The Snow Line is Moving South

Guest post by Steven Goddard

As we have been discussing on WUWT, three of the last four months have seen top ten Northern Hemisphere snow extents and the decadal trend has been towards increasing (and above normal) snow extent during the autumn and winter.  It appears that this month will achieve snow extent among the top two Februaries on record.

As you can see in the Rutgers University maps below for mid-February, the excess snow cover is necessarily found at lower latitudes.  Snow cover radiates out from the pole, so the only place where snow extent can increase is towards the south.

The implication of the observed trend towards increasing snow extent is that the Northern Hemisphere autumn/winter snow line is moving southwards over the last ten to twenty years.

Daily Departure – February 13, 2010 (Day 44)

Source : Rutgers University Global Climate Lab

Daily Snow – February 13, 2010 (Day 44)

Source : Rutgers University Global Climate Lab

We see southern snow cover this year in places like Greece, Northern China, and Alabama that are not normally covered with snow in mid-February.  The map below shows the “normal” snow extent measured since 1966.

Daily Climatology – February 13 (Day 44)

Source : Rutgers University Global Climate Lab

Some people have been claiming that the anomalous snow this winter is due to warming temperatures.   The New York Times reports on the record snow :

Most climate scientists respond that the ferocious storms are consistent with forecasts that a heating planet will produce more frequent and more intense weather events.

It doesn’t make a lot of sense that warming temperatures would cause the snow line to move south.  Lower latitudes normally receive rain rather than snow, because the air is already too warm for snow.  Further warming would be expected to move the snow line north – not south – and that is exactly what the climate models predict.  Indeed, Time Magazine claims that this has already happened: “large-scale cold-weather storm systems have gradually tracked to the north in the U.S. over the past 50 years.”

As far as snow depth goes, Washington D.C. recently broke their 1899 snow record of 54.4 inches and now has a new record of 54.9 inches.  We are told that the new record is due to “extreme weather” caused by “global warming.”  If so, what caused the nearly identical “extreme weather” over a century ago?  Alarmists tell us that heavy snow used to be caused by cold, but now is caused by warmth.  The 1899 record was set long before the hockey stick brought temperatures to “unprecedented levels.”

Now lets take their poor logic one step further.  Ice ages occur when the snow line moves very far south.  If “most climate scientists” are claiming that global warming is causing the snow line to move south, then the logical corollary is that ice ages are caused by further warming temperatures.  Clearly that is not true.

Wikipedia map of the last ice age

Furthermore, Hansen correctly tells us that as the snow line moves south, the earth’s albedo increases causing further cooling.

The sensible theory is that the snow line moves south when the climate is cold, and north when the climate is warm.  And the record snow we are seeing this winter is due to cold, not warm temperatures.

Today’s NBA All-Star game in Dallas is covered with snow.  Last time I checked, Texas was in the South.

2010 NBA All-Star Game in Dallas, Texas.
2010 NBA All-Star Game in Dallas, Texas.

Image from examiner.com

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As glaciers expand, will sealevels drop, thus providing more land for we Northerners to move South too? I am making friends in Venezuela, so we might have a warm place to go (once they chuck Chavez into the dumpster.)
Has Al Gore been dug out of the snow yet?

Mia Nony

THE TROUBLE is that people have been so focused on proving or disproving warming that as a whole they are largely COMPLETELY UNPREPARED for a very severe prolonged COOLING TREND. Google “The Year Summer Never Came”. Late 1700s, I think, During the lifetime of the author of Frankenstein, who documented this as well. It was like a plague. It became very very cold. Millions died, in Europe and in North America, and there were vast crop failures. Are we wasting valuable time now?
[REPLY – 1816. Eighteen-hundred-and-froze-to-death. The Tambora eruption (inter alia). ~ Evan]

RIP IPCC

Rotten snow!!!

Well, every religion must have it`s miracles!

Joe Black

That albedo thing can be a real problem for calculating radiative equilibrium.

Stacey

It snowed in Rome over the weekend, the first time in a generation?
Sorry that’s weather not climate?

