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2010 - 2011: Earth's most extreme weather since 1816?

Posted on 27 June 2011 by Jeff Masters

Every year extraordinary weather events rock the Earth. Records that have stood centuries are broken. Great floods, droughts, and storms affect millions of people, and truly exceptional weather events unprecedented in human history may occur. But the wild roller-coaster ride of incredible weather events during 2010, in my mind, makes that year the planet's most extraordinary year for extreme weather since reliable global upper-air data began in the late 1940s. Never in my 30 years as a meteorologist have I witnessed a year like 2010--the astonishing number of weather disasters and unprecedented wild swings in Earth's atmospheric circulation were like nothing I've seen. The pace of incredible extreme weather events in the U.S. over the past few months have kept me so busy that I've been unable to write-up a retrospective look at the weather events of 2010. But I've finally managed to finish, so fasten your seat belts for a tour through the top twenty most remarkable weather events of 2010. At the end, I'll reflect on what the wild weather events of 2010 and 2011 imply for our future.

Earth's hottest year on record
Unprecedented heat scorched the Earth's surface in 2010, tying 2005 for the warmest year since accurate records began in the late 1800s. Temperatures in Earth's lower atmosphere also tied for warmest year on record, according to independent satellite measurements. Earth's 2010 record warmth was unusual because it occurred during the deepest solar energy minimum since satellite measurements of the sun began in the 1970s. Unofficially, nineteen nations (plus the the U.K.'s Ascension Island) set all-time extreme heat records in 2010. This includes Asia's hottest reliably measured temperature of all-time, the remarkable 128.3°F (53.5°C) in Pakistan in May 2010. This measurement is also the hottest reliably recorded temperature anywhere on the planet except for in Death Valley, California. The countries that experienced all-time extreme highs in 2010 constituted over 20% of Earth's land surface area.


Figure 1. Climate Central and Weather Underground put together this graphic showing the nineteen nations (plus one UK territory, Ascension Island) that set new extreme heat records in 2010.

Most extreme winter Arctic atmospheric circulation on record; "Snowmageddon" results
The atmospheric circulation in the Arctic took on its most extreme configuration in 145 years of record keeping during the winter of 2009 - 2010. The Arctic is normally dominated by low pressure in winter, and a "Polar Vortex" of counter-clockwise circulating winds develops surrounding the North Pole. However, during the winter of 2009 - 2010, high pressure replaced low pressure over the Arctic, and the Polar Vortex weakened and even reversed at times, with a clockwise flow of air replacing the usual counter-clockwise flow of air. This unusual flow pattern allowed cold air to spill southwards and be replaced by warm air moving poleward. Like leaving the refrigerator door ajar, the Arctic "refrigerator" warmed, and cold Arctic air spilled out into "living room" where people live. A natural climate pattern called the North Atlantic Oscillation (NAO), and its close cousin, the Arctic Oscillation (AO) were responsible. Both of these patterns experienced their strongest-on-record negative phase, when measured as the pressure difference between the Icelandic Low and Azores High.

The extreme Arctic circulation caused a bizarre upside-down winter over North America--Canada had its warmest and driest winter on record, forcing snow to be trucked in for the Winter Olympics in Vancouver, but the U.S. had its coldest winter in 25 years. A series of remarkable snow storms pounded the Eastern U.S., with the "Snowmageddon" blizzard dumping more than two feet of snow on Baltimore and Philadelphia. Western Europe also experienced unusually cold and snowy conditions, with the UK recording its 8th coldest January. A highly extreme negative phase of the NAO and AO returned again during November 2010, and lasted into January 2011. Exceptionally cold and snowy conditions hit much of Western Europe and the Eastern U.S. again in the winter of 2010 - 2011. During these two extreme winters, New York City recorded three of its top-ten snowstorms since 1869, and Philadelphia recorded four of its top-ten snowstorms since 1884. During December 2010, the extreme Arctic circulation over Greenland created the strongest ridge of high pressure ever recorded at middle levels of the atmosphere, anywhere on the globe (since accurate records began in 1948.) New research suggests that major losses of Arctic sea ice could cause the Arctic circulation to behave so strangely, but this work is still speculative.


Figure 2. Digging out in Maryland after "Snowmageddon". Image credit: wunderphotographer chills.

Arctic sea ice: lowest volume on record, 3rd lowest extent
Sea ice in the Arctic reached its third lowest areal extent on record in September 2010. Compared to sea ice levels 30 years ago, 1/3 of the polar ice cap was missing--an area the size of the Mediterranean Sea. The Arctic has seen a steady loss of meters-thick, multi-year-old ice in recent years that has left thin, 1 - 2 year-old ice as the predominant ice type. As a result, sea ice volume in 2010 was the lowest on record. More than half of the polar icecap by volume--60%--was missing in September 2010, compared to the average from 1979 - 2010. All this melting allowed the Northwest Passage through the normally ice-choked waters of Canada to open up in 2010. The Northeast Passage along the coast of northern Russia also opened up, and this was the third consecutive year--and third time in recorded history--that both passages melted open. Two sailing expeditions--one Russian and one Norwegian--successfully navigated both the Northeast Passage and the Northwest Passage in 2010, the first time this feat has been accomplished. Mariners have been attempting to sail the Northwest Passage since 1497, and have failed to accomplish this feat without an icebreaker until the 2000s. In December 2010, Arctic sea ice fell to its lowest winter extent on record, the beginning of a 3-month streak of record lows. Canada's Hudson Bay did not freeze over until mid-January of 2011, the latest freeze-over date in recorded history.


Figure 3. The Arctic's minimum sea ice extent for 2010 was reached on September 21, and was the third lowest on record. Image credit: National Snow and Ice Data Center.

Record melting in Greenland, and a massive calving event
Greenland's climate in 2010 was marked by record-setting high air temperatures, the greatest ice loss by melting since accurate records began in 1958, the greatest mass loss of ocean-terminating glaciers on record, and the calving of a 100 square-mile ice island--the largest calving event in the Arctic since 1962. Many of these events were due to record warm water temperatures along the west coast of Greenland, which averaged 2.9°C (5.2°F) above average during October 2010, a remarkable 1.4°C above the previous record high water temperatures in 2003.


Figure 4. The 100 square-mile ice island that broke off the Petermann Glacier heads out of the Petermann Fjord in this 7-frame satellite animation. The animation begins on August 5, 2010, and ends on September 21, with images spaced about 8 days apart. The images were taken by NASA's Aqua and Terra satellites.

