Report on different definitions of net-zero emission targets

The concept of net-zero targets has gained attention in climate policy since the Paris Agreement called for a balance between anthropogenic emissions and removals in 
the second half of this century. Accordingly, many countries have set up net-zero targets, but formulated in different ways. In this study, we explore how the different 
formulations of net-zero on a global scale can shift the exact timing of net-zero, which can also have implications for national net-zero targets. Our analysis is based on the IPCC scenario database and own calculations using a simple integrated assessment model. Our findings indicate that applying different Global Warming Potentials can 
shift the timing of net-zero CO2 and greenhouse gas (GHG) emissions by a few decades, both for <1.5°C targets (with and without overshoot) and <2°C targets. The 
net-zero year also depends on by how much emissions are reduced in the short term: higher 2030 emission levels implies that a faster transition after 2030 is needed, 
leading to earlier net-zero emissions and more net-negative emissions. Our results indicate the importance of specifying the exact conditions of net-zero targets of  countries, especially regarding GWP metrics and which gases are included. Moreover, for achieving 1.5°C with no or small overshoot, immediate rapid emission reductions 
are more important than achieving net-zero GHGs.