Volcanic Winter

By: Dr. Jeff Masters , 1:18 PM GMT on April 24, 2009

"The sun was dark and its darkness lasted for eighteen months; each day it shone for about four hours; and still this light was only a feeble shadow; the fruits did not ripen and the wine tasted like sour grapes." As this Michael the Syrian quote regarding the weather of 536 A.D. demonstrates, a climate catastrophe that blots out the sun can really spoil your day. Procopius of Caesarea remarked: "During this year [536 A.D.] a most dread portent took place. For the sun gave forth its light without brightness. and it seemed exceedingly like the sun in eclipse, for the beams it shed were not clear." Many documents from 535 - 536 A.D.--the time of King Arthur in Britain--speak of the terrible "dry fog" or cloud of dust that obscured the sun, causing widespread crop failures in Europe, and summer frosts, drought, and famine in China. Tree ring studies in Europe confirm several years of very poor growth around that time, and ice cores from Greenland and Antarctica show highly elevated levels of atmospheric sulfuric acid dust existed.

Though some scientists believe the climate calamity of 535-536 A.D. was due to a comet or asteroid hitting the Earth, it is widely thought that the event was probably caused by the most massive volcanic eruption of the past 1500 years. This eruption threw so much sulfur dioxide (SO2) gas into the stratosphere that a "Volcanic Winter" resulted. Sulfur dioxide reacts with water to form sulfuric acid droplets (aerosol particles), which are highly reflective and reduce the amount of incoming sunlight. The potential eruption that led to the 535 - 536 A.D. climate calamity would have likely been a magnitude 7 event on the Volcanic Explosivity Index (VEI)--a "super colossal" eruption that one can expect to occur only once every 1000 years. The Volcanic Explosivity Index is a logarithmic scale like the Richter scale used to rate earthquakes, so a magnitude 7 eruption would eject ten times more material than the two largest eruptions of the past century--the magnitude 6 eruptions of Mt. Pinatubo in the Philippines (1991) and Novarupta in Alaska (1912).

Figure 1. An 18 km-high volcanic plume from one of a series of explosive eruptions of Mount Pinatubo beginning on 12 June 1991, viewed from Clark Air Base (about 20 km east of the volcano). Three days later, the most powerful eruption produced a plume that rose nearly 40 km, penetrating well into the stratosphere. Pinatubo's sulfur emissions cooled the Earth by about 1°F (0.5°C) for 1 - 2 years. (Photograph by David H. Harlow, USGS.)

Super-colossal eruptions
There has been only one other magnitude 7 "super-colossal" eruption in the past 1500 years--the massive eruption of the Indonesian volcano Tambora in 1815. The sulfur pumped by this eruption into the stratosphere dimmed sunlight so extensively that global temperatures fell by about 2°F (1°C) for 1 - 2 years afterward. This triggered the famed Year Without a Summer in 1816. Killing frosts and snow storms in May and June 1816 in Eastern Canada and New England caused widespread crop failures, and lake and river ice were observed as far south as Pennsylvania in July and August. The Tambora eruption was about 40% smaller than the 535 - 536 A.D. event, as measured by the number of sulfur aerosol particles deposited in Greenland ice cores.

In an article published in 2008 in the American Geophysical Union journal EOS, Dr. Ken Verosub of the University of California, Davis Department of Geology estimated that future eruptions capable of causing "Volcanic Winter" effects severe enough to depress global temperatures by 2°F (1°C) and trigger widespread crop failures for 1 - 2 years afterwards should occur about once every 200 - 300 years. Even a magnitude 6 eruption, such as the 1600 eruption of the Peruvian volcano Huaynaputina, can cause climatic change capable of killing millions of people. The Huaynaputina eruption is blamed for the Russian famine of 1601-1603, which killed over half a million people and led to the overthrow of Tsar Boris Godunov. Thankfully, the climatic impacts of all of these historic magnitude 6 and 7 eruptions have been relatively short-lived. After about two years, the sulfuric acid aerosol particles have settled out of the stratosphere, returning the climate to its former state.

