When we see records being broken and unprecedented events such as this, the onus is on those who deny any connection to climate change to prove their case. Global warming has fundamentally altered the background conditions that give rise to all weather. In the strictest sense, all weather is now connected to climate change. Kevin Trenberth
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Geophysical Research Letters, 39 (2012) L19804; doi: 10.1029/2012GL053268
The recent shift in early summer Arctic atmospheric circulation
Key Points
There is an apparent sustained shift in early summer Arctic winds since 2007
Such Arctic changes are linked to increased North American atmospheric blocking
Highlights potential connectivity of Arctic climate and mid-latitude weather
James E. Overland (Pacific Marine Environmental Laboratory, NOAA, Seattle, WA, U.S.A.),Jennifer A. Francis (Institute of Marine and Coastal Sciences, Rutgers, State University of New Jersey, New Brunswick, NJ, U.S.A.),Edward Hanna (Department of Geography, University of Sheffield, Sheffield, U.K.)and Muyin Wang (Joint Institute for the Study of the Atmosphere and Oceans, University of Washington, Seattle, WA, U.S.A.)
Abstract
The last six years (2007–2012) show a persistent change in early summer Arctic wind patterns relative to previous decades. The persistent pattern, which has been previously recognized as the Arctic Dipole (AD), is characterized by relatively low sea-level pressure over the Siberian Arctic with high pressure over the Beaufort Sea, extending across northern North America and over Greenland. Pressure differences peak in June. In a search for a proximate cause for the newly persistent AD pattern, we note that the composite 700-hPa geopotential height field during June 2007–2012 exhibits a positive anomaly only on the North American side of the Arctic, thus creating the enhanced mean meridional flow across the Arctic. Coupled impacts of the new persistent pattern are increased sea ice loss in summer, long-lived positive temperature anomalies, and ice sheet loss in west Greenland, and a possible increase in Arctic–subarctic weather linkages through higher-amplitude upper-level flow. The North American location of increased 700-hPa positive anomalies suggests that a regional atmospheric blocking mechanism is responsible for the presence of the AD pattern, consistent with observations of unprecedented high-pressure anomalies over Greenland since 2007.
Received 24 July 2012; accepted 31 August 2012; published 10 October 2012.
Overland, J. E., J. A. Francis, E. Hanna, and M. Wang. (2012). The recent shift in early summer Arctic atmospheric circulation, Geophys. Res. Lett., 39, L19804, doi:10.1029/2012GL053268.
SST and circulation trend biases cause an underestimation of European precipitation trends
R. van Haren (KNMI), G. J. van Oldenborgh (KNMI), G. Lenderink (KNMI), M. Collins (University of Exeter, Exeter, U.K.) and W. Hazeleger (KNMI)
Abstract
Clear precipitation trends have been observed in Europe over the past century. In winter, precipitation has increased in northwestern Europe. In summer, there has been an increase along many coasts in the same area. Over the second half of the past century precipitation also decreased in southern Europe in winter.
An investigation of precipitation trends in two multi-model ensembles including both global and regional climate models shows that these models fail to reproduce the observed trends. In many regions the model spread does not cover the trend in the observations.
In contrast, regional climate model (RCM) experiments with observed boundary conditions reproduce the observed precipitation trends much better. The observed trends are largely compatible with the range of uncertainties spanned by the ensemble, indicating that the boundary conditions of RCMs are responsible for large parts of the trend biases. We find that the main factor in setting the trend in winter is atmospheric circulation, for summer sea surface temperature (SST) is important in setting precipitation trends along the North Sea and Atlantic coasts. The causes of the large trends in atmospheric circulation and summer SST are not known. For SST there may be a connection with the well-known ocean circulation biases in low-resolution ocean models. A quantitative understanding of the causes of these trends is needed so that climate model based projections of future climate can be corrected for these precipitation trend biases.
A link between Arctic sea ice and recent cooling trends over Eurasia
S. D. Outten and I. Esau (G. C. Rieber Climate Institute, Nansen Environmental and Remote Sensing Center, Thormhlensgt. 47, 5006 Bergen, Norway)
Abstract
A band of cooling that extends across mid-latitude Eurasia is identified in the wintertime surface air temperatures of the latest ECMWF reanalysis. This cooling is related to extreme warming around the Kara Sea through changes in the meridional temperature gradient. Surface temperatures in the Arctic have risen faster than those at lower latitudes, and as the Arctic warming increases, this north–south temperature gradient is weakened. This change in the meridional temperature gradient causes a decrease in the westerly winds that help maintain the mild European climate by transporting heat from the Atlantic. Since decreasing sea ice concentrations have been shown to be a driving factor in Arctic amplification, a singular value decomposition analysis is used to confirm the co-variability of the Arctic sea ice, including the Kara Sea, and the temperatures over the mid-latitude Eurasia. These findings suggest that decreasing sea ice concentrations can change the meridional temperature gradient and hence the large-scale atmospheric flow of the Northern Hemisphere.
