Climate Denial Crock of the Week

Nitrous Oxide – more powerful than methane.

Nature Reviews:

Soils are sources of the potent greenhouse gas nitrous oxide (N₂O) globally, but emissions from permafrost-affected soils have been considered negligible owing to nitrogen (N) limitation. Recent measurements of N₂O emissions have challenged this view, showing that vegetated soils in permafrost regions are often small but evident sources of N₂O during the growing season (~30 μg N₂O–N m⁻² day⁻¹). Moreover, barren or sparsely vegetated soils, common in harsh climates, can serve as substantial sources of N₂O (~455 μg N₂O–N m⁻²day⁻¹), demonstrating the importance of permafrost-affected soils in Earth’s N₂O budget. In this Review, we discuss N₂O fluxes from subarctic, Arctic, Antarctic and alpine permafrost regions, including areas that likely serve as sources (such as peatlands) and as sinks (wetlands, dry upland soils), and estimate global permafrost-affected soil N₂O emissions from previously published fluxes. We outline the below-ground N cycle in permafrost regions and examine the environmental conditions influencing N₂O dynamics. Climate-change-related impacts on permafrost ecosystems and how these impacts could alter N₂O fluxes are reviewed, and an outlook on the major questions and research needs to better constrain the global impact of permafrost N₂O emissions is provided.

Key Points:

• Published studies suggest that permafrost-affected soils are a source of nitrous oxide (N₂O).
• Compared with measurements of carbon dioxide and methane fluxes, measurements of N₂O fluxes in permafrost regions are sparse and lacking during the non-growing season, making the magnitude of N₂O fluxes across the vast permafrost regions uncertain.
• Permafrost-affected soils store large amounts of nitrogen, but only a fraction is in bioavailable form. Strong plant–microorganism competition causes a general nitrogen limitation in permafrost-affected soils, often preventing N₂O production and release.
• Plant-regulatory effects on the size of the soil N pool are important, and N₂O-emission hotspots occur in barren ground features, especially permafrost peatlands.
• Climate warming and associated permafrost thaw, and other disturbances, could turn permafrost regions into a globally relevant source of N₂O, creating a non-carbon permafrost feedback to the global climate system.