Second most extreme shift from El Niño to La Niña
The year 2010 opened with a strong El Niño event and exceptionally warm ocean waters in the Eastern Pacific. However, El Niño rapidly waned in the spring, and a moderate to strong La Niña developed by the end of the year, strongly cooling these ocean waters. Since accurate records began in 1950, only 1973 has seen a more extreme swing from El Niño to La Niña. The strong El Niño and La Niña events contributed to many of the record flood events seen globally in 2010, and during the first half of 2011.


Figure 5. The departure of sea surface temperatures from average at the beginning of 2010 (top) and the end of 2010 (bottom) shows the remarkable transition from strong El Niño to strong La Niña conditions that occurred during the year. Image credit: NOAA/NESDIS.

Second worst coral bleaching year
Coral reefs took their 2nd-worst beating on record in 2010, thanks to record or near-record warm summer water temperatures over much of Earth's tropical oceans. The warm waters caused the most coral bleaching since 1998, when 16 percent of the world's reefs were killed off. "Clearly, we are on track for this to be the second worst (bleaching) on record," NOAA coral expert Mark Eakin in a 2010 interview. "All we're waiting on now is the body count." The summer 2010 coral bleaching episodes were worst in the Philippines and Southeast Asia, where El Niño warming of the tropical ocean waters during the first half of the year was significant. In Indonesia's Aceh province, 80% of the bleached corals died, and Malaysia closed several popular dive sites after nearly all the coral were damaged by bleaching. In some portions of the Caribbean, such as Venezuela and Panama, coral bleaching was the worst on record.


Figure 6. An example of coral bleaching that occurred during the record-strength 1997-1998 El Niño event. Image credit: Craig Quirolo, Reef Relief/Marine Photobank, in Climate, Carbon and Coral Reefs

Wettest year over land
The year 2010 also set a new record for wettest year in Earth's recorded history over land areas. The difference in precipitation from average in 2010 was about 13% higher than that of the previous record wettest year, 1956. However, this record is not that significant, since it was due in large part to random variability of the jet stream weather patterns during 2010. The record wetness over land was counterbalanced by relatively dry conditions over the oceans.


Figure 7. Global departure of precipitation over land areas from average for 1900 - 2010. The year 2010 set a new record for wettest year over land areas in Earth's recorded history. The difference in precipitation from average in 2010 was about 13% higher than that of the previous record wettest year, 1956. Image credit: NOAA's National Climatic Data Center.

Amazon rainforest experiences its 2nd 100-year drought in 5 years
South America's Amazon rainforest experienced its second 100-year drought in five years during 2010, with the largest northern tributary of the Amazon River--the Rio Negro--dropping to thirteen feet (four meters) below its usual dry season level. This was its lowest level since record keeping began in 1902. The low water mark is all the more remarkable since the Rio Negro caused devastating flooding in 2009, when it hit an all-time record high, 53 ft (16 m) higher than the 2010 record low. The 2010 drought was similar in intensity and scope to the region's previous 100-year drought in 2005. Drought makes a regular appearance in the Amazon, with significant droughts occurring an average of once every twelve years. In the 20th century, these droughts typically occurred during El Niño years, when the unusually warm waters present along the Pacific coast of South America altered rainfall patterns. But the 2005 and 2010 droughts did not occur during El Niño conditions, and it is theorized that they were instead caused by record warm sea surface temperatures in the Atlantic.

We often hear about how important Arctic sea ice is for keeping Earth's climate cool, but a healthy Amazon is just as vital. Photosynthesis in the world's largest rainforest takes about 2 billion tons of carbon dioxide out of the air each year. However, in 2005, the drought reversed this process. The Amazon emitted 3 billion tons of CO2 to the atmosphere, causing a net 5 billion ton increase in CO2 to the atmosphere--roughly equivalent to 16 - 22% of the total CO2 emissions to the atmosphere from burning fossil fuels that year. The Amazon stores CO2 in its soils and biomass equivalent to about fifteen years of human-caused emissions, so a massive die-back of the forest could greatly accelerate global warming.


Figure 8. Hundreds of fires (red squares) generate thick smoke over a 1000 mile-wide region of the southern Amazon rain forest in this image taken by NASA's Aqua satellite on August 16, 2010. The Bolivian government declared a state of emergency in mid-August due to the out-of-control fires burning over much of the country. Image credit: NASA.

Global tropical cyclone activity lowest on record
The year 2010 was one of the strangest on record for tropical cyclones. Each year, the globe has about 92 tropical cyclones--called hurricanes in the Atlantic and Eastern Pacific, typhoons in the Western Pacific, and tropical cyclones in the Southern Hemisphere. But in 2010, we had just 68 of these storms--the fewest since the dawn of the satellite era in 1970. The previous record slowest year was 1977, when 69 tropical cyclones occurred world-wide. Both the Western Pacific and Eastern Pacific had their quietest seasons on record in 2010, but the Atlantic was hyperactive, recording its 3rd busiest season since record keeping began in 1851. The Southern Hemisphere had a slightly below average season. The Atlantic ordinarily accounts for just 13% of global cyclone activity, but accounted for 28% in 2010--the greatest proportion since accurate tropical cyclone records began in the 1970s.

A common theme of many recent publications on the future of tropical cyclones globally in a warming climate is that the total number of these storms will decrease, but the strongest storms will get stronger. For example, a 2010 review paper published in Nature Geosciences concluded that the strongest storms would increase in intensity by 2 - 11% by 2100, but the total number of storms would fall by 6 - 34%. It is interesting that 2010 saw the lowest number of global tropical cyclones on record, but an average number of very strong Category 4 and 5 storms (the 25-year average is 13 Category 4 and 5 storms, and 2010 had 14.) Fully 21% of 2010's tropical cyclones reached Category 4 or 5 strength, versus just 14% during the period 1983 - 2007. Most notably, in 2010 we had Super Typhoon Megi. Megi's sustained winds cranked up to a ferocious 190 mph and its central pressure bottomed out at 885 mb on October 16, making it the 8th most intense tropical cyclone in world history. Other notable storms in 2010 included the second strongest tropical cyclone on record in the Arabian Sea (Category 4 Cyclone Phet in June), and the strongest tropical cyclone ever to hit Myanmar/Burma (October's Tropical Cyclone Giri, an upper end Category 4 storm with 155 mph winds.)


Figure 9. Visible satellite image of Tropical Cyclone Phet on Thursday, June 3, 2010. Record heat over southern Asia in May helped heat up the Arabian Sea to 2°C above normal, and the exceptionally warm SSTs helped fuel Tropical Cyclone Phet into the second strongest tropical cyclone ever recorded in the Arabian Sea. Phet peaked at Category 4 strength with 145 mph winds, and killed 44 people and did $700 million in damage to Oman. Only Category 5 Cyclone Gonu of 2007 was a stronger Arabian Sea cyclone.