I find it systematically tends to get underplayed and it often gets underplayed by my fellow scientists. Because one of the opening statements, which I’m sure you’ve probably heard is “Well you can’t attribute a single event to climate change.” But there is a systematic influence on all of these weather events now-a-days because of the fact that there is this extra water vapor lurking around in the atmosphere than there used to be say 30 years ago. It’s about a 4% extra amount, it invigorates the storms, it provides plenty of moisture for these storms and it’s unfortunate that the public is not associating these with the fact that this is one manifestation of climate change. And the prospects are that these kinds of things will only get bigger and worse in the future.
That’s Dr. Kevin Trenberth, head of the Climate Analysis Section at the National Center for Atmospheric Research, on the warming-deluge connection. I interviewed him a couple weeks ago about Tennessee’s 1000-year deluge aka Nashville’s ‘Katrina’.
Here is the audio (plus transcript) of the interview with one of the country leading scientific authorities on climate change and extreme weather:
Part I:
Part II:
Note: I sent the transcript to Dr. Trenberth, so it has been corrected in a couple of places. You can find links to the studies Dr. Trenberth refers to here: “Northeast hit by record global-warming-type deluge.” Before the interview, I sent him this jaw-dropping figure (explained here):
Joseph Romm: I wanted to talk mostly about this Tennessee rain storm which didn’t get a lot of attention. And the potential link to global warming got virtually no attention at all. I sent you this link that the National Weather Service and NOAA put together of just how extreme an event it was.
Kevin Trenberth: Yes I just looked at it.
JR: This seems astounding to me. I’ve never seen anything like this. I’d just be interested in your thoughts on the unprecedented nature of this storm, and how you would characterize it in an age where scientists predicted as we warmed we’d get these kind of extreme deluges.
KT: That’s indeed true and that’s consistent with the expectations with regards to global warming. It’s also consistent with things that we’ve already seen … including happening in the US. So there was a study a few years ago now, that only went through 2002 but it was looking at the 20th century and at that point the average rainfall over the 48 contiguous states had gone up 7% but the heavy rainfall events had gone up 20%. And so the heavy rainfall events have been documented as increasing across the United States.
There was a more recent study that looked at somewhat different statistics and showed that the really heavy rainfall events — the top 1% and the top 0.3% — had gone up at even more alarming levels something like 27% as I recall over the last 30 or 40 years [actually 1967 to 2006]. And indeed most of those changes have occurred since about 1970.
Now the physical cause for this is very much related to the water vapor that flows into these storms. And these kinds of storms, well all storms for that matter, reach out on average — this is very much a gross average — about 4 times the radius or 16 times the area of the region that’s precipitating, the rain. And for these kinds of storms a lot of the moisture is coming out of the sub-tropical Atlantic and even the tropical Atlantic; some of it comes out of the Gulf of Mexico. And so the moisture actually travels about 2000 miles where it gets caught up in these storms and then it rains down. And the key thing is, that in the tropical and sub-tropical Atlantic the sea temperatures are at very high levels and in fact they’re the highest on record at the moment right in the eastern tropical Atlantic. It’s going to be interesting to see what that does for this hurricane season coming up.
For every one degree Fahrenheit increase in sea temperature, the water holding capacity for the atmosphere goes up by 4%. And since the 1970s on average there’s about a 4% increase in water vapor over the Atlantic Ocean and when that gets caught into a storm, it invigorates the storm so the storm itself changes, and that can easily double the influence of that water vapor and so you can get up to an 8% increase, straight from the amount of water vapor that’s sort of hanging around in the atmosphere. This is reasonably well established.
And so then, when you have the right conditions, and in the spring time, these conditions tend to occur, and the storm stalls a little bit (it ran up against a roadblock for a while), then this is one of the consequences.
So although a lot of aspects of this is the sort of thing that happens is weather and natural variability, one could easily argue that up to about a 10% enhancement of this is associated with global warming. And possibly even more in terms of some of the other things that are going on but which are much harder to pin down. So that’s the link.
It’s directly related to the fact that there’s more water vapor in the atmosphere. There’s warmer sea temperatures over the ocean that provide that moisture in the atmosphere. And then the right storm comes along, the right conditions, especially slow moving, and bingo.
