Is U.S. climate getting more extreme?

By: Dr. Jeff Masters , 1:54 PM GMT on March 13, 2009

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Is the climate in the U.S. getting more extreme? The answer to this question depends upon how one defines "extreme". For example, the number of extreme tornadoes (violent EF-4 and EF-5 twisters) has not increased in recent years. We lack the data to judge whether there has been an increase in severe thunderstorms and hail. There has been a marked increase in Atlantic hurricane activity since 1995 (though the possible contribution of human-caused global warming to this increase is not something hurricane scientists agree upon). Since it is difficult to quantify how severe storms like tornadoes and hurricanes are changing, a better measure of how climate extremes are changing is to look at temperature and precipitation, which are well-measured. NOAA's National Climatic Data Center (NCDC) has developed a Climate Extremes Index to attempt to quantify whether or not the U.S. climate is getting more extreme. The Climate Extremes Index (CEI) is based upon three parameters:

1) Monthly maximum and minimum temperature
2) Daily precipitation
3) Monthly Palmer Drought Severity Index (PDSI)

The temperature data is taken from 1100 stations in the U.S. Historical Climatology Network (USHCN), a network of stations that have a long period of record, with little missing data. The temperature data is corrected for the Urban Heat Island effect, as well as for station and instrument changes. The precipitation data is taken from 1300 National Weather Service Cooperative stations. The Climate Extremes Index defines "much above normal" as the highest 10% of data, "much below normal" as the lowest 10%, and is the average of these five quantities:

1) The sum of (a) percentage of the United States with maximum temperatures much below normal and (b) percentage of the United States with maximum temperatures much above normal.

2) The sum of (a) percentage of the United States with minimum temperatures much below normal and (b) percentage of the United States with minimum temperatures much above normal.

3) The sum of (a) percentage of the United States in severe drought (equivalent to the lowest tenth percentile) based on the Palmer Drought Severity Index (PDSI) and (b) percentage of the United States with severe moisture surplus (equivalent to the highest tenth percentile) based on the PDSI.

4) Twice the value of the percentage of the United States with a much greater than normal proportion of precipitation derived from extreme (equivalent to the highest tenth percentile) 1-day precipitation events.

5) The sum of (a) percentage of the United States with a much greater than normal number of days with precipitation and (b) percentage of the United States with a much greater than normal number of days without precipitation.


Figure 1. The Annual Climate Extremes Index (CEI), updated through 2008, shows that U.S. climate has been getting more extreme since the early 1970s. Image credit: National Climatic Data Center. On average since 1910, 20% of the U.S. has seen extreme conditions in a given year (thick black line).

As summarized by Gleason et al. (2008), the National Climatic Data Center concludes that based on the Climate Extremes Index, the percentage of the U.S. seeing extreme temperatures and precipitation generally increased since the early 1970s. These increases were most pronounced in the summer. No trend in extremes were noted for winter. The annual CEI index plot averaged for all five temperature and precipitation indices (Figure 1) showed that five of the fifteen most extreme years on record occurred since 1997. Shorter-lived periods with high CEI values occurred in the 1930s and 1950s, in association with widespread extreme drought and above-average temperatures. The most extreme year in U.S. history was 1998, with 1934 a close second. The year 1998 was the hottest year in U.S. history, with a record 78% of the U.S. experiencing minimum temperatures much above normal. That year also had a record 23% of the U.S. with much greater than normal precipitation from extreme 1-day precipitation events. The 1934 extreme in CEI was due in large part because of the most widespread drought of the century--a full 52% of the U.S. was affected by severe or extreme drought conditions. That year also saw a record 64% of the U.S. with much above normal maximum temperatures.

The impact of maximum and minimum temperatures on the Climate Extreme Index
It is very interesting to look at the five separate indices that go into the Climate Extremes Index. Today I'll look at temperature, and next week, I'll focus on drought and precipitation. The portion of the U.S. experiencing month-long maximum temperatures either much above normal or much below normal has been about 10% over the past century (black lines in Figure 2). However, over the past decade, about 20-25% of the U.S. has been experiencing monthly maximum temperatures much above normal, and the portion of the U.S. experiencing much colder than normal high temperatures has been near zero. Minimum temperatures show a similar behavior, but have increased more than the maximums (Figure 3). Over the past decade, minimum temperatures much above normal have affected 25-35% of the U.S. This means that the daily range of temperature (difference between minimum and maximum) has decreased over the past decade, which is what global warming says should be happening if greenhouse gases are primarily to blame for the rise in temperatures.

