Study: Water-vapor feedback is “strong and positive,” so we face “warming of several degrees Celsius”
A new study in Geophysical Research Letters (subs. req’d), “Water-vapor climate feedback inferred from climate fluctuations, 2003–2008” analyzed recent variations in surface temperature and “the response of tropospheric water vapor to these variations.” They concluded that the “water-vapor feedback implied by these observations is strongly positive” and “similar to that simulated by climate models.” The analysis concludes:
The existence of a strong and positive water-vapor feedback means that projected business-as-usual greenhouse-gas emissions over the next century are virtually guaranteed to produce warming of several degrees Celsius. The only way that will not happen is if a strong, negative, and currently unknown feedback is discovered somewhere in our climate system.
A “warming of several degrees Celsius” = the end of life as we know it (see “Is 450 ppm politically possible? Part 0: The alternative is humanity’s self-destruction“).
While some denyers/delayers/inactivists, like MIT’s Richard Lindzen, have argued that negative feedbacks dominate the climate — all of the evidence points to amplifying feedbacks dominating (except the one negative feedback that the deniers fiercely fight, discussed below).
That was a key point of my post “Are Scientists Underestimating Climate Change, Part 1“: In the real world, key climate change impacts — sea ice loss, ice sheet melting, desertification, and sea level rise — all are either near the top or actually in excess of their values as predicted by the IPCC’s climate models. For a more recent detailed discussion of accelerating climate impacts and what that portends for the future on our current emissions path, see the newClimate Change: faster, stronger, sooner
The major climate models are missing key amplifying feedbacks, some of which were discussed in “Are Scientists Underestimating Climate Change, Part II.” These feedbacks include: