According to a new paper by Gerald E. Marsh (PDF), they do. If true, this has great implications for the debate over whether humans are causing global warming, or whether it is a natural phenomenon. More about Marsh here.Marsh says that changes in carbon dioxide levels simply can’t account for the differences in temperatures between interglacials, while changes in cloud cover caused by a change in galactic cosmic ray flux can.Changes in cosmic rays The conventional global warming explanation for the Ice Ages and interglacial periods (we are in one right now), is that a change in the Earth’s orbit...