OT: Anthony gets yet another front page citation, this time from Telegraph Online
on poorly sited temp stations
http://www.telegraph.co.uk/earth/environment/climatechange/7236011/UN-global-warming-data-skewed-by-heat-from-planes-and-buildings.html

aMINO aCIDS iN mETEORITES

As far as snow depth goes, Washington D.C. recently broke their 1899 snow record of 54.4 inches and now has a new record of 54.9 inches. We are told that the new record is due to “extreme weather” caused by “global warming.” If so, what caused the nearly identical “extreme weather” over a century ago?
=================================================
Important question.

Scarlet Pumpernickel

Watch OUT! Soon the glaciers will start growing again and it’ll be panic stations, they’ll be engulfing towns.
I would have thought glaciers receding is good, more land!

aMINO aCIDS iN mETEORITES

more snow is in the forecast for tonight and tomorrow in the ‘Deep South’ of the US:
http://apnews.myway.com/article/20100214/D9DS1MSO0.html
And it looks like it’s headed toward Washington where they’ve already had record snow:
http://www.intelliweather.com/popup/nat_rad_popup.htm

Daniel H

“Most climate scientists respond that the ferocious storms are consistent with forecasts that a heating planet will produce more frequent and more intense weather events.”
Who are these climate scientists? Did the NYT reporter, John Broden, actually conduct some sort of informal survey of climate scientists from around the world in order to arrive at that conclusion? Or did he just email his pals over at RealClimate and use their opinions as a proxy for the opinions of “most climate scientists”? Broden has so expertly mastered the art of crap-alarmist-junk-journalism that I suspect he’s being groomed to take Andy Revkin’s place.

Mia Nony

1816 also became know as the Poverty Year. The following poem from Eileen Marguet summed up the year:
It didn’t matter whether your farm was large or small.
It didn’t matter if you had a farm at all.
Cause everyone was affected when water didn’t run.
The snow and frost continued without the warming sun.
One day in June it got real hot and leaves began to show.
But after that it snowed again and wind and cold did blow.
The cows and horses had no grass, no grain to feed the chicks.
No hay to put aside that time, just dry and shriveled sticks.
The sheep were cold and hungry and many starved to death,
Still waiting for the warming sun to save their labored breath.
The kids were disappointed, no swimming, such a shame.
It was in 1816 that summer never came.

Mia Nony

http://www.history-magazine.com/volcanoes.html
The Year Without a Summer
The eruption of Indonesia’s Mount Tambora on 5 April 1815 was one of the largest eruptions in history. Tambora spewed sulphur-rich gases that rose to a height of 28 miles and created a giant sun filter in the northern hemisphere that caused the spring and summer of 1816 to be extremely cold across Europe and North America. Snowfalls and frost occurred in June, July and August and all but the hardiest grains were destroyed. Destruction of the corn crop caused farmers to slaughter their livestock. Soup kitchens were opened to feed the hungry. Sea ice formed in the Atlantic shipping lanes and glaciers advanced down mountain slopes to exceptionally low levels. Hundreds of thousands died of starvation as crops failed, touching off a wave of migration to the American South and Midwest. Farmers repeatedly tried to get a crop in the ground, but each time a killer frost withered the tender roots. Corn and grain prices shot up to $5 and $10 per bushel and oats that had been 12 cents a bushel rose to 92 cents. Riots erupted in Britain and France as starving citizens broke into grain warehouses and left them empty. Violence was even worse in Switzerland where the government declared a national emergency and grain purchases from Russia were intercepted at the border and confiscated by hungry citizens.

Wayne R

This looks serious. Thank heaven I still have IPCC to keep me worried about Global Warming.

OT.
Some feedback from the Australian ABC regarding questions posed about their somewhat biased climate timeline.
Attention is drawn to the Ordovician Ice age, Roman Warm Period and NIPCC that remain missing in action, The Medieval Warm Period that remains poorly referenced, and Al Gore’s movie that remains un-corrected by a British judge. Information about the Northern sea passages remain uncertain.
If anyone has further suggestions please feel free to leave a comment.
http://abcnewswatch.blogspot.com/2010/02/climate-time-line-or-time-lie-response.html

So we can infer that as the globe gets warmer, then there should be an increase in precipitation. Yet, as the EPA data shows, warmer does not equal wetter.

Baa Humbug

Doesn’t a US Govt department publish frost lines? I believe it’s important for the integrity of buildings and structures etc as well as agriculture.
Would be interesting to see if the frost line has also shifted south.