JR: Stu Ostro, the senior meteorologist of the Weather Channel, he wrote a post on the storm that hit Georgia in the fall, and he talked about the atmospheric warming resulting in increase in the 1000 to 500 millibar thickness creating … basically an increase in 500 millibar heights.
KT: Right, It’s warmer in the lower half of the atmosphere, yes.
JR: This, what he called, “exceptionally strong ridges of high pressure sometimes accompanied by strong, persistent cut off flows…. So this is sort of another aspect of the climate change.
KT: Yes, The change in the storm tracks, or the change in the weather patterns is an aspect of it. That’s a little harder to pin down as directly relating to global warming. There might be some natural variability aspects to that, but you’ve only got to look around and so last year, if my memory serves me right, there was extensive flooding along the Mississippi River, and they were talking about 500 year storms, and yet in 1993 they had similar flooding along the Mississippi River, and again they were talking about 500 year storms. Here you are having these 500 year storms so to speak in slightly different areas but at the same time of year. This is a part of a pattern that exists.
We’ve seen other examples out in Seattle last year, and also of course the flooding in New England and the exceptionally heavy snow storms in Washington, DC, this year….
The same mechanism actually applies to the heavy snow, all you have to do is have the right weather conditions and for it to be cold enough and this precipitation just turns into snow. The very heavy snowfall amounts are actually related to the fact that the moisture that’s coming into that region is coming off of the tropical or sub tropical Atlantic where there’s abundant moisture and more moisture than there used to be: demonstrably more moisture than there used to be 30 years ago. So there’s a number of other examples you can point to as well.
JR: It seems to me the media hasn’t figured out a way to talk about this so they often just don’t talk about it at all.
KT: That’s correct.
JR: And as a result the public never learns the connection to climate change. I’m just wondering if you have any comments about that and what you would suggest is the right way to talk about it and the like.
KT:I find it systematically tends to get underplayed and it often gets underplayed by my fellow scientists. Because one of the opening statements, which I’m sure you’ve probably heard is “Well you can’t attribute a single event to climate change.” But there is a systematic influence on all of these weather events now-a-days because of the fact that there is this extra water vapor lurking around in the atmosphere than there used to be say 30 years ago. It’s about a 4% extra amount, it invigorates the storms, it provides plenty of moisture for these storms and it’s unfortunate that the public is not associating these with the fact that this is one manifestation of climate change. And the prospects are that these kinds of things will only get bigger and worse in the future.
KT: That’s right and so the weather events happened, the spring storms happen, you certainly expect these kinds of things at this time of year, but the odds are that when these happen getting flooding out of them is increasing substantially. And most of the time, even if there is this modest increase of say 5% or 5% to 10%, it’s still within the realm of natural variability frequently, but every so often you go outside of the realm of natural variability and that’s how you get these 100-, 500-, 1,000-year storm events that are occurring. And so this becomes the straw that breaks the camel’s back. Were just seeing more and more instances of that and the odds of that kind of thing happening are increasing.
JR: Yes, “Straw that breaks the camels back” is a phrase you used about Katrina as I recall.
KT: Again it’s the same sort of thing, where there’s an enhancement, there’s a global warming component. You can argue that it’s not the dominant component, especially on an individual storm like Katrina. But then in the 2005 season was just so exceptional, we had all these storms that went off in to the Greek alphabet, there was Rita and Wilma. Wilma, the strongest recorded storm on record. And Ophelia, that year, that churned around for 3 or 4 days right off of there coast of the Carolinas there. So it was not any individual storm there that you would really want to point to, but all these storms collectively are a clear indication that there was a warming component and at that points to the sea temperatures in the Gulf, and the Caribbean and in the tropical Atlantic which were by far the highest on record, and they were the fuel for that. As I say, this year in the Eastern Atlantic it’s even higher than that. But this year the Caribbean and the Gulf are somewhat cooler than average, and so how this hurricane season pans out is going to be an interesting one to see. But those are the factors that come into play.
JR: We’ve only warmed a little bit so far compared to what some of the models project. If we don’t reserve emissions trends soon, what kind of storms are we looking at in a few decades?
KT: The key number is this number in this case, which is pretty rock solid. For a 1 ° F increase in air temperature the water holding capacity goes up by 4%. Pretty close to 4%. And so if the sea temperatures go up by one degree, as they have, then the air temperatures probably go up a little bit more than that in fact. And so when you start talking about 3, 4, 5 degrees then you’re talking about 20% increases in the water vapor in the atmosphere.
