Salby hasn’t been working in a vacuum. Swedish climate scientist Pehr Björnbom has replicated his finding that temperature drives CO2 emission. University of Oslo geosciences professor Ole Humlum published a landmark 2012 paper demonstrating that changes of CO2 follow changes of temperature, implying the same cause and effect. Richard Lindzen, an atmospheric physicist at MIT, believes that Salby is correct about the IPCC’s failure to evaluate the effects of diffusion in ice cores on the proxy CO2 record and to consider sources of lighter carbon other than fossil-fuel burning. Salby is a “serious scientist” whose arguments deserve a hearing, Lindzen says.