Mari Warcwm

Quite right, Mia Nony. All our great leaders are looking in the wrong direction. The Great Polar Bear, in the meantime, may be sneaking up behind us and will catch us unawares.
As David Archibald says in his excellent book ‘Solar Cycle 24’ when discussing interglacials, ‘Relative to the last four interglacials, we may be somewhere near the end of the current interglacial. The end of the Holocene will be a brutal time for humanity.’
But then we must not be alarmist. We’ve paid enough for that kind of thing already.

el gordo

‘But then we must not be alarmist’. Perfectly true, but it may be time to raise the concern flag.

Perhaps its got something to do with the movement of the magnetic north pole…

Graeme W

Just one small point:

Ice ages occur when the snow line moves very far south. If “most climate scientists” are claiming that global warming is causing the snow line to move south, then the logical corollary is that ice ages are caused by further warming temperatures.

This logic is faulty. If A implies C and B implies C, then this does not mean that A and B are the same.
Taking the (ridiculous) statement of global warming is causing the snow line to move south as a given, and that in ice ages, the snow line moved south, that doesn’t mean that global warming = ice age. All it means is that the result (snow line moving south) can be achieved by more than one mechanism.
Having said that, I could possible accept an argument that global warming has altered ‘traditional’ weather patterns, and has resulted in severe winters in part of the globe, but even with that argument I’m yet to be convinced. I’d need more evidence (as shown by long term altered wind patterns, for example) before I’d accept it.

Rhys Jaggar

I think there must be some context to the ‘warming temperatures produce more snow’ etc.
It’s pretty clear to me that the following is true:
Snowfall is MOST EXTREME when the temperature is around ZERO.
If it’s minus twenty it’s too cold to snow enormous amounts. Plus six and it’s rain instead.
So my take is this:
Places with cold, cold winters will get more snow if the temperature is a bit warmer.
Places with winters around zero may get less snow and more rain if the temperature is a bit warmer.
So the net effect of warming might be:
Higher snowfall in the upper mountains, thereby replenishing glaciers at the top end. Higher snowfall in interior Siberia, China, interior Alaska/Canada and the Antarctic.
Lower snowfall at the margins, in Alpine lowlands, at the southern extremes of mountain ranges like the Rockies, the Italian Apennines, Lebanon etc.
The net effect of cooling might be: greater snowfall further south in the midwestern plains of the US, more snow in Spain, more snow in North Africa, more snow in Australia and more snow in South Africa.
Of course, with the complex climate we know about, you might get a mixture of the two – warmer arctic temperatures and cooler interior temperatures. That might produce more snow both in the polar regions AND on the southern extremities of the winter snowline.
And for those who accept the data of ice cores etc, you will see that prior to each ice age is a rapid rise in temperatures followed by a big, rapid drop.
Is the polar warming/interior cooling option a possible way to trigger an ice age??

David, UK

“The sensible theory is that the snow line moves south when the climate is cold, and north when the climate is warm.”
“Sensible” being the operative word.

Tom P

Steven Goddard,
Looking at the Rutgers seasonal data there is no significant trend in the fall and winter snow extents for the northern hemisphere. As for spring and summer, the trend is significantly down over the last few decades.
http://climate.rutgers.edu/snowcover/chart_seasonal.php?ui_set=nhland&ui_season=3
Your post should have been titled: “The Snow Line is Moving North.”

TimiBoy

True? Hell’s teeth, I hope Global Warming will make it cooler here in Oz. Bloody hot here right now, but don’t panic, it always is in Summer! Damn it’s got to come a long way down for it to snow here, though.
Please – I’m joking!
I don’t think the AGW Leviathan has died yet, but I’m hoping the silver bullet will hit it’s tiny brain soon and stop this farce. We can only hope that a lesson in caution on behalf of our populace and politicians is learn’t this time…

Tom P (01:43:18) :
Steven Goddard,
Your post should have been titled: “The Snow Line is Moving North.”

By the time you two settle this my hairline will have moved north and my waistline will have moved south.

D. Ch.

I noticed that in the chart of where the ice sheets were during the last ice age, that North America seemed to have a disproportionately large amount of ice compared to Asia, particularly in Siberia. Also, why no ice in Northern Alaska? Are there any explanations for this counterintuitive distribution of glaciers?

