A new paper predictably makes a big splash in this week’s Nature magazine:
Attribution of observed surface humidity changes to human influence
Katharine M. Willett1,2, Nathan P. Gillett1, Philip D. Jones1 & Peter W. Thorne2
Climatic Research Unit, School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, UK
Met Office Hadley Centre, FitzRoy Road, Exeter EX1 3PB, UK
Water vapour is the most important contributor to the natural greenhouse effect, and the amount of water vapour in the atmosphere is expected to increase under conditions of greenhouse-gas-induced warming, leading to a significant feedback on anthropogenic climate change. Theoretical and modelling studies predict that relative humidity will remain approximately constant at the global scale as the climate warms, leading to an increase in specific humidity. Although significant increases in surface specific humidity have been identified in several regions and on the global scale in non-homogenized data, it has not been shown whether these changes are due to natural or human influences on climate. Here we use a new quality-controlled and homogenized gridded observational data set of surface humidity, with output from a coupled climate model, to identify and explore the causes of changes in surface specific humidity over the late twentieth century. We identify a significant global-scale increase in surface specific humidity that is attributable mainly to human influence. Specific humidity is found to have increased in response to rising temperatures, with relative humidity remaining approximately constant. These changes may have important implications, because atmospheric humidity is a key variable in determining the geographical distribution and maximum intensity of precipitation, the potential maximum intensity of tropical cyclones, and human heat stress16, and has important effects on the biosphere and surface hydrology.
Also in Nature News:
Humans have made the skies more moist
Study models rises in atmospheric water vapour.
Human activity is behind the rising levels of water vapour in the lower atmosphere over the past few decades, climatologists have concluded. The rises in humidity could affect patterns of extreme storms, they warn.
Nature’s editor likes it too:
………using a new data set of surface specific humidity observations, along with output from a coupled climate model, Willett et al. identify a significant increase in global mean surface specific humidity during the late twentieth century that is mainly attributable to human influence.
Luke Walker thinks the paper is significant and sent a link to ABC’s predictable take:
Rising humidity fuels greenhouse effect
We also had this report from the BBC in November 2005:
Water builds the heat in Europe
“Water vapour rather than carbon dioxide in the atmosphere is the main reason why Europe’s climate is warming, according to a new study.”
The BBC are up to speed with the new Nature paper:
Warmth makes the world more humid
I wonder how evaporation equalling precipitation globally over the past 20 years fits into this?
The paper also tries to make a link with increased tropical cyclones, but the case for a link is weak.
Scant publicity by comaprison for the recent Spencer et al paper ‘Cloud and radiation budget changes associated with tropical intraseasonal oscillations’. Geophys. Res. Lett., Vol. 34, No. 15, 9 August 2007.
Read the article ‘Global Warming and Nature’s Thermostat’ by Roy W. Spencer:
August 9, 2007 RESEARCH UPDATE!: Our peer-reviewed paper showing the natural cooling behavior of tropical cirrus clouds in response to warming has been published today in Geophysical Research Letters. (The UAH news release is here.) This natural cooling mechanism constitiutes a strong “negative feedback” (reducing warming tendencies), while all leading climate models have cirrus clouds behaving in a positive feedback manner (amplifying warming tendencies). As is usually the case in this business, however, there is no way to know with any level of confidence whether this mechanism is operating in the context of manmade global warming………
Jennifer Marohasy BSc PhD is a critical thinker with expertise in the scientific method.
The paper is significant as it nails greenhouse gases not “other hypothesised mechanisms” and that is is a complex technical bit of work that explains a greenhouse prediction come true.
The paper explains observations with models rather than “model” a future.
This paper has been building for some time with bits released elsewhere so Paul’s “Spencer et al was ignored” comment falls on bare ground – so also ignored was ” Identification of human-induced changes in atmospheric moisture content” in PNAS this year. Including same author.
http://www.pnas.org/cgi/content/abstract/104/39/15248 interestingly also using microwave sounders.
