Based on our current scientific understanding, what is the best pathway to follow for a fast decarbonization of our economies to mitigate climate change as much as possible?
Decarbonization mainly needs two types of actions. One is to reduce the production of greenhouse gas emissions, and the other is to absorb emissions from the atmosphere.
To reduce the production, effective ways include:

- Use zero-carbon energy sources, such as wind, solar, hydropower, and geothermal instead of fossil fuels. To smooth out the intermittency of some energy sources such as wind and solar, more low-cost energy storage is required. Power plants also need to be more efficient by utilizing their waste heat.

- Redisgn industrial processes to reach a higher energy efficiency, or turn to zero-carbon energy sources. This is especially important but hard for processes highly dependent on fossil fuel combustion, such as steel, cement, and chemical production.

- Expand the usage of electric vehicles and mass transit options. For vehicles difficult to electrify such as airplanes, freighters, and long-haul trucks, low-carbon fuels, and better fuel efficiency are required. This can be achieved by developing hydrogen and synthetic liquid fuels, reusing waste heat, reducing drag, etc.

- Reduce the methane emission from agriculture. The methane from livestock production can be collected and utilized instead of directly emitted.

- Improve the efficiency of buildings. For example, switching to electric heat pumps for heating and cooling, improving insulation, and implementing smart management systems.

To absorb emissions, effective ways include:

- Afforestation and reforestation. This requires not only planting additional trees to remove and store carbon from the atmosphere, but also careful management to reduce negative impacts, such as pests and wildfires. Agriculture also needs to improve the utilization of land, which afforestation could compete for.

- Soil carbon sequestration. This is a low-cost method that can be deployed immediately by covering crops, crop rotation, and leaving crop residues on the field. However, the soil can become saturated after 10 to 100 years.

- Carbon mineralization. Injecting CO2 into natural reactive materials like peridotite or basaltic lava to form solid carbonate minerals can store it for millions of years.