While there have been a few years (1921, 1934) when the portion of the U.S. experiencing much above normal maximum temperatures was greater than anything observed in the past decade, the sustained lack of maximum temperatures much below normal over the past decade is unique. The behavior of minimum temperatures over the past decade is clearly unprecedented--both in the lack of minimum temperatures much below normal, and in the abnormal portion of the U.S. with much above normal minimum temperatures. Remember that these data ARE corrected for the Urban Heat Island effect, so we cannot blame increased urbanization on the increase in temperatures. Recall that the all-time record maximum and minimum temperature data, which I presented in a post in February, are not corrected for the Urban Heat Island Effect, but look very similar to the CEI maximum and minimum temperature trends presented here.

A lot of people have told me that they believe we are experiencing more wild swings of temperature from hot to cold from day to day in recent years, but the CEI data does not answer this question. To my knowledge, a study of this kind has not been done.


Figure 2. The Annual Climate Extremes Index (CEI) for maximum temperature, updated through 2008, shows that 20-25% of U.S. has had maximum temperatures much above normal over the past decade. Image credit: National Climatic Data Center.


Figure 3. The Annual Climate Extremes Index (CEI) for minimum temperature, updated through 2008, shows that 25-35% of U.S. has had minimum temperatures much above normal over the past decade. Image credit: National Climatic Data Center.

References
Gleason, K.L., J.H. Lawrimore, D.H. Levinson, T.R. Karl, and D.J. Karoly, 2008: "A Revised U.S. Climate Extremes Index", J. Climate, 21, 2124-2137.

Annual WeatherDance contest ready for registration!
Armchair forecasters, now's your chance to shine! WeatherDance, based on teams in the men's and women's NCAA basketball tournaments, allows players to predict which team's city will be hotter or colder on game day in each round of the Big Dance. Beginning today, players can make their forecasts at the Weather Dance Web site at: www.weatherdance.org. The site will be updated with cities promptly after NCAA seeding announcements. First round Weather Dance selections must be entered by 11:59 p.m. EDT Wednesday, March 18.

"Officially, Weather Dance began as a class project to get students involved in weather forecasting, but we kept it around because it got popular. People think they can do better forecasting than the meteorologists. Well, here's their shot!" said Perry Samson, WeatherDance creator, co-founder of the The Weather Underground, Inc., and Professor in the Department of Atmospheric, Oceanic and Space Sciences at the University of Michigan.

This is the fifth year for the game. Last year more than 2,000 people played. Most play merely for the thrill, but many K-12 science teachers involve their classes as part of meteorology units. The winning teacher will receive an expense-paid trip to join the Texas Tech/University of Michigan Storm Chasing team this spring for a day of tornado chasing in Tornado Alley. Other winners will receive a Weather Underground umbrella, "Extreme Weather" mugs, or a copy of the book "Extreme Weather," by Christopher C. Burt.

I'll talk about drought and precipitation trends in my next post, Monday or Tuesday.

Jeff Masters

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Quoting vortfix:
There is a dedicated featured blog for all Portlight business.

Here is the link


And your point! This site is also a good spot!
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Quoting KEHCharleston:
Ok.... Will do

BTW, I like your website - nicely done


thanks
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Ok.... Will do

BTW, I like your website - nicely done
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Quoting KEHCharleston:
515. TampaSpin
Thursday evening is not too late is it?


The brackets auto lock out before the games begin! You must be complete by 12 noon on Thursday!
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515. TampaSpin
Thursday evening is not too late for March Madness Charity pick is it?
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Good evening everyone....i hope we get some response to the Charity Event for Portlight. Please let me know if you don't know what to do! I hope it is explained well....

March Madness Charity Link
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513. Lived there for twenty years...I know the seasons by now...not fond of fire - did the whole fire thing back in 2003 (Cedar fires and then Otay fires and then everything fires!) - right up to our house but we were okay...earthquakes...not fond either. Gotta love no GNATS, NO BITING FLIES though.

Gotta pick your poison!
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Quoting melwerle:
Thanks Surfmom!!!! Totally celebrating and trying to make all the plans - finally feel like the feet are out of the mud!

Anyone need a place to crash during evac...San Diego is awfully nice weather...

Actually, my son who lives near San Diego says they have four seasons: Drought, Fire, Earthquake, and Mudslide.
You can run, but you can't hide!
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i know there is no co-relation but if we get no big severe season we may get no big cane season and it just may end up very dry very hot summer season for all of north america dry everything right up mom nature is thowing a curve ball going to be interesting
Member Since: July 15, 2006 Posts: 170 Comments: 53548
Hey Surfmom,
We're waiting for those summer daily showers, but then we'll be ducking the lightning. Can we make it through without anything severe in April, or burning the state down in May? Can't fight the weather, got to live on it's schedule if you're outdoors much.
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Thanks Surfmom!!!! Totally celebrating and trying to make all the plans - finally feel like the feet are out of the mud!

