Stratospheric water vapor decline credited with slowing global warming

By: Dr. Jeff Masters , 6:18 PM GMT on January 29, 2010

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After a steep rise in global average temperatures in the 1990s, the 2000s have seen relatively flat temperatures, despite increasing levels of CO2 emissions by humans. This reduced warming may be partially due to a sharp decrease in stratospheric water vapor that began after 2000, according to research published yesterday in Science by a team of researchers led by Dr. Susan Solomon of NOAA's Earth System Research Laboratory in Boulder. Water vapor is a potent greenhouse gas capable of significantly warming the planet, and its potency is much higher when it is located in the lower stratosphere where temperatures are extremely cold. Greenhouse gases located in cold regions of the atmosphere are more effective at heating the planet because they absorb heat radiation from the Earth's relatively warm surface, but then re-emit energy at a much colder temperature, resulting in less heat energy lost to space. Even though stratospheric water vapor can exist at concentrations more than 100 times lower than at the surface, the 10% drop in stratospheric water vapor since 2000 noted by Solomon et al. acted to slow down global warming by 25% between 2000 - 2009, compared to that which would have occurred due only to carbon dioxide and other greenhouse gases.


Figure 1. Stratospheric water vapor in the tropics, between 5°S - 5°N, as measured by the HALOE instrument on the Upper Atmosphere Research Satellite (UARS), between 1993 - 2005. The bottom portion of the plot shows the lower stratosphere, just above where tall thunderstorms are able to transport water vapor into the stratosphere. A strong yearly cycle is evident in the water vapor, due to the seasonal variation in heavy thunderstorms over the tropics. Once in the lower stratosphere, the waver vapor takes about 1.2 years to travel to the upper stratosphere, as seen in the bending of the contours to the right with height. Note that beginning in 2001, very low water vapor concentrations less than 2.2 parts per million by volume (ppmv) began appearing in the lower stratosphere, due to substantial cooling. Image credit: Rosenlof, K. H., and G. C. Reid (2008), Trends in the temperature and water vapor content of the tropical lower stratosphere: Sea surface connection, J. Geophys. Res., 113, D06107, doi:10.1029/2007JD009109.

The observations
We haven't been able to observe water vapor in the stratosphere very long--accurate global measurements only go back to 1991, when the HALOE instrument aboard the Upper Atmosphere Research Satellite (UARS) began taking data (Figure 1). Stratospheric water vapor showed an increase of about 0.5 parts per million by volume (ppmv) during the 1990s. But after 2000, a sudden drop of 0.4 ppmv was observed, and this decrease has persisted into 2009. To see how these changes impacted the amount of global warming, Solomon et al. fed the observations into a specialized high-resolution model that computed the change in heat from the fluctuating water vapor levels. They found that the increase in stratospheric water vapor in the 1990s led to about a 30% increase in the amount of global warming observed during that decade, and the decrease of 0.4 ppmv since 2000 led to a 25% reduction between 2000 - 2009.

How water vapor gets into the stratosphere
The stratosphere has two main sources of water vapor: transport from the lower atmosphere (the troposphere) via tall thunderstorms, and the chemical breakdown of methane gas into water vapor and carbon dioxide. With regard to greenhouse effect warming, transport of water vapor by thunderstorms is the most important source, since this mechanism delivers water vapor to the lowest part of the stratosphere, where temperatures are coldest and greenhouse gases are more effective at warming the climate. There is a limit as to how much water vapor that can enter the stratosphere via thunderstorms, though. Temperature decreases with altitude from the surface to the bottom of the stratosphere, where they begin to rise with height due to the solar energy-absorbing effect of the stratospheric ozone layer. As moisture-laden air rises in thunderstorms towards the lower stratosphere, it encounters the atmosphere's "cold point"--the coldest point in the lower atmosphere, at the base of the stratosphere. Since the amount of water vapor that can be present in the atmosphere decreases as the temperature gets colder, and moisture being transported to the stratosphere must traverse through the "cold point" of the atmosphere, the air gets "freeze dried" and loses most of its moisture.


Figure 2. The departure from average of tropopause temperature (dark line) and Sea Surface Temperature (light dashed line) for the tropical Pacific Ocean between 10°S - 10°N, from 1981 - 2007. The tropopause is the bottom boundary of the stratosphere. The SST data is for 139°W - 171°W longitude, and is from the NOAA Optimal Interpolation v2 data set. The tropopause data is from balloon soundings, for the region 171°W - 200°W. The SST is plotted so that the anomalies increase as one looks down. Note that prior to about 2000, tropopause temperatures and SSTs increased and decreased together, but that beginning in 2000 - 2001, a sharp climate shift occurred, and the two quantities became anti-correlated. The sudden drop in tropopause temperature in 2000 - 2001 caused a sharp drop in stratospheric water vapor. Image credit: Rosenlof, K. H., and G. C. Reid (2008), Trends in the temperature and water vapor content of the tropical lower stratosphere: Sea surface connection, J. Geophys. Res., 113, D06107, doi:10.1029/2007JD009109.

