Category 6™

A cautionary tale--the PETM

By: JeffMasters, 1:53 PM GMT on April 29, 2009

One frequently hears comments like, "Earth has had many periods of warmth far exceeding the warmth of today's climate, so we should not be surprised if the current warming of the globe is a natural phenomena". This view is especially prevalent among geologists, who take a very long view of history and are among the most skeptical scientists regarding the reality of human-caused climate change. It is true that Earth's past has had many episodes of natural global warming that we can learn from. But the greatest natural global warming episode of the past 65 million years, the Paleocene-Eocene Thermal Maximum (PETM) event of 55 million years ago, presents us with a cautionary tale of how massive releases of greenhouse gases--similar in scale to what humans are now producing--may cause extreme warming of the climate.

Earth's orbital variations--the most common form of natural global warming
The most common cause of natural global warming over time has been changes in Earth's orbit. Three oscillations in Earth's orbit with periods of 26,000, 41,000, and 100,000 years (called Milankovitch cycles) cause ice ages to be triggered when summer sunshine at 65°N reaches a minimum. The reduced sunlight over Canada, Siberia, and Scandinavia allows winter snowfall to persist through the summer, and thus accumulate and build Northern Hemisphere ice sheets. There isn't enough land in the Southern Hemisphere to allow large, land-based ice sheets to build there, so it is the growth and decay of Northern Hemisphere ice sheets that has controlled the timing of ice ages and warm inter-glacial periods over the past three million years. Earth's orbit is currently in a phase where the amount of sunlight falling at 65°N is changing very little. Thus, the primary mechanism for past natural global warming events is not to blame for the current warming. According to the "official" word on climate, the 2007 report of the U.N.'s Intergovernmental Panel on Climate Change (IPCC), the amount of sunlight falling at 65°N is expected to change little over the next 30,000 years, and "it is very unlikely that the Earth would naturally enter into another ice age for at least 30,000 years".

Pumping huge amounts of carbon into the atmosphere coincided with extreme climate warming during the PETM
Natural global warming has also occurred in the past due to changes in solar brightness, and natural emissions of natural carbon dioxide (CO2) and methane (methane is the primary component of the natural gas we use to heat our homes, is a potent greenhouse gas 20 - 25 more effective at heating the Earth than than CO2, with a lifetime of about 9 years in the atmosphere before reacting with the OH radical to form CO2). I discussed one example of natural global warming in my previous post--volcanoes have emitted enough CO2 over time to account for a large portion of Earth's natural greenhouse effect. However, volcanoes only put about 1 - 3% as much CO2 per year into the atmosphere as human activities do. What, then, does Earth's past tell us about what might happen if we dump 100 times more carbon than volcanoes do into the atmosphere, over a period of a few centuries?

The end of Earth's Paleocene era, 55 million years ago, was a time of great warmth on planet Earth. Subtropical vegetation grew in Greenland and Patagonia, and crocodiles swam off the coast of Greenland. Sea surface temperatures at the North Pole were a toasty 64°F (18°C). Tropical palm forests in northern Wyoming played host to early primates. Despite the fact that the sun put out 0.5% less energy than today (equivalent to a global temperature that would be 0.5°C cooler), there was no polar ice cap or Greenland Ice Sheet. The higher temperatures of that era were probably due to high carbon dioxide levels of 560 - 600 ppm. This is far higher than the 280 ppm seen in the 1800s, and the 383 ppm as of 2009. The continents had a different configuration due to continental drift, and this may have kept the world warmer as well.


Figure 1. Global temperature change (right scale) as inferred from oxygen-18 isotope measurements (left scale) from fossil ocean microorganisms (Zachos et al., 2001). Oxygen-18 levels in these fossils are proportional to the temperatures of the era when the fossils were formed. The Paleocene-Eocene Thermal Maximum (labeled PETM) shows a sharp upward spike in temperatures occurred. This spike is likely to be understated by a factor of 2 - 4 due to coarse sampling and averaging in this data set. For more detail, see the Wikipedia entry for the PETM.

Then, 55 million years ago, the fossil record shows that an extraordinary drop in the ratio of carbon-13 to carbon-12 occurred, indicating that a massive amount of "light" carbon with low levels of the carbon-13 isotope was emitted into the atmosphere in a very short amount of time--just 500 - 20,000 years. The most likely source of carbon-13 depleted carbon would have been methane from ocean sediments or land vegetation. If it was methane, about 1,000 - 2,000 gigatons of carbon would have had to be injected into the atmosphere, in order to account for the observed fossil deposits. For comparison, the total amount of carbon in today's atmosphere, primarily as CO2, is a factor of two or three less--about 810 gigatons. The fossil record shows that extreme climatic warming occurred nearly simultaneously with this massive release of carbon into the atmosphere. Global average temperatures rose 9°F (5°C) in a geological instant--1,000 - 10,000 years (Sluijs et al., 2007). Average sea surface temperatures at the North Pole reached 74°F (23°C). The warmth lasted 120,000 - 220,000 years before weathering of silicate rocks was able to remove the CO2 from the atmosphere and return the climate to its former state. This was the largest global warming event since the time of the dinosaurs, 65 million year ago (Moran et al., 2006). The resulting impact on Earth's climate was so severe that a new geological era was born--the Eocene. The warming event has been dubbed the Paleocene-Eocene Thermal Maximum (PETM), since it occurred at the boundary of these two eras. Ocean circulation patterns changed radically during the first 5,000 years of the PETM (Nunes and Norris, 2006), and the deep oceans became 11°F (6°C) warmer, severely depleted in oxygen, and more acidic. A mass extinction of deep ocean microorganisms resulted, though the exact reasons remain unclear. The PETM did not cause mass extinctions on land of plants and animals, but a major turnover in mammalian life occurred at that time. Many of today's major mammalian orders emerged in the wake of the PETM. The new geological era it ushered in, the Eocene, is named for the Greek goddess of the dawn (Eos), since this was the dawn of the era of large mammals.

It is extremely difficult to explain the warmth of the PETM without assuming that the huge amount of "light" carbon pumped into the atmosphere created intense warming due to the greenhouse effect. The controversial question is, how did this carbon get into the atmosphere? Did PETM happen because of the greenhouse effect from all the carbon added to the atmosphere, or did the carbon get released into the atmosphere in response to climatic warming from another cause (and boosting the warming that was already occurring?) The mystery is a difficult one to unravel, since our vision of what happened so long ago is very fuzzy. A recent high-resolution study of ocean sediments laid down in New Jersey during the PETM (Sluijs et al., 2007) argued that about half of the PETM warming occurred 1,000 - 1,500 years before the 1,000 - 2,000 gigatons of "light" carbon got injected into the atmosphere. The authors theorize that global warming due to some other cause heated up the deep oceans enough to release methane stored in the form of methane hydrate, a form of methane 'ice' that forms in cold bottom water under great pressures and is widely distributed and plentiful in sediments on the outer edges of continental margins. The methane released was the huge pulse of "light" carbon seen in the fossil record, and this methane warmed the planet even further via the greenhouse effect. The authors argued that the warming that triggered the PETM could have been due to a variation in Earth's orbit, or due to a pulse of greenhouse gases that didn't happen to be enriched in light carbon. A wide variety of other theories abound. Dickens (2004) theorizes that a volcano in the North Atlantic erupted through a huge fossil fuel deposit in overlying ocean sediments, releasing massive amounts of the stored carbon into the atmosphere. Pancost et al. 2006 found evidence that the warming of the PETM significantly increased as carbon stored on land in wetlands was released in the form of methane. Huber (2008) argued that temperatures got so hot during the PETM that a huge die-off of tropical vegetation resulted, creating vast deserts and putting thousands of gigatons of carbon dioxide into the atmosphere, further increasing temperatures.