Anyone need a place to crash during evac...San Diego is awfully nice weather...
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Quoting clwstmchasr:
I'm reading comments about FL being in a severe drought. I know that it has been dry here in the Tampa area and to our north but didn't most of the state get excessive rains from Faye last year?

that was last year
this year whole different ballgame excessive dry spell over s fla and it may continue for a time yet
as for fay thats all but a memory
iam also a little concearned for lack of a severe season so far been rather light which has me thinking about whats yet to come
Member Since: July 15, 2006 Posts: 170 Comments: 53548
Celebrate!!! May your new journey be blessed with fair skies!!!!!
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ok kids...off topic and I'm willing to take the ban but I gotta yell it - WE'RE OUTTA HERE!!!!!!!!!!!!! Back to San Diego and hopefully before hurricane season starts....



Link
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aww heck Hiexpress -- you know it felt good to cycle in the rain --Lordy, I can't wait to run in the rain, sit in the rain -- DANCE IN THE RAIN
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Quoting Skyepony:


It would be interesting to see how the chaos equation would do in peer review. Math has come a ways in figuring out natural shapes, movements & patterns, like how a school of fish would react to a ripple. Not sure if it has nailed chaos yet or my 5 day forcast should be better. Also his idea of a climate shift is totally different than what is being refured to in climate change. His work is the little ups & downs, the patterns over one to a few decades. To compare it to ENSO he is watching every little up & down, not the big picture~ as in if overall we are trending up & down. He's throwing out alot of peer reviewed stuff saying we don't understand natural forcings so how can we understand human's forcings.. That cooling in the '70s was a huge volcano. ENSO cycles, the sun cycles, how the earth travels cycles we do understand these things. (not that every question is answered but he's tossing baby with bath water here). Sounds like a steeper study in math than climate & geology.

This aerosol thing isn't new. Pan evaperation rates (which farmers have done & recorded for centuries) is a solid base for the data. Google PBS Dimming the Sun, very comprehensive, all angles. Some is caused by contrails. After 911 & taking the planes out of the sky for 3 days the studies concluded contrails make the USA ~5ºF cooler. Others contributers is industry. We used to make things here, the aerosols released caused that huge drought & famine in Etheopia, documents released from the govt said was the result of their studies. Those paticular aerosols prevented water from grasping them, so no rain could be made down wind. We stopped making what ever it was in the NE & Etheopia once again got rain. My aunt who lives in Calif jokes their drought is from living down wind from China now that all our crap is made there.. Maybe the down swing in the economy has brought them rain..lol.

Back from the tangent, it really is no suprise we just had our coolest year in the last 10 years..with Aerosols at an all time high, during back to back La Niñas & a period of very low sunspot activity I would have thought it would have been cooler had it not been for the record greenhouse emissions & the 0 attempt at reducing the black soot that ends up on the ice at the north pole. The soot itself is blamed for a +5ºF increase in temps so in the math of it all, 2 forms of pollution, the soot & aerosols about cancel each other out.


Thanks Skyepony, that's what we are looking for overall. It has become very difficult to decipher what is right, what is wrong, and what is real and not. All we have is us to figure it out and we will.
Member Since: June 12, 2005 Posts: 6 Comments: 8186
502. Skyepony (Mod)
Vort~ I'll check it out in a bit. I gotta run for now.
Member Since: August 10, 2005 Posts: 162 Comments: 37822
Record Report

Statement as of 4:30 PM EDT on March 16, 2009

... Record high temperature set at Daytona Beach...

a record high temperature of 90 degrees was set at Daytona Beach
today. This breaks the old record of 89 set in 1973.

A little rain in the area missed my parched front lawn, but got me when I went out for a 15 mile bike ride.
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Quoting Ossqss:


Well, what is your take on the info? I found it pretty disturbing considering the pre-existing conditions and positioning from the previous VP along with his business ventures. What gives?
Even if it is true (and the Snopes people are pretty good about doing research into this stuff, so I'd give them credit for accuracy) it just makes the Bush position on oil vs. alternate energy sources that much more hypocritical. When it comes to his personal energy bill, he has no intention of being held hostage by the oil barons,American and international. OTOH, it's ok to let the oil barons screw the rest of the US into the ground.