Why did stratospheric water vapor drop in 2000?
Tall thunderstorms capable of delivering water vapor into the stratosphere occur primarily in the tropics, particularly over the Western Pacific, where a huge warm pool with very high Sea Surface Temperatures (SSTs) exists. In 2000, this region experienced a sharp increase in SST of 0.25°C, which has remained consistent though the 2000s (Figure 2). Coincident with this increase in SST came a sharp drop in the "cold point" temperature of the tropopause--the lower boundary of the stratosphere. This reduction in "cold point" temperature meant that less water vapor could make it into the stratosphere over the Tropical Pacific, since more thunderstorm water was getting "freeze dried" out. Did global warming trigger this increase in Pacific SST, resulting in cooling of the "cold point" and less water vapor in the stratosphere? Or was it random variation due to some decades-long natural cycle? This key question was left unanswered by the Solomon et al. study, and observations of stratospheric water vapor don't go back far enough to offer a reasonable guess. One factor arguing against global warming having triggered a negative feedback of this nature is that prior to 2000, increases in Western Pacific SST caused increases in "cold point" temperatures--behavior opposite of what has been seen since 2000.

If global warming has triggered the decrease in stratospheric water vapor seen since 2000, it could mean that the climate models have predicted too much global warming, since they don't predict that such a negative feedback exists. On the other hand, if this is a natural cycle, we can expect the recent flattening in global temperatures to average out in the long run, with a return to steeper increases in temperature in the coming decades. Climate models currently do a poor job modeling the complex dynamics of water vapor in the stratosphere, and are not much help figuring out what's going on. Complicating the issue is the fact that about 15% of all thunderstorms capable of delivering water vapor into the stratosphere are generated by tropical cyclones (Rosenlof and Reid, 2008), and tropical cyclones are not well-treated by climate models. We also have to factor in the impact of stratospheric ozone loss, which acts to cool the lower stratosphere. This effect should gradually decrease in future decades as CFC levels decline, though. The stratosphere is a devilishly complicated place that can have a significant impact on global climate change, and we are many years from understanding what is going on there.

References
Romps, D.M., and Z. Kuang, "Overshooting convection in tropical cyclones", Geophysical Research Letters, 2009; 36 (9): L09804 DOI: 10.1029/2009GL037396

Rosenlof, K. H., and G. C. Reid (2008), Trends in the temperature and water vapor content of the tropical lower stratosphere: Sea surface connection, J. Geophys. Res., 113, D06107, doi:10.1029/2007JD009109.

Portlight Haiti update
Paul Timmons, who directs the Portlight.org disaster-relief charity that has sprung up from the hard work and dedication of many members of the wunderground.com community, was interviewed by NBC yesterday. The reporter doing the story is planning to follow the Portlight-donated goods to Haiti and interview the people with disabilities that receive the donations. It is uncertain when the story will be aired, but I'll try to give everyone a heads-up.

Next post
My next post will probably be Tuesday (Groundhog's Day), when I plan to discuss Phil's forecast for the rest of winter. I'll throw in my two cents worth, too.

Jeff Masters

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The last 2 weeks of 15F above normal temps have spoiled me.

The low today at the DFW AP TX was 26F, the high only reached 31F as of 3:53PM CST. I want my 70F afternoon's back!
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351. Hey Taz. I lived in the Northeast, on Long Island. Many of our major snowstorms featured temps in the 22-30F range. The 18F is a lil unusual, however an Arctic area of High pressure is to the North. The intensifying Low is creating a pressure gradient, pulling Arctic air into the system.
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P451 WU mail
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Quoting severstorm:

Hi,Rather uneventful rain here in w cfl today


Do you wanna trade? It's 34F and overcast in Arlington, TX.
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P451....Thast's cool as all get out!!!!!!!!!
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from yesterdays' WHO Haiti Healthcare Cluster Report:

• As far as medical supplies are concerned, crutches are in high demand.
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Hi,Rather uneventful rain here in w cfl today
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If it is any consolation to my WU friends in the Northeast, Midwest and Mid Atlantic states, here is North Texas, in Arlington, TX at 3:38 PM

Current conditions: Overcast
Temp: 34F
No appreciable wind chill
Rel Hum: 74%
Dew Pt: 26F
Winds: NW at 7 MPH
Bar Press: 30.24" and rising
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The Liberty Schooner sailing leisurely from Key West to New York City.