A hyperactive Atlantic hurricane season: 3rd busiest on record
Sea surface temperatures that were the hottest on record over the main development region for Atlantic hurricanes helped fuel an exceptionally active 2010 Atlantic hurricane season. The nineteen named storms were the third most since 1851; the twelve hurricanes of 2010 ranked second most. Three major hurricanes occurred in rare or unprecedented locations. Julia was the easternmost major hurricane on record, Karl was the southernmost major hurricane on record in the Gulf of Mexico, and Earl was the 4th strongest hurricane so far north. The formation of Tomas so far south and east so late in the season (October 29) was unprecedented in the historical record; no named storm had ever been present east of the Lesser Antilles (61.5°W) and south of 12°N latitude so late in the year. Tomas made the 2010 the 4th consecutive year with a November hurricane in the Atlantic--an occurrence unprecedented since records began in 1851.


Figure 10. Hurricane Earl as seen from the International Space Station on Thursday, September 2, 2010. Image credit: NASA astronaut Douglas Wheelock.

A rare tropical storm in the South Atlantic
A rare tropical storm formed in the South Atlantic off the coast of Brazil on March 10 - 11, and was named Tropical Storm Anita. Brazil has had only one landfalling tropical cyclone in its history, Cyclone Catarina of March 2004, one of only seven known tropical or subtropical cyclones to form in the South Atlantic, and the only one to reach hurricane strength. Anita of 2010 is probably the fourth strongest tropical/subtropical storm in the South Atlantic, behind Hurricane Catarina, an unnamed February 2006 storm that may have attained wind speeds of 65 mph, and a subtropical storm that brought heavy flooding to the coast of Uruguay in January 2009. Tropical cyclones rarely form in the South Atlantic Ocean, due to strong upper-level wind shear, cool water temperatures, and the lack of an initial disturbance to get things spinning (no African waves or Intertropical Convergence Zone.)


Figure 11. Visible satellite image of the Brazilian Tropical Storm Anita.

Strongest storm in Southwestern U.S. history
The most powerful low pressure system in 140 years of record keeping swept through the Southwest U.S. on January 20 - 21, 2010, bringing deadly flooding, tornadoes, hail, hurricane force winds, and blizzard conditions. The storm set all-time low pressure records over roughly 10 - 15% of the U.S.--southern Oregon, California, Nevada, Arizona, and Utah. Old records were broken by a wide margin in many locations, most notably in Los Angeles, where the old record of 29.25" set January 17, 1988, was shattered by .18" (6 mb). The record-setting low spawned an extremely intense cold front that swept through the Southwest. Winds ahead of the cold front hit sustained speeds of hurricane force--74 mph--at Apache Junction, 40 miles east of Phoenix, and wind gusts as high as 94 mph were recorded in Ajo, Arizona. High winds plunged visibility to zero in blowing dust on I-10 connecting Phoenix and Tucson, closing the Interstate.


Figure 12. Ominous clouds hover over Arizona's Superstition Mountains during Arizona's most powerful storm on record, on January 21, 2010. Image credit: wunderphotographer ChandlerMike.

Strongest non-coastal storm in U.S. history
A massive low pressure system intensified to record strength over northern Minnesota on October 26, 2010, resulting in the lowest barometric pressure readings ever recorded in the continental United States, except for from hurricanes and nor'easters affecting the Atlantic seaboard. The 955 mb sea level pressure reported from Bigfork, Minnesota beat the previous low pressure record of 958 mb set during the Great Ohio Blizzard of January 26, 1978. Both Minnesota and Wisconsin set all time low pressure readings during the October 26 storm, and International Falls beat their previous low pressure record by nearly one-half inch of mercury--a truly amazing anomaly. The massive storm spawned 67 tornadoes over a four-day period, and brought sustained winds of 68 mph to Lake Superior.


Figure 13. Visible satellite image of the October 26, 2010 superstorm taken at 5:32pm EDT. At the time, Bigfork, Minnesota was reporting the lowest pressure ever recorded in a U.S. non-coastal storm, 955 mb. Image credit: NASA/GSFC.

Weakest and latest-ending East Asian monsoon on record
The summer monsoon over China's South China Sea was the weakest and latest ending monsoon on record since detailed records began in 1951, according to the Beijing Climate Center. The monsoon did not end until late October, nearly a month later than usual. The abnormal monsoon helped lead to precipitation 30% - 80% below normal in Northern China and Mongolia, and 30 - 100% above average across a wide swath of Central China. Western China saw summer precipitation more than 200% above average, and torrential monsoon rains triggered catastrophic landslides that killed 2137 people and did $759 million in damage. Monsoon floods in China killed an additional 1911 people, affected 134 million, and did $18 billion in damage in 2010, according to the WHO Collaborating Centre for Research on the Epidemiology of Disasters (CRED). This was the 2nd most expensive flooding disaster in Chinese history, behind the $30 billion price tag of the 1998 floods that killed 3656 people. China had floods in 1915, 1931, and 1959 that killed 3 million, 3.7 million, and 2 million people, respectively, but no damage estimates are available for these floods.


Figure 14. Paramilitary policemen help evacuate residents from Wanjia village of Fuzhou City, East China's Jiangxi province, June 22, 2010. Days of heavy rain burst the Changkai Dike of Fu River on June 21, threatening the lives of 145,000 local people. Image credit: Xinhua.

No monsoon depressions in India's Southwest Monsoon for 2nd time in 134 years
The Southwest Monsoon that affects India was fairly normal in 2010, bringing India rains within 2% of average. Much of the rain that falls in India from the monsoon typically comes from large regions of low pressure that form in the Bay of Bengal and move westwards over India. Typically, seven of these lows grow strong and well-organized enough to be labelled monsoon depressions, which are similar to but larger than tropical depressions. In 2010, no monsoon depressions formed--the only year besides 2002 (since 1877) that no monsoon depressions have been observed.

The Pakistani flood: most expensive natural disaster in Pakistan's history
A large monsoon low developed over the Bay of Bengal in late July and moved west towards Pakistan, creating a strong flow of moisture that helped trigger the deadly Pakistan floods of 2010. The floods were worsened by a persistent and unusually-far southwards dip in the jet stream, which brought cold air and rain-bearing low pressure systems over Pakistan. This unusual bend in the jet stream also helped bring Russia its record heat wave and drought. The Pakistani floods were the most expensive natural disaster in Pakistani history, killing 1985 people, affecting 20 million, and doing $9.5 billion in damage.