I also wonder how old each of these houses is. I have a feeling the Gore house may be more traditionally heated because that's the way it's always been heated. Even so, it behooves Mr. Gore to put his energy source where his mouth is. . .
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499. Skyepony (Mod)
On 2nd thought my cancelling math would be wrong. I only took in account the cooling from chemtrails from planes, not other aerosols. I don't think they are exactly sure how much we are cooling with aerosols total. Some climate engineers have suggested off setting some global warming with more. NOAA has already shot down the idea. Probibly good. I've had a few growing seasons where plants were hard pressed to get enough sun from all the clouds being born day after day to contrails.
Member Since: August 10, 2005 Posts: 162 Comments: 37822
I think I left it at your place...
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AMEN!!Apocalypse-induced Misanthropic Environmental nervousness!!
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Quoting vortfix:
.....IF I understood correctly, there's concerns a mower could spark causing a fire......


It's possible if you park any vehicle with exhaust underneath in high grass or weeds...Poof!



yikeS.... I had no clue!!!
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494. Skyepony (Mod)
Quoting Ossqss:
Would the clear sky dimming item not go against the global warming fundamentals? Perhaps the revamped analysis of the GW perspective from post 390 is right?



It would be interesting to see how the chaos equation would do in peer review. Math has come a ways in figuring out natural shapes, movements & patterns, like how a school of fish would react to a ripple. Not sure if it has nailed chaos yet or my 5 day forcast should be better. Also his idea of a climate shift is totally different than what is being refured to in climate change. His work is the little ups & downs, the patterns over one to a few decades. To compare it to ENSO he is watching every little up & down, not the big picture~ as in if overall we are trending up & down. He's throwing out alot of peer reviewed stuff saying we don't understand natural forcings so how can we understand human's forcings.. That cooling in the '70s was a huge volcano. ENSO cycles, the sun cycles, how the earth travels cycles we do understand these things. (not that every question is answered but he's tossing baby with bath water here). Sounds like a steeper study in math than climate & geology.

This aerosol thing isn't new. Pan evaperation rates (which farmers have done & recorded for centuries) is a solid base for the data. Google PBS Dimming the Sun, very comprehensive, all angles. Some is caused by contrails. After 911 & taking the planes out of the sky for 3 days the studies concluded contrails make the USA ~5ºF cooler. Others contributers is industry. We used to make things here, the aerosols released caused that huge drought & famine in Etheopia, documents released from the govt said was the result of their studies. Those paticular aerosols prevented water from grasping them, so no rain could be made down wind. We stopped making what ever it was in the NE & Etheopia once again got rain. My aunt who lives in Calif jokes their drought is from living down wind from China now that all our crap is made there.. Maybe the down swing in the economy has brought them rain..lol.

Back from the tangent, it really is no suprise we just had our coolest year in the last 10 years..with Aerosols at an all time high, during back to back La Niñas & a period of very low sunspot activity I would have thought it would have been cooler had it not been for the record greenhouse emissions & the 0 attempt at reducing the black soot that ends up on the ice at the north pole. The soot itself is blamed for a +5ºF increase in temps so in the math of it all, 2 forms of pollution, the soot & aerosols about cancel each other out.
Member Since: August 10, 2005 Posts: 162 Comments: 37822
Press.... you got a Breast Plate ??
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FYI -- all the Deering Lawn mower people who keep the greens cut and the Polo club "clipped" have been issued Fire extinguishers.....IF I understood correctly, there's concerns a mower could spark causing a fire......
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Quoting surfmom:
SWFL/East I75 The land is parched, the grass and bush between the lack of water and the cold front freezes - is dry fire fuel - when you're out riding the open land where the cattle graze ( of which there is nothing) the word is COMBUSTION.

It's already way worse then last year.... the water holes for the horses -- which usually reflects ground water levels is already at the level I'd expect to see it at just b/4 rainy season.

Florida is quickly, if not already, a poster girl for what happened in Australia. I'm begging Ma Nature for rain -- but she's got me on IGNORE


I hear ya
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SWFL/East I75 The land is parched, the grass and bush between the lack of water and the cold front freezes - is dry fire fuel - when you're out riding the open land where the cattle graze ( of which there is nothing) the word is COMBUSTION.

It's already way worse then last year.... the water holes for the horses -- which usually reflects ground water levels is already at the level I'd expect to see it at just b/4 rainy season.

Florida is quickly, if not already, a poster girl for what happened in Australia. I'm begging Ma Nature for rain -- but she's got me on IGNORE
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Quoting vortfix:
Well, what is your take on the info? I found it pretty disturbing considering the pre-existing conditions and positioning from the previous VP along with his business ventures. What gives?


I'm sure you are intelligent enough to get the facts without a website or myself to help you.