Figure 2. Photographs of methane hydrate as nodules, veins, and laminae in sediment. Intense warming of the deep oceans during the PETM may have released huge quantities of methane gas from ocean sediments with methane hydrates in them. Image credit: United States Geological Survey.

Computer climate models fail to reproduce the PETM
A big concern about the climate models that we are using to forecast climate for the coming century is that they do a poor job of reproducing the climate of the Eocene, and, in particular, the PETM. These models fail to reproduce the high temperatures observed in the polar regions relative to the tropics during the PETM. However, in the words of climate scientists Daniel Schrag and Richard Alley in a 2004 article in Nature, "It would be a grave mistake to take these lessons from ancient climates as a reason to disregard the projections from climate models." If the observations of the climate in this far-ago era are correct, the reason that the climate models fail to correctly simulate this past climate is because the climate is more sensitive to CO2 than believed. There is a missing "feedback" causing increased warming near the pole that the models are missing. Sluijs et al. (2006) theorize that the models may be missing how hurricanes transport heat to the poles, or how polar stratospheric clouds may act to trap heat over the poles. In short, the failure of the models to correctly simulate the PETM may mean that our current estimates of the amount of global warming likely over the coming century (1.1°C - 6.4°C) are far too low. The other possibility, mentioned by Huber (2008) is that the models are correct, but the temperatures inferred for the tropics from the fossil record are in error. This wouldn't be the first time that measurements were found to be in error and the models vindicated.

Comparison with today
Since the beginning of the Industrial Revolution, humans have pumped about 500 gigatons of carbon into the atmosphere. There are about 5,000 gigatons in the planet's coal reserves, while oil and traditional natural gas deposits are hundreds of gigatons each (Rogner, 1997). Given that humans are now adding about 10 gigatons of carbon to the atmosphere each year (Global Carbon Project, 2007), we will surpass the 1,000 gigaton mark 50 years from now at current emission rates. This is at the lower end of the 1,000 - 2,000 gigatons of carbon that are estimated to have been added to the atmosphere during the PETM--the most extreme natural global warming event of the past 65 million years. Though our view of events so long ago is very fuzzy, the PETM should serve as a cautionary tale. We cannot rule out the possibility that continuation of our current rates of fossil fuel burning will lead to an extreme climatic warming event like the PETM. In particular, we need to keep a careful eye on the huge reservoirs of methane hydrate stored in marine sediments (500 - 10,000 gigatons of carbon) and stored in permafrost (7.5 - 400 gigatons). Continued warming of the planet could trigger substantial releases of these massive reservoirs of greenhouse gases, leading to a repeat of the PETM event. However, a 2008 study by the U.S. Climate Change Science Program (CCSP, 2008) concludes that there is currently no evidence that a sudden catastrophic release of methane stored in ocean sediments or in permafrost will happen over the next century. It should take at least a century for global warming to penetrate the deep oceans and permafrost regions containing these significant reservoirs of methane hydrates. The study concludes, "Catastrophic release of methane to the atmosphere appears very unlikely in the near term (e.g., this century)...Although the prospect of a catastrophic release of methane to the atmosphere as a result of anthropogenic climate change over the next century appears very unlikely based on current knowledge, many of the processes involved are still poorly understood, and developing a better predictive capability requires further work. On a longer time scale, methane release from hydrate reservoir is likely to be a major influence in global warming over the next 1,000 to 100,000 years". So, the bottom line is: don't expect global warming to be able to cause huge releases of methane hydrates in the coming century, such as may have occurred during PETM. But it is wise to ponder that a release of greenhouse gases similar in magnitude to what we are doing now coincided with the most extreme global warming event of the last 65 million years. We should not be surprised if our human greenhouse gas emissions cause a similar massive climate perturbation over the next 1,000 years, leading the dawn of a new geological era--the Anthropocene.

For more information
The best resource I found while researching this was a December 2008 report from the U.S. Climate Change Science Program (CCSP), titled, Abrupt Climate Change. Chapter 5, "Potential for Abrupt Changes in Atmospheric Methane" [1.3 Mb] was the relevant chapter.

References
Archer, D., 2007, "Methane hydrate stability and anthropogenic climate change", Biogeosciences, 4, 521544,.

Dickens, G.R., 2004, "Hydrocarbon-driven warming", Nature 42, 429, pp513-515, 3 June 2004.

Huber, M., 2008, "A Hotter Greenhouse?", Science 321, no. 5887, pp. 353-354, DOI: 10.1126/science.1161170

Moran, et al., 2006, "The Cenozoic palaeoenvironment of the Arctic Ocean", Nature 441, 601-605 (1 June 2006) | doi:10.1038/nature04800.

Nunes, F. and R.D. Norris, 2006, "Abrupt reversal in ocean overturning during the Paleocene/Eocene warm period", Nature 439 (7072): 603. doi:10.1038/nature04386

Pancost, R.D., et al., 2006, "Increased terrestrial methane cycling at the Palaeocene-Eocene thermal maximum", Nature 449, 332-335 (20 September 2007) | doi:10.1038/nature06012

Rogner, H.-H, 1997, "An assessment of world hydrocarbon resources", Annu. Rev. Energy Environ., 22, 217-262.

Sluijs, A., et al., 2006, "Subtropical Arctic Ocean temperatures during the Palaeocene/Eocene thermal maximum", Nature 441, 610-613 (1 June 2006) | doi:10.1038/nature04668

U.S. Climate Change Science Program (CCSP), 2008: Abrupt Climate Change. A report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research [Clark, P.U., A.J. Weaver (coordinating lead authors), E. Brook, E.R. Cook, T.L. Delworth, and K. Steffen (chapter lead authors)]. U.S. Geological Survey, Reston, VA, 459 pp.