Member Since: July 3, 2005 Posts: 421 Comments: 127664
Quoting drg0dOwnCountry:
The wisdom of Solomon
http://www.realclimate.org/index.php/archives/2010/01/the-wisdom-of-solomon/

From above link:

A quick post for commentary on the new Solomon et al paper in Science express. We’ll try and get around to discussing this over the weekend, but in the meantime I’ve moved some comments over. There is some commentary on this at DotEarth, and some media reports on the story – some good, some not so good. It seems like a topic that is ripe for confusion, and so here are a few quick clarifications that are worth making.

First of all, this is a paper about internal variability of the climate system in the last decade, not on additional factors that drive climate. Second, this is a discussion about stratospheric water vapour (10 to 15 km above the surface), not water vapour in general. Stratospheric water vapour comes from two sources – the uplift of tropospheric water through the very cold tropical tropopause (both as vapour and as condensate), and the oxidation of methane in the upper stratosphere (CH4+2O2 –> CO2 + 2H2O NB: this is just a schematic, the actual chemical pathways are more complicated). There isn’t very much of it (between 3 and 6 ppmv), and so small changes (~0.5 ppmv) are noticeable.

The decreases seen in this study are in the lower stratosphere and are likely dominated by a change in the flux of water through the tropopause. A change in stratospheric water vapour because of the increase in methane over the industrial period would be a forcing of the climate (and is one of the indirect effects of methane we discussed last year), but a change in the tropopause flux is a response to other factors in the climate system. These might include El Nino/La Nina events, increases in Asian aerosols, or solar impacts on near-tropopause ozone – but this is not addressed in the paper and will take a little more work to figure out.

The study includes an estimate of the effect of the observed stratospheric water decadal decrease by calculating the radiation flux with and without the change, and comparing this to the increase in CO2 forcing over the same period. This implicitly assumes that the change can be regarded as a forcing. However, whether that is an appropriate calculation or not needs some careful consideration. Finally, no-one has yet looked at whether climate models (which have plenty of decadal variability too) have phenomena that resemble these observations that might provide some insight into the causes.

Member Since: September 22, 2005 Posts: 11 Comments: 2032
Quoting PcolaDan:


Maybe a flag with the logo if the other is not feasible.


excellent fallback position...
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Quoting presslord:
I'm working on figuring out how to affix the WU logo to that headsail for the rice trip in a couple weeks...


Maybe a flag with the logo if the other is not feasible.
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I'm working on figuring out how to affix the WU logo to that headsail for the rice trip in a couple weeks...
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it has been simply incredible to watch people from all over come together to make all of this possible and feasible, you guys rock!!! (:
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A lot of folks from all over are making this relief mission PcolaDan,and we wanna thank them all..

.."Thanks to everyone for making the portlight relief Mission to Haiti a continuing success"...

and to the crew of...The schooner "Liberty", fair winds, a Guiding Star and Godspeed.

Member Since: July 3, 2005 Posts: 421 Comments: 127664
Quoting Portlight:
Portlight Haiti relief update
Link


I had just read that, and since I can't comment there, I'll do it here. That is just some AMAZING stuff you guys have accomplished in such a short time. The contacts, the perseverance, the "don't get in our way" attitude is fantastic. Keep up the great work.
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Portlight.org update

The UN sub cluster on disability will convene its' first meeting today in PauP @ 2:30PM local time. We have connected Richard into that. Also, the USAID coordination call on Monday will focus exclusively on disability issues...as the result of our insistence. That call will be followed by a Portlight hosted call of about 15 NGO's on the ground in Haiti with the focus on coordinating our work on scene. We are placing a "Disability Czar" on scene in the next few days who will serve as a focal point and clearinghouse for all disability related activities in Haiti. We have secured the donation of 20,000lbs of instant rice which we will be delivering. Our pipeline of DME into Haiti continues to flow.

The Schooner Liberty sailed from Miami for Jacamel today with a crew of 12 and 10,000lbs of supplies to be distributed there. I spoke with Cap't. Phillip and he assures me Weather Underground is his source of choice for weather information. Liberty will arrive Wednesday in Jacamel...and will also be the method of conveyance for the rice mentioned above.

Member Since: July 3, 2005 Posts: 421 Comments: 127664
Quoting KEEPEROFTHEGATE:
remember we just dont really understand as much as we think we understand

Debate, Confuse, we know actualy nothing, praise ignorance - praise the Oil and Fossil's!
Member Since: September 22, 2005 Posts: 11 Comments: 2032
remember we just dont really understand as much as we think we understand
Member Since: July 15, 2006 Posts: 169 Comments: 53296
Portlight Haiti relief update
Link
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Member Since: July 15, 2006 Posts: 169 Comments: 53296
Member Since: July 15, 2006 Posts: 169 Comments: 53296
Quoting Firesword:
This whole global warming thing is a hoax. Flawed and cooked data, shifted around just to get grant money.. The whole global warming scam is collapsing faster than the Berlin Wall
Member Since: July 15, 2006 Posts: 169 Comments: 53296
Quoting dsauder:
That is right Dr Masters. You are beginning to sound sensible. Water vapor RULES the global warming scene! All this nonsense about carbon dioxide was a bunch of eco-terrorist baloney perpetrated by people who had no real understanding of what really goes on in the big picture. They are just evil schemers wanting to make a buck off of the rest of us.