The way in which we think this is going to happen is that the intervals between storms will be longer, but then when you do have the storms they are apt to be a doozie. When it rains it pours, so to speak. So you can really get deluges, and there are times when you have longer dry spells in between so there’s the risk of drought if you happen to miss these storms. And they are very much of a hit and miss nature. But then when you do get hit by them suddenly you’ve got a deluge.
And so this is a real challenge as to how you deal with that from a water management standpoint, from a drainage standpoint. In some sense, when this happens you’ve got all this water there, and water can actually be a valuable resource if you can put it into a reservoir, or a lake or something like that where you can use it in the future: it actually gets transitioned to a valuable resource. In the mean time, some of it just inundates areas and causes a major problem. And that relates to what kind of drainage systems you have, what kind of culverts you have. One of the ways in which city councils and the Corp of Engineers manage these things is to always build structures to deal with these things. But another key part of it is: can you put the water somewhere where you can use it in the future? Because these longer dry spells in between times are something else you’re going to have to contend with.
JR: Yeah and the issue is, of course, the rain when it comes down in the deluges , it overwhelms the capacity of the storm drainage and you get these runoff… We have so many combined sewage/storm water systems, we may have to rethink that…
KT: If they’re combined in that nature then you have water quality problems and you can get disease and cholera and things like that which can come out of that kind of situation. It’s the same thing even in open fields, that a lot more water gets transported across the surface of the field, and so all of the feces from animals can contaminate the water and cause various kinds of water contamination problems.
Edited by Barbara J. Finlayson-Pitts, University of California, Irvine, Irvine, CA, and approved November 25, 2009 (received for review October 20, 2009.
Abstract
We present laboratory studies and field observations that explore the role of aminium salt formation in atmospheric nanoparticle growth. These measurements were performed using the Thermal Desorption Chemical Ionization Mass Spectrometer (TDCIMS) and Ultrafine Hygroscopicity Tandem Differential Mobility Analyzers. Laboratory measurements of alkylammonium—carboxylate salt nanoparticles show that these particles exhibit lower volatilities and only slightly lower hygroscopicities than ammonium sulfate nanoparticles. TDCIMS measurements of these aminium salts showed that the protonated amines underwent minimal decomposition during analysis, with detection sensitivities comparable to those of organic and inorganic deprotonated acids. TDCIMS observations made of a new particle formation event in an urban site in Tecamac, Mexico, clearly indicate the presence of protonated amines in 8–10 nm diameter particles accounting for about 47% of detected positive ions; 13 nm particles were hygroscopic with an average 90% RH growth factor of 1.42. Observations of a new particle formation event in a remote forested site in Hyytiälä, Finland, show the presence of aminium ions with deprotonated organic acids; 23% of the detected positive ions during this event are attributed to aminium salts while 10 nm particles had an average 90% RH growth factor of 1.27. Similar TDCIMS observations during events in Atlanta and in the vicinity of Boulder, Colorado, show that aminium salts accounted for 10–35% of detected positive ions. We conclude that aminium salts contribute significantly to nanoparticle growth and must be accounted for in models to accurately predict the impact of new particle formation on climate.
Nature Reports Climate Change, published online 11 June 2009; doi: 10.1038/climate.2009.55
Abnormal nitrogen
by Alicia Newton, Science324, 5932 (2009)
MEREDITH HASTINGS
Nitrate concentrations in Greenland ice have almost doubled since the onset of the Industrial Revolution, according to scientists. The rise in nitrate is accompanied by a sharp drop in the isotopic signature of the nitrogen, beginning just as humans started pumping nitrogen oxides into the atmosphere.
Meredith Hastings of Brown University and colleagues used a 100-metre-long ice core from Summit, Greenland, to track changes in nitrogen composition over the past three centuries. Beginning in 1850, the isotopic ratio of the nitrogen, which in part reflects the source of the nitrate, began to decline, just as greenhouse gas concentrations were starting to rise in response to the widespread burning of fossil fuels. The sharpest jump in the isotopic ratio came between 1950 and 1980, when emissions also soared. This overall trend would be difficult to explain through changing chemical processes in the snow or atmosphere alone, leaving fossil fuel combustion as the most likely driver.
Nitrogen oxides are among the six greenhouse gases regulated under the Kyoto Protocol. The team hopes that further work will allow them to determine how changes in climate influence natural nitrogen oxide sources.
Lightning storms at mid-latitudes and in the subtropics produce more nitrogen oxides (NOx) than previously thought, finds a new study. What's more, most of the NOx pollution — a precursor to the greenhouse gas ozone — ends up in the upper troposphere, where it has a strong influence on climate.