Zachos, J. C., U. Rohl, S.A. Schellenberg, A. Sluijs, D.A. Hodell, D.C. Kelly, E. Thomas, M. Nicolo, I. Raffi, L.J. Lourens, H. McCarren, and D. Kroon, 2005, "Rapid Acidification of the Ocean During the Paleocene-Eocene Thermal Maximum", Science, 308, 1611-1615

Portlight.org relief walk in Destin, FL a big success
Over the weekend, the portlight.org disaster relief charity ran a highly successful relief walk in Destin, FL, to raise money for the disaster relief. The theme of this walk was to raise relief money not only for people, but for pets as well, with 25% of the money raised intended for taking care of pets injured or abandoned during disasters. As detailed in the portlight.org blog, the pet theme was a great way to raise money, and about $5000 was raised. The other relief walks this year raised $1500 in New Orleans and $542 in Kissimmee. Many more walks are planned this year, with the next one being this weekend (May 2) in Summerville, SC. Portlight also helped out with disaster relief operations for the South Carolina fires yesterday.



Jeff Masters

Climate Change

Volcanic Winter

By: JeffMasters, 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.

References
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

Climate Change Volcano

Earth Day Photos, 2009

By: JeffMasters, 1:14 PM GMT on April 22, 2009

Today is Earth Day, and as is my tradition on Earth Day, I'll present my nominations for best wunderphotos uploaded to our web site over the past year. This year's photos are truly remarkable, and I want to thank everyone who uploaded weather photos for their contributions to what has become one of the world's best weather photo galleries. Enjoy Earth Day!

Update on portlight.org charity errorts
The portlight.org disaster relief charity is sponsoring a Portlight Relief Event Series of fund raising events in cities across the U.S. this Spring. The next event is the Destin Dog Walk, which will take place Sunday, April 26th at Harbor Walk Village in Destin, Florida. Portlight Strategies board chair, Paul Timmons (wunderground handle, presslord) will be in attendance and will have the live webcam running, so please join in. Wunderbloggers code1, sugarsand, and FWBLinda have done an excellent job of putting this event together. It should be a beautiful day and a fun-filled event.

Portlight is also continuing to look for generous people to sponsor walkers for this event. If you would like to contribute, please use the Paypal button or send checks to the address in the Portlight Disaster Relief blog. Make sure to note "For Destin Dog Walk." Twenty-five percent of the proceeds from this event will provide disaster relief for pets. The remaining proceeds will support Portlight's disaster relief efforts for rural communities and people with disabilities.

Many thanks to all of you who have supported Portlight's efforts in one way or another! With yet another hurricane season approaching, they continue to need your help. The Portlight Relief Event Series is a critical part of preparing a more efficient and effective relief effort. If you would like to help coordinate a walk or other fundraising event in your area, please contact Paul Timmons, paul@portlight.org



Jeff Masters

Atmospheric Phenomena

Old ice at a record low in Arctic as melting season begins

By: JeffMasters, 1:33 PM GMT on April 20, 2009

March 2009 Northern Hemisphere sea ice extent was the 6th lowest since 1979, according to the National Snow and Ice Data Center. The record March low was set in 2006, and it has now been nearly two years since we have set any record monthly minimums for Arctic sea ice. While it is good news that the area of sea ice coverage has not been reaching record lows recently, there is concern about the recent record loss of thick, multi-year ice in the Arctic. Strong winter winds pushed a considerable amount of multi-year-old ice out of the Arctic this year, leaving the Arctic Ocean with its lowest amount of old sea ice on record (Figure 1). Sea ice more than two years old fell below 10% for the first time since satellites began observing the ice in 1979. This is a factor of three lower than the 30% coverage for the period 1981 through 2000.


Figure 2. These images show declining sea ice age, which indicates a thinning Arctic sea ice cover more vulnerable to melting in summer. Ice older than two years now accounts for less than 10% of the ice cover. Image credit: National Snow and Ice Data Center, courtesy J. Maslanik and C. Fowler, University of Colorado.

As the ice melting season begins this year, the exceptionally low amount of old, thick ice leaves the Arctic very vulnerable to melting. Air temperatures over the Arctic Ocean this past winter were 1 - 2°C (1.8 - 3.6°F) above average, and a continuation of conditions this warm would probably cause record melting of the Arctic ice cap this summer. On the other hand, the amount of 1 - 2 year old in the Arctic increased in 2008 compared to 2007, so if the Arctic experiences below average temperatures this summer and throughout 2010, the potential exists for old ice to make a comeback. However, the Arctic has experienced very warm temperatures in excess of 1°C above average for most of the past decade (Figure 2). The latest Arctic Report Card 2008 concludes that "it is becoming increasingly likely that the Arctic will change from a perennially ice-covered to an ice-free ocean in the summer". The best hope I see for the Arctic sea ice to recover in the next few years is for a major volcanic eruption in the tropics to create a "Volcanic Winter" cooling effect for a year or two. Such an eruption would probably not allow for a complete recovery of Arctic sea ice, but might delay the transition to a summertime ice-free state by several years.


Figure 2. Arctic-wide annual averaged surface air temperature anomalies (60°-90°N) based from 1900 - 2007 on land stations north of 60°N relative to the 1961 - 1990 mean. From the CRUTEM 3v dataset, (available online at www.cru.uea.ac.uk/cru/data/temperature/). Note this curve does not include ship observations. The year 2007 was the warmest year on record in the Arctic. The year 2008 (not plotted) was cooler than 2007. Image credit: Arctic Report Card 2008.

As usual, I'm saying little about Antarctic sea ice, since the ice at the bottom of the world is not changing much and has a small impact on global climate compared to Arctic sea ice. Antarctic sea ice is currently quite a bit above average in extent, making total global sea ice above average this month. However, as I explained in a post earlier this year, drawing attention to this statistic is not a very intelligent thing to do, and hides the important fact that Arctic sea ice is in serious danger.

My next post will be on Wednesday--Earth Day--when I'll pick my top wunderphotos from the past year. I'll talk more about "Volcanic Winter" on Friday.

Jeff Masters

Climate Change

La Niña conditions end; 10th warmest March on record for the globe

By: JeffMasters, 12:53 PM GMT on April 17, 2009

Sea Surface Temperatures (SSTs) and deep water temperatures have warmed significantly in the equatorial Eastern Pacific over the first two weeks of April, and La Niña conditions are no longer present. While NOAA's Climate Prediction Center has not yet declared an end to this La Niña episode and dropped their La Niña advisory, it is very likely that the La Niña event that began in December 2008 is now over. The big question is whether an El Niño event will rapidly form in its place, in time for hurricane season. This did happen after the 1976 La Niña, which ended in April, with a weak El Niño beginning in September. However, it can take a few months for the atmosphere to adjust to the formation of a new El Niño, and there is no guarantee that a weak El Niño for the coming hurricane season would act to dramatically reduce Atlantic hurricane activity.The number of Atlantic hurricanes is typically reduced in an El Niño year, due to increased wind shear from strong high-level winds. Nearly all the model forecasts for the Niño 3.4 region predict neutral conditions for the August - October peak of hurricane season. Four out of 21 El Niño models are predicting an El Niño event for hurricane season; three are predicting a La Niña, and fourteen are predicting neutral conditions.