Figure 15. Local residents attempt to cross a washed-out road during the Pakistani flood catastrophe of 2010. Image credit: Pakistan Meteorology Department.

The Russian heat wave and drought: deadliest heat wave in human history
A scorching heat wave struck Moscow in late June 2010, and steadily increased in intensity through July as the jet stream remained "stuck" in an unusual loop that kept cool air and rain-bearing low pressure systems far north of the country. By July 14, the mercury hit 31°C (87°F) in Moscow, the first day of an incredible 33-day stretch with a maximum temperatures of 30°C (86°F) or higher. Moscow's old extreme heat record, 37°C (99°F) in 1920, was equaled or exceeded five times in a two-week period from July 26 - August 6 2010, including an incredible 38.2°C (101°F) on July 29. Over a thousand Russians seeking to escape the heat drowned in swimming accidents, and thousands more died from the heat and from inhaling smoke and toxic fumes from massive wild fires. The associated drought cut Russia's wheat crop by 40%, cost the nation $15 billion, and led to a ban on grain exports. The grain export ban, in combination with bad weather elsewhere in the globe during 2010 - 2011, caused a sharp spike in world food prices that helped trigger civil unrest across much of northern Africa and the Middle East in 2011. At least 55,000 people died due to the heat wave, making it the deadliest heat wave in human history. A 2011 NOAA study concluded that "while a contribution to the heat wave from climate change could not be entirely ruled out, if it was present, it played a much smaller role than naturally occurring meteorological processes in explaining this heat wave's intensity." However, they noted that the climate models used for the study showed a rapidly increasing risk of such heat waves in western Russia, from less than 1% per year in 2010, to 10% or more per year by 2100.


Figure 16. Smoke from wildfires burning to the southeast of Moscow on August 12, 2010. Northerly winds were keeping the smoke from blowing over the city. Image credit: NASA.

Record rains trigger Australia's most expensive natural disaster in history
Australia's most expensive natural disaster in history is now the Queensland flood of 2010 - 2011, with a price tag as high as $30 billion. At least 35 were killed. The Australian Bureau of Meteorology's annual summary reported, "Sea surface temperatures in the Australian region during 2010 were the warmest value on record for the Australian region. Individual high monthly sea surface temperature records were also set during 2010 in March, April, June, September, October, November and December. Along with favourable hemispheric circulation associated with the 2010 La Niña, very warm sea surface temperatures contributed to the record rainfall and very high humidity across eastern Australia during winter and spring." In 2010, Australia had its wettest spring (September - November) since records began 111 years ago, with some sections of coastal Queensland receiving over 4 feet (1200 mm) of rain. Rainfall in Queensland and all of eastern Australia in December was the greatest on record, and the year 2010 was the rainiest year on record for Queensland. Queensland has an area the size of Germany and France combined, and 3/4 of the region was declared a disaster zone.


Figure 17. The airport, the Bruce Highway, and large swaths of Rockhampton, Australia, went under water due to flooding from the Fitzroy River on January 9, 2011. The town of 75,000 was completely cut off by road and rail, and food, water and medicine had to be brought in by boat and helicopter. Image credit: NASA.

Heaviest rains on record trigger Colombia's worst flooding disaster in history
The 2010 rainy-season rains in Colombia were the heaviest in the 42 years since Colombia's weather service was created and began taking data. Floods and landslides killed 528, did $1 billion in damage, and left 2.2 million homeless, making it Colombia's most expensive, most widespread, and 2nd deadliest flooding disaster in history. Colombia's president Juan Manuel Santos said, "the tragedy the country is going through has no precedents in our history."


Figure 18. A daring rescue of two girls stranded in a taxi by flash flood waters Barranquilla, northern Colombia on August 14, 2010.

Tennessee's 1-in-1000 year flood kills 30, does $2.4 billion in damage
Tennessee's greatest disaster since the Civil War hit on May 1 - 2, 2010, when an epic deluge of rain brought by an "atmospheric river" of moisture dumped up to 17.73" of rain on the state. Nashville had its heaviest 1-day and 2-day rainfall amounts in its history, with a remarkable 7.25" on May 2, breaking the record for most rain in a single day. Only two days into the month, the May 1 - 2 rains made it the rainiest May in Nashville's history. The record rains sent the Cumberland River in downtown Nashville surging to 51.86', 12' over flood height, and the highest level the river has reached since a flood control project was completed in the early 1960s. At least four rivers in Tennessee reached their greatest flood heights on record. Most remarkable was the Duck River at Centreville, which crested at 47', a full 25 feet above flood stage, and ten feet higher than the previous record crest, achieved in 1948.


Figure 19. A portable classroom building from a nearby high school floats past submerged cars on I-24 near Nashville, TN on May 1, 2010. One person died in the flooding in this region of I-24. Roughly 200 - 250 vehicles got submerged on this section of I-24, according to wunderphotographer laughingjester, who was a tow truck operator called in to clear out the stranded vehicles.

When was the last time global weather was so extreme?
It is difficult to say whether the weather events of a particular year are more or less extreme globally than other years, since we have no objective global index that measures extremes. However, we do for the U.S.--NOAA's Climate Extremes Index (CEI), which looks at the percentage area of the contiguous U.S. experiencing top 10% or bottom 10% monthly maximum and minimum temperatures, monthly drought, and daily precipitation. The Climate Extremes Index rated 1998 as the most extreme year of the past century in the U.S. That year was also the warmest year since accurate records began in 1895, so it makes sense that the warmest year in Earth's recorded history--2010--was also probably one of the most extreme for both temperature and precipitation. Hot years tend to generate more wet and dry extremes than cold years. This occurs since there is more energy available to fuel the evaporation that drives heavy rains and snows, and to make droughts hotter and drier in places where storms are avoiding. Looking back through the 1800s, which was a very cool period, I can't find any years that had more exceptional global extremes in weather than 2010, until I reach 1816. That was the year of the devastating "Year Without a Summer"--caused by the massive climate-altering 1815 eruption of Indonesia's Mt. Tambora, the largest volcanic eruption since at least 536 A.D. It is quite possible that 2010 was the most extreme weather year globally since 1816.

Where will Earth's climate go from here?
The pace of extreme weather events has remained remarkably high during 2011, giving rise to the question--is the "Global Weirding" of 2010 and 2011 the new normal? Has human-caused climate change destabilized the climate, bringing these extreme, unprecedented weather events? Any one of the extreme weather events of 2010 or 2011 could have occurred naturally sometime during the past 1,000 years. But it is highly improbable that the remarkable extreme weather events of 2010 and 2011 could have all happened in such a short period of time without some powerful climate-altering force at work. The best science we have right now maintains that human-caused emissions of heat-trapping gases like CO2 are the most likely cause of such a climate-altering force.