Mega-colossal eruptions
Even more extreme eruptions have occurred in Earth's past--eruptions ten times more powerful than the Tambora eruption, earning a ranking of 8 out of 8 on the Volcanic Explosivity Index (VEI). These "mega-colossal" eruptions occur only about once every 10,000 years, but have much longer-lasting climatic effects and thus are a more significant threat to human civilization. According to the Toba Catastrophe Theory, a mega-colossal eruption at Toba Caldera, Sumatra, about 74,000 years ago, was 3500 times greater than the Tambora eruption. According to model simulations, an eruption this large can pump so much sulfur dioxide gas into the stratosphere that the atmosphere does not have the capacity to oxidize all the SO2 to sulfuric acid aerosol. The atmosphere oxidizes as much SO2 as it can, leaving a huge reservoir of SO2 in the stratosphere. This SO2 gradually reacts to form sulfuric acid as the OH radicals needed for this reaction are gradually produced. The result is a much longer-lasting climate effect than the 1 - 2 years that the magnitude 6 and 7 events of 535, 1600, 1815, and 1991 lasted. A magnitude 8 eruption like the Toba event can cool the globe for 6 - 10 years (Figure 3), which may be long enough to trigger an ice age--if the climate is already on the verge of tipping into an ice age. Rampino and Self (1992) argued that the sulfur aerosol veil from Toba was thick and long-lasting enough to cool the globe by 3 - 5°C (5 - 9°F), pushing the climate--which was already cooling and perhaps headed towards an ice age--into a full-scale ice age. They suggested that the response of Canada to the volcano played a particularly important role, with their model predicting a 12°C (22°F) reduction in summer temperatures in Canada. This would have favored the growth of the Laurentide ice sheet, increasing the reflectivity (albedo) of the Earth, reflecting more sunlight and reducing temperatures further. The controversial Toba Catastrophe Theory asserts that the resulting sudden climate change reduced the Earth's population of humans to 1,000 - 10,000 breeding pairs. More recent research has shed considerable doubt on the idea that the Toba eruption pushed the climate into an ice age, though. Oppenheimer (2002) found evidence supporting only a 2°F (1.1°C) cooling of the globe, for the 1000 years after the Toba eruption. Zielinski et al. (1996) argued that the Toba eruption did not trigger a major ice age--the eruption merely pushed the globe into a cool period that lasted 200 years. Interestingly, a previous super-eruption of Toba, 788,000 years ago, coincided with a transition from an ice age to a warm period.

Figure 2. The 100x30 square kilometer Toba Caldera is situated in north-central Sumatra around 200 km north of the Equator. It is comprised of four overlapping calderas aligned with the Sumatran volcanic chain. Repeated volcanic cataclysms culminated in the stupendous expulsion of the Younger Toba Tuff around 74,000 years ago. The lake area is 100 square kilometers. Samosir Island formed as a result of subsequent uplift above the evacuated magma reservoir. Such resurgent domes are typically seen as the concluding phase of a large eruption. Landsat Enhanced Thematic Mapper Plus (ETM+) browse images for path/row 128/58 (6 September 1999) and 129/58 (21 January 2001) from http://landsat7.usgs.gov/. Copyright USGS. Image source: Oppenheimer, C., 2002, "Limited global change due to the largest known Quaternary eruption, Toba 74 kyr BP?"Quaternary Science Reviews, 21, Issues 14-15, August 2002, Pages 1593-1609.

Figure 3. Total mass of sulfur dioxide and sulfate aerosol in the stratosphere (heavy solid and dotted lines, respectively) modeled for a 6 petagram stratospheric injection of SO2. Observed SO2 and aerosol mass for the 1991 Pinatubo eruption are shown for comparison. The much larger amount of SO2 in the Toba simulation soaks up all available oxidants in the stratosphere leading to a much longer lifetime of SO2 and, in turn, prolonging the manufacture of sulfate aerosol. Data from Read et al. (1993) and Bekki et al. (1996). Image source: Oppenheimer, C., 2002, "Limited global change due to the largest known Quaternary eruption, Toba 74 kyr BP?"Quaternary Science Reviews, 21, Issues 14-15, August 2002, Pages 1593-1609.

When can we expect the next mega-colossal eruption?
Given the observed frequency of one mega-colossal magnitude 8 volcanic eruption every 1.4 million years, the odds of another hitting in the next 100 years is about .014%, according to Mason et al., 2004. This works out to a 1% chance over the next 7200 years. Rampino (2002) puts the average frequency of such eruptions at once every 50,000 years--about double the frequency with which 1-km diameter comets or asteroids capable of causing a similar climatic effect hit the Earth. A likely location for the next mega-colossal eruption would be at the Yellowstone Caldera in Wyoming, which has had magnitude 7 or 8 eruptions as often as every 650,000 years. The last mega-colossal eruption there was about 640,000 years ago. But don't worry, the seismic activity under Yellowstone Lake earlier this year has died down, and the uplift of the ground over the Yellowstone caldera that was as large as 7 cm/yr (2.7 inches/yr) between 2004 - 2006 has now fallen to 4 cm/yr, according to the Yellowstone Volcano Observatory. The USGS states that "the Yellowstone volcanic system shows no signs that it is headed toward such an eruption. The probability of a large caldera-forming eruption within the next few thousand years is exceedingly low".

