Anthony Watts:
Just because something is said to be an amplifier doesn’t mean it actually is doing so, plus other datasets don’t show an increase in water vapor. See below. Also, you gotta love the big burning ball of hot they included with the press release.
This is a color enhanced satellite image of upper tropospheric water vapor.
From the University of Miami Rosenstiel School of Marine & Atmospheric Science
Scientists suggest that water vapor will intensify future climate change projections
MIAMI – A new study from scientists at the University of Miami Rosenstiel School of Marine and Atmospheric Science and colleagues confirms rising levels of water vapor in the upper troposphere – a key amplifier of global warming – will intensify climate change impacts over the next decades. The new study is the first to show that increased water vapor concentrations in the atmosphere are a direct result of human activities.
“The study is the first to confirm that human activities have increased water vapor in the upper troposphere,” said Brian Soden, professor of atmospheric sciences at the UM Rosenstiel School and co-author of the study.
To investigate the potential causes of a 30-year moistening trend in the upper troposphere, a region 3-7 miles above Earth’s surface, Soden, UM Rosenstiel School researcher Eui-Seok Chung and colleagues measured water vapor in the upper troposphere collected by NOAA satellites and compared them to climate model predictions of water circulation between the ocean and atmosphere to determine whether observed changes in atmospheric water vapor could be explained by natural or man-made causes.Using the set of climate model experiments, the researchers showed that rising water vapor in the upper troposphere cannot be explained by natural forces, such as volcanoes and changes in solar activity, but can be explained by increased greenhouse gases, such as CO2.
IMAGE: This is an illustration of annual mean T2-T12 field that provides a direct measure of the upper-tropospheric water vapor. Purple = dry and Red = moist.
Greenhouse gases raise temperatures by trapping the Earth’s radiant heat inside the atmosphere. This warming also increases the accumulation of atmospheric water vapor, the most abundant greenhouse gas. The atmospheric moistening traps additional radiant heat and further increases temperatures.
Climate models predict that as the climate warms from the burning of fossil fuels, the concentrations of water vapor will also increase in response to that warming. This moistening of the atmosphere, in turn, absorbs more heat and further raises the Earth’s temperature.
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The paper, titled “Upper Tropospheric Moistening in response to Anthropogenic Warming,” was published in the July 28th, 2014 Early Addition on-line of the journal Proceedings of the National Academy of Sciences (PNAS). The paper’s authors include Chung, Soden, B.J. Sohn of Seoul National University, and Lei Shi of NOAA’s National Climatic Data Center in Ashville, North Carolina.
http://www.pnas.org/content/early/2014/07/23/1409659111.abstract
Full paper: http://www.pnas.org/content/early/2014/07/23/1409659111.full.pdf
Supporting Information:http://www.pnas.org/content/suppl/2014/07/23/1409659111.DCSupplemental/pnas.201409659SI.pdf#nameddest=STXT
Abstract
Water vapor in the upper troposphere strongly regulates the strength of water-vapor feedback, which is the primary process for amplifying the response of the climate system to external radiative forcings. Monitoring changes in upper-tropospheric water vapor and scrutinizing the causes of such changes are therefore of great importance for establishing the credibility of model projections of past and future climates. Here, we use coupled ocean–atmosphere model simulations under different climate-forcing scenarios to investigate satellite-observed changes in global-mean upper-tropospheric water vapor. Our analysis demonstrates that the upper-tropospheric moistening observed over the period 1979–2005 cannot be explained by natural causes and results principally from an anthropogenic warming of the climate. By attributing the observed increase directly to human activities, this study verifies the presence of the largest known feedback mechanism for amplifying anthropogenic climate change
Significance
The fact that water vapor is the most dominant greenhouse gas underscores the need for an accurate understanding of the changes in its distribution over space and time. Although satellite observations have revealed a moistening trend in the upper troposphere, it has been unclear whether the observed moistening is a facet of natural variability or a direct result of human activities. Here, we use a set of coordinated model experiments to confirm that the satellite-observed increase in upper-tropospheric water vapor over the last three decades is primarily attributable to human activities. This attribution has significant implications for climate sciences because it corroborates the presence of the largest positive feedback in the climate system.
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I note this graph from their SI, the trend seems tiny, and one wonders if they have done all the appropriate orbital drift corrections that people often like to mention about Christy and Spencer:
Fig. S1.Decadal trends of observed brightness temperatures as a function of time span for (A) HIRS channel 12 (T12), (B) MSU channel 2 (T2), and (C)MSUchannel 2–HIRS channel 12 (T2–T12). Years specified on abscissa denote the end year of time period starting from 1979. Error bars denote ±2 SE of the linear trend.
However, this dataset below of relative humidity, from reanalysis of in-situ radiosonde measurements (not from remote sensing) suggests water vapor has not been on the increase in the upper troposphere, nor in the middle, nor in the lower troposphere.
