It is technically possible for one of two things to occur that would create a mini ice age, even if those pushing this are really anti-science global warming deniers.
1. The Alaska to Northern California subduction zone "jumps", triggering massive tsunamis and setting off nearby earthquake unzipping along the Alaska, BC, Washington, Oregon, and Northern California linked fault lines, which could (but most likely would not) cause some of the active volcanoes near this line (like Mount Hood, Mount Rainier, and so on) to activate in full eruption. The resulting atmospheric emissions would cause a mini ice age similar to that during the last mini ice age (also called the Dark Ages).
2. Yellowstone could erupt. If that happens, you have a lot more to worry about, other than the mini ice age that would certainly occur.
That said, those pushing this are really just anti-science global warming deniers, desperate for continuing government subsidies for their dying fossil fuel industries.