What would happen if a magnitude 8 mega-colossal eruption were to occur today?
If a mega-colossal eruption were to occur today, it would probably not be able to push Earth into an ice age, according to a modeling study done by Jones et al. (2005). They found that an eruption like Toba would cool the Earth by about 17°F (9.4°C) after the first year (Figure 3), and the temperature would gradually recover to 3°F (1.8°C) below normal ten years after the eruption. They found that the eruption would reduce rainfall by 50% globally for the first two years, and up to 90% over the Amazon, Southeast Asia, and central Africa. This would obviously be very bad for human civilization, with the cold and lack of sunshine causing widespread crop failures and starvation of millions of people. Furthermore, the eruption would lead to a partial loss of Earth's protective ozone layer, allowing highly damaging levels of ultraviolet light to penetrate to the surface.

Not even a mega-colossal eruption of this magnitude would stop global warming, though. The level of greenhouse gases in the atmosphere would not be affected by the volcanic eruption, and warming would resume where it left off once the stratospheric dust settled out in a decade. With civilization crippled by the disaster, greenhouse gas emissions would be substantially reduced, though (small solace!) If we really want to say goodbye to civilization, a repeat of the only magnitude 9 eruption in recorded history should do the trick--the magnitude 9.2 La Garita, Colorado blast of 27.8 million years ago (Mason et al., 2004).

Figure 4. Annual near-surface temperature anomalies for the year following a mega-colossal volcanic eruption like the Toba eruption of 74,000 years ago, if it were to occur today. Most land areas cool by 22°F (12°C) compared to average. Some areas, like Africa, cool by 29°F (16°C). Image credit: Jones, G.S., et al., 2005, "An AOGCM simulation of the climate response to a volcanic super-eruption", Climate Dynamics, 25, Numbers 7-8, pp 725-738, December, 2005.

What would happen if a magnitude 7 super-colossal eruption were to occur today?
An eruption today like the magnitude 7 events of 535 A.D. or 1815 would cause cause wide-spread crop failures for 1 - 2 years after the eruption. With food supplies in the world already stretched thin by rising population, decreased water availability, and conversion of cropland to grow biofuels, a major volcanic eruption would probably create widespread famine, threatening the lives of millions of people. Wars over scarce resources might result. However, society's vulnerability to major volcanic eruptions is less than it was, since the globe has warmed significantly in the past 200 years. The famines from the eruptions of 1600 and 1815 both occurred during the Little Ice Age, when global temperatures were about 1.4°F (0.8°C) cooler than today. Crop failures would not be as wide-spread with today's global temperatures, if a suer-colossal eruption were to occur. Fifty years from now, when global temperatures are expected to be at least 1°C warmer, a magnitude 7 eruption should only be able to cool the climate down to year 2009 levels.

Volcanoes also warm the climate
While volcanoes cool the climate on time scales of 1 - 2 years, they act to warm the climate over longer time scales, since they are an important source of natural CO2 to the atmosphere. Volcanoes add 0.1 - 0.3 gigatons (Gt) of carbon to the atmosphere each year, which is about 1 - 3% of what human carbon emissions to the atmosphere were in 2007, according to the Global Carbon Project. In fact, volcanoes are largely responsible for the natural CO2 in the atmosphere, and helped make life possible on Earth. Why, then, haven't CO2 levels continuously risen over geologic time, turning Earth into a steamy hothouse? In fact, CO2 levels have fallen considerably since the time of the dinosaurs--how can this be? Well, volcano-emitted CO2 is removed from the atmosphere by chemical weathering. This occurs when rain and snow fall on rocks containing silicates. The moisture and silicates react with CO2, pulling it out of the air. The carbon removed from the air is then washed into the sea, where it ends up in ocean sediments that gradually harden into rock. Rates of chemical weathering on Earth have accelerated since the time of the dinosaurs, largely due to the recent uplift of the Himalaya Mountains and Tibetan Plateau. These highlands undergo a tremendous amount of weathering, thanks to their lofty heights and the rains of the Asian Monsoon that they capture. Unfortunately, chemical weathering cannot help us with our current high levels of greenhouse gases, since chemical weathering takes thousands of years to remove significant amounts of CO2 from the atmosphere. It takes about 100,000 years for silicate weathering to remove 63% of the CO2 in the atmosphere. Thus, climate models predict that chemical weathering will solve our greenhouse gas problem in about 100,000 - 200,000 years.

