Heat Waves (4) A Climate Case Study:

By: Dr. Ricky Rood , 6:26 AM GMT on July 19, 2011

Share this Blog
9
+

Heat Waves (4) A Climate Case Study:

In the last article I wrote that the extreme events of 2011 were providing us with the opportunity to think about climate and how to cope with a warming world. The U.S. is experiencing an extreme heat event this week (Masters @ WU). This heat wave is the consequence of a strong, stationary high pressure system over the central U.S., and it will move to the east over the next few days. Back on July 14th The Capital Weather Gang did a nice write up on the forecast of the heat wave. At the end of this blog are links to my previous blogs on heat waves and human health.

When thinking about weather, climate, and extreme events an important idea is “persistence.” For example, a heat wave occurs when there are persistent high temperatures. Persistent weather patterns occur when high and low pressure systems get large and stuck; that is, they don’t move. In the Figure below, you need to imagine North America and the United States. There is a high pressure center over the proverbial Heartland. With blue arrows I have drawn the flow of air around the high pressure system, and in this case moist air. There is moisture coming from the Gulf of Mexico and, in fact on the date when this was drawn, from the Pacific. This is common in the summer to see both the Gulf of Mexico and Pacific as sources of continental moisture.



Figure 1: Schematic of a high pressure system over the central United States in July. While generic, this is drawn to represent some of the specifics of 2011. The green-shaded area is where there have been floods in 2011. The brown-shaded area represents sustained drought in the southern part of the nation.

At the center of this high pressure system there is a suppression of rain, because the air is moving downward. This sets up a situation where the surface heats from the Sun’s energy. There is not much mixing and cooling, because of the suppression of the upward motion that produces rain. Hence, if this high pressure system gets stuck, then there is persistent heat. This is a classic summer heat wave.

Let’s think about it some more. There is lot of moisture being drawn around the edge of the high pressure system, and this moisture contributes to the discomfort of people. People – just a short aside about people: if we think about heat and health, then we are concerned about people’s ability to cool themselves. It is more difficult to cool people when it is humid because sweat does not evaporate. Suppose that in addition to this moisture, there is a region where the ground is soaked with water from flooding. Then on top of already moist air coming from the Gulf, there is local evaporation into the air being warmed by the Sun. If on the interior of the high, where the rain is suppressed, there is hot, wet air, then it becomes dangerous heat.

It’s not easy to derive a number that describes dangerous heat. But in much of the eastern U.S. a number that somehow combines temperature and humidity is useful. Meteorologists often use the heat index. It’s the summer time version of “it’s 98 degrees, but it feels like 105.” For moist climates, the heat index is one version of the “it feels like” temperature. Jeff Masters tells me that in Newton, Iowa yesterday, July 17, 2011, the heat index was 126 degrees F. (see here, and 131 F in Knoxville, Iowa on July 18)

Another measure of heat and humidity is the dew point; that is, the temperature at which dew forms, and effectively limits the nighttime low. The dew points in Iowa, South Dakota, Minnesota, and Wisconsin are currently very high and setting records. Here is a map of dew point for July 19, 2011.



Figure 2: Exceptionally high dew points centered on Iowa.


Now if I was a public health official, and I was trying to understand how a warming planet might impact my life, then here is how I would think about it. First, the Gulf of Mexico and the Pacific are going to be warmer, and hence, there will be more humid air. This will mean, with regard to human health for the central U.S., heat waves will become more dangerous, without necessarily becoming hotter. It is also reasonable to expect heat waves will become more frequent and last longer, because those persistent, stuck high pressure systems are, in part, forced by the higher sea surface temperatures. If I am a public health official here is my algorithm – heat waves are already important to my life, and they are likely to get more dangerous, more frequent, and of longer duration. But by how much? Do I need to know by how much before I decide on a plan for action?

If I think about the air being more humid, then I might expect to see trends in the heat index. I might expect to see trends in dew points, and trends in the nighttime minimum temperatures getting higher. (That’s where a greenhouse effect really matters.) I worry about persistent heat, warm nights, and the inability of people and buildings to cool themselves. I worry about their being dangerous heat in places where people and emergency rooms are not used to dangerous heat – not acclimated to heat – not looking for heat-related illness.

