 The carbon budget approximation is useful for translating policy relevant temperature objectives into CO2 emissions pathways, but when non-CO2 forcing changes along with CO2 forcing, errors increase. Using the GCAM model, an ensemble of 30000 scenarios shows that linked changes in CO2, aerosol, and non-CO2 greenhouse gas forcing lead to an increase in total non-CO2 forcing over the 21st century across mitigation scenarios. This increase makes the relationship between instantaneous temperature and cumulative CO2 emissions more complex, particularly for low temperature objectives such as 1.5 degrees Celsius. Additionally, linked changes in emissions contribute to a near-term increase in aerosol forcing that places a limit on how low peak temperature can be constrained through GHG mitigation alone. Specifically, 23% of scenarios that include CCS achieve a temperature objective of 1.5 degrees Celsius without temperature overshoot, while only 1% of scenarios that do not include CCS achieve the same. This article was authored by Felipe Feiju, Brian Caimignone, Harines Keshti, and others. We are article.tv, links in the description below.