In any case the new paper is about actual observations more than a modelled future.
Gillett has been quietly doing a stack of science for some time on this theme. http://www.cru.uea.ac.uk/~nathan/publications.html
Pauls’ reference to “Water vapour rather than carbon dioxide in the atmosphere is the main reason why Europe’s climate is warming, according to a new study.” The ACTUAL paper here was called “Anthropogenic greenhouse forcing and strong water vapor feedback increase temperature in Europe” by Rolf Philipona et al.” Here http://www.agu.org/pubs/crossref/2005…/2005GL023624.shtml and discussed extensively here http://www.realclimate.org/index.php/archives/2005/11/busy-week-for-water-vapor/
I wouldn’t have brought this one out – the paper is actually about strong water vapour feedback caused by CO2. Double whammy. And builds on a series of papers by Philipona confirming the greenhosue flux with radiometers.
So if you add this interesting new paper to a cooling stratosphere, Philipona’s empirical measurements and feedback work, Lockwood and Frolich, Tung’s indirect solar veification of 3C for 2x CO2, Smith el al on internal variability – to the rest of the fingerprinting and attribution work – I’d say the AGW case is mounting very strongly indeed.
*crickets chirping*
Thanks for the info, Luke.
Big warming via CO2 exists only in computer models and on the basis of a low understanding, or worse, for many climate factors. If climate was as sensitive to CO2 as computer models claim, and positive feedbacks were large – we wouldn’t be here now.
We know the world has warmed and it started over 250 years ago. Even L&F acknowledge an ‘unknown’ amplifier of solar irradiance and the expected fall in solar activity, with an uncertain effect on climate.
Paul
half the point is that we have had a remarkably stable climate, and that stability is what has allowed civilisation to flourish. Too bad if that comes to an end, due to our own actions, before it needed to, due to natural change.
Hansen has warned, the climate in the past has undergone radical swings. Is that what you want for your children?
Well no – we have not had 6 billion humans and 30 days food supply and an interlinked financial system before. It’s all new ! And we are already very exposed to climate risk. See how Australian farmers have just shrugged off the the drought as a mere inconvenience (NOT!). Katrina victims just laughed it off. – Not ! (and I didn’t ascribe any AGW involvement).
If solar does decline so will the CO2 greenhouse effect by definition. But it doesn’t do away and when the solar upswings again you’ll get the increased effect.
The fact that the climate is stable, CO2 being many times higher than now in the past, shows that climate sensitivity to CO2 is low.
Hansen? Non-objective, alarmist. I’m not worried about CO2, but I am worried about the amount of effort and money wasted on futile attempts to manipulate a harmless gas, when there are real problems that need to be solved.
But it’s not stable is it – temperatures rising, glaciers melting, droughts, hurricanes, major changes in ocean temperatures, SAM changing, Artic changing ? That’s stable?
When CO2 was many times higher in the past we did not have the world as we have it today?
Tell the farmers on the Murray there are no real problems ! Tell anyone on the receiving end of an El Nino that there are no problems.
Might be OK sitting a benign UK climate – a lot of us are not.
“But it’s not stable is it – temperatures rising, glaciers melting, droughts, hurricanes, major changes in ocean temperatures, SAM changing, Artic changing ? That’s stable?”
It’s nothing unusual for this interglacial – trying to claim that it is unusual and link it largely or soley to humans is disingenuous.
Tell the farmers on the Murray thay can control the climate by trying to manipulate the atmospheric longevity of CO2?
Well it’s much more disengenous to claim as this is not unusual and that we don’t have any ideas. It’s called DENIALISM !
Gee Paul – fancy all these things happening simultaneously all round the world. And for no reason at all. No apparent driver. No solar change. It’s “NATURE”. How grande. How interesting.
Shall we do the checklist yet again. No we all know by now.
Put the Rainforests back as they were .It is the only chance we have, otherwise don`t bother with anything !
You know it is not going to happen!