Estimate human-originating net CO2 emissions in 2050, excluding emissions from land use change.

First preference will be to use the data from the Global Carbon Project or an obvious successor organisation, if still extant, which is currently available from ourworldindata: https://ourworldindata.org/grapher/annual-co2-emissions-per-country?country=~OWID_WRL. Second preference for whatever source ourworldindata is using at the time. If neither are producing updates, the most widely-considered authoritative source will be used.

Small print:

If humanity is reduced to below 5% of its current level, this resolves as ambiguous. Only earth-based emissions are included.