Abstract The boreal forest biome is warming rapidly, impacting disturbance regimes and global climate. Boreal forest fires have intensified, initiating both climate warming (positive) and climate cooling (negative) impacts across spatial and temporal scales. Here we estimate climate impacts from boreal fires in Alaska and western Canada between 2001 and 2019 using integrated net radiative forcing metrics combining greenhouse gas and aerosol emissions from combustion, vegetation recovery, greenhouse gas emissions from fire-induced permafrost thaw and changes in surface albedo over a 70-year period. We find that fires across Alaska contributed, on average, to net climate warming (0.35 ± 4.66 W m −2 of burned area; one standard deviation), while fires across Canada contributed to net cooling (−2.88 ± 4.17 W m −2 of burned area; one standard deviation). Climate-warming fires occur preferentially in dry, high-elevation, steep permafrost landscapes with high pre-fire black spruce coverage and combust more carbon per unit area. Climate-cooling fires are driven by longer spring snow exposure and occur more frequently in continental regions near the treeline. This fine-scale characterization of component and net radiative forcing advances our understanding of the biogeophysical impacts of fires on high-latitude climate and highlights the need to prioritize fire management in carbon-rich permafrost regions to curb long-term warming.

Abstract The history of the lunar magnetic field is a longstanding controversy. Many palaeomagnetic studies provide evidence for either a persistent, weak magnetic field or the lack of an intrinsic magnetic field between 1.020 and 3.580 billion years ago. However, for the period between 3.580 and 3.854 billion years ago, palaeomagnetic studies have recovered strong intrinsic fields (>40 µT) distributed among weak or null intensity measurements. Crustal magnetic anomalies from this period have also been interpreted as evidence for the presence of both strong and weak magnetic fields. Here we explore potential links between published palaeointensity, rock magnetic and geochemical data for lunar basalts. We find there is a statistically significant relationship only between recovered palaeointensity and the titanium content of lunar basalts. By modelling the heat flux across the core–mantle boundary, we suggest that there is a causal link between lunar dynamo generation and the eruption of high-titanium basalts. Such a link may result from the intermittent melting of ilmenite-bearing cumulates at the core–mantle boundary. The coincidence of these rare events probably reflects sampling bias near high-titanium basaltic terranes.

Abstract Congo Basin lakes Mai Ndombe and Tumba are major CO 2 sources. Here we show that their dissolved inorganic carbon is some 2,170–3,515 14 C years old and partially (39–40%) originates from the surrounding peatlands. This implies a loss pathway for peat carbon, in which microbes respire old carbon within the peat and the resulting CO 2 is transported to the lakes and outgassed, linking these immense ancient stores to the modern carbon cycle.