Human-caused climate change has fundamentally altered the atmosphere by adding more heat and moisture. Observations confirm that global atmospheric water vapor has increased by about 4% since 1970, which is what theory says should have happened given the observed 0.5°C (0.9°F) warming of the planet's oceans during the same period. Shifts of this magnitude are capable of significantly affecting the path and strength of the jet stream, behavior of the planet's monsoons, and paths of rain and snow-bearing weather systems. For example, the average position of the jet stream retreated poleward 270 miles (435 km) during a 22-year period ending in 2001, in line with predictions from climate models. A naturally extreme year, when embedded in such a changed atmosphere, is capable of causing dramatic, unprecedented extremes like we observed during 2010 and 2011. That's the best theory I have to explain the extreme weather events of 2010 and 2011--natural extremes of El Niño, La Niña and other natural weather patterns combined with significant shifts in atmospheric circulation and the extra heat and atmospheric moisture due to human-caused climate change to create an extraordinary period of extreme weather. However, I don't believe that years like 2010 and 2011 will become the "new normal" in the coming decade. Many of the flood disasters in 2010 - 2011 were undoubtedly heavily influenced by the strong El Niño and La Niña events that occurred, and we're due for a few quiet years without a strong El Niño or La Niña. There's also the possibility that a major volcanic eruption in the tropics or a significant quiet period on the sun could help cool the climate for a few years, cutting down on heat and flooding extremes (though major eruptions tend to increase drought.) But the ever-increasing amounts of heat-trapping gases humans are emitting into the air puts tremendous pressure on the climate system to shift to a new, radically different, warmer state, and the extreme weather of 2010 - 2011 suggests that the transition is already well underway. A warmer planet has more energy to power stronger storms, hotter heat waves, more intense droughts, heavier flooding rains, and record glacier melt that will drive accelerating sea level rise. I expect that by 20 - 30 years from now, extreme weather years like we witnessed in 2010 will become the new normal.

Finally, I'll leave you with a quote from Dr. Ricky Rood's climate change blog, in his recent post,Changing the Conversation: Extreme Weather and Climate: "Given that greenhouse gases are well known to hold energy close to the Earth, those who deny a human-caused impact on weather need to pose a viable mechanism of how the Earth can hold in more energy and the weather not be changed. Think about it."

Reposted from Weather Underground by Dr Jeff Masters, Director of Meteorology.

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  1. Brilliant Post Dr Masters, read it over at wunderground.

    Oh and all SkS readers, check out the current UAH discover websites temperatures we've been near record highs all June.
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  2. http://discover.itsc.uah.edu/amsutemps/

    Link here, seems to be a huge amount of warm water in the Pacific atm.
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  3. Yeah, I'm picking El Nino by years end, based on an Indian Ocean Dipole paper. The NOAA SST page seems to suggest an El Nino might on the way too.

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  4. You mention Indonesia's volcano Tambora (1815) and the year without a summer. What effect will, in your opinion, Chile's Puyehue volcano (2011)have?
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  5. Kudos to Dr. Masters on very well written and most timely article.

    The graphics stunningly amplify the text.
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  6. Puyehue is having a tiny eruption compared with Tambora (1815), with a Volcanic Explosivity Index (VEI) of 4 compared to Tambora's 6.5 - 7. (mostly from BigThink)

    "From: NASA's Earth Observing Project Science Webpage: Volcanoes and Global Climate Change, May 2000
    Volcanic eruptions are thought to be responsible for the global cooling that has been observed for a few years after a major eruption. The amount and global extent of the cooling depend on the force of the eruption and, possibly, its latitude." USGS publication

    Latitude may matter because there is more solar gain in the tropics than at the poles. At the extreme, SO2 (etc.) blocking some equatorial sunshine will affect a season's weather more than blocking all polar winter "sunshine". Of course, the ash and gasses don't remain at the latitude at which they were erupted and can affect weather for multiple seasons. Equatorial eruptions tend to affect weather in both hemispheres while higher-latitude eruptions affect mostly only their own hemisphere.
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  7. Dr. Masters - great post - I found it on WeatherUnderground and thought it would be a great fit here - it is!

    Speaking from a position of ignorance - is global warming going to lead to much faster El Nino/La Nina cycles? I see that Jeff thinks we are due for a few quiet years, but I'm thinking more along the lines of Rob Painting. It seems a system seeking balance would experience more ENSO shifts, and very recent trends support that.
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  8. Ref to La Nina El Nino. NOAA seems to be forcasting a return to La Nina contions quit soon.

    NOAA Prediction
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  9. Dr. Masters:
    Do you think the intensity and number of hurricanes/tropical cyclones etc will continue as low in intensity and numbers as research by Dr. Maue shows?

    Dr. Maue's findings
    0 0
  10. Camburn @8,

    What is the fascination that "skeptics" have for La Ninas? Is it becasue they can cause a transient drop in global temperatures of up to 0.2 C? "Skeptics" have to keep focusing on the potential for cooling (real or imaginary) and ignore the long term trends it seems...

    And from your NOAA link:

    "ENSO-neutral conditions are expected to continue at least through the Northern Hemisphere summer 2011."

    Your definition of "soon" must differ quite a bit from that of NOAA's. Please do not misrepresent NOAA.

    For an idea of what all the dynamical and statistical guidance is suggesting, go here.



    [Source]
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  11. Albatross:
    If you had read the NOAA link, you would have seen the IRI graph.
    I stated plainly that NOAA is predicting a La Nina quit soon. NOAA is the US, where I live, predominant weather/climate forcaster.
    As far as my interest in La Nina? Where I live a La Nina keeps us cold and wet. An El Nino has a very limited effect, whereas a La Nina has a huge effect.
    Nothing to do with being skeptical, everything to do on where one lives.
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  12. Go to the NOAA link, go to page 28:

    "The CFS.v1 ensemble mean (black dashed line) predicts La Nina conditions by late Northern Hemisphere Fall 2011."
    0 0
  13. Late fall is pretty dog gone soon Albatross.
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  14. Camburn - Big spread of ENSO predictions. Interesting that NOAA are predicting La Nina when the tell-tale signs of El Nino seem to be taking shape in the equatorial Pacific.