Figure 1. The difference of Sea Surface Temperature (SST) from average for the Niña 3.4 region of the equatorial Eastern Pacific (the area 5°N - 5°S, 120°W - 170°W). La Niña conditions are defined as occurring when the 1-month mean temperature anomaly in the Niña 3.4 region cools below -0.5°C. La Niña conditions began in December 2008 and ended in late March 2009. Image credit: NOAA Climate Prediction Center.

Tenth warmest March on record for the globe
Global temperatures remained about where they've been the past two years, with the planet recording its 10th warmest March on record, according to statistics released by the National Climatic Data Center. The period January - March was the eighth warmest such period on record.

An average March for the U.S.
For the contiguous U.S., March temperatures were the 51st warmest in the 115-year record, according to the National Climatic Data Center. The month had near-average precipitation, ranking as the 42nd wettest March. Three states (Delaware, Maryland, and New Jersey) experienced their driest year-to-date period ever. In neighboring states, Pennsylvania recorded its second driest year-to-date period and Massachusetts and West Virgnia experienced their fourth and fifth driest, respectively. The below-normal precipitation averages led to the driest ever start to the year for the Northeast region. Record amounts of snow fell in North Dakota during March. Fargo received 28.1 inches, which was nearly 2 more inches than the previous March record set in 1997. Fargo also recorded 4.62 inches of precipitation which set a new monthly record. Runoff from the record precipitation led to the highest flood levels ever observed on the Red River in North Dakota. The river crested in Fargo at a record level of 12.4 m (40.8 feet), shattering the previous record of 12.2 m (40.1 feet) set in 1897.

Through March, the U.S. has only seen about 50% of normal tornado activity for the year, according to NOAA's Storm Prediction Center. There were just 9 tornado deaths through March, compared to 70 deaths through March of 2008, and the 3-year average of 44 deaths.

On April 14, 2009, 17% of the contiguous United States was in moderate-to-exceptional drought. This is a drop from the 21% figure observed January through March.

Bahamas 2009 Weather Conference
This week, many of the world's hurricane experts are gathered at the Bahamas Hurricane Conference. Check out their web site for short videos by some of the presenters. The 3-minute talk by NHC Director Bill Read and former NHC Director Max Mayfield on the inadequacy of our familiar Category 1-2-3-4-5 Saffir-Simpson scale is interesting. They make the point that no one scale will ever be able to capture the threats a hurricane poses, since these depend greatly on exactly what track the storm takes, and our forecasts will never be able to precisely pinpoint the track. Thus, introducing a new scale to quantify storm surge risk is not a complete solution to the inadequacies of the Saffir-Simpson scale. Coastal residents need to heed the detailed wind and storm surge forecasts for their area, regardless of what Category storm is approaching.

Jeff Masters

Climate Summaries

Outspoken hurricane scientist Ivor van Heerden cut loose by LSU

By: JeffMasters, 12:38 PM GMT on April 14, 2009

Louisiana State University (LSU) will not renew the contract of controversial hurricane scientist Ivor van Heerden, according to nola.com . Dr. van Heerden has been stripped of his title as deputy director of the LSU Hurricane Center, and will lose his job in May 2010. The Director of the LSU Hurricane Center, engineering professor Marc Levitan, resigned from that post in protest over the firing of van Heerden. LSU has given no reason why it is removing Dr. van Heerden, but said it was not because of his performance. Van Heerden, who holds a Ph.D. degree in marine sciences from LSU, was one of the most outspoken scientists on the vulnerability of New Orleans before Katrina struck in 2005. He worked extensively with FEMA, the Army Corps of Engineers, and political figures at the local, state, and U.S. Congressional levels to try to improve New Orleans' disaster readiness. In the aftermath of the storm, he provided support for the search and rescue efforts and plugging of the levee breaches, then headed one of the teams assigned to figure out what caused the levees to fail. PBS's NOVA did a nice story on him in 2006, featuring interviews before and after Katrina. He was highly critical of the Army Corps of Engineers and politicians at the local, state, and federal level for allowing the Katrina disaster to happen, and for their abysmal response to the storm's aftermath.

It is no surprise that van Heerden has been fired, as he has also been very critical of the LSU administration. His May 2006 book, The Storm: What went wrong and why during Hurricane Katrina--the inside story from one Louisiana scientist, (see my review), tells of a case in November 2005 after Katrina where two LSU assistant chancellors told him to stop talking to the press, because it was "hurting LSU's quest for federal funding across the board." Van Heerden further remarked:

A balanced view on research is lacking at many universities obsessed with competing for the big brownie points, where upper administrators' egos and boasting rights are more important than solving problems to the benefit of society at large. You would think that our work before, during, and after Katrina might have turned some heads at LSU, but not really. Witness the gag order placed on me by the school during the levee investigation a couple of months later (soon rescinded with apologies)

Van Heerden is a big proponent of building a flood protection system that will protect Louisiana from a Category 5 hurricane. He proposes doing this by restoring wetlands, building armored levees, and installing huge flood gates on Lake Pontchartrain, similar to what the Dutch use to protect their country from the North Sea. I especially like his emphasis on the importance of doing good science. He is not a fan of what politicians and business leaders do with good science:

The science is the easy part. The hard part is overcoming the narrow-mindedness and selfishness of politics and business as usual. For decades the two have undermined plan after plan to restore wetlands, build new ones, and thereby protect people and property. They have played hell with improving the existing levee system. We must do better now, or we can kiss it all good-bye for good. I was not exaggerating in the introduction when I said that politics and business as usual in Louisiana will eventually put everything below Interstate 10 underwater. Science and engineering can save the day, but not if they're censored or manipulated. If that's to be the case, just shelve them and start packing. It's over.

According to an article in The Nation, Dr. van Heerden is scheduled to testify in a trial that begins in federal court on April 20. Judge Stanwood Duval will rule on a claim by six homeowners that the Corps failed to heed environmental laws in building and maintaining the Mississippi River-Gulf Outlet shipping shortcut, which they claim led to the catastrophic flooding of New Orleans during Katrina. A second trial will begin shortly after that--a large class action suit seeking hundreds of millions in damages from the Corps. When Dr. van Heerden was first asked to testify at these trials in spring 2007, LSU's then-president, Sean O'Keefe, told plaintiffs' attorneys that if van Heerden testified against the Corps he would be fired (O'Keefe had served as head of NASA under George W. Bush between 2001 - 2005, and stepped down as LSU chancellor in January 2008). According to van Heerden, the LSU president said "nobody from LSU was going to embarrass the Bush administration or upset the major Republican companies that benefit from Corps of Engineers contracts." LSU has officially blocked Dr. van Heerden from testifying as an "expert witness" in the upcoming trials, but he can still testify as a "fact witness".

Regardless of where he winds up next, I'm sure Van Heerden will continue to voice his valuable views on the science of what is best for Louisiana and New Orleans. In an interview with the Associated Press, Dr. van Heerden said Friday he would appeal the college's decision and was considering legal action. "Before going that route, I hope LSU will recognize the signal they've sent to the world is that academic freedom does not exist at LSU. The folks who are going to lose in this is LSU, not me. I will find a job rather easily. There have already been some offers."