A team led by Lesley Ott of NASA's Goddard Earth Sciences and Technology Center in Greenbelt, Maryland, used data collected during lightning storms in Germany and the United States between 1985 and 2002, along with a cloud simulation model, to estimate the amount of NOx produced by an average flash of lightning. They found that a single lightning strike produces about 7 kilograms of chemically reactive NOx. Worldwide, this amounts to an annual production of 8.6 million metric tonnes. As none of the data were collected in the tropics — where lightning may yield less NOx per flash — the global estimate may be on the high end, say the researchers.
They speculate, however, that if lightning storms become more frequent in the future, as predicted by some theoretical models, increased NOx in the upper atmosphere could affect global climate change.
See also:
Ott, L., K. Pickering, G. Stenchikov, D. Allen, A. DeCaria, B. Ridley, R.-F. Lin, S. Lang, and W.-K. Tao (2009), Production of lightning NOx and its vertical distribution calculated from 3-D cloud-scale chemical transport model simulations, J. Geophys. Res., doi: 10.1029/2009JD011880, in press.
Nuuk Climate Days 2009 -- Changes of the Greenland Cryosphere Workshop & The Arctic Freshwater Budget International Symposium, Nuuk, Greenland, 25-27 August 2009
Primary author: CHEN, Linling (Nansen-Zhu International research center/Institute of Atmospheric Physics,
Chinese Academy of Sciences), lin-ling.chen@nersc.no ; Co-authors: JOHANNESSEN, Ola M. (Nansen Environmental and Remote Sensing Center); WANG, Huijun (Nansen-Zhu International research center/Institute of Atmospheric Physics, Chinese Academy of Sciences); KHVOROSTOVSKY, Kirill (Nansen Environmental and Remote Sensing Center)
Abstract ID: F4
Greenland Ice Sheet’s elevation change in winter and atmospheric circulation
Data from ERS-1, ERS-2 and Envisat Satellites are analyzed to identify the relationship between winter elevation variations of Greenland ice sheet and sea level pressure during 1993-2007. It is found that the North Pacific oscillation and the North Atlantic oscillation, the two major teleconnection patterns of surface pressure fields in North Hemisphere, both have significant impacts on the Greenland ice sheet winter elevation change by influencing accumulation. In addition, we are evaluating modeled precipitation data over Greenland based on comparison with accumulation data from all available ice core records and meteorological station, in order to better understand how the atmospheric circulation impact the Greenland Ice Sheet’s Elevation.
Nature Geoscience, published online 23 August 2009; doi: 10.1038/ngeo607
Quantification of the troposphere-to-ionosphere charge transfer in a gigantic jet
Steven A. Cummer1, Jingbo Li1, Feng Han1, Gaopeng Lu1, Nicolas Jaugey1, Walter A. Lyons2 and Thomas E. Nelson2
Abstract
Gigantic jets are the clearest manifestation of direct electrical coupling between tropospheric thunderstorms and the ionosphere. They are leaders1, 2, 3 that emerge from electrical breakdown near the top of thunderstorms4 and extend all the way to the lower edge of the ionosphere near 90-km altitude5. By contrast, blue jets6 and other related events7, 8 terminate at much lower altitudes. Gigantic jets have been observed from the ground5, 9, 10 and from orbit11. Some seem to be consistent with an upward-propagating negative discharge of 1,000-2,000 C km total charge moment change 9, but others have not been connected to distinguishable electromagnetic signatures10. Here we report simultaneous low-light video images and low-frequency magnetic field measurements of a gigantic jet that demonstrate the presence and dynamics of a substantial electric charge transfer between the troposphere and the ionosphere. The signatures presented here confirm the negative polarity of gigantic jets4 and constrain the lightning processes associated with them. The observed total charge transfer from the thunderstorm to the ionosphere is 144 C for the assumed channel length of 75 km, which is comparable to the charge transfer in strong cloud-to-ground lightning strokes.
¹Electrical and Computer Engineering Department, Duke University, Durham, NC 27708, U.S.A.
²FMA Research, Inc., Yucca Ridge Field Station, Fort Collins, CO 80524, U.S.A.
Gigantic jets blast electricity into upper atmosphere
The gigantic jet observed by Steven Cummer and his team. The thunderstorm that produced this jet was over 300 kilometres away, below the visible horizon (Image: Steven Cummer)
by Michael Marshall, New Scientist, August 23, 2009
The ancient Greeks might have thought Zeus was furious with heaven itself. The power of lightning strikes that shoot upwards from storm clouds has been measured for the first time – and they turn out to be every bit as powerful as normal lightning.
