Greenhouse gas abatement can be viewed as an alternative to conventional capital formation. Somehow, society must agree on how to split its limited resources between investment in region-specific physical capital and global investment in environmental capital. Now, since restrictions on the international mobility of capital affect regional investment decisions, it might be expected that significant interregional differences in rates of return could affect global climate policy decisions. This is the issue addressed here. With a "descriptive" view of the world, we obtain an invariance result. That is, the pareto-optimal amount of greenhouse gas abatement is virtually independent of the restrictions on capital flows. We conclude with conjectures on this outcome.