Less politics and better science would go a long ways towards reducing our vulnerability to hurricanes. Ivor van Heerden has been a much-needed critical voice in advocating this, and I applaud his tenacity in calling it as he sees it. Louisiana very much needs Dr. van Heerden's input over the coming decades on how to move ahead to protect the vulnerable coast of the state against the twin threats of hurricanes and rising sea levels. The move by Louisiana's flagship university to silence his voice should concern everyone in the path of the next Katrina.

Jeff Masters

Climate Change

Nuclear winter revisited

By: JeffMasters, 2:00 PM GMT on April 10, 2009

In the 1980s and early 1990s, a series of scientific papers published by Soviet scientists and Western scientists (including prominent scientists Dr. Carl Sagan, host of the PBS "Cosmos" TV series, and Nobel Prize winner Paul Crutzen) laid out the dire consequences on global climate of a major nuclear exchange between the U.S. and Soviet Union. The nuclear explosions would send massive clouds of dust high into the stratosphere, blocking so much sunlight that a nuclear winter would result. Global temperatures would plunge 20°C to 40°C for several months, and remain 2-6°C lower for 1-3 years. Up to 70% of the Earth's protective stratospheric ozone layer would be destroyed, allowing huge doses of ultraviolet light to reach the surface. This UV light would kill much of the marine life that forms the basis of the food chain, resulting in the collapse many fisheries and the starvation of the people and animals that depend it. The UV light would also blind huge numbers of animals, who would then wander sightlessly and starve. The cold and dust would create widespread crop failures and global famine, killing billions of people who did not die in the nuclear explosions. The "nuclear winter" papers were widely credited with helping lead to the nuclear arms reduction treaties of the 1990s, as it was clear that we risked catastrophic global climate change in the event of a full-scale nuclear war.

Even a limited nuclear exchange can cause a climate disaster
Well, it turns out that this portrayal of nuclear winter was overly optimistic, according to a series of papers published over the past few years by Brian Toon of the University of Colorado, Alan Robock of Rutgers University, and Rich Turco of UCLA. Their most recent paper, a December 2008 study titled, "Environmental Consequences of Nuclear War", concludes that "1980s predictions of nuclear winter effects were, if anything, underestimates". Furthermore, they assert that even a limited nuclear war poses a significant threat to Earth's climate. The scientists used a sophisticated atmospheric/oceanic climate model that had a good track record simulating the cooling effects of past major volcanic eruptions, such as the Philippines' Mt. Pinatubo in 1991. The scientists injected five terragrams (Tg) of soot particles into the model atmosphere over Pakistan in May of 2006. This amount of smoke, they argued, would be the likely result of the cities burned up by a limited nuclear war involving 100 Hiroshima-sized bombs in the region. India and Pakistan are thought to have 109 to 172 nuclear weapons of unknown yield.


Figure 1. Global average temperature departure from normal since 1880 (top) and A.D. 1000 (bottom) in black, and those projected after a limited nuclear exchange between Pakistan and India of 100 Hiroshima-sized weapons in 2006 (in red). Temperatures are forecast to plunge 1.2°C (2.2°F) after such a war, reaching levels colder than anything seen in the past 1000 years. The 1815 eruption of Tambora in Indonesia produced a similar cooling, and led to the notorious "Year Without a Summer". Image credit: "Climatic consequences of a regional nuclear conflict" by Robock et al., Atmospheric chemistry and Physics, 7, 2003-2012, 2007.

The intense heat generated by the burning cities in the models' simulations lofted black smoke high into the stratosphere, where there is no rain to rain out the particles. The black smoke absorbed far more solar radiation than the brighter sulfuric acid aerosol particles emitted by volcanic eruptions. This caused the smoke to heat the surrounding stratospheric air by 30°C, resulting in stronger upward motion of the smoke particles higher into the stratosphere. As a result, the smoke stayed at significant levels for over a decade (by contrast, highly reflective volcanic aerosol particles do not absorb solar radiation and create such circulations, and only stay in the stratosphere 1-2 years). The black soot blocked sunlight, resulting in global cooling of over 1.2°C (2.2°F) at the surface for two years, and 0.5°C (0.9°F) for more than a decade (Figures 1 and 2). Precipitation fell up to 9% globally, and was reduced by 40% in the Asian monsoon regions.

This magnitude of this cooling would bring about the coldest temperatures observed on the globe in over 1000 years (Figure 1). The growing season would shorten by 10-30 days over much of the globe, resulting in widespread crop failures. The effects would be similar to what happened after the greatest volcanic eruption in historic times, the 1815 Tambora eruption in Indonesia. This cooling from this eruption triggered the infamous Year Without a Summer in 1816 in the Northern Hemisphere, when killing frosts disrupted agriculture every month of the summer in New England, creating terrible hardship. Exceptionally cold and wet weather in Europe triggered widespread harvest failures, resulting in famine and economic collapse. However, the cooling effect of this eruption only lasted about a year. Cooling from a limited nuclear exchange would create two to three consecutive "Years Without a Summer", and over a decade of significantly reduced crop yields. The authors found that the smoke in the stratosphere causes a 20% reduction in Earth's protective ozone layer, with losses of 25-45% over the mid-latitudes where the majority of Earth's population lives, and 50-70% ozone loss at northern high latitude regions such as Scandinavia, Alaska, and northern Canada. A massive increase in ultraviolet radiation at the surface would result, capable of causing widespread and severe damage to plants and animals. Thus, even a limited nuclear exchange could trigger severe global climate change capable of causing economic chaos and widespread starvation.


Figure 2. Top: Time variation of global average surface air temperature and precipitation for a limited nuclear exchange between Pakistan and India of 100 Hiroshima-sized weapons, assuming they inject 5 Tg of Black Carbon (BC) into the stratosphere. The global average precipitation is 3 mm/yr, so the changes in years 2-4 represent a 9% global average reduction in precipitation. Bottom: Time variation of sunlight (shortwave radiation) at the surface, in watts per meter squared, due to the 1991 eruption of Mt. Pinatubo in the Philippines (blue line) and the limited nuclear war between India and Pakistan (black line). The effects of a limited nuclear war are far more severe and long lasting than the eruption of Pinatubo, the greatest eruption of the 20th century. Image credit: "Climatic consequences of a regional nuclear conflict" by Robock et al., Atmospheric chemistry and Physics, 7, 2003-2012, 2007.