Let’s go back to the figure. Rain is suppressed in the middle of the high pressure system, but around the edge of the high pressure system it will rain; there will be storms. (see Figure 3 at the end) The air around the edge of high is warm and very wet. Wet air is energetic air, and it is reasonable to expect local severe storms. (See Severe Storm on Lake Michigan) And if the high pressure is persistent, stuck, then days of extreme weather are possible. If this pattern sets up, then there is increased likelihood of flooding. If I am that public health official, then I am alerted to the possibility of more extreme weather and the dangers thereof. But, again, can the increase of extreme weather be quantified? Do I need to quantify it before I decide on a plan of action?

Still with the figure - what about that region of extended drought and the heat from the high pressure system? Dehydration becomes a more important issue. As a public health official, I start to see the relation of the heat event to other aspects of the weather, the climate. I see the relation to drought. I see the flood, and it’s relation to the winter snow pack and spring rains.

So what I have presented here is to look at the local mechanisms of the weather – what are the basic underlying physics responsible for hot and cold, wet and dry – for moist air? If I stick to these basic physics, and let the climate model frame the more complex regional and global picture, what can I say about the future? Do I have to have a formal prediction to take action? Here in 2011, I see drought and flood and hot weather and warm oceans that interact together to make a period of sustained, dangerous heat. It does not have to “set a record” to convey the reality of the warming earth. It tells me the type of event that is likely to come more often, of longer duration, and of, perhaps, of greater intensity. If I am a public health planner, then I can know this with some certainty. The question becomes, how do I use that information in my planning?

r



Figure 3: Radar loop showing precipitation around the edge of the large high pressure system in the middle of the continent. July 19, 2011.

Previous Blogs on Heat Waves

Hot in Denver: Heat Waves (1)

Heat Waves (2): Heat and Humans

Heat Waves (3): Role of Global Warming




Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 18 - 1

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 — Blog Index

Quoting cat5hurricane:

Actually, the vast majority of climate scientists initially jumped upon the theory the globe was cooling. It was only until the Earth climate changed before they realized they probably jumped to conclusions.

Silly scientists.

No, they didn't. And no matter how many times that particular fantasy is repeated, it'll never be true. Here, allow me to help:

Strike One: "Not true, climatologist Thomas C. Peterson of the National Climatic Data Center in Asheville, N.C., and his colleagues report in the September Bulletin of the American Meteorological Society. The team’s survey of major journal papers published between 1965 and 1979 found that only seven articles predicted that global average temperature would continue to cool. During the same period, 44 journal papers indicated that the average temperature would rise and 20 were neutral or made no climate predictions."

"When...skeptics mention previous concerns about global cooling, they typically cite media reports from the 1970s rather than journal papers —'a part of their tremendous smoke screen on this issue,' says Peterson. Among major magazines, Time and Newsweek ran articles expressing concern about the previous decades’ cooling trend, juxtaposing the specter of decreased food production with rising global population.

Strike Two: "But even a cursory review of 1970s media accounts shows that there was no consensus about global cooling among journalists, either, Peterson says. In May 1975, the headline of a New York Times article warned that 'major cooling may be ahead.' Three months later, another headline in the same paper — atop a feature written by the same reporter — stated that two recent journal articles 'counter [the] view that [a] cold period is due.'"

Strike Three: "When global warming skeptics draw misleading comparisons between scientists' nascent understanding of climate processes in the 1970s and their level of knowledge today, 'it's absolute nonsense,' Schneider says. Back then, scientists were just beginning to study climate trends and their causes, and the probability of finding evidence to disprove a particular hypothesis was relatively high. Nowadays, he contends, 'the likelihood of new evidence to overthrow the concept of global warming is small. Warming is virtually certain.'"

So, that whole "They predicted global cooling in the 70s" thing? It's out...
Member Since: November 8, 2009 Posts: 4 Comments: 13579
Quoting cat5hurricane:

There it is. The muscles are flexing. The brain is working. Someone has got their thinking cap on.