First caught on camera in 2003, "gigantic jets" shoot upwards from thunderclouds and can reach altitudes above 80 kilometres. But it wasn't until 21 July last year that Steven Cummer at Duke University in Durham, North Carolina, and his colleagues managed to measure the electrical discharge from a single gigantic jet, released from tropical storm Cristobal.
"No one had been very close to one with the right radio instrumentation before," Cummer says. "So we didn't know whether they just petered out without doing anything much, or whether they actually took some charge and dumped it somewhere."
Electric jet
The jet came out of a high storm cloud, beginning at an altitude of about 14 kilometres, and shot upwards for a further 75 kilometres.
At those heights, the atmosphere is a much better electrical conductor than at ground level because of ionising radiation from space. As a result, the jet was able to discharge 144 coulombs of charge into the upper atmosphere in about 1 second.
This is comparable to the charge transferred by a large cloud-to-ground lightning strike.
"It's fantastic that they see such a high charge transfer between the thundercloud and the ionosphere," says Victor Pasko of Pennsylvania State University in University Park.
"There is this newly identified path for discharging the thunderstorm, and a lot of charge can be moved," says Cummer. "In storms that can produce gigantic jets, it might influence what other lightning is happening in the storm."
This time, however, the team found no difference in the rate of ordinary lightning strikes around the time of the gigantic jet. "I'm surprised they saw no drop in lightning rates before or after the jet – but that might be because of the sheer size of the storm," says Pasko.
Gigantic jets are one of a host of new atmospheric phenomena discovered in recent years. Other examples are sprites and blue jets.
Proceedings of the National Academy of Sciences, published online before print August 19, 2009; doi: 10.1073/pnas.0907610106
The physical basis for increases in precipitation extremes in simulations of 21st-century climate change
Paul A. O'Gorman* (Massachusetts Institute of Technology, Cambridge, MA 02139, U.S.A.) and Tapio Schneider (California Institute of Technology, Pasadena, CA 91125, U.S.A.)
Communicated by Kerry A. Emanuel, Massachusetts Institute of Technology, Cambridge, MA; July 14, 2009 (received for review March 24, 2009).
Abstract
Global warming is expected to lead to a large increase in atmospheric water vapor content and to changes in the hydrological cycle, which include an intensification of precipitation extremes. The intensity of precipitation extremes is widely held to increase proportionately to the increase in atmospheric water vapor content. Here, we show that this is not the case in 21st-century climate change scenarios simulated with climate models. In the tropics, precipitation extremes are not simulated reliably and do not change consistently among climate models; in the extratropics, they consistently increase more slowly than atmospheric water vapor content. We give a physical basis for how precipitation extremes change with climate and show that their changes depend on changes in the moist-adiabatic temperature lapse rate, in the upward velocity, and in the temperature when precipitation extremes occur. For the tropics, the theory suggests that improving the simulation of upward velocities in climate models is essential for improving predictions of precipitation extremes; for the extratropics, agreement with theory and the consistency among climate models increase confidence in the robustness of predictions of precipitation extremes under climate change.
Mysterious, glowing clouds appear across America’s night skies
by Alexis Madrigal
Wired Science, July 16, 2009
Mysterious, glowing clouds previously seen almost exclusively in Earth’s polar regions have appeared in the skies over the United States and Europe over the past several days.
Photographers and other sky watchers in Omaha, Paris, Seattle, and other locations have run outside to capture images of what scientists call noctilucent (”night shining”) clouds. Formed by ice literally at the boundary where the earth’s atmosphere meets space 50 miles up, they shine because they are so high that they remain lit by the sun even after our star is below the horizon.
The clouds might be beautiful, but they could portend global changes caused by global warming. Noctilucent clouds are a fundamentally new phenomenon in the temperate mid-latitude sky, and it’s not clear why they’ve migrated down from the poles. Or why, over the last 25 years, more of them are appearing in the polar regions, too, and shining more brightly.
“That’s a real concern and question,” said James Russell, an atmospheric scientist at Hampton University and the principal investigator of an ongoing NASA satellite mission to study the clouds. “Why are they getting more numerous? Why are they getting brighter? Why are they appearing at lower latitudes?”
Nobody knows for sure, but most of the answers seem to point to human-caused global atmospheric change.
