Spark Climate Solutions staff submitted a comment in September 2025 to the U.S. Environmental Protection Agency seeking to better inform their reconsideration of the Endangerment Finding. The 2009 determination by the EPA found that the concentrations of six key well-mixed greenhouse gases in the atmosphere — carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF₆) — threatened the public health and welfare of current and future generations. Led by Chief Scientist Phil Duffy, the comment shares reasons that "the scientific case for endangerment is overwhelming, and stronger than ever." Spark's comments included contributions from Professor Dan Farber at UC Berkeley Law and from Dr. John Balbus at Climate Care Consulting, LLC.

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