Yes, this is a particular model from the theory, comprised of the old manipulated, falsified, altered, and botched data. So, why use misguided data to feed a climate model? To get pretty graphs? Maybe. To extract something out in left field? You're getting warmer...

In other words, the old format from the old model. Wonder why the URL to that link is stale-lighted? Hmmm. But it could be true? We'll just have to be patient and see.


The warming is not in the future it is here now. The NOAA/NASA graphs prove it. Can you dig it?
Member Since: January 2, 2006 Posts: 127 Comments: 20401
If you all would kindly notice also on this graphic the high extent for this year was also the lowest since 1979. Currently we are in 28th place and falling fast for low arctic ice extent. Will this years record low high extent give us a new record low this year? Time will tell. I will be posting this graph a lot so we can track it here.


Member Since: January 2, 2006 Posts: 127 Comments: 20401
Quoting Patrap:
www.ncdc.noaa.gov/indicators


Global Climate Change Indicators
National Oceanic and Atmospheric Administration
National Climatic Data Center

Climate Model Indications and the Observed Climate


Simulated global temperature in experiments that include human influences (pink line), and model experiments that included only natural factors (blue line). The black line is observed temperature change

Global climate models clearly show the effect of human-induced changes on global temperatures. The blue band shows how global temperatures would have changed due to natural forces only (without human influence). The pink band shows model projections of the effects of human and natural forces combined. The black line shows actual observed global average temperatures. The close match between the black line and the pink band indicates that observed warming over the last half-century cannot be explained by natural factors alone, and is instead caused primarily by human factors.



That should tell people if we are affecting climate in this warmer way we should be able to affect climate in a cooling way. This is why we need to get a handle on what we do with the climate. To think man has no effect is ludicrous.
Member Since: January 2, 2006 Posts: 127 Comments: 20401
www.ncdc.noaa.gov/indicators


Global Climate Change Indicators
National Oceanic and Atmospheric Administration
National Climatic Data Center

Climate Model Indications and the Observed Climate


Simulated global temperature in experiments that include human influences (pink line), and model experiments that included only natural factors (blue line). The black line is observed temperature change

Global climate models clearly show the effect of human-induced changes on global temperatures. The blue band shows how global temperatures would have changed due to natural forces only (without human influence). The pink band shows model projections of the effects of human and natural forces combined. The black line shows actual observed global average temperatures. The close match between the black line and the pink band indicates that observed warming over the last half-century cannot be explained by natural factors alone, and is instead caused primarily by human factors.

Member Since: Posts: Comments:
OUCH! RECORD LOW SINCE 1979??????

Member Since: January 2, 2006 Posts: 127 Comments: 20401
NSIDC

July 18, 2011
Early sea ice melt onset, snow cover retreat presage rapid 2011 summer decline

Arctic sea ice extent declined at a rapid pace through the first half of July, and is now tracking below the year 2007, which saw the record minimum September extent. The rapid decline in the past few weeks is related to persistent above-average temperatures and an early start to melt. Snow cover over Northern Eurasia was especially low in May and June, continuing the pattern seen in April.






Overview of conditions
As of July 17, 2011, Arctic sea ice extent was 7.56 million square kilometers (2.92 million square miles), 2.24 million square kilometers (865,000 square miles) below the 1979 to 2000 average. Sea ice is particularly low in the Barents, Kara, and Laptev Seas (the far northern Atlantic region), Hudson Bay and Baffin Bay.Conditions in context
Arctic sea ice extent declined rapidly through the first two weeks of July, at a rate averaging nearly 120,000 square kilometers (46,000 square miles) per day. Ice extent is now tracking below the year 2007, which saw the record minimum September extent.

OUCH!