Climate change and the Doomsday Clock
It is sobering to realize that the nuclear weapons used in the study represented only 0.3% of the world's total nuclear arsenal of 26,000 warheads. Fortunately, significant progress was made in the 1990s and 2000s to reduce the threat of nuclear war. If the 2002 Strategic Offensive Reductions Treaty (SORT) is fully implemented by the U.S. and Russia as planned, by 2012 the world's stockpile of nuclear weapons will be just 6% of the 70,000 warheads that existed at the peak of the cold war in 1986. However, the threat of a more limited regional nuclear war has increased in recent decades, since more countries have been joining the nuclear club--an average of one country every five years. The 2007 move by the Bulletin of the Atomic Scientists to move the hands of their Doomsday Clock two minutes closer to midnight--the figurative end of civilization--helped call attention to this increased threat. In addition, they also mentioned climate change for the first time as part of the rationale for moving the clock closer to midnight. I believe that climate change does not pose an immediate threat to civilization--at least for the next 20 years or so--and there is still time to significantly reduce the threat of "doomsday" levels of climate change to civilization if strong action is taken in the next 20 years to cut carbon emissions. Thus, setting the hands of the clock closer to midnight because of climate change is probably premature. However, climate change triggered by a limited nuclear war is a whole different situation. The twin disasters of a limited nuclear war, coupled with the devastating global climate change it could wreak, should remind us that there is no such thing as a small scale nuclear war. Even a limited nuclear war is a huge threat to Earth's climate. Thus, there is no cause more important to work for than peace, so, this Easter weekend, I plan on making myself--and thus the world--more peaceful.

Jeff Masters

Average hurricane season foreseen by CSU, but TSR predicts an active season

By: JeffMasters, 5:01 PM GMT on April 07, 2009

A near-average Atlantic hurricane season is on tap for 2009, according to the latest seasonal forecast issued today by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The Klotzbach/Gray team is calling for 12 named storms, 6 hurricanes, and 2 intense hurricanes. An average season has 10-11 named storms, 6 hurricanes, and 2 intense hurricanes. The new forecast is a step down from their December forecast, which called for 14 named storms, 7 hurricanes, and 3 intense hurricanes. The new forecast calls for a near-average chance of a major hurricane hitting the U.S., both along the East Coast (32% chance, 31% chance is average) and the Gulf Coast (31% chance, 30% chance is average). The Caribbean is also forecast to have an average risk of a major hurricane.

The forecasters cited several reasons for reducing their forecast from an active season to an average season:

1) Sea surface temperature (SST) anomalies in the tropical Atlantic have cooled considerably since December. In fact, these SST anomalies are at their coolest level since July 1994. Cooler-than-normal waters provide less heat energy for developing hurricanes. In addition, an anomalously cool tropical Atlantic is typically associated with higher sea level pressure values and stronger-than-normal trade winds, indicating a more stable atmosphere with increased levels of vertical wind shear detrimental for hurricanes. Part of the reason for the substantial cooling since December is because a stronger than average Bermuda-Azores High drove strong trade winds. These strong winds acted to evaporate more water from the ocean, cooling it. Higher winds also increase the mixing of cool waters to the surface from below. However, in March, the Bermuda-Azores High weakened. The resulting weaker trade winds may allow SSTs to warm to above average levels by the coming hurricane season, if this weaker Bermuda-Azores High persists.

2) Hurricane activity in the Atlantic is lowest during El Niño years and highest during La Niña or neutral years. The CSU team expects current weak La Niña conditions to transition to neutral and perhaps weak El Niño conditions (50% chance) by this year's hurricane season. April and May are typically the months when the atmosphere will swing between El Niño and La Niña, which makes any seasonal forecasts of hurricane activity during April low-skill. The current computer models used to predict El Niño (Figure 1) mostly favor neutral conditions for the coming hurricane season. These models are primarily based on statistical methods that observe how previous El Niño events have evolved. Three of the newer computer-intensive dynamical models (similar to the GFS model we use to make weather forecasts) do predict an El Niño event by hurricane season. The reliability of all of these models is poor.


Figure 1. Computer model forecasts of El Niño/La Niña made in March. The forecasts that go above the red line at +0.5°C denote El Niño conditions; -0.5°C to +0.5°C denote neutral conditions, and below-0.5°C denote La Niña conditions. Three computer models predict El Niño conditions for hurricane season (ASO, August-September-October). However, most of the models predict neutral conditions. Image credit: Columbia University's IRI.

Analogue years
The CSU team picked five previous years when atmospheric and oceanic conditions were similar in April to what we are seeing this year. Those five years were 2001, featuring Category 4 storms Michelle, which hit Cuba, and Iris, which hit Belize; 1985, which had Category 3 Gloria in New England and Category 3 Elena in the Gulf of Mexico; 1976, which had Category 1 Hurricane Belle in New England; 1968, which had Category 1 Hurricane Gladys north of Tampa; and 1951, which had only one landfalling hurricane, Category 3 Hurricane Charlie in Mexico. The mean activity for these five years was 11 named storms, 7 hurricanes, and 3 intense hurricanes.

How accurate are the April forecasts?
This year's April forecast uses the same formula as last year's April forecast, which did quite well predicting the 2008 hurricane season. Last year's forecast included the statement, "These real-time operational early April forecasts have not shown forecast skill over climatology" during the 13-year period 1995-2007. Unfortunately, this year's forecast neglects to mention this fact. In fact, when looking at Excel spreadsheet of their forecast errors (expressed as a mathematical correlation coefficient, where positive means a skilled forecast, and negative means they did worse than climatology) their April forecasts have had negative skill between 1995-2008. In other words, you would have been better off using climatology than believing their April forecasts.

2009 Atlantic hurricane season forecast from Tropical Storm Risk, Inc.
The British private forecasting firm Tropical Storm Risk, Inc. (TSR), issued their 2009 Atlantic hurricane season forecast yesterday, but they are calling for an active year: 15 named storms, 7.8 hurricanes, and 3.6 intense hurricanes. TSR predicts a 63% chance of an above-average hurricane season, 24% chance of a near-normal season, and only a 13% chance of a below normal season. They give a 63% chance that 2009 will rank in the top third of most active hurricane seasons on record. The April 2009 TSR forecast is virtually identical to their December 2008 forecast, and is also quite close to their April 2008 forecast made for the 2008 hurricane season.

I like how TSR puts their skill level right next to the forecast numbers: 11% skill above chance at forecasting the number of named storms, 9% skill for hurricanes, and 7% skill for intense hurricanes. That's not much better than flipping a coin, but is better than the negative forecast skill of the Klotzbach/Gray April forecasts.

TSR projects that 4.8 named storms will hit the U.S., with 2.1 of these being hurricanes. The averages from the 1950-2008 climatology are 3.2 named storms and 1.5 hurricanes. Their skill in making these April forecasts for U.S. landfalls is 10-15% above chance. In the Lesser Antilles Islands of the Caribbean, TSR projects 1.4 named storms, 0.6 of these being hurricanes. Climatology is 1.1 named storms and 0.5 hurricanes.

TSR cites one main factor for their forecast of an active season: slower than normal trade winds from July - September over the Main Development Region (MDR) for hurricanes over the Atlantic (the region between 10° - 20° N from Central America to Africa, including all of the Caribbean). Trade winds are forecast to be 0.4 meters per second (about 1 mph) slower than average in this region, which would create greater spin for developing storms, and allow the oceans to heat up due to reduced evaporational cooling. TSR forecasts that SSTs will be near average in the MDR during hurricane season, and will not have an enhancing or suppressing effect on hurricane activity.