BLOGGER'S NOTE: This marvelous photo of the Eiffel Tower on Bastille Day with exploding fireworks and noctilucent clouds was taken by flickr user Breff. Wired Science ripped it off his flickr without asking permission, which is how it came to be posted here, because I ripped off Wired Science without asking their permission. It is not at all clear to me that those are noctilucent clouds in the background, but hey, this is a fantastic photo, any way you look at it. The original can be found at: http://www.flickr.com/photos/breff/3722358660/in/set-72157621611065989/
Not only that, but photographer Breff has a series of fab photos of the Eiffel Tower and fireworks here, and if I had money and could buy the poster and put it up in my house, I would, no kidding, they are that cool: http://www.flickr.com/photos/breff/3721417815/in/set-72157621611065989/
Noctilucent clouds were first observed in 1885 by an amateur astronomer. No observations of anything resembling noctilucent clouds before that time has ever been found. There is no lack of observations of other phenomena in the sky, so atmospheric scientists are fairly sure that the phenomenon is recent, although they are not sure why.
Over the last 125 years, scientists have learned how the clouds form. At temperatures around minus 230 °F, dust blowing up from below or falling into the atmosphere from space provides a resting spot for water vapor to condense and freeze. Right now, during the northern hemisphere’s summer, the atmosphere is heating up and expanding. At the outside edge of the atmosphere, that actually means that it’s getting colder because it’s pushed farther out into space.
It’s not hard to see how a warming Earth could change those dynamics: as the globe heats up, the top of the atmosphere should get colder.
“The prevailing theory and most plausible explanation is that CO2 buildup, at 50 miles above the surface, would cause the temperature decrease,” Russell said. He cautioned, however, that temperature observations remain inconclusive.
The global changes that appear to be reshaping noctilucent cloud distribution could be much more complex, said Vincent Wickwar, an atmospheric scientist at Utah State University whose team was first to report a mid-latitude noctilucent cloud in 2002. Temperature does not explain their observations from around 42 degrees latitude.
“To get the noctilucent clouds you need temperatures that are about 20 degrees Kelvin colder than what we see on average up there,” Wickwar said. “We may have effects from CO2 or methane but it would only be a degree or a fraction of a degree.”
Instead, Wickwar’s explanation is that a vertical atmospheric wave discovered in their LIDAR data lowered the temperature in the region above their radar installation near Logan, Utah. But then you have to ask, he noted, “Where’d the wave come from?”
They don’t really have an answer yet. Other facilities around the world with similar LIDAR capacity haven’t reported similar waves. And the Rocky Mountains, near Wickwar’s lab, can cause atmospheric waves, which could be a special feature of his location.
Other theories abound to explain the observed changes in the clouds. Human-caused increases in atmospheric methane, which oxidizes into carbon dioxide and water vapor, could be providing more water for ice in the stratosphere. Increases in the amount of cosmic or terrestrial dust in the stratosphere could also increase the number of brightly shining clouds.
Two years into Russell’s NASA project, more questions exist than firm answers. They will have at least three and a half more years, though, to gather good data on upper atmospheric dynamics.
The recent observations of noctilucent clouds at all kinds of latitudes provide an extra impetus to understand what is going on up there. Changes are occurring faster than scientists can understand their causes.
“I suspect, as many of us feel, that it is global change, but I fear we don’t understand it,” Wickwar said. “It’s not as simple as a temperature change.”
Image: 1. The sky over Omaha on July 14th, 2009, snapped by Mike Hollingshead at Extreme Instability 2. Noctilucent clouds lit up the Paris sky behind the Bastille Day fireworks show at the Eiffel Tower. Captured by flickr user, breff 3. A rendering of the noctilucent clouds created from data obtained by Russel’s NASA project, AIM. Video: NASA.
Hello, You've used one of my photos in your blog. This photo is protected under a Creative Commons Attribution-Noncommercial-No Derivative Works 2.0 Generic license. You have cropped the photo (thus removing my logo) which violates the licence. The photo doesn't link back to my site (because you copy-pasted it from WIRED). And a tiny link at the bottom of the page is definitely pushing the definition of Attribution. If you wish to continue using this photo, please use the uncropped version and link it directly to my site using the 'blog this' link creator on top of the photo in flickr (http://www.flickr.com/photos/breff/3722358660/in/set-72157621611065989/).
If you're not willing to respect the licence please stop using the photo.
I did not crop your photo. Somehow it occurred when I did a screen capture from the Wired article. I am myself very surprised that this occurred, and am only seeing it because you pointed it out to me.
Please note that this blog of mine has no commercial purpose whatsoever. I am only trying to disseminate as much information as possible concerning climate change.
I am fully aware that I violate copyright all the time.