Britannic no-see-um

‘At least I had the satisfaction of pointing out that while the House was voting for a bill based on the assumption the world is getting warmer, it was snowing in London in October for the first time in 74 years. I was told, “extreme cold is a symptom of man made global warming.” ‘
Peter Lilley MP in
http://www.peterlilley.co.uk/article.aspx?id=14&ref=1511

Anthony and team, hope you can also monitor if the southward movement of snowline is also happening on the other side of the globe, in Asia. I have read about the “worst winter” in Korea, north China, Mongolia, etc in January. I wonder if the trend continued until this month.
Here in Metro Manila and surrounding provinces, El Nino is kicking rather hard. It can be cloudy on some days but the clouds don’t fall even as light showers.

Jimbo

OT
[sorry but this comment on the BBC site IMHO sums up climate scientists.]
laughingdevil wrote:

“For my ALevel Statistics coursework I set out to prove – and easily managed to – that smokers had a better chance of living to 100. The fact that most people older than 100 were of a smoking generation is neither here nor there, the facts backed my hypothisis, and therefore by the rules of statistical maths it was true.”

Moderator – please feel free to snip

brian

Two important points to remember here:
1. Increased snowfall is a direct result of AGW.
2. Decreased snowfall is a direct result of AGW.

The snow line is moving in phase with the solar cycles activity, further South now that it is at a minimum, and was further North with more warming when it was much more active for the 50 years before this cycle…….
How hard can it be to figure out???
sun+- changes in climate
CO2+ still changes with the sun???

rbateman

http://www.climatechange.umaine.edu/Research/projects/laurentide.html
http://www.museum.state.il.us/exhibits/ice_ages/laurentide_deglaciation.html
What I remember finding some time back was a stated tendency for high-pressure systems to sit over Ice Sheets. As it was described, the present day effect of high pressure over the West running storms up into B.C. didn’t happen during the Laurentide. The storms went predominately West-East and the desert Southwest was a fertile grasslands/deciduous forest.
How it (Laurentide) got started I can’t find much on.
Why an ice-free Alaska? Must be some sort of predominant low and ocean current/wind pattern thing got set up. Who knows.

Daniel H

@D. Ch.
“North America seemed to have a disproportionately large amount of ice compared to Asia, particularly in Siberia. Also, why no ice in Northern Alaska? Are there any explanations for this counterintuitive distribution of glaciers?”
The unglaciated area of the Alaskan interior formed part of the “Beringia Corridor” which extended west into Siberia. That area was ice-free because most of the moisture in the air had been depleted by the mountain ranges to the South and North of the corridor. Hence, very little precipitation fell on Alaska’s interior lowland and arctic coastal plain. You can read more about it on Wikipedia which gives a decent explanation:
http://en.wikipedia.org/wiki/Beringia
Also see here for a more thorough history:
http://esp.cr.usgs.gov/research/alaska/alaskaC.html

rbateman

So if Global Warming causes Global Cooling, then Global Cooling causes Global Warming.
Global Warming, therefore, caused the LIA, and Global Cooling stopped the glaciers in the Swiss Alps, not the cardinal. Froze that puppy in it’s tracks.
That’s got to be it. Global Warming gets so cold that ice stops moving and melts. Yeah.
And Global Cooling gets so hot at the Poles that it shoves the Polar Caps south. Makes ice move so fast it cannot melt, and the centrifugal force slings the Arctic Cap out over N.A. and Siberia in 2 giant halves.
Only trouble is, with logic that bad and ice that fast, how’s a feller supposed to figure out which one’s going on at any given time?
Global warming causes global cooling is one really messed up theory.
Stars are not condensed out of galactic stuff: They are black holes in the opposite universe pumping matter into this universe.
Warning: This kind of thinking can lead to excessive drinking.

TLM

I have been looking at this myself, and something quite odd is going on.
The winter Northern Hemisphere snow cover has been increasing since about 1998, having been declining for some time before that. But at the same time, summer snow cover has been decreasing – quite drastically.
The whole point about an ice age is not the winter snow cover, but the summer snow cover. If the snow cannot last the summer then it does not matter how far south it goes in Winter.
I attach links to a couple of (very amateur) graphs I have done to show this. Snow reaches a maximum (usually) in January and a minimum in August. So I have calculated an average over the 30 years 1975-2005 for each month (the satellite record only goes back to 1973) and show the variance from that.
http://img502.imageshack.us/img502/7003/nhsnowjanuary.png
http://img710.imageshack.us/img710/7197/nhsnowaugust.png
What these do not show is that in percentage terms the summer snow melt is much bigger – in fact snow has now virtually disappeared from the NH land mass in August.
Another trend is that the snow is melting earlier, as temperatures are increasing in March/April, which is primarily what has been driving the reducing summer snow extent.
I think it would be plain stupid to attribute this either to AGW or global cooling at this stage. This does not fit the expected pattern of either and clearly is a form of “climate change” not yet built into anybody’s models.
This needs a lot more research and calling the trend as proof of either AGW or natural variability is premature – although if I were a betting man I would put my money on the latter rather than the former.