Member Since: July 15, 2006 Posts: 169 Comments: 53296
The wisdom of Solomon
http://www.realclimate.org/index.php/archives/2010/01/the-wisdom-of-solomon/
Member Since: September 22, 2005 Posts: 11 Comments: 2032
This whole global warming thing is a hoax. Flawed and cooked data, shifted around just to get grant money.. The whole global warming scam is collapsing faster than the Berlin Wall
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That is right Dr Masters. You are beginning to sound sensible. Water vapor RULES the global warming scene! All this nonsense about carbon dioxide was a bunch of eco-terrorist baloney perpetrated by people who had no real understanding of what really goes on in the big picture. They are just evil schemers wanting to make a buck off of the rest of us.
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Quoting P451:
Nice truck Tornadodude. How many mailboxes did you take out with that thing?



haha none actually :p I loved that truck, really regret selling it. had a 305 v8, sounded beautiful
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all so have any one noted how fast this E coast storm is moveing
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Quoting tornadodude:


maybe I just dont understand why it would matter what size the town is

ha yeah, seems like we pass it on pretty quickly too! like last sunday, it was 50 degrees. monday, 25 and two inches of snow Lol


Thanks...this time!

I think(?) I know what Taz is thinking about, re big city. We don't get the concrete-heat effect, like Phoenix (that is not the correct terminology, because I can't think of it on the fly).

We are not really a big city, DC proper isn't very large -- add in the MD/VA suburbs and we do become quite large, and Baltimore isn't far.

We are very fortunate to have a great system of parks, creeks, dams, preserves and other natural retreats. Only the highways and traffic -- and of course all the "hot air" coming from Capitol Hill, make it uncomfortable to live here at times!! :)

ADD: Oh yeah, and the afore-mentioned humidity can make it uncomfortable, too! Our spring and fall are often just perfect, imo.
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un less one of them biger city are in one of them colder states then its not that rare too see snow fall be low temper in the teens
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the biger the city the wammer the temper is the smaller the city the colder it gets so in other words snowing in a big city like DC with temper of 18 is vary rare
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Quoting Tazmanian:




may be you seen it for a small town or some what biger town but where talking about a big city wish i find odd of a temper with snow falling at 18


maybe I just dont understand why it would matter what size the town is

Quoting AwakeInMaryland:


We often get Indiana's weather 1 or 2 days later.
I've been stuck on the ground at National Airport, talking to a friend in Indiana, when we'd just received a weather "present" from her! :)


ha yeah, seems like we pass it on pretty quickly too! like last sunday, it was 50 degrees. monday, 25 and two inches of snow Lol
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Quoting AwakeInMaryland:


It's the humidity -- it's always the humidity when you live on swampland, lol. That's our standard answer for anything; not much surprises us.

Seriously, it is a bit weird, Taz. DOES it have anything to do with the humidity, which is currently at 89 percent?




not sure
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Quoting tornadodude:


I personally dont think it is odd, Ive seen it snow plenty of times when it has been in the teens


We often get Indiana's weather 1 or 2 days later.
I've been stuck on the ground at National Airport, talking to a friend in Indiana, when we'd just received a weather "present" from her! :)
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Quoting tornadodude:


I personally dont think it is odd, Ive seen it snow plenty of times when it has been in the teens




may be you seen it for a small town or some what biger town but where talking about a big city wish i find odd of a temper with snow falling at 18
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Quoting TheCaneWhisperer:



Steeda, Rouch, P51


The P51 was a supercharged monster modeled after the WWII P51 Mustang fighter jet. Still building them today. Roush is another popular upgrade

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Quoting Tazmanian:
dont you guys find it odd with snow falling inn DC right now in DC the temper for them is 18 and they are geting snow dont you guys think it odd for them to be geting snow at a temper of 18??? i find it kind of rare and not some in you see or find all the time


I personally dont think it is odd, Ive seen it snow plenty of times when it has been in the teens
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Quoting Tazmanian:
dont you guys find it odd with snow falling inn DC right now in DC the temper for them is 18 and they are geting snow dont you guys think it odd for them to be geting snow at a temper of 18??? i find it kind of rare and not some in you see or find all the time


It's the humidity -- it's always the humidity when you live on swampland, lol. That's our standard answer for anything; not much surprises us.

Seriously, it is a bit weird, Taz. DOES it have anything to do with the humidity, which is currently at 89 percent?

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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.