Is the Tropospheric Hotspot a Problem for Climate Science?
Since warm air holds more moisture, any rise in surface temperatures, regardless of the cause of that rise, will cause more evaporation and thus more water vapor in the atmosphere. This means that a rise in surface temperatures decreases the “lapse rate” - the rate of cooling as altitude increases. The lapse rate is slower at the equator than at the poles - the rate at the equator is about half that of the subtropics. Because of this, it’s been predicted that there should be a tropospheric “hot spot” in the tropics. Climate models predict this because there is good reason to expect it, and this is true regardless of what is causing the warming. It should be there whether warming is caused by an increase in TSI or an increase in GHGs. Finding that hotspot would not mean that we have detected an anthropogenic signature of warming due to GHGs; it rather would mean that we understand how surface warming affects lapse rates. Not finding the hotspot means either: 1) we have more to learn abo...