Abstract We highlight a mechanism for the coproduction of research with local communities as a means of elevating the social relevance of the geosciences, increasing the potential for broader and more diverse participation. We outline the concept of an “Equitable Exchange” as an ethical framework guiding these interactions. This principled research model emphasizes that “currencies”—the rewards and value from participating in research—may differ between local communities and geoscientists. For those engaged in this work, an Equitable Exchange emboldens boundary spanning geoscientists to bring their whole selves to the work, providing a means for inclusive climates and rewarding cultural competency.

Abstract The core tools of science (data, software, and computers) are undergoing a rapid and historic evolution, changing what questions scientists ask and how they find answers. Earth science data are being transformed into new formats optimized for cloud storage that enable rapid analysis of multi‐petabyte data sets. Data sets are moving from archive centers to vast cloud data storage, adjacent to massive server farms. Open source cloud‐based data science platforms, accessed through a web‐browser window, are enabling advanced, collaborative, interdisciplinary science to be performed wherever scientists can connect to the internet. Specialized software and hardware for machine learning and artificial intelligence are being integrated into data science platforms, making them more accessible to average scientists. Increasing amounts of data and computational power in the cloud are unlocking new approaches for data‐driven discovery. For the first time, it is truly feasible for scientists to bring their analysis to data in the cloud without specialized cloud computing knowledge. This shift in paradigm has the potential to lower the threshold for entry, expand the science community, and increase opportunities for collaboration while promoting scientific innovation, transparency, and reproducibility. Yet, we have all witnessed promising new tools which seem harmless and beneficial at the outset become damaging or limiting. What do we need to consider as this new way of doing science is evolving?

Abstract The 2018 drought and heatwave over northern Europe were exceptional, with unprecedented forest fires in Sweden, searing heat in Germany and water restrictions in England. Monthly, daily, and hourly data from ERA5, verified with in situ soil water content and surface flux measurements, are examined to investigate the subseasonal‐to‐seasonal progression of the event and the diurnal evolution of tropospheric profiles over Britain to quantify the anomalous land surface contribution to heat and drought. Data suggest the region entered an unprecedented condition of becoming a “hot spot” for land‐atmosphere coupling, which exacerbated the heatwave across much of northern Europe. Land‐atmosphere feedbacks were prompted by unusually low soil water over wide areas, which generated moisture limitations on surface latent heat fluxes, suppressing cloud formation, increasing surface net radiation, and driving temperatures higher during several multiweek episodes of extreme heat. We find consistent evidence in field data and reanalysis of a threshold of soil water content at most locations, below which surface fluxes and daily maximum temperatures become hypersensitive to declining soil water. Similar recent heatwaves over various parts of Europe in 2003, 2010, and 2019, combined with dire climate change projections, suggest such events could be on the increase. Land‐atmosphere feedbacks may play an increasingly important role in exacerbating extremes, but could also contribute to their predictability on subseasonal time scales.

Abstract Oxygen is a promising exoplanet biosignature due to the evolutionary advantage conferred by harnessing starlight for photosynthesis, and the apparent low likelihood of maintaining oxygen‐rich atmospheres without life. Hypothetical scenarios have been proposed for non‐biological oxygen accumulation on planets around late M‐dwarfs, where the extended pre‐main sequence may favor abiotic O2 accumulation. In contrast, abiotic oxygen accumulation on planets around F, G, and K‐type stars is seemingly less likely, provided they possess substantial non‐condensable gas inventories. The comparative robustness of oxygen biosignatures around larger stars has motivated plans for next‐generation telescopes capable of oxygen detection on planets around sun‐like stars. However, the general tendency of terrestrial planets to develop oxygen‐rich atmospheres across a broad range of initial conditions and evolutionary scenarios has not been explored. Here, we use a coupled thermal‐geochemical‐climate model of terrestrial planet evolution to illustrate three scenarios whereby significant abiotic oxygen can accumulate around sun‐like stars, even when significant noncondensable gas inventories are present. For Earth‐mass planets, we find abiotic oxygen can accumulate to modern levels if (1) the CO2:H2O ratio of the initial volatile inventory is high, (2) the initial water inventory exceeds ∼50 Earth oceans, or (3) the initial water inventory is very low (<0.3 Earth oceans). Fortunately, these three abiotic oxygen scenarios could be distinguished from biological oxygen with observations of other atmospheric constituents or characterizing the planetary surface. This highlights the need for broadly capable next‐generation telescopes that are equipped to constrain surface water inventories via time‐resolved photometry and search for temporal biosignatures or disequilibrium combination biosignatures to assess whether oxygen is biogenic.

