Second, all mainstream climate models predict a hotspot, a warming in the upper troposphere (about 10 km or 6 miles up, in the tropics) caused by an ascending water vapor emissions layer, during periods of warming such as the 1980s and 1990s. This is crucial, because two thirds of their predicted warming is from water vapor; only one third is directly due to increasing carbon dioxide. So no hotspot means not much cause for alarm. Our only suitable instruments for detecting the hotspot are weather balloonsthirty million of them since the 1950s, released from hundreds of locations, twice a day. They show no hotspot, and indicate that the water vapor emissions layer descended slightly instead. Satellites are unsuitable because they intrinsically aggregate information from several vertical kilometers into each data point, but the predicted ascent is only tens of meters.