Heat Waves (4) A Climate Case Study:
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?
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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
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So how hot would it be now if that heat hasn't been going into the arctic to melt more ice?
Correct head pressure is a function of altitude. Look it up sometime.
What does that matter? What is your point?
Then explain the video Mr. smarty pants!
Dude the water was flowing 20 times slower in that video than it does in the gulfstream. Depth is a non issue here because the pressure in the pipe is the same as the pressure outside the pipe. It is the kinetic energy at the tunnel inlet which forces the water up the pipe. Comprende?
I can't tell you what Bill Gates thinks. But I can tell you his idea does not produce electricity nor does it work if no waves are present. Ever see how calm the seas are two or three days prior to a storms arrival? His idea can not regulate the SST's either.
That header graphic may be one of the funniest things I've ever seen. Cherry-picking temperature data starting with 1998 as they've done is like going to the beach at high-tide, observing the water levels for six hours, then proclaiming that the ocean is draining. Silly denialists...
And it's not just the graphic that's laughable; the whole premise upon which the text is based is anti-science comedy at it's best. Apparently the writer isn't aware that "all-time record high heat" is identical to "unprecedented heat". And when he starts comparing numbers, I've really got to chuckle. Do you think he knows that 48 all-time record high temps were set or tied Friday and Saturday alone? Think he knows that daily record highs have outnumbered daily record lows across the U.S. 3,573 to 120 over the past week alone, a ratio of nearly 30 to 1? Think he knows that record daily highs for the year outnumber record daily lows by 15,327 to 6,255, or 2.45 to 1?
As always, a spate of record temps in either direction doesn't prove or disprove GW. But in a neutral world, one would rightly expect record highs and record lows to roughly balance out. The fact that each passing decade sees an increasingly disproportionate large number of record highs, then, is very telling.
Greenpeace and the IPCC – The Edenhofer Excuse
"It has been a recurring pattern that the most dramatic of conclusions arrived by the IPCC, are shown to arise from unsubstantiated or exaggerated claims in literature put out by environmental pressure groups. The latest addition to the list is the Greenpeace-generated factoid that ‘80% of the world’s energy demand could be met by renewable sources’ which found its way onto the IPCC pedestal."
714, so please explain why the first 3 months of this year the Global Temperature was below normal? UAH records show it quite clearly.
Why switch arguments? I was talking about the ignorance or evil (or maybe both) of cherry-picking as on the site that was linked; what's that got to do with a small group of cooler temps?
"Hey, look! I've been timing the minutes of sunlight every day since June 21, and they're getting shorter every day! I predict that a year from now the planet will be plunged into perpetual darkness!" ;-)
;-) backatcha
Yet another example of the baseless smears against science and scientists from the non-degreed one-time small-market TV weather reader. Surprising. :-\
Temp records go back to the late 1800s. The graph on the silly denialist graph went back to 1998. The former is science. The latter is cherry-picking.
;-) backatcha
Small group of cooler temps?
Global temps being below normal for a quarter year is not a small group.
The inability to respond speaks volumes.
Scripted retorts can't protect your Conscience.
According to the NASA GISS record, the first 3 months of this year were 0.48 deg C above the 1951-80 global average. That's a little lower than recent years due to the cooling influence of La Nina. Here's the link.
http://data.giss.nasa.gov/gistemp/tabledata/GLB.T s+dSST.txt
Now, can you provide a link to support your claim?
Oh, come, now, you can't change the subject simply because you realize you've talked yourself into a corner. Again. I mean, I suppose you can if you wish--but too many people see right through that tactic for it to be effective. No, 'tis far better to stick with the original argument...or should I just assume that your own "inability to respond" means you agree with me that using 1998 as a starting date to "prove" global cooling is false? Gosh, I sure hope so... ;-)
The post wasn't from Anthony Watts. It was on his website, probably because it has high traffic. The usual M.O. of the warmists: insult the messenger when you can't refute the message.