Abstract Recent studies have produced conflicting results as to whether coastal wetlands can keep up with present‐day and future sea‐level rise. The stratigraphic record shows that threshold rates for coastal wetland submergence or retreat are lower than what instrumental records suggest, with wetland extent that shrinks considerably under high rates of sea‐level rise. These apparent conflicts can be reconciled by recognizing that many coastal wetlands still possess sufficient elevation capital to cope with sea‐level rise, and that processes like sediment compaction, ponding, and wave erosion require multidecadal or longer timescales to drive wetland loss that is in many cases inevitable.

Key Point The editors thank the 2020 peer reviewers

Abstract Rivers around the world have been heavily engineered, and these man‐made changes are affecting important biogeochemical cycles. Rivers play a key role in the global carbon cycle, by mobilizing organic carbon from land and delivering it to the oceans. River engineering techniques, like levees that prevent flooding, change the way carbon is cycled through rivers, but it is difficult to identify and quantify these changes. Shen et al. (2021) were able to quantify changes in river organic carbon fluxes induced by bank stabilization in the Mississippi River. The authors compared the age distribution of organic carbon in modern river sediment and old river sediment deposited before the construction of extensive levee systems. They found that bank stabilization significantly reduces the amount of time organic carbon spends in the river system before being exported to the Gulf of Mexico. As a result, less organic carbon is oxidized to CO2 and more organic carbon is exported to the ocean, ultimately reducing atmospheric CO2. This study highlights an important effect of anthropogenic activity on river carbon fluxes that should be considered in global carbon cycle models.

Abstract Satellite remote sensing observations show an increased greenness trend over land in recent decades. While greenness observations can indicate increased productivity, estimation of total annual productivity is highly dependent on vegetation response to climate and environmental conditions. Models have been struggling to determine how much carbon is taken up by plants as a result of increased atmospheric CO2 fertilization. Current remote sensing light use efficiency (LUE) models contain considerable uncertainty due to the lack of spatial and temporal variability in maximum LUE parameter and climate sensitivity defined for global plant functional types (PFTs). We used the optimum LUE (LUEopt) previously derived from the global FLUXNET network to improve estimation of global gross primary productivity (GPP) for the period 1982–2016. Our results indicate increasing GPP in northern latitudes owing to reduced cold temperature constraints on plant growth, thereby suggesting increasing negative carbon‐climate feedback in high latitudes. In the tropics, by contrast, our results indicate an emerging positive climate feedback, mainly due to increasing atmospheric vapor pressure deficit (VPD). Further pervasive VPD increase is likely to continue to reduce global GPP and amplify carbon emissions.

Key Points We used in situ whole-ecosystem manipulations to evaluate peatland carbon cycle changes to a range of warming conditions and elevated CO2 Warming caused variable responses for vegetation and losses of CO2 and CH4 for a linear response of 31.3 g C·m−2·year−1·°C−1 Models are capable of capturing C cycle responses to temperature under ambient CO2 conditions but overpredict sensitivity to elevated CO2

Key Points The reduced ocean carbon sink in the decade of the 1990s can be explained by the slowed growth rate of atmospheric CO2 The global sea surface temperature response to Mt Pinatubo in 1991 explains the intra-decadal pattern of the ocean carbon sink in the 1990s There will be an immediate reduction in ocean carbon uptake as atmospheric pCO2 responds to cuts in anthropogenic CO2 emissions