Does this mean we can skip painting our roofs white?
Here’s another view of the current N.H. snow & ice cover, compared with last year: click

Stephen Wilde

From the late 70’s the average global latitudinal position of the air circulation systems, most notably the mid latitude jets moved fitfully poleward in response to warming sea surfaces.
Since 2000 following the 1998 El Nino peak of warm ocean surfaces the air circulation systems stopped moving poleward and ever since have been drifting slowly and fitfully back equatorward.
At the same time the sea surfaces have been gradually cooling albeit fitfully.
How much more empirical evidence do we need ?

Peter of Sydney

Yes it would be ironic if the whole world fell into a severe cooling snap. Would even be more ironic to see official temperatures still rising. It would prove once and for all how fraudulent the whole game is being played by the likes of CRU, NOAA and NASA. They already have egg on face. If the cooling trend continues they are totally discredited. Sad though as I held NASA and NOAA with high regard many years ago. Now they have turned into political spin con artists.

blcjr

Baa Humbug (01:16:07) :
Doesn’t a US Govt department publish frost lines? I believe it’s important for the integrity of buildings and structures etc as well as agriculture.
Would be interesting to see if the frost line has also shifted south.

I don’t know the answer, but it made me think of the parallel to growing seasons. Most reports I am aware of are that growing seasons have been getting longer. But that raises a question: longer relative to what time frame? Like temperature trends themselves, we can come up with just about any answer we want, depending on where we start and stop the time frame of analysis. I don’t doubt that growing seasons became longer, in recent decades, to some earlier decades. But all that may be changing.
An interesting paper abstracted here:
http://adsabs.harvard.edu/abs/2005AGUFM.B43B0265N
ties a later start to the growing seasons since 1998 to a possible shift in the PDO.

Tenuc

Here’s a chart of the last 450ky from the Vostok ice core data.
http://www.ianschumacher.com/img/iceagetemphist.png
As can be easily seen, Earth’s chaotic climate fluctuates between periods of being warm and cool on a regular basis, with cool being the predominant mode. The changes between cooling and warming mode are quite rapid and we are at the top of the peak at the moment.
I think that a series of small events which coincide with a conjunction of the regular quasi-cycles our climate exhibits, can in the right circumstances, cause these shifts.
Here’s a list of ‘possible’ events which could catalyse the change:-
Triggers for cool-mode climate – happening now.
Low latitude jet stream in the northern hemisphere.
Low Ap index.
Weak NH polar vortex.
Less UV hitting Earth’s atmosphere.
Low density/speed solar wind.
Reduced depth of Earth atmosphere.
Increase in cosmic rays.
Enhanced cloud cover.
PDO turning negative.
El Nino conditions weak.
Weak Gulf Stream.
Increased albedo from extra NH snow.
Additional potential triggers – yet to happen.
Big volcanic eruptions.
Strong La Nina.
Thanks to all at WUWT for helping compile this list.

Aelfrith

Rome has just had the first snow fall for a generation
http://current.newsweek.com/budgettravel/2010/02/live_from_rome_snow.html

blcjr

Tom P (01:43:18) :
Steven Goddard,
Looking at the Rutgers seasonal data there is no significant trend in the fall and winter snow extents for the northern hemisphere. As for spring and summer, the trend is significantly down over the last few decades.
http://climate.rutgers.edu/snowcover/chart_seasonal.php?ui_set=nhland&ui_season=3
Your post should have been titled: “The Snow Line is Moving North.”