    Actually Thoughtful - global warming has already sped up the frequency/intensity of ENSO during the 20th century. Whether it will continue to build up steam, has been much debated in scientific circles. The answer is we don't yet know - see The impact of global warming on the tropical Pacific Ocean and El Niño -Collins 2010.

    As for Jeff Masters expectation of a quiet period, he may turn out to be right, but it's probably just wishful thinking.
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  15. Does anyone know why CFS:



    is so different from IRI posted by Albatross above? A related question, the CFS forecasts have varied considerably up and down this year. Anybody know why they are so variable? Back in January, the forecast was for strong La Nina all summer (http://www.cpc.ncep.noaa.gov/products/people/wwang/cfs_fcst_history/) The E1 predictions are especially bad (using oldest data for initial conditions) as compared to E2 and E3, I wonder why they even bother?
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  16. Eric:
    Good question. NOAA long term climate predictions have been very accurate tho and they are based on the models they use to predict Enso. Luck of the draw?
    0 0
  17. "The countries that experienced all-time extreme highs in 2010 constituted over 20% of Earth's land surface area."
    From a climate standpoint, country borders are arbitrary and meaningless.

    A highly extreme negative phase of the NAO and AO returned again during November 2010, and lasted into January 2011. Exceptionally cold and snowy conditions hit much of Western Europe and the Eastern U.S. again in the winter of 2010 - 2011.
    Not substantially different from the 1970's.

    It is rather easy to find extremes if that is all one is looking for. OTOH, there are higher probabilities of some types of extremes with AGW, but hard to quantify, trending very slowly and heavily modulated by the atmospheric and oceanic circulation phases (which may be influenced by AGW although trends are not yet forthcoming).
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  18. Camburn,
    Thank for the link. The paper says the majority of the models predict neutral (page 27). But NCEP CFS.v1 and v2 predict La Nina conditions (page 28). I don't know what NCEP is, but I assume that is the NOAA folks.

    They are predicting La Nina conditions, but they don't include it in their summary, and they are at pains to point out that no one agrees with them, and that all multi-model outlooks disagree.

    But I do give you credit for providing a complete link to a credible source, I don't always perceive you as doing that.

    Rob - well I guess you and I are expecting what no one else is at this point. If the current trend on page 26 continues (+.3/month) - you get to be right!

    That page itself is interesting (only 10 years though) 35 months of El Nino conditions and only 19 months of La Nina. Eyeballing the previous page it looks like there was more balance between all three (neutral, cold and hot) in the 30 years prior to 2002 (which is what you said).
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  19. For Eric, Camburn, Albatross, and others who were wondering: The IRI graph is a collection of a great number of statistical and dynamical model SST predictions from various agencies around the globe. The CFS model is included in that suite, listed as "NCEP CFS" in the legend and denoted by blue squares. CPC's CFS model is run as a deterministic solution (seen in the IRI graphic) as well as in an ensemble, and the CFS ensemble graphic is also presented in CPC's outlook so that you can see the envelope of possibilities from that one model.

    Also, addressing #15 (Eric) above, CFS has been variable this year because it's a natural model tendency to not have good predictability during the spring and early summer, especially when the signals are less than clear (i.e. development of a cold or warm phase episode is not imminent). It's termed the "spring frailty" and remains a barrier to ENSO predictability. ENSO is most predictable in the late summer through the winter.

    I hope that helps, and I'll be happy to clarify if there are any other questions!
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  20. And, to clarify for actually thoughtful and any others...

    NOAA = National Oceanic and Atmospheric Administration
    NWS = National Weather Service (under NOAA)
    NCEP = National Centers for Environmental Prediction (under NWS)
    CPC = Climate Prediction Center (under NCEP... at least for now. If Congress approves the National Climate Service, the chain of command will be NOAA/NCS/CPC)
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  21. windbarg@19
    Thank you for the explanation.
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  22. Windbarb - thanks for the information. What is the difference between an deterministic solution and an ensemble?

    Is the CPC hedging their bets on their La Nina conditions prediction? (by which I mean not including it in their summary and having the disclaimer about the majority of models disagreeing)? Or is this just how the report always looks?

    Many thanks for you sharing your knowledge.
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  23. It seems Jeff Masters must have a very short memory.

    He states: "The pace of incredible extreme weather events in the U.S. over the past few months have kept me so busy that I've been unable to write-up a retrospective look at the weather events of 2010."
    (-SNIP-).

    I checked the US extreme weather events for the last 10 years and 2010 is rather mediocre. Of the last 11 years only 2000 and 2002 had lower overall damage (dollars). About in the middle for number of deaths.

    Source of Data I used.

    (Offensive link label snipped)
    0 0
    Moderator Response: (DB) Very offensive accusations of fraud and dishonesty snipped. Needless to say, participation in this Forum is a privilege which WILL be rescinded if you repeat this behavior.
  24. Norman,
    When I open your link I see a graph indicating 2010 had unusually high fatalities. Perhaps you care more about dollars than people. I imagine when Dr. Masters referred to "the past few months" he meant 2011, which is not included in your summary. Tornadoes, floods, drought and fires have all been at record extent in the US over that time period. Perhaps you could document when Dr. Masters would have had time in between all these extreme events to write out a summary of last year.

    The US is only 2 or 3% of global land area. The title of the thread is "Earth's Extrme Weather". Just because the US did not get hit last year does not mean that Globally it was not bad.
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  25. 23, Norman,

    Dr. Masters clearly used a more intelligent and insightful method, one of examining weather events around the globe, from the unique perspective of someone who deals with them regularly and so is capable of clearly noticing when something is amiss, and based not on some linear measure such as dollars of damage, but rather by how likely such events are to occur in any particular year.

    Your own method of cherry picking one statistic (dollars in damages) for one small fraction of the globe (the US) hardly holds up to scrutiny. Your aggressive and condescending tone when posting your (inadequate) counter-claim speaks volumes by itself.
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  26. michael sweet @ 24

    2010 was in the middle of the fatalities for the 11 years (2000-2011). 5 years had more and 5 years had fewer.

    To get little files that break down the deaths and damage by type of extreme weather event, click on US summaries, click on any date in the list and it brings up a file that breaks down the death and damage from weather related disasters.
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  27. 26, Norman,

    Stop ignoring the fact that your numbers are not global, and are a cherry-picked statistic. Your attempt at undermining Dr. Master's post is lame, at very best.

    It's more, clear evidence of how the Denial Team operates.
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  28. Norman,
    You questioning of Dr. Master's motives is a violation of the comments policy. I do think it detracts from whatever point you were trying to make.