Figure 2. Accuracy of long-range forecasts of Atlantic hurricane season activity performed by Phil Klotzbach and Bill Gray of Colorado State University (colored squares) and TSR (colored lines). The CSU team's April forecast skill is not plotted, but is less than zero. The skill is measured by the Mean Square Skill Score (MSSS), which looks at the error and squares it, then compares the percent improvement the forecast has over a climatological forecast of 10 named storms, 6 hurricanes, and 2 intense hurricanes. TS=Tropical Storms, H=Hurricanes, IH=Intense Hurricanes, ACE=Accumulated Cyclone Energy, NTC=Net Tropical Cyclone Activity. Image credit: TSR.

Jeff Masters

Hurricane

A future Space Weather catastrophe : a disturbing possibility

By: JeffMasters, 1:42 PM GMT on April 03, 2009

Shortly after midnight on September 2, 1859, campers in the Rocky Mountains were awakened by an "auroral light, so bright that one could easily read common print. Some of the party insisted that it was daylight and began the preparation of breakfast", according to the Rocky Mountain News. Magnetic observatories world-wide recorded disturbances in Earth's field so extreme that magnetometer traces were driven off scale, and telegraph networks experienced major disruptions and outages. The electricity which attended this beautiful phenomenon took possession of the magnetic wires throughout the country, the Philadelphia Evening Bulletin reported, and there were numerous side displays in the telegraph offices where fantastical and unreadable messages came through the instruments, and where the atmospheric fireworks assumed shape and substance in brilliant sparks. In several locations, operators disconnected their systems from the batteries and sent messages using only the current induced by the aurora. In Havana, Cuba, the sky that night appeared "stained with blood and in a state of general conflagration" and auroras were observed as far south as Hawaii and northern Venezuela (Figure 1). A British amateur astronomer, Richard Carrington, observed an outburst of "two patches of intensely bright and white light" from a large and complex group of sunspots the the center of the Sun's disk the previous day, and so the solar storm of 1859 has been dubbed "the Carrington event". It remains the most severe solar storm to affect the Earth in recorded history.


Figure 1. Locations of reported auroral observations during the first ~1.5 hours of the September 2, 1859, magnetic storm (orange dots). Courtesy J.L. Green, NASA.

What would happen if another solar outburst with the magnitude of the Carrington event were to hit Earth today? With society so much more dependent on electricity, the effects could be tremendously expensive, causing serious disruption to the economies of nations in the northernmost and southernmost portions of the globe. An example of this vulnerability occurred during the March 13, 1989 geomagnetic "Superstorm" when a severe geomagnetic storm triggered strong direct currents in the long wires of the Canadian electric power grid. The grid was not designed to handle this, and the result was a power outage that knocked out power to the entire province of Quebec, Canada--six million people--for nine hours. The 1989 event very nearly brought down the electrical power grid over a large portion of the U.S., as well, and we were very lucky that the storm was not stronger. The 1859 Carrington event was three times more powerful than the 1989 "Superstorm", and would likely cause the failure of a huge portion of the U.S. power grid were it to hit today.

Top geomagnetic storm events of recorded history
The intensity of a geomagnetic storm can be measured by counting the number of solar charged particles that enter the Earth's magnetic field near the Equator. This number is called the Disturbance storm time, or Dst. Reliable Dst measurements go back to the 1950s. Bruce Tsurutani of NASA used magnetic field measurements taken on the ground in Bombay, India to estimate the Dst for the Carrington event. Based on Dst, the strongest geomagnetic storms in history were in 1921 and 1859. I also show on this list the strongest storms since 1960:

1) Dst = -1600, Carrington event, September 2, 1859
2) Dst = -900, May 14-15, 1921
3) Dst = -589, March 13, 1989 Superstorm
4) Dst = -472, November 20, 2003
5) Dst = -401, October 30, 2003

The 1921 event wiped out telegraph service east of the Mississippi. The currents induced in some telegraph wires were so strong that numerous fires were caused and several operators were injured by exploding consoles. Radio reception was completely lost in New Zealand, but was strengthened in Europe. Auroras were seen as far south as Puerto Rico.

Another measure of geomagnetic storm intensity is the change in amplitude of the magnetic field over time, dB/dt. Using this measure, the 1859 Carrington event was ten times stronger than the 1989 Superstorm.

Reduced vulnerability to geomagnetic storms?
One argument against a major disaster due to a repeat of the 1859 Carrington event is that increased awareness by system operators and improved forecasts since the 1989 event have made electric grids safer. Operators of the North American power grid constantly review and analyze the potential risks associated with space weather events, consulting space weather forecasts such as those produced by NOAA's Space Weather Prediction Center. They also monitor voltages and ground currents in real time and have emergency procedures in place to follow should a major geomagnetic storm hit. In October 2003, when a significant solar flare and coronal mass ejection (CME) triggered a geomagnetic storm about 75% as intense as the 1989 storm, NOAA's Space Weather Prediction Center issued a series of alerts, warnings, and predictions, giving power grid operators advance warning that severe space weather conditions were imminent that would put the power grid at risk. Despite severe geomagnetically-induced currents (GICs), power transmission equipment was protected and the grid maintained continuous operation.


Figure 2. Computer model study showing electrical systems that might be affected by a geomagnetic storm equivalent to the May 14-15, 1921 event. The regions outlined by the heavy black lines are susceptible to system collapse lasting months or years. A population in excess of 130 million might be affected, at a cost of $1-2 trillion in the first year after the event. The network of thin black lines shows the location of the nearly 80,000 miles long-distance heavy-hauling 345kV, 500kV and 765kV transmission lines in the U.S.--the main arteries of the U.S. electrical grid. The circles indicate magnitudes of geomagnetically-induced current (GIC) flow at each transformer in the network, and the color of the circle indicates the polarity of the current. Image credit: John Kappenman, Metatech Corp., The Future: Solutions or Vulnerabilities?, presentation to the space weather workshop, May 23, 2008.

Increased vulnerability to geomagnetic storms?
On the other hand, the evolution of open access on the electrical transmission system in recent years has resulted in the transport of large amounts of energy across the power system in order to maximize the economic benefit of delivering the lowest-cost energy to demand centers. The magnitude of power transfers has grown, and the increased level of transfers, coupled with multiple equipment failures, could aggravate the impacts of a storm. For example, the long distance between Hydro-Quebec's hydro-generation stations and load centers is one of the factors that is believed to have contributed to its crash during the 1989 Superstorm. In a remarkable 2008 National Academy of Sciences report, "Severe Space Weather Events--Understanding Societal and Economic Impacts Workshop Report", John Kappenman of Metatech Corporation theorizes that a future repeat of the Carrington event or the 1921 geomagnetic storm could result in catastrophic failure of large portions of the electrical grid that would last for years, costing 1-2 trillion dollars in the first year, and putting million of lives at risk. Full recovery from the event would take 4-10 years. The possible extent of a power system collapse from a repeat of the great magnetic storm of May 14-15, 1921--the second strongest geomagnetic storm in recorded history (Figure 2)--shows that a large region of the U.S. with a population of 130,000,000 might be affected.