But I would never crop out someone's watermark -- I used to be a photographer myself many years ago.
I will see if I can get the entire image onto this post, ok?
July 21, 2009 2:00 PM
N.B. It seems the cropping was caused by the allowable limit of text width on the pages of the blog.
Proceedings of the National Academy of Sciences, 2009, Vol. 106, No. 27, pp. 10949-10954; published online before print June 22, 2009; doi: 10.1073/pnas.0902817106
The large contribution of projected HFC emissions to future climate forcing
Edited by Mark H. Thiemens, University of California at San Diego, La Jolla, CA, and approved May 14, 2009 (received for review March 13, 2009)
Abstract
The consumption and emissions of hydrofluorocarbons (HFCs) are projected to increase substantially in the coming decades in response to regulation of ozone depleting gases under the Montreal Protocol. The projected increases result primarily from sustained growth in demand for refrigeration, air-conditioning (AC) and insulating foam products in developing countries assuming no new regulation of HFC consumption or emissions. New HFC scenarios are presented based on current hydrochlorofluorocarbon (HCFC) consumption in leading applications, patterns of replacements of HCFCs by HFCs in developed countries, and gross domestic product (GDP) growth. Global HFC emissions significantly exceed previous estimates after 2025 with developing country emissions as much as 800% greater than in developed countries in 2050. Global HFC emissions in 2050 are equivalent to 9–19% (CO2-eq. basis) of projected global CO2 emissions in business-as-usual scenarios and contribute a radiative forcing equivalent to that from 6–13 years of CO2 emissions near 2050. This percentage increases to 28–45% compared with projected CO2 emissions in a 450-ppm CO2 stabilization scenario. In a hypothetical scenario based on a global cap followed by 4% annual reductions in consumption, HFC radiative forcing is shown to peak and begin to decline before 2050.
Author contributions: G.J.M.V., D.W.F., J.S.D., M.M., and S.O.A. designed research; G.J.M.V. performed research; G.J.M.V. analyzed data; and G.J.M.V., D.W.F., J.S.D., M.M., and S.O.A. wrote the paper. This article contains supporting information online at www.pnas.org/cgi/content/full/0902817106/DCSupplemental.
↵* McFarland M (2008) Potential climate benefits of a global cap and reduction agreement for HFCs. Presentation at 20th meeting of the Parties to the Montreal Protocol, Doha, Qatar.
Freely available online through the PNAS open access option.
Ozone hole has unforeseen effect on ocean carbon sink
by Kate Ravilious, NewScientist, June 26, 2009
The Southern Ocean has lost its appetite for carbon dioxide, and now it appears that the ozone hole could be to blame.
The Antarctic ozone hole (Image: NASA / Goddard Space Flight Center / SVS)
In theory, oceans should absorb more CO2 as levels of the gas in the atmosphere rise. Measurements show that this is happening in most ocean regions, but strangely not in the Southern Ocean, where carbon absorption has flattened off. Climate models fail to reproduce this puzzling pattern.
The Southern Ocean is a major carbon sink, guzzling around 15% of CO2 emissions. However, between 1987 and 2004, carbon uptake in the region was reduced by nearly 2.5 billion tonnes – equivalent to the amount of carbon that all the world's oceans absorb in one year.
Premature effect
To figure out what is going on, Andrew Lenton, from the University of Pierre and Marie Curie in Paris, France, and his colleagues created a coupled ocean and atmosphere climate model, to investigate carbon absorption in oceans. Crucially, they included changes in the concentration of stratospheric ozone since 1975.
By running their model with and without the ozone depletion since 1975, Lenton and his colleagues were able to show that the ozone hole is responsible for the Southern Ocean's carbon saturation.
The effect could be down to the way decreasing stratospheric ozone and rising greenhouse gases are altering the radiation balance of the Earth's atmosphere. This has been predicted to alter and strengthen the westerly winds that blow over the Southern Ocean.
"We expected this transition to a windier regime, but it has occurred much earlier than we thought, seemingly because of the ozone hole," says Lenton.
'Unexpected effect'
Stronger surface winds enhance circulation of ocean waters, encouraging carbon-rich waters to rise from the deep, limiting the capability of surface water to absorb carbon from the atmosphere. Furthermore, the higher carbon levels in surface waters make them more acidic – bad news for many forms of ocean life, such as coral and squid.
"This result illustrates how complex the chain of cause and effect can be in the Earth system. No one would ever have predicted from first principles that increasing CFCs would have the effect of decreasing uptake of ocean carbon dioxide," says Andrew Watson, from the University of East Anglia, U.K.
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