    The problem with the content of your post (beyond the gratuitous cheap shot at Dr. Masters) is: 1) it is factually incorrect (2009 total damage: $7.5 billion, 2010 $9.9 billion (impossible according to your "analysis")) - but more importantly -

    2) Dr. Masters is writing about global weirding (his delightful turn of phrase). You respond with your erroneous analysis that only covered the United States. Dr. Masters' reference to the United States was for the weather unfolding now in 2011, for which the statistics have not yet been compiled.

    [But to give you a sense of why the good Doctor was delayed - JUST the Mississippi flooding south of Memphis is at $9 billion (ie more than 2009 for the whole country, for the whole year and approaching 2010 already - just for one small region! and the year isn't even half done!!).
    “I am going to estimate in the $6 billion to $9 billion range for total damages from Memphis southward to the gulf,” Mr. Hicks said.
    http://www.nytimes.com/2011/05/18/us/18river.html]

    If I may call you Horatio:
    There are more things in heaven and earth, Horatio,
    Than are dreamt of in your philosophy. (William Shakespeare)
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  29. Norman @23, thank you for exposing for all to see both your hypocrisy and your agenda. In the extreme weather thread you have been very busily arguing that records of increased extreme weather events are purely a function of increased damage done. Here, because it is convenient, you argue exactly the reverse, ie, that because there is less damage done there were fewer extreme weather events. The cherry picked nature of your argument (using just US data, and just 2010 when global events over 2010 and 2011 where being discussed) has been noted by others.

    It turns out that you are just another denier who poses as a neutral questioner, but whose real agenda is to raise doubt - any doubt regardless of rationality - with relation to any evidence for AGW.
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  30. actually thoughtful @ 28

    Thanks for the correction. It would be 2009, 2002, and 2000 as the years with less damage than 2010.

    I did find this report on Global death rate based upon weather related events. It has been going down not up. The paper references you concerns that Climate Change may cause more extreme weather related events.

    Here is a link to the study..

    Global Death rate from weather related causes.
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  31. 31, Norman,

    Your Global Death rate study is meant not to study the effects of weather events due to climate change, but rather the impacts of advancing society on the detrimental effects of weather. It also stops at 2006.

    That's why it says this (emphasis mine):

    If extreme weather has indeed become more extreme for whatever reason, global and U.S. declines in mortality and mortality rates are perhaps due to increases in societies’ collective adaptive capacities.


    and this:

    Moreover, if the frequency, intensity and duration of extreme weather events has increased in recent decades – all empirical issues best left to climatologists – there is no signal of that in the data on either mortality rates or (more importantly) mortality, despite an increase in populations at risk.
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  32. Tom Curtis @30

    In the previous thread you reference I was not arguing that point. I was arguing the validity of Munich Re study (not a scientific research group). I am not arguing either point that there are more or less hazardous weather because of damage done. I do not think there is enough information available to make any declarative statement. My main goal is to not to blindly accept these posters view without some really good validation. Jeff Masters post picks some of the extreme events of 2010 and is using this as evidence that Global Warming is the cause. At this time I still do not know if the events are more or less extreme than previous years or close to the same as have been for years. My belief is that the focus and reporting is now on extreme weather events and it makes it look as if things are getting much worse.
    0 0
  33. Sphaerica @ 32

    I did find a link that shows global events in type and size (unfortunately not intensity).

    If you are interested scroll down the page on the link I will provide. Go to the heading Recent Years and click on the link that reads "Monthly and Seasonal Global Temperatures and Precipitation". This will bring up a grid of x's. Click on the Monthly X's for Global Map of Weather events.

    I have not been through each year (some years use a rotating globe and it is harder to compare this with the flat maps)

    I was hoping you can tell me why 2010 looks worse than 2009? Or maybe anyother year you choose to compare it with.

    Link to maps

    Link to Global Weather maps.
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  34. Tom Curtis @30

    "It turns out that you are just another denier who poses as a neutral questioner, but whose real agenda is to raise doubt - any doubt regardless of rationality - with relation to any evidence for AGW."

    Actually Tom I think the physics to AGW is valid. People are burning lots of carbon based fuel and are most likely increasing the amount of Carbon Dioxide in the atmosphere.

    It will cause some warming of the Globe. As this website states, a denier is one who will not change based upon valid evidence. I am a skeptic in this issue (Weather extermes due to Global warming). I will change my view when valid evidence is presented to prove this conclusion. What I have been requesting is balance with historical data as well as wanting some mechanisms to explain why warming is causing the extremes. If it be flooding, drought etc. what is the warming atmophere doing to cause these events to take place at a greater frequency or intensity. Jeff Masters lists a lot of bad events that happened in 2010 but provides very little linking mechanisms to explain how global warming was responsible.
    He is a PhD meterologist and would have the knowledge to provide links and mechanisms. If I am given this type of information and would still deny it, then your label of "denier" would be most correct. (-Snip-).
    0 0
    Moderator Response: (DB) As it stands at this time, you are very close to relinquishing your ability to participate in this Forum - please be very circumspect with your formulation of your comments from now on. Accusations of fraud and dishonesty are NOT "questioning" anything.
  35. The snows, temp etc of the 2010-2011 winter in the US were not a result of AGW. This is what NOAA has found:

    NOAA climate slueths
    0 0
  36. Ooops......2009-2010 snows etc.
    0 0
  37. windbarb, thanks for the answers. I have a more general question, are these ENSO prediction models similar to or different from the GCMs for long term climate prediction? It seems to me that the main difference is the availability of detailed initial conditions for ENSO prediction. We had a discussion on another thread on whether ENSO was becoming more extreme (in amplitude). Do the models yield any insight on possible trends?
    0 0
  38. Norman "It will cause some warming of the Globe. ... as well as wanting some mechanisms to explain why warming is causing the extremes."

    Just checking before going further with this. When you accept the science of 'warming', do you accept that a warmer atmosphere holds more moisture? Given that, do you accept the commonly cited figure of 4% more moisture related to the measured warming so far?

    More moisture requires more precipitation - sometime, somewhere. Would taking that into account go any distance as an explanation of 'warming causing the extremes' for you?
    0 0
  39. This report is for you Tom Curtis.

    Global Environmental Change.
    0 0
  40. Norman @34, your original statement was:

    "
    Basically the Munch Re report can not be used to determine the frequency of extreme weather events (hazards). An EF5 tornado is only a hazard in a field with no people present. It is recorded as a disaster when it strikes a populated area. Disasters are increasing but not enough data is available to determine if hazards are increasing."

