How much of the expected climate change is the consequence of feedback processes?
What is the contribution of clouds and water vapor feedbacks? Water plays a key role in the radiative balance of the atmosphere: water vapor is the most important of the greenhouse gases, and clouds (whether liquid or ice) affect both vertical heating profiles and geographic heating patterns. In addition, results from climate models suggest there will be an overall increase in water vapor as the climate warms. Predictions of climate change vary in large part because of differences in the way that the various feedback processes are represented in the models. The greatest differences are those associated with water vapor and cloud processes. For example, scientists do not know how the amount and distribution of clouds will change, both vertically and horizontally, as the water vapor in the atmosphere changes. More importantly, they do not know how the associated changes in radiative forcing and precipitation will affect climate. The feedback to the Earth’s radiative balance and cloud str
