A standard assumption in integrated assessment of models of climate change is that population and technology are growing, but at a decreasing rate. We explore the significance of the assumption of population and technology growth for greenhouse gas control levels. After all, there has been no long run slow down in the growth of technology over the past few centuries, and the rate of population growth has actually been increasing for the past 19 centuries. Even if either of these growth rates were expected to slow, by how much is subject to great uncertainty. We show computationally that such continued growth greatly increases the severity of climate change. Indeed we find that climate change is a problem in large part "caused" by exogenous population and technology growth. Rapid reductions in growth make climate change a small problem; smaller reductions in growth imply climate change is a very serious problem indeed.