilization of the information from shorter timescales which are particularly affected by the irregularity. In addition, our results suggest that the Haar structure function is the safer choice of interpolation-free method since the Lomb–Scargle periodogram is unreliable when the underlying process generating the time series is not stationary. Given that we cannot know a priori what kind of scaling behaviour is contained in a palaeoclimate time series, and that it is also possible that this changes as a function of timescale, it is a desirable characteristic for the method to handle both stationary and non-stationary cases alike.

Description: RV METEOR Expedition M191 „SUAVE“, 16.07. – 05.08.2023, Algeciras – Piraeus.

Description: The breakup of the Norwegian-Greenland Sea 56 million years ago was associated with massive basaltic magmatism and a short-lived global warming episode, the Paleocene-Eocene Thermal Maximum (PETM). Scientific drilling in 2021 targeted sediments and volcanic rocks on the mid-Norwegian margin to test hypotheses related to the formation of large igneous provinces as well as global warming associated potentially with the igneous activity. High-resolution 3D site survey data facilitated optimal borehole locations during the drilling; key reflections were targeted using the high-resolution 3D data, and PETM stratigraphic intervals were recognized during shipboard core descriptions. Igneous seismic geomorphological interpretation, furthermore, reveals distinct volcanic morphologies on the marginal high, related to different volcanic emplacement environments.

Description: Nitrous oxide (N2O) is a long-lived potent greenhouse gas and stratospheric ozone-depleting substance, which has been accumulating in the atmosphere since the pre-industrial period. The mole fraction of atmospheric N2O has increased by nearly 25 % from 270 parts per billion (ppb) in 1750 to 336 ppb in 2022, with the fastest annual growth rate since 1980 of more than 1.3 ppb yr-1 in both 2020 and 2021. As a core component of our global greenhouse gas assessments coordinated by the Global Carbon Project (GCP), we present a global N2O budget that incorporates both natural and anthropogenic sources and sinks, and accounts for the interactions between nitrogen additions and the biochemical processes that control N2O emissions. We use Bottom-Up (BU: inventory, statistical extrapolation of flux measurements, process-based land and ocean modelling) and Top-Down (TD: atmospheric measurement-based inversion) approaches. We provide a comprehensive quantification of global N2O sources and sinks in 21 natural and anthropogenic categories in 18 regions between 1980 and 2020. We estimate that total annual anthropogenic N2O emissions increased 40 % (or 1.9 Tg N yr-1) in the past four decades (1980–2020). Direct agricultural emissions in 2020, 3.9 Tg N yr−1 (best estimate) represent the large majority of anthropogenic emissions, followed by other direct anthropogenic sources (including ‘Fossil fuel and industry’, ‘Waste and wastewater’, and ‘Biomass burning’ (2.1 Tg N yr−1), and indirect anthropogenic sources (1.3 Tg N yr−1). For the year 2020, our best estimate of total BU emissions for natural and anthropogenic sources was 18.3 (lower-upper bounds: 10.5–27.0) Tg N yr-1, close to our TD estimate of 17.0 (16.6–17.4) Tg N yr-1. For the period 2010–2019, the annual BU decadal-average emissions for natural plus anthropogenic sources were 18.1 (10.4–25.9) Tg N yr-1 and TD emissions were 17.4 (15.8–19.20 Tg N yr-1. The once top emitter Europe has reduced its emissions since the 1980s by 31 % while those of emerging economies have grown, making China the top emitter since the 2010s. The observed atmospheric N2O concentrations in recent years have exceeded projected levels under all scenarios in the Coupled Model Intercomparison Project Phase 6 (CMIP6), underscoring the urgency to reduce anthropogenic N2O emissions. To evaluate mitigation efforts and contribute to the Global Stocktake of the United Nations Framework Convention on Climate Change, we propose establishing a global network for monitoring and modeling N2O from the surface through the stratosphere. The data presented in this work can be downloaded from https://doi.org/10.18160/RQ8P-2Z4R (Tian et al. 2023).