The usual modus operandi of the denialists. Accuse the other side of using your own shabby tactics.
Judging from the emails I've received from Herr Watts, he is the site and the site is him--did you know the "Watts" in "WattsUpWithThat" comes from his last name?--and there's nothing that goes on there without him first marking it with a big round stamp of approval. IOW, where WUWT is concerned, the message is inseparable from the messenger.
Complain, Denigrade, Blame and Incorporate Political Idealogy without forming a clear, realistic argument or solution
http://vortex.nsstc.uah.edu/data/msu/t2lt/uahncdc .lt
Okay, here's a clear, realistic argument which I know will be totally ignored by the denialists as they have no answer to it.
Scientists believe that pre-industrial levels of greenhouse gases contribute around 33 deg C of warming at the Earth's surface. Without this trapped heat, Earth would be a snowball in space, with perhaps a narrow tundra region around the equator where life might exist.
Man has increased atmospheric CO2 by 40%, methane by 153% and water vapour has increased by 4%.
If you don't believe that greenhouse gases contribute around 33 deg C of warming, explain where the scientists have gone wrong.
If you do believe that greenhouse gases contribute this amount of warming, explain why you don't think the additional man made contribution warms the planet.
A truth loving argument if ever there was one, which is why there will be no response.
You mistakenly ingnore water vapor in your grossly simplified statistics. You might want to try to understand the significance of such.
You also oversimplify the overall complexity of climate to meet you simplified needs.
You might also want to garner a better understanding of the role of cloud cover as part of your equation.
Then you can start looking at the things that are responsible, at the most fundamental level, for making those clouds.
Out>
The reference period for those stats are 1981-2010
The usual reference period for temperature comparisons is 1951-80, which is the period immediately prior to recent global warming, and is the reference period used by NASA GISS.
The first 3 months were indeed a few hundredths of a degree below the average for the 1981-2010 reference period. However, the average for the first six months is 0.08 deg C above the 1981-2010 average. You have cherry picked January to March to favour your argument.
It's called 'natural variation', in this case caused mainly by La Nina.
Well, perhaps the NASA GISS reference period of 1951-80 is different from that of the other organisations.
Are you really interested in learning? Or trying to score points? If it's the former, I'll be glad to help you. If it's the latter, I'll just move on.
I've posted the manmade vs. volcanic CO2 comparison numbers several times in the past two weeks. Perhaps this time you can mark them down? Or, better yet, bookmark this link?
Global volcanic CO2 emissions (highest preferred estimate): 0.26 billion tonnes per year (Gt/y)
Anthropogenic CO2 in 2010: 35.0 Gt/y
Mount St. Helens: 0.01 Gt
Number of MSH-equivalent eruptions to equal annual anthropogenic CO2: 3,500
Mount Pinatubo: 0.05 Gt
Number of Pinatubo-equivalent eruptions to equal annual anthropogenic CO2: 700
(As I've explained before, a person correcting a factual error in a comment is not the "gotcha" you seem to think it is; it's called being honest. Only a fool knowingly posts false information then leaves it up.)
In brief, scientists know that manmade CO2 is driving the current heating for the simple fact that the natural carbon cycle adds and removes CO2 in roughly equal amounts, keeping it in balance. But there are no mechanisms for removing the extra fossil fuel CO2 we're creating; the oceans absorb a but less than half of it, and the rest simply stays in the atmosphere where it contributes to warming. In short, the level of atmospheric CO2 is building up, that additional CO2 is being produced by burning fossil fuels, and that build up is accelerating.
Link
Who cares what China does?
I think that's one of those cynical "We can't do anything about China, so why should we do anything at all?" things that the Koch Brothers love for their minions to say. Every time someone says that, a little cash register sound goes off in their heads.
As I guessed, nymore, you're clearly not interested in learning, but in trying to score points in some game of your own imagining. But it's not a game; it's real. It's here. It's dire. Amnd we're doing nothing about it.
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