The strong electric currents that would flow through the the electrical grid during a repeat of the Carrington event are likely to cause melting and burn-through of large-amperage copper windings and leads in electrical transformers. These multi-ton, multi-million dollar devices generally cannot be repaired in the field, and if damaged in this manner, they need to be replaced with new units. There are only a handful of spares in reserve, so most of the region affected by the collapse would remain without power until new transformers could be custom built. During the March 13, 1989 Superstorm, geomagnetic-induced currents (GICs) melted the internal windings of a 500kV transformer in the Salem Nuclear plant in southern New Jersey (Figure 3). The entire nuclear plant was unable to operate until this damaged transformer was replaced. Fortunately, a spare from a canceled nuclear plant in Washington State was available, and the Salem plant was able to reopen 40 days later. Had the spare not been available, a new custom-built transformer would have been required, potentially idling the power plant for years. The typical manufacture lead times for these transformers are 12 months or more. According to a January 2009 press release from Metatech, Inc., 300 Extra High Voltage (EHV) transformers in the U.S. would be at risk of permanent damage and require replacement in the event of a geomagnetic storm as intense as the 1921 or 1859 events. Here's where it gets really scary. According to the press release:

* Manufacturing capability in the world for EHV-class transformers continues to be limited relative to present market demand for these devices. Further, manufacturers would be unable to rapidly supply the large number of replacement transformers needed should the U.S. or other power grids suffer a major catastrophic loss of EHV Transformers.
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* Manufacturers presently have a backlog of nearly 3 years for all EHV transformers (230 kV and above). The earliest delivery time presently quoted for a new order is early 2011.
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* Only one plant exists in the U.S. capable of manufacturing a transformer up to 345 kV. No manufacturing capability exists in the U.S. at present for 500 kV and 765 kV transformers, which represent the largest group of At-Risk transformers in the U.S.

We have the very real possibility that a geomagnetic storms of an intensity that has happened before--and will happen again--could knock out the power to tens of millions of Americans for multiple years. The electrical grids in Europe and northern Asia have similar vulnerabilities, so a huge, years-long global emergency affecting hundreds of millions of people and costing many trillions of dollars might result from a repeat of the 1859 or 1921 geomagnetic storms.


Figure 3. The Salem nuclear plant transformer (exterior shot is one of three phases) and two images of internal heating damage to conductors and insulation from stray flux heating caused by geomagnetically-induced currents from the March 13, 1989 Superstorm. Image credit: John Kappenman, Metatech Corporation.

When might another Carrington event occur?
Geomagnetic storms on the scale of the 1859 or 1921 events are very rare, and no one knows when such an event may recur. Huge geomagnetic storms can occur at any portion of the 11-year sunspot cycle, but are most likely within a year of solar maximum. The 1921 event occurred three years after solar maximum, and the 1859 and 1989 events within a year of solar maximum. According to NASA's Bruce Tsurutani, a massive X22+ solar flare event on April 2, 2001, near the peak of the last solar cycle, was even larger than the flare that triggered the 1859 Carrington event. Fortunately, the 2001 flare was not pointed at the Earth, and we escaped a repeat of the Carrington event.


Figure 4. The largest solar flare ever recorded was observed on April 2, 2001. It was rated X-22 on a scale that only goes from one to twenty. The flare was more powerful than the flare that accompanied the worst geomagnetic storm in history, the 1859 Carrington event. Fortunately, the 2001 flare was not aimed at the Earth. Image credit: NASA.

We're currently at the deepest solar minimum since 1913, according to NASA. The sun has been remarkably free of sunspots this year, and it now looks like the next solar maximum will be at least 13 years removed from the previous peak in 2000. It could be much longer than that--unpublished research at the University of Michigan suggests that it might not be until 2030 that we'll see the next real solar maximum. A similar quiet solar period, called the Maunder Minimum, occurred in the late 1600s.

Given our history of two geomagnetic storms capable of causing large U.S. blackouts in the past 160 years, the odds of a potentially catastrophic space weather event are probably around 1-2% per year. A catastrophic failure of the electrical system from such an event is not a sure thing, but we should anticipate the possibility. Doing the research for this post has made me quite concerned about the possibility of long-term blackouts in the U.S., and I am planning on keeping a few more emergency supplies on hand as a result (this includes enough gasoline to drive to Michigan's Upper Peninsula, which would be less likely to get hit with power outages). Blackouts like the August 2003 blackout that affected 50 million people and lasted for 24-36 hours can also occur due to such mundane causes as trees interfering with power lines. Had that blackout occurred in winter, it could have lasted several days longer, since power plants take a much longer time to start in cold weather. Emergency generators typically only have fuel for 72 hours, so everything from hospital services to water pumping ability to natural gas delivery for heating will be threatened by large regional blackouts lasting more than 72 hours.

What can be done to reduce our vulnerability?
According to a January 2009 press release from Metatech, Inc., the installation of supplemental transformer neutral ground resistors to reduce GIC flows is relatively inexpensive, has low engineering trade-offs, and can produce 60-70% reductions of GIC levels for storms of all sizes. A Congressionally mandated "EMP Commission" has estimated the cost of this hardening in the existing U.S. power grid infrastructure to be on the order of $150 million. It would also be helpful to replace the ailing ACE satellite, which monitors solar storms and can provide advance warning of when a major geomagnetic storm is imminent. In any case, the future expansion of the electrical grid throughout the world needs to be designed with geomagnetic storms in mind. If large solar and wind power generation plants are developed, they will likely require an extensive new network of 765 kV transmission lines to deliver this energy. The higher voltage transformers needed for this expansion are the most vulnerable type of transformers to geomagnetic storms, and the new power system should be carefully designed to reduce this vulnerability.

For further reading
A May 2013 study by AER and Lloyd's (available here) concluded that the total US population at risk of extended power outage from a Carrington-level storm is between 20-40 million, with durations of 16 days to 1-2 years. The duration of outages will depend largely on the availability of spare replacement transformers. If new transformers need to be ordered, the lead-time is likely to be a minimum of five months. The total economic cost for such a scenario is estimated at $0.6-2.6 trillion USD.

January 2009 press release from Metatech, Inc., "An Overview of the National Academy of Sciences Report on Severe Space Weather and the Vulnerability of US Electric Power Grid".

August 2008 Scientific American article, "Bracing the Satellite Infrastructure for a Solar Superstorm".

2008 National Academy of Sciences study, , "Severe Space Weather Events--Understanding Societal and Economic Impacts Workshop Report"

March 2009 newscientist.com article on Space Weather threats.

Excellent 2007 lecture by John Kappenman of Metatech Corporation, "Electric Power Grid Vulnerability to Geomagnetic Storms" (50 minutes).

Jeff Masters

Atmospheric Phenomena


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather