Using carbon monoxide retrievals and an atmospheric inversion model, we show that CO₂ emissions from boreal wildfires in 2021 shattered records: 1.8 GtCO₂. If such high levels of fire emissions become normal, stabilizing climate will be even more difficult than we expected.

We assess nine possible pathways to achieve net-zero emissions from aviation, including changes and trade-offs in demand, energy efficiency, propulsion systems, and alternative fuels for both passenger and freight transport, as well as atmospheric carbon removal to offset non-CO₂ radiative forcing.

We estimate how many tons of steel, copper, silver, rare earth metals, and other materials will be needed to build power generation facilities across a wide range of scenarios. Although wind and solar energy require lots of such materials and current production will need to increase, availability of metals and materials will not constrain the projected expansion.

Global modeling shows that potential climate benefits of farming seaweed are large but sensitive to uncertain yields and competition with phytoplankton. We also find that carbon removal by sinking seaweed is much costlier than avoiding emissions by substituting seaweed for land-based crops.

Ultra-high-resolution modeling of Los Angeles flood risks reveals risks that are vastly larger than suggested by federally-defined floodplains and with both racial and socio-economic inequalities in exposure. Our approach points to opportunities for assessing and equitably reducing flood risks in densely-populated urban areas.

Annually, 27% of land-use emissions are related to agricultural products consumed in a different region from where they were produced. The largest transfers are land-use change emissions from Brazil, Indonesia, and Argentina embodied in products consumed in Europe, the US, and China. Our results highlght the importance of trade in stopping deforestation and making food systems more sustainable.