During the first half of July, a high-pressure cell persisted over the northern Beaufort Sea, as it did in June, and is linked to the above-average air temperatures over much of the Arctic Ocean. To date in July, air temperatures over the North Pole were 6 to 8 degrees Celsius (11 to 14 degrees Fahrenheit) higher than normal, while temperatures along the coasts of the Laptev and East Siberian seas were 3 to 5 degrees Celsius (5 to 9 degrees Fahrenheit) higher than average. By contrast, temperatures through the first half of July in the Kara Sea have been 2 to 5 degrees Celsius (4 to 9 degrees Fahrenheit) lower than average. A closer look at sea ice concentration
The sea ice extent data that NSIDC uses come from the Special Sensor Microwave Imager/Sounder (SSMIS) on U.S. Department of Defense satellites. Data from other satellites, while not as useful for studying long-term trends, can show more detail about ice cover in particular regions. Currently data from two NASA satellite sensors, the Moderate Resolution Imaging Spectroradiometer (MODIS) and Advanced Microwave Scanning Radiometer for EOS (AMSR-E), show areas of low ice concentration north of Alaska. Ice in these areas is likely to melt out in coming weeks.

Both the Northwest Passage (through the channels of the Canadian Arctic Islands) and the Northern Sea Route (along the Siberian coast) are still choked with ice. Early start to Arctic melt
When sea ice starts to melt in spring, small ponds known as melt ponds form on its surface. The small pools create a darker surface (a lower albedo) that fosters further melt. How early sea ice melt starts is one indicator of how much the ice will melt in a given year. New research by Don Perovich and colleagues shows that an early start to sea ice melt increases the total amount of sunlight absorbed through the melt season.



Data processed by researchers Thorsten Markus and Jeffrey Miller at the NASA Goddard Space Flight Center reveal that melt began earlier than normal in both the Chukchi Sea, just north of the Bering Strait, and the Barents, Kara, and Laptev seas. Surface melting on the sea ice began from two weeks to two months earlier than the 1979 to 2000 average in these areas. However, in Baffin Bay and Hudson Bay, a cool spring led to a later start for surface melt, especially in Hudson Bay. Subsequent warm conditions have nevertheless led to rapid ice melt.



Low summer snow cover in the Northern Hemisphere
As noted in our May 4 post, snow cover in central Russia retreated early in response to warm conditions this spring. Updated analyses provided by the Global Snow Cover Lab at Rutgers University reveal that snow cover remained very low for May and June. Even though some mountain regions in the U.S. and Canada saw greater-than-normal snow cover, snow cover for the Northern Hemisphere as a whole for May and June was the second lowest since the start of snow cover records in 1966.

According to David Robinson, head of the Rutgers Snow Cover Lab, a new pattern is emerging in which the Northern Hemisphere is cloaked in above-average snow during late autumn, winter, and early spring, followed by rapid melt and retreat in May and June. While snow cover varies from year to year, the far north has seen a clear trend towards less spring snow cover over the last thirty years.

Member Since: January 2, 2006 Posts: 127 Comments: 20401
Quoting cat5hurricane:
...the last indications are for trending colder winters coupled with hotter summers.


Be careful not to believe or post everything you see. I remember after the brutal winters in the 1970's and 1980's the dawn of the next ice age is upon us. And, well, did that pan out?


Re part 1: if you're talking about North America, that's not what the data show:

uh-oh

So far as part 2, few climatologists believed that an ice age was on its way. But if you have actual proof stating otherwise, I'd love to see it.
Member Since: November 8, 2009 Posts: 4 Comments: 13579
Quoting cat5hurricane:
What exactly have you done about it, CB?


Click here:

Link


Member Since: January 2, 2006 Posts: 127 Comments: 20401


In this first image you can see the "High Pressure" Rick is talking about beautifully here on this NOAA image of the Eastern US. The storms he talks about around the periphery of the high is also known as the ring of fire in meteorology but it is not to be confused with the ring of fire in vulcanology which basically circles the pacific ocean. You can also see the clear section of the middle of the country where the suppression of rain exists because of falling air.





In this second image of the Gulf Of Mexico:




You can see how hot it is and the hotter it gets the more moisture it creates in the atmosphere thus adding to the dangerous heat wave. So oppressive heat with moisture becomes a dangerous combination for us humans. So at some point we must think of ways that we can tweak the climate back to what it was because it is becoming to dangerous for our survival. I keep reading articles like this.