Description: Experts release a roadmap for harnessing the potential of assisted evolution to help save corals. The IPCC predicts that if warming reaches 2°C, 99% of all coral reefs will be lost in less than 30 years. It is clear that to ensure the future of corals, the highest priority must be reducing global greenhouse gas emissions. However, even with swift and substantial reductions in emissions, corals will continue to face increasing temperatures for the foreseeable future, which can result in extensive coral mortality and local extinction of some coral species. While recent studies have shown that corals may exhibit some degree of adaptation to ocean warming, it is unclear whether corals are able to survive the rate of temperature change during heat waves that will become more frequent under several climate change scenarios. If corals lack what it takes to naturally rapidly adapt to new environmental regimes, they may fail to survive a warming ocean. This is where assisted evolution could be a game-changer. Growing our understanding of the power of adaptation In January 2023, we held a workshop on assisted evolution co-organized with the Australian Institute of Marine Sciences (AIMS) as part of CORDAP’s Scoping Studies (a series of planning sessions and technology roadmap studies to shape our funding priorities). Our aim was to develop a visionary roadmap, offering recommendations on how to prioritise assisted evolution in R&D investment in the future. Assisted evolution is the use of human interventions to speed up the natural evolutionary process. It may allow coral species to adapt faster than they would if left unaided, allowing reefs and corals to keep better pace with the ocean’s environmental changes. The first step in creating this strategy was to pinpoint where we are now in our understanding regarding the potential and impacts of assisted evolution on enhancing coral tolerance to stress conditions like ocean warming. Our experts unanimously agreed that assisted evolution methods cannot be understood and evaluated without a solid foundational understanding of natural adaptation, and identified some knowledge gaps that can be closed with relatively minimal effort and others that will require substantial investment of time and resources. Key Findings: - Standardising methods, experimental designs, species selection guidelines, and terminologies will help to understand natural adaptation and assisted evolution more rapidly. - Long-term funding is critical to facilitate multigenerational studies, which are needed to deliver essential but largely missing information about coral evolution. Building the best pathway for research and investment This roadmap sets out tangible recommendations for future investment and research, to help fill critical knowledge gaps that could assist natural adaptation and evolution of coral reefs in a warming world. Overall, the roadmap recommends investment in a mixed portfolio of R&D, ranging from technologies with lower perceived risks to those with higher percieved risks and longer R&D horizons. This strategy is advised because of the uncertainty around future heating trajectories and thus requirements for enhancement of tolerance. The roadmap outlined four main areas of work that need to be undertaken: 1. Leading global coordination and synthesis. Recommendation: Building global infrastructure to support research would dramatically accelerate the generation of knowledge around the natural and assisted evolution of corals. This could include compiling and committing to a set of standards and methods that will allow more studies to be used in predictive models, as well as establishing a global resource-sharing network and database to facilitate meta-analysis and synthesis. 2. Optimising generation and use of knowledge. Recommendation: Make sure new studies are well designed and timely. Optimize published and future studies by characterizing relationships between heat stress metrics and other facets of coral fitness. Having funding set aside to be able to quickly respond to bleaching events will ensure vital knowledge is captured rather than lost if and when those events occur. 3. Filling critical knowledge gaps in multigenerational coral data in the laboratory and field. Recommendation: Given the slow-growing nature of coral, longer-term funding would allow researchers to gain critical knowledge needed to estimate the multi-generational benefits and risks of implementing assisted evolution methods in the wild. Standardised approaches repeated in different parts of the world would add confidence to generalise those results. 4. Supporting the advance of existing and new technologies. Recommendation: Methods that may yield a larger effect (e.g., gene editing, hybridisation between species, and assisted migration) are also potentially of greater risk and would need considerable R&D. Expanding support for some of the riskier long-term projects currently being overlooked, could potentially offer a greater return on investment, but should be balanced with continued investment in less risky technologies. CORDAP will be using these recommendations to prepare new accelerator program and we believe that they will assist academia in understanding gaps and needs for future research as well as helping to guide funding agencies on where their money will be most effective. The roadmap identifies the funding structures and research priorities that are most likely to yield the knowledge needed to ensure that assisted evolution methods can be implemented effectively. Ultimately, conserving and restoring coral reefs in warming climates will require an inclusive infrastructure involving many partners at a local, national, and international level.