Once again the media continues to use this event as a Global Warming rallying cry saying that this US centered heat wave is a direct result of Global Warming.
Months ago, I wrote about the need for the media to report the complete story on these hot button science issues. Informing the public on "the whys" in simple, easy-to-digest terms can be done. Yet reporters continue to latch onto one element that sells without telling the entire scientific story. This recent heat wave coverage is another example.
I am not diminishing the significance of this heat wave by any stretch. Our dry winter has given way to a drier spring and summer. Drought conditions now envelop more than 50% of the 48 contiguous states.
corn prices are already bring felt as corn futures were lowered by 12% July 11th. Yet two weeks of record breaking heat and increasingly worse drought conditions from the west to the Ohio Valley is an invitation for the media to release the proverbial global warming dogs warning that this drought, is driven by Global warming.
As I have repeatedly stated, I am not debating Global Warming. I am not here to debate the temperature data sets used in determining global temperatures. I am highly critical of using Anthropogenic Global Warming (regardless of what data set you use) as the root cause of every weather disaster from US landfall hurricanes to east coast snowstorms to heat waves. I said this when the east coast was hit with Hurricane Irene last August. I said this during the extreme cold felt in Alaska last winter. I said this especially during the recent tornado outbreaks this past spring. Sighting Global Warming as the cause the recent US heat wave is putting the cart before the horse. What the National media fails to address are the antecedent conditions that are needed to produce heatwaves. What are these antecedent conditions? Let's work backward from each effect to its cause or causes. Its not a simple linear cause-and-effect relationship as one might expect. Addressing each one individually helps put into context each ingredient from what we see and feel--the heat and drought--to the more nebulous concepts in the atmosphere--the jet stream for example--that drive them.
First, the warming needs to not only be present at the surface where we measure it but throughout the mid levels of the atmosphere. This warming is driven by the large scale high pressure ridge which develop each summer across the continent varying in strength from year to year. This high pressure ridge promotes sinking air and little cloud cover. The drought conditions in the midwest enhance this ridge making it stronger which warms the atmosphere further and higher which suppresses cloud development further which makes the drought conditions worse. This feedback mechanism becomes self-sustaining which is necessary in making the heat more record-setting and long lasting and tougher to break. This high pressure heat ridge is called a "block".
Ridges like the one in late June/early July are created by the overall wave pattern across the hemisphere. Now its getting a bit nebulous so stay the course here! The atmosphere flows like a river of water. In fact, the fluid equations that describe blood flow through the heart are similar to what describes atmospheric motion. Liquid water, blood, oil or air. They are all fluids. Now imagine a rock in a stream which deflects the flow water. Ever notice the little "spins" of water on the other side of the rock?
Landmasses like North America act like a rock in a stream deflecting, shifting, slowing or speeding up the behavior of the atmosphere that flows above it. Remember that the earth spin like a top. The speed of the earth's rotation increases closer to the north and south pole than at the equator. This change in velocity at different latitudes and its interaction with landmasses causes turbulent spins like a rock in a stream which causes persistent low and high pressure areas. Each low and high resides in these troughs and ridges around the hemisphere.
Often times, the wave pattern can get struck. Instead of the waves flowing in a typical "trough-ridge-trough" pattern, the waves stop progressing. The jet stream "breaks the wave". Either you get stuck under a trough (unsettled, cooler pattern) or a ridge (dry and warmer pattern).
Click on this link for an animation of the current jet stream pattern.
This past winter, the US was stuck under a ridge (milder winter) yet Europe was stuck under a persistent trough (cold and snowy). Are the waves slowing down causing more blocks and persistent weather? According to one paper, it depends on what season you look at. Little change in speed has been observed during the summer months since 1980. Notice how flat the red line is in the following graphic.
|Image courtesy of "http://earlywarn.blogspot.com/2012/04/slowing-rossby-waves-leading-to-extreme.html"
Experts at the National Center for Atmospheric Research have found these connections to El Nino and La Nina. “Teleconnections are important,” says NCAR's Kevin Trenberth, who has studied ENSO's global impacts extensively. “A lot of blocking is traceable back to the nature of convection in the tropics.”
Ultimately, are these "blocks" that cause heat waves more frequent and what does the future hold? According to NCAR, computer projections are not very good at predicting the beginnings of these blocks and how long they will last. "Looking toward the end of this century, the preliminary analysis indicates a slight increase in blocking overall. However, two recent studies suggest that blocking might actually decrease in the northern Atlantic and Pacific, as the average location of the polar jet stream shifts northward." According to the following study.
1) Heatwaves caused are local events caused by heat ridges governed by the wave pattern across the hemisphere
2) Hemispheric waves slow or speed up depending on the season. Jet stream behavior causes wave breaking which creates a "block"3) The behavior in the tropics both in the oceans and the tropical atmosphere can enhance the development of a ridge over the US
4) The changing oceans outside of the tropics (North Pacific, North Atlantic, Arctic Ocean et all) can effect the overall wave pattern
5) The drought conditions present in the central US feed the ridge which reinforces the blocking ridge even further
6) Computer projections of blocking patterns for the future decades are not very reliable
6) Some scientists believe that changing arctic ice due to Anthropogenic Global Warming could have an effect on the overall wave pattern
7) Randomness inherent in the atmosphere makes blocking ridges very difficult to forecast
Here they are. Seven bullet points. Some easy to understand; some not so basic. Remember that these often don't exhibit a linear relationship. The simple "butterfly effect" looks good but its an over simplification. I mentioned in a previous post months ago that predicting the influence of teleconnections like El Nino on regional weather patterns is like trying to recreate Grandma's soup. You can measure each ingredient exactly, cook the soup yet it might not taste quiet the same each time.
Once again, the science gets overly simplified by the media. Simplification becomes the mantra for these type of stories. Maybe that's what the general public wants. Maybe that's what sells and gets ratings.
I realize that in this flash-and-dash media world we live, simplification is more important than getting it right. But just once, couldn't a reporter take just one or two of these points, expand on one or two of them as they relate to the recent heatwave/drought?
Is this too much to ask?