Why focus on just the spring and summer? Why not look at the complete picture, as in this link, from the same source?
http://climate.rutgers.edu/snowcover/images/anom_nhland.gif
The 12-month moving average has moved up sharply since 2007. And since it is a centered moving average, it doesn’t include the most recent 6 months, which are sharply positive, so the trend line will continue to move up over the next few months, probably bringing it back to, or near to (if not actually above) the zero anomaly line for the entire base period, which covers all months back to November 1966.
Would you perhaps, also, notice a regime-shift-like transition in the late 1970’s in this graph? I wonder what that means? Natural climate variability, perhaps?
“If you torture the data long enough, it will confess; even to crimes it did not commit.”

blcjr

Stephen Wilde (03:43:18) :
From the late 70’s the average global latitudinal position of the air circulation systems, most notably the mid latitude jets moved fitfully poleward in response to warming sea surfaces.
Since 2000 following the 1998 El Nino peak of warm ocean surfaces the air circulation systems stopped moving poleward and ever since have been drifting slowly and fitfully back equatorward.
At the same time the sea surfaces have been gradually cooling albeit fitfully.
How much more empirical evidence do we need ?

Stephen, what is the evidence for this? Not that I doubt you, but I’d like to look at it for myself. Are there data, anywhere, for the position of the jet stream over time?

chrisH

Uk headline today.THE GREAT CLIMATE CHANGE RETREAT
http://www.dailyexpress.co.uk/posts/view/158214

Brian

Slightly off topic…but still in the realm of snow… perhaps this is a clue as to why we don’t hear about Kilimanjaro any more??? From the NY post :
Last Updated: 3:49 AM, February 15, 2010
Posted: 1:21 AM, February 15, 2010
Yahoo! BuzzDiggRedditFark ItNewsvineStumbleUponTwitterFacebook RSSKick Kennedy, granddaughter of Robert F. Kennedy, recently climbed Mount Kilimanjaro to raise awareness about the water crisis in Africa. The Stanford University senior made the summit with Jessica Biel, Emile Hirsch, Lupe Fiasco, Santigold, Isabel Lucas, Elizabeth Gore and Alexandra Cousteau as cameras recorded the adventure for MTV, which will air “Summit on the Summit” on March 14. “We had historically bad weather,” Kennedy told Page Six. “On the seven-day ascent, it rained or snowed every day, and we had a complete whiteout at the summit.” Kennedy is also working with Consuelo Vanderbilt-Costin and Sara Delano Roosevelt for the Legacy Group, which auctioned a blouse she designed for $14,000 — for charity, of course.
Read more: http://www.nypost.com/p/pagesix/rugged_ascent_4aoyrc6Gj533JwgWszUYLL#ixzz0fbdClh9n

Ralph

I’ve read that scientists want to drop something into the atmosphere to simulate a erupting volcano to reduce AGW. What are these people thinking? Are they really caught up in the AGW religion that deeply?

Curiousgeorge

I’ve reached the conclusion that very many of the people involved in “Climate Science” are not Scientist’s but merely skilled Technicians who are very good at the mechanics of their field, but lack the philosophical sense that leads to true understanding. I believe Hume would agree with me.

Tom P

Basil (04:04:57) :
“Why focus on just the spring and summer?”
I’m not, but they are the only seasons with significant decadal trends. There’s little of any significance that can be concluded by looking at two or three years’ worth of data.
It’s probably not coincidental that arctic sea ice has also shown the greatest relative loss during the summer months over the last three decades:
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seaice.anomaly.arctic.png

Icarus

Alarmists tell us that heavy snow used to be caused by cold…
Cite?
Northern Hemisphere snow cover is declining:
http://climate.rutgers.edu/snowcover/chart_anom.php?ui_set=0&ui_region=nhland&ui_month=1
… and:
http://www.ipcc.ch/publications_and_data/ar4/wg1/en/figure-spm-3.html
And the record snow we are seeing this winter is due to cold, not warm temperatures.
Quantity of precipitation is related to atmospheric moisture content, not temperature. Antarctica is extremely cold but nevertheless has dry valleys (free of ice and snow) which cover about 0.03% of the continent. The planet is warming, therefore atmospheric moisture content is rising*, therefore we are seeing more heavy precipitation.
* “The average atmospheric water vapour content has increased since at least the 1980s over land and ocean as well as in the upper troposphere. The increase is broadly consistent with the extra water vapour that warmer air can hold.” – IPCC AR4, WG1 –
http://www.ipcc.ch/publications_and_data/ar4/wg1/en/spmsspm-direct-observations.html