13 deaths in Midwest tied to heat wave
Poultry farmers deploy fans; heat to reach East Coast later this week

OKLAHOMA CITY — The heat was on Monday for millions of Americans from the Upper Midwest to Texas and Oklahoma, where roads buckled and poultry farmers deployed fans and watered rooftops to protect flocks.

The National Weather Service put 18 states stretching from North Dakota to Texas and East to Ohio under a heat warning, watch or advisory. It said as many 13 deaths in the past week in the Midwest could be blamed on the effects of the heat.

When humidity was factored in, the heat index made it feel as hot as 110 degrees in a broad swath of the nation.

"This is unusual," said Pat Slattery, spokesman for the Weather Service. "There's no sugar-coating anything here."

In steamy Oklahoma City, 13 state government buildings at the capitol were closed after a break in a water main that shut off air-conditioning systems.

Computer systems in Oklahoma's state agencies were turned off and 1,000 employees sent home, said spokeswoman Sara Cowden of the Department of Central Services.

"We're shutting everything down that generates heat," she said.

Link

There comes a time when you have to say "you know ole CB is on to something here when he says we have to cool the GOM". People are dying folks when you going to do something about it? I have done my part don't you think?
Member Since: January 2, 2006 Posts: 127 Comments: 20401
Thank you, Dr. Rood.

First, congrats on reaching 200; that's a whole lotta writing. I think I speak for everyone when I tell you that it is very much appreciated.

Second, those heat indices were even higher yesterday. Here are a few from Iowa:

KNOXVILLE 131
NEWTON 129
ATLANTIC 126
COUNCIL BLUFFS 126

Third, there's every indication that this kind of heat not only will become more and more normal, but likely already is:

Stanford climate scientists forecast permanently hotter summers beginning in 20 years

The tropics and much of the Northern Hemisphere are likely to experience an irreversible rise in summer temperatures within the next 20 to 60 years if atmospheric greenhouse gas concentrations continue to increase, according to a new climate study by Stanford University scientists. The results will be published later this month in the journal Climatic Change Letters.

In the study, the Stanford team concluded that many tropical regions in Africa, Asia and South America could see "the permanent emergence of unprecedented summer heat" in the next two decades. Middle latitudes of Europe, China and North America – including the United States – are likely to undergo extreme summer temperature shifts within 60 years, the researchers found.

"According to our projections, large areas of the globe are likely to warm up so quickly that, by the middle of this century, even the coolest summers will be hotter than the hottest summers of the past 50 years," said the study's lead author, Noah Diffenbaugh, an assistant professor of environmental Earth system science and fellow at the Woods Institute for the Environment at Stanford. The study is co-authored by Stanford research assistant Martin Scherer.

- - - - - - - - - -

To determine the seasonal impact of global warming in coming decades, Diffenbaugh and Scherer analyzed more than 50 climate model experiments –including computer simulations of the 21st century when global greenhouse gas concentrations are expected to increase, and simulations of the 20th century that accurately "predicted" the Earth's climate during the last 50 years. The analysis revealed that many parts of the planet could experience a permanent spike in seasonal temperatures within 60 years.

"We also analyzed historical data from weather stations around the world to see if the projected emergence of unprecedented heat had already begun," Diffenbaugh said. "It turns out that when we look back in time using temperature records, we find that this extreme heat emergence is occurring now, and that climate models represent the historical patterns remarkably well."

Stanford Report Article...

NOTE: that report isn't claiming there haven't been extreme heat waves in the past; it's saying, rather, that they are going to become more frequent and more severe.
Member Since: November 8, 2009 Posts: 4 Comments: 13579

Viewing: 18 - 1

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 — Blog Index

Top of Page

About RickyRood

I'm a professor at U Michigan and lead a course on climate change problem solving. These articles often come from and contribute to the course.

Local Weather

Scattered Clouds
50 °F
Scattered Clouds