For further information
PBS TV special on the 535-536 A.D. disaster.
Newspaper articles on the 535-536 A.D. disaster.
Volcanic winter article from wikipedia.
Realclimate.org has a nice article that goes into the volcano-climate connection in greater detail.

Bekki, S., J.A. Pyle, W. Zhong, R. Toumi, J.D. Haigh and D.M. Pyle, 1996, "The role of microphysical and chemical processes in prolonging the climate forcing of the Toba eruption", Geophysical Research Letters 23 (1996), pp. 2669-2672.

Jones, G.S., et al., 2005, "An AOGCM simulation of the climate response to a volcanic super-eruption", Climate Dynamics, 25, Numbers 7-8, pp 725-738, December, 2005.

Rampino, M.R., and S. Self, 1993, "Climate-volcanism feedback and the Toba eruption of 74,000 years ago", Quaternary Research 40 (1993), pp. 269-280.

Mason, B.G., D.M. Pyle, and C. Oppenheimer, 2004, "The size and frequency of the largest observed explosive eruptions on Earth", Bulletin of Volcanology" 66, Number 8, December 2004, pp 735-748.

Oppenheimer, C., 2002, "Limited global change due to the largest known Quaternary eruption, Toba 74 kyr BP?"Quaternary Science Reviews, 21, Issues 14-15, August 2002, Pages 1593-1609.

Rampino, M.R., 2002, "Supereruptions as a Threat to Civilizations on Earth-like Planets", Icarus, 156, Issue 2, April 2002, Pages 562-569.

Read, W.G., L. Froidevaux and J.W. Waters, 1993, "Microwave Limb Sounder measurements of stratospheric SO2 from the Mt. Pinatubo eruption", Geophysical Research Letters 20 (1993), pp. 1299-1302.

Verosub, K.L., and J. Lippman, 2008, "Global Impacts of the 1600 Eruption of Peru's Huaynaputina Volcano", EOS 89, 15, 8 April 2008, pp 141-142.

Zielinski, G.A. et al., 1996, "Potential Atmospheric Impact of the Toba Mega-Eruption 71,000 Years Ago", Geophysical Research Letters, 23, 8, pp. 837-840, 1996.

Portlight moves to provide relief for South Carolina wildfires
South Carolina's biggest wildfire in more than three decades --a blaze four miles wide--destroyed dozens of homes near Myrtle Beach yesterday. Portlight Strategies, Inc. is preparing to respond to this disaster, focusing on providing drinks and sanitary products to firefighters, particularly to rural volunteer fire departments and other first responders which do not have the same resources as some of the larger paid departments. To help out, visit the Portlight South Carolina fire relief web page. Thanks!

Jeff Masters

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GFS 06Z; A hurricane and a Tropical Storm.....

Today will be crazy in this blog lol

Member Since: July 19, 2008 Posts: 43 Comments: 4051
up b/4 the crack of dawn - 65 degrees SWFL, We are parched and looking for RAIN. SURF???? NO Waves, GOOD NEWS...tourista's are gone.
Glassy lines of skim peeling down the beach this morning will keep the sliders happy, but the surfers will have to sit on the side lines. A steady East/NE wind today will creep up and let the kiters get some time on the water today and tomorrow. Great beach day, go out and enjoy it!
Gulf Temp 78
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782. HadesGodWyvern (Mod)
Tropical Cyclone Warning Center Darwin
High Seas (Gale Warnings)
4:30 PM CST April 26 2009

At 6:00 AM UTC, Tropical Low (1004 hPa) located at 7.6S 135.2E has 10 minute sustained winds of 25 knots with gusts of 40 knots. The low is reported as moving west-northwest at 5 knots.

winds above gale force developing in southern semicircle only, extending to 60 nautical miles from center, with rough seas and moderate

forecast and intensity
12 HRS: 7.0S 134.6E - 25 knots
24 HRS: 6.3S 133.8E - 30 knots
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Rainy season in S. FL typically starts in mid May- Early June depending on the year. April is normally one of our drier months. Having said that the little rain that we normally get this time of year we are well behind on.
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Well goodnight and take care everyone!
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777. HadesGodWyvern (Mod)
Tropical Cyclone Warning Center Darwin
Tropical Cyclone Outlook
Northern Territory, Australia 125E-142E
2:15 PM CST April 26 2009

A Developing Tropical Low [1005 hPa] is situated in the northern Arafura Sea, near 8S 135E. The low is expected to move slowly northwest away from the NT coast. The potential for development into a Tropical Cyclone has increased in the past 24 hours.

