evidence: Carbon isotope ratios are actually one of the key measurements that show human-caused emissions are responsible for climate change. CO2 emissions from fossil fuels have lower concentrations of both carbon-13 and carbon-14 than CO2 placed in the atmosphere by the natural carbon cycle. Therefore, burning fossil fuels is linked to decreased concentrations of both isotopes in atmospheric CO2. [...] An article authored by Chris Morrison in The Daily Sceptic, an outlet with a track record of scientifically unfounded messages, makes a conflicting claim: that changing isotope signatures in atmospheric CO2 result from the biosphere, rather than human causes like fossil fuel emissions. The article primarily cites "a new paper" published in February 2024 and supports its claim with a second paper published two years earlier. The article then upholds the two papers’ findings as scientific evidence that the human impact on climate change is "non-discernible". [...] Therefore, the scenario that a more productive biosphere could simultaneously push down δ13CO2 and increase the amount of CO2 in the atmosphere makes little sense. "If [the carbon-12] were coming from the biosphere, we would have had to lose carbon," Graven told Science Feedback.