    (My emphasis)

    Despite your obvious awareness of the distinction between "hazards" and "disasters", in 23 above you dispute Master's observations about the number of hazards solely on the basis of evidence relating to, not even the number, but just the scale of the disasters. So strong do you believe this evidence of the scale of disasters in the United States over part of the period of discussion, you consider it not only grounds to dismiss Master's observations about the number of hazards globally over a longer period, but sufficient grounds for accusations of fraud and dishonesty. In other words, what counts as a reason to believe something completely reverses for you, depending on what it will require you to believe.

    This has been evident before. Shen presented with evidence showing the danger of AGW you strain at gnats in your critical analysis, going so far as to quote the sexual scandal in a subsidiary of Munich Re as a reason to believe Munich Re's reported statistics on natural disasters are falsified. In contrast, when presented with evidence purporting to show the opposite, even evidence which has been refuted, you show no critical analysis. Instead you just thank the denier for the information, or just accept it as something that needs to be disproved.

    Your pose is well and truly exposed by your hypocritical response to Master's post.

    Finally, a denier is somebody who refuses to accept evidence that AGW is real and/or sufficiently dangerous to warrant taking effective action against it. You have been presented evidence that the number of weather related disasters is increasing faster than can be accounted for without reference to global warming. You have been presented evidence that warm conditions result in more frequent El Nino or La Nina states (ie, fewer years of neutral ENSO states), and in more intense El Nino and La Nina's, both of which would result in more and more intense weather extremes. You have been presented evidence of increased strengths of convective events, of increase water in the hydrological cycle due to the straightforward correlation between increased surface temperatures and increased evaporation. None of this is enough for you.

    Given the fact that evidence of a low number of disasters over 2% of the Earth's surface over twelve months is sufficient evidence for you to suggest fraud in somebody claiming a high frequency of hazards over the entire globe over eighteen months, clearly your failure to be convinced is not due to your high evidentiary standards.
    0 0
  41. adelady:
    Please cite literature for that 4% increase in moisture.
    0 0
  42. Tom:
    What evidence do you have that Enso has increased numerically?
    0 0
  43. Camburn your link at 35 demonstrates the what - El Nino an a negative NAO. You would do well to think about the "why" of those two events.

    There isn't any claim that weird weather hasn't happened in the past. The claim is that there is more weird weather now, and it is intensifying. It is an interesting link, but I left it feeling very unsatisfied that they didn't dig into the why.
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  44. adelady @ 38

    Why would a 4% increase in atmospheric moisture lead to several % increase in precipitation (that is why I ask for mechanisms). Extreme weather events seem to be caused by storms stalling or tracking over the same area. And it seems it has happened forever. Drought and flood cycle is a yearly event somewhere. Some places get much below their normal moisture and others get much above. What is global warming doing to the forces that cause drought and flood to increase?

    Here is a link from climate scientists who were asked the very same question being discussed here.

    Climate scientists debate the issue.

    If you read Roger A. Pielke Jr's response to the question you will see what my current position is and why I am questioning Skeptical Scientists posts on the issue.
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  45. Camburn read the ENSO report you linked earlier in this thread. It answers your question in 42
    0 0
  46. Tom Curtis @40

    "You have been presented evidence that warm conditions result in more frequent El Nino or La Nina states (ie, fewer years of neutral ENSO states), and in more intense El Nino and La Nina's, both of which would result in more and more intense weather extremes."

    You have presented this but at the same time I find information that does not support this.

    El Nino events:

    16th Century: 17
    17th Century: 21
    18th Century: 28
    19th Century: 30
    20th Century: 24
    21th Century: 4 so far

    Link to source of information

    Historical El Nino's.
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  47. windbarb, if you have a chance, I would like add ENSO frequency to my question. I noticed that the ensemble members that are steepest are usually labeled "latest" forecast members and the less steep ones are labeled "earliest" (at least that is the case now during a forecasted transition back to La Nina). But in earlier forecasts this year the blue and red members were more evenly distributed (+/-), was that just because it was early season forecast (and less reliable)? Is there some indication from these models that inflection points are more closely spaced and/or slopes are steeper?
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  48. norman - first things first.

    That 4% increase is averaged over the whole atmosphere. The average automatically requires that in some places at some times, there will be much more than 4% increase and in others a decrease. Once we take that into account, it's much easier to see why there are more floods caused by unusually intense deluges - Pakistan, Colombia and Toowoomba being the classic examples, and others in the USA.

    The increased average moisture just means that the expected drought/flood variations around the world become more exaggerated. Australia and the USA provide the obvious examples of extensive flooding in some regions matched by equally intense drought and wildfire in others. Queensland and Victoria flooding while Perth is on fire, Missouri and Mississipi rivers flooding huge areas while parched Texas and Arizona burn.
    0 0
  49. Norman, to take the key sentence from Pielke Jr's response, he looks at "tornadoes, large-scale river floods (in unaltered river basins), and landfalling hurricanes" to make his assertion.

    That seems to be a nicely cherry-picked selection of criteria. Let me offer my opinions:

    Tornadogenesis is a very difficult question at the best of times. But it seems obvious from my reading on the subject that it requires severe thunderstorms in combination with strong wind-shear aloft to induce rotation, forming supercells. Well, the Gulf of Mexico had abnormally high sea surface temperatures this northern Spring. Combine that with higher moisture content due to a warmer atmosphere, and you've got the ingredients you need for a lot of very strong thunderstorms. So there may be a link (though tenuous, yet) between global warming and tornados. I understand the jet-stream (which causes the high altitude wind-shear) is predicted to move further north as the planet warms further, so perhaps we might see a long-term downward trend in tornados, despite the increased thunderstorms. Then again, maybe they'll just move further north, and the Canadians will get hammered instead of folks in the US central plains.

    Secondly, 'unaltered river basins' would restrict you to a very small subset of the world's major rivers... and that qualification seems designed to exclude pretty much every major river basin in the US, as they've all been altered. A convenient way to 'exclude' the record flooding in the Tennessee, Ohio, Mississippi, and Missouri basins over the past 12 months or so. Also the Indus river in Pakistan (which displaced 20 million people when it flooded last year), and the major flooding experienced here in Australia over last summer.

    And restricting hurricanes to land-falling only allows him to discount the 2010 Atlantic hurricane season, which was the second most active on record, despite almost no storms affecting the US.

    A pretty bunch of cherries, indeed...
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  50. Norman without looking at your source for veracity - 4 so far this century, extrapolated, would be 36 this century - or a 50% increase over last century.

    So even your own data support Tom Curtis's point. I can't speak as to whether your data is accurate or not, just that it supports the point that more heat will lead to more frequent El Ninos and La Ninas.
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