Tropical Cyclone Formation Potential
Monday: moderate
Tuesday: moderate
Wednesday: moderate
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Quoting Weather456:

An upper level high pressure will eventually setup over the Central Caribbean and the resultant flow on its western side will pull moisture from an active ITCZ norhward. A tropical system within this shouls ehance precipitation levels.

Looks like the areas that really need the rain, might actually be getting it.

I just hope this possible tropical system isn't a harbinger of an extraordinarily active season, like last year, 2004, or 2005.
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Quoting KoritheMan:
I personally think the GFS's forecast of a possible tropical cyclone in the Caribbean will likely not verify, but I do foresee a fair possibility of a large surge of moisture in the Caribbean in the coming weeks, due to the eastward propagation of the upward MJO pulse.

An upper level high pressure will eventually setup over the Central Caribbean and the resultant flow on its western side will pull moisture from an active ITCZ norhward. A tropical system within this surge should enhance precipitation levels.

This high will also play a role in the fictional TC system by providing 15 knots of southerly-southeasterly shear over the system.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting plywoodstatenative:
Kori, that means our rainy season might start?

Doesn't Florida's rainy season typically start around this time?
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MLC, unbelievable!

Northern OK is getting hit hard. I hope everyone there is safe! The 3 things I hated about living in the south; 1) storms that came at night, 2) HUMIDITY & 3) bugs.
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well i seen the run now iam off to bed see ya all tomorrow for another phatom invest debate lol
later ya all
Member Since: July 15, 2006 Posts: 193 Comments: 60409
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Kori, I agree. In addition to the MJO pulse, the AB high should weaken a little and with the ITCZ transitioning more northward, the moisture should definitely increase.
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nice system cen s atlantic

Very nice indeed
Member Since: July 24, 2005 Posts: 407 Comments: 19076

Man, we're really stirring the spaghetti on this one early! ;P It's gonna tare up the Yucatan! Wow!
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Kori, that means our rainy season might start?
Member Since: November 15, 2005 Posts: 16 Comments: 4189

nice system cen s atlantic
Member Since: July 15, 2006 Posts: 193 Comments: 60409
I personally think the GFS's forecast of a possible tropical cyclone in the Caribbean will likely not verify, but I do foresee a fair possibility of a large surge of moisture in the Caribbean in the coming weeks, due to the eastward propagation of the upward MJO pulse.
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the 00Z GFS model 360 has drastically change from the last model run with a system now further west, and this comes at no surprise since a forecast that far out is subject to change. This scenario the GFS is forecasting has a 5% chance of physically manifesting.

Member Since: July 24, 2005 Posts: 407 Comments: 19076
Vortex95 - bird? crow?
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Thanks Storm! Is the anti-cyclone over SC negatively impacting potential precipitation there?
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I've also noticed a gradual but definite decline in wind shear over the southwestern Caribbean in recent days.
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The GFS forms it again...

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754. JRRP
Member Since: August 16, 2007 Posts: 0 Comments: 6939
Quoting hurricane23:
When the ECMWF/UKMET jump on development let me know.

Now ya talkin!
I will be sure to let you know..
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750. beell
Great letter to your friend, hurricane23!
Thanks for posting.

It may be possible to get somewhat close to accuracy on large scale features like long-wave troughs or the A/B high. Maybe...
Hard to be much more than an excercise in fun to place very much faith in a model 120 days out if we can't put much faith in one 10 days out! I realize this is an apples to oranges thing (large scale/small scale) but it seems to be quite a stretch.

Well, thanks for posting it for a bit lol!

Member Since: September 11, 2007 Posts: 156 Comments: 18691
When the ECMWF/UKMET jump on development let me know.
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Quoting StormW:

Looking at WV satellite loop, looks like some moisture being pumped in by a small area of the Subtropical Jet. Current surface analysis map from NHC indicates there may be the slight presence of an inverted trof. Orographic lift could very well be aiding this, as the upper levels are currently displaying a confluent flow over the area.

Thanks Storm. Is this the surface link you are using ?Link because I am not seeing a trough...
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Thank You StormW!
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Storm, so you think the Carribean will see more action?
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If anyone is interested in the Bermuda-Azores High this year check out my blog. 2009 Hurricane Season FAQ
Member Since: July 24, 2005 Posts: 407 Comments: 19076
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Quoting StormW:

Actually, closer to last season come AUG/SEP. Looking at the mean pressure for Sep, we're looking at around 1019 mb.

Let me check on the other for you.

Would that make the pressure Below or Above Average for the peak in the Atlantic Basin?
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Quoting StormW:
Hey Adrian!

Hey storm!

Trying calling you a few weeks back hope all is ok health wise for you and also your family.
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Dr. Jeff Masters' WunderBlog


Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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