Swanson-Hysell and Macdonald (2017) follow Kump et al.’s (1999) proposal that decreasing temperatures through the Ordovician (e.g., Trotter et al., 2008) are largely explained by CO2 sequestration with weathering of silicates exposed by Taconic arc-Laurentia collision. They propose higher weatherability of the west-east-trending Taconic orogen that they shift to a more equatorial, wet-tropical setting. The concerns that may be raised by a reader are whether the following are all responses to this orogeny: (1) the Ordovician temperature record, (2) the strontium and neodymium isotope record interpreted to reflect the Taconic orogeny (Swanson-Hysell and Macdonald, 2017), and (3) the interpreted pCO2.