Climate Change in Two Figures

On July 29, 2025 the Department of Energy released “A Critical Review of Impacts of Greenhouse Gas Emissions on the U.S. Climate” by the Climate Working Group (CWG). The Environmental Protection Agency relied on this report for its proposed reconsideration of the EPA’s 2009 Endangerment Finding that “current and projected concentrations of… greenhouse gases… threaten the public health and welfare of current and future generations.” The CWG report seeks to cast doubt on our knowledge of climate change, emphasizing, for example, uncertainties in modeling of CO2 uptake by land and ocean processes, and in modeling climate sensitivity. The report also portrays anthropogenic climate change as just another contribution to the natural variability of global climate. While the CWG report has been comprehensively addressed by the “Climate Experts’ Review of the DOE Climate Working Group Report”, there remains the need for a clear but brief response to the CWG arguments, understandable by a non-technical audience. This is powerfully provided by two figures: a plot of atmospheric CO2 concentrations versus cumulative greenhouse gas emissions; and a plot of the global mean temperature versus the logarithm of the atmospheric CO2 concentration. Both are straight lines. They provide a powerful visual affirmation of our knowledge of climate change. Further, the fluctuations in the plots clearly demonstrate that natural fluctuations are dwarfed by human-induced climate change over the course of the past 65 years.