New paper shows IPCC models exaggerate warming from water vapor

Global monthly average total precipitable water vapor

The theory of global warming claims that a trivial warming from CO2 levels will result in more water vapor in the atmosphere and an alleged 'runaway greenhouse effect'. However, satellite observations published in a new paper show that global water vapor has instead declined over the past 12 years despite steadily rising concentrations of CO2. These observations provide further support that the positive water vapor feedback in IPCC models is overstated and therefore claims of future warming greatly exaggerated. 


Climate scientist Roger Pielke Sr. comments on the new paper:

However, the figure [above], if it turns about to be robust, raises fundamental issues with respect to the ability of global climate models to skillfully model the role of humans in altering the climate. Indeed, the Vonder Haar et al 2012 provides further support to the conclusion by De-Zheng Sun in the paper 

Sun, D.-Z., Y. Yu, and T. Zhang, 2009: Tropical Water Vapor and Cloud Feedbacks in Climate Models: A Further Assessment Using Coupled Simulations.J. Climate, 22, 1287-1304 

that I posted on in

Tropical Water Vapor and Cloud Feedbacks in Climate Models: A Further Assessment Using Coupled Simulations by De-Zheng Sun, Yongqiang Yu, and Tao ZhangAs part of their conclusions, they wrote

“The extended calculation using coupled runs confirms the earlier inference from the AMIP runs that underestimating the negative feedback from cloud albedo and overestimating the positive feedback from the greenhouse effect of water vapor over the tropical Pacific during ENSO is a prevalent problem of climate models. 

While De-Zheng was reluctant to relate his findings to multi-decadal global climate model simulations of the role of humans in the climate system, the new Vonder Haar et al 2012 paper provides further support that the water vapor feedback is overstated by the IPCC models.

Related: posts on water vapor as a negative feedback