The silicate + CO2 -
> different silicate + carbonate chemical weathering rate tends to increase with temperature globally, and so is a negative feedback (but is too slow to damp out short term
changes)-- but chemical weathering is also affected by
vegetation, land area, and terrain (and minerology, though I'm not sure how much that varies among entire mountain ranges or climate zones)-- ie mountanous regions which are
in the vicinity of a warm rainy climate are ideal for enhancing chemical weathering (see Appalachians
in the Paleozoic, more recently the Himalayas).