\\

Easy way out after the humor you found in the question/ and I did think it was quite so. My bad. Sorry to stir things.

CUL8R
Member Since: June 12, 2005 Posts: 6 Comments: 8186
Quoting clwstmchasr:
I'm reading comments about FL being in a severe drought. I know that it has been dry here in the Tampa area and to our north but didn't most of the state get excessive rains from Faye last year?


Ya we got 12in of rain but that was almost 8 months ago
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From St. Patrick's Breast Plate...seems kinda appropriate for this site..

I bind to myself today to
The power of Heaven,
The light of the sun,
The brightness of the moon,
The splendour of fire,
The flashing of lightning,
The swiftness of wind,
The depth of sea,
The stability of earth,
The compactness of rocks.
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Quoting vortfix:
It depends on "which" truth you seek.

You know how it is.
It's just another damn website.



Well, what is your take on the info? I found it pretty disturbing considering the pre-existing conditions and positioning from the previous VP along with his business ventures. What gives?
Member Since: June 12, 2005 Posts: 6 Comments: 8186
Quoting vortfix:
Does Snopes tell the truth?


Bwahahahahahahahahahahahahahahahahahahaha...HA!



So you are saying it is not correct?
Member Since: June 12, 2005 Posts: 6 Comments: 8186
Link

Wow, I finally got tired of the political emails and actually verified some facts on the ever going chain of them. Interesting stuff. Does Snopes tell the truth?
Member Since: June 12, 2005 Posts: 6 Comments: 8186
477. HadesGodWyvern (Mod)
an area of convection (92P) has persisted near 13.1s 121.6e,
approximately 470 nm north-northeast of Port Hedland, Australia.
Animated infrared satellite imagery shows a mid-level circulation
consolidating to the surface with weak and limited formative
convective band wrapping around the southwest quadrant into the
western side of the center. A 162159z SSMI image shows deep
convection forming near the center and along the western edge. The
LLCC is under the upper level ridge axis and in area of low vertical
wind shear. Maximum sustained surface winds are estimated at 18 to
22 knots. Minimum sea level pressure is estimated to be near 1005
mb. Because convection has been flaring and quickly dissipating in
the vicinity the potential for the development of a significant
tropical cyclone within the next 24 hours is poor.

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476. Skyepony (Mod)
An oil spill polluting popular tourist beaches on Australia's northeast coast is 10 times worse than originally reported, the state government said.

Initial estimates put the spill at 20 to 30 tons of oil. But Paul Lucas, Queensland state's deputy premier, told public radio that "it is now apparent that it was about 230 tons."


The crisis was sparked when high seas whipped up by Cyclone Hamish toppled 31 containers of ammonium nitrate fertiliser from the ship's deck.

As they fell, the containers punctured the hull, before taking 620 tons of the explosive chemical to the ocean floor.

The ship's owners, Swire Shipping, said an inspection of the hull by a diver on Friday had found that the damage was greater than initially believed and "it is likely that substantially more oil has spilled than the earlier estimate".

Member Since: August 10, 2005 Posts: 162 Comments: 37822
Would the clear sky dimming item not go against the global warming fundamentals? Perhaps the revamped analysis of the GW perspective from post 390 is right?

Member Since: June 12, 2005 Posts: 6 Comments: 8186
467. plywoodstatenative 4:59 PM PDT on March 16, 2009
Okay teddy I am going to go bury my head in the sand now that you said that



LOL
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473. Skyepony (Mod)
Clear Sky Visibility Has Decreased over Land Globally from 1973 to 2007
Kaicun Wang,1* Robert E. Dickinson,2 Shunlin Liang1
Visibility in the clear sky is reduced by the presence of aerosols, whose types and concentrations have a large impact on the amount of solar radiation that reaches Earth's surface. Here we establish a global climatology of inverse visibilities over land from 1973 to 2007 and interpret it in terms of changes in aerosol optical depth and the consequent impacts on incident solar radiation. The aerosol contribution to "global dimming," first reported in terms of strong decreases in measured incident solar radiation up to the mid-1980s, has monotonically increased over the period analyzed. Since that time, visibility has increased over Europe, consistent with reported European "brightening," but has decreased substantially over south and east Asia, South America, Australia, and Africa, resulting in net global dimming over land.

1 Department of Geography, University of Maryland, College Park, MD 20742, USA.
2 Department of Geological Sciences, University of Texas, Austin, TX 78712, USA.


* To whom correspondence should be addressed. E-mail: kcwang@umd.edu

Member Since: August 10, 2005 Posts: 162 Comments: 37822
Yep so if things hold up looks like we are in for a very active season.
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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