Recently, there has been a lot of talk about carbon neutrality, which means achieving zero emissions of carbon dioxide and other greenhouse gases by subtracting the amount absorbed by forests, etc. How are greenhouse gas emissions and absorption measured?

First of all, the bottom-up approach is a method that compares emissions based on the annual greenhouse gas emission reports of each country with the estimated carbon absorption capacity of the earth.

On the other hand, the European Space Agency is using satellite observations to measure the amount of greenhouse gases in the atmosphere from space and trace the sources of emissions and sinks in the land and oceans. While land use by humans (mainly agriculture) accounts for a quarter of greenhouse gas emissions, forests are the largest sink on the ground. Forest fires and wildfires are also a source of carbon emissions to the atmosphere, while phytoplankton in the ocean plays an important role as a carbon sink.

Using both bottom-up and top-down approaches, and combining observations with model estimates, it is possible to improve the refinement of greenhouse gas emission source estimates and distinguish carbon emissions from agriculture and fossil fuels from natural processes.

A video produced by the European Space Agency shows whether we can meet the goal of the Paris Agreement, a multilateral international agreement on climate change mitigation, to limit temperature increase to 1.5°C compared to pre-industrial levels. As shown in the video, if we look at this as a carbon budget, it means that we have only 10 years left at the current rate of emissions to reduce greenhouse gas emissions equivalent to 17% of carbon dioxide emissions to keep global warming below 1.5°C.

Contributor: IIYAMA Miyuki (Director, Information Program)