Averaging the Extremes: With the drought that much of Texas is enduring, a number of folks were actually looking forward to Tropical Storm Edouard last week. Despite the threat of flooding and other damaging events, it offered the promise of relief from the hot, dry conditions. A lot of Central Texas is now feeling cheated. For instance, Edouard brought a day of overcast and almost no rain to Austin and surroundings. It wasn't long until the unusual bout of 100 degree weather returned.
On Friday, Austin had its 44th 100 degree day, the highest number since the record year way back in 1925, when it hit 100 a staggering 69 times. There are still 21 record highs on the books from April through October of 1925...which folks had to endure sans air conditioning. Unsurprisingly, that was also a drought year; low humidity and few clouds are key parts of the formula in much of Texas for hitting 100 degrees.
The drought ended abruptly, with that October still being the wettest on record. There were major storms in Central Texas from Oct 12-17, with the 13th still having Austin's record rainfall for that day--6.95 inches. That's well above October's average monthly rainfall of 3.97 inches. This was an example of the fact that droughts build slowly--day by day, but they don't often end that way.
Neither the hot temperatures nor the soggy October in 1925 count towards today's weather averages. Normal temperatures and rainfalls are calculated once per decade, using the previous three decades' data. That stormy October 13th added a bit over 0.22 inches to October's normal rainfall in the 1930s through the 1950s. Ever since then, 1925's record weather has been just a historical footnote.
Ominously Quiet: One of the contributing factors to the current drought in much of the Southeast is the fact that remnants of hurricanes haven't had much impact there the last couple of years. More often than not, at least one tropical cyclone hits the area each year. The following maps show all of the named storms (tropical depressions and up) in the Atlantic for 2007...
...and 2006.
When these often soggy storm systems drag over the southern Appalachians, they can cause deadly and damaging flooding...which also soaks the ground and helps fill--sometimes overflow--lakes and reservoirs.
Bear in mind that when one hears about reservoirs hitting record lows, most reservoirs have a shorter history than our weather records, and nearly all are impacted by man's increasing water usage. Both weather and man can cause droughts.
The Good Old Days: Sometimes the weather that we grew up with and came to think of as normal really wasn't. Here are some thoughts offered during a drought in the Southeast at the end of the previous decade.
Georgia's State Climatologist David Stooksbury, who also is a professor of engineering in the University of Georgia College of Agricultural and Environmental Sciences, doesn't see drought as strange or even unusual.
"The state of Georgia now has returned to a more normal climate pattern, with greater year-to-year variability," says Stooksbury. "Drought is part of the overall history of the Southeast. But the history also contains long periods of wetter weather.
"We will have more years that are extremely wet and more years that are extremely dry, which historically is the more common pattern."
If you are ignorant of past climatological trends, it's easier to blame current trends on something being abnormal.
Farmers who were around during the 1960s and 1970s can recall extended times of wet, mild weather, says Stooksbury, and that weather makes the current drought seem that much more unusual. But those weather patterns could not be characterized as "normal," says the climatologist.
"If you look back at droughts, the 1960s and 1970s were the abnormal years. There was very little variation," he continues.
In the 1960s, central Georgia experienced only one month of drought, says Stooksbury. And throughout the 1970s, the same area saw only 13 months of moderate, extreme or severe drought.
The 1960s was a relatively typical decade for tropical cyclones hitting Georgia, while the 1970s was abnormally quiet in both Georgia (previous blog here) and the entire Atlantic. The 60s have already been dropped from the calculations regarding normal weather, and the rather cool 70s won't be around much longer.
FYI, the Southeast is one of the few areas of the world that cooled over the previous century.
Returning to Normalcy: Remember all the coverage last year of the low water levels in the Great Lakes? As Lake Superior approached and then finally set a record low for the month of September (previous blog here), many folks were citing this as evidence of climate change. But then it started raining...and eventually snowing. The record monthly low from October 1864 held, as did the all-time record low from April 1926.
Lake Superior is now back to its long-term average and Lakes Michigan and Huron have recovered somewhat and are now about a foot below average. Lakes Erie and Ontario weren't impacted much by the drier conditions upstream and are currently above average. Despite the fact that neither the dry spell from 1997-2007 nor the recent burst of precip are anywhere near long enough to indicate anything about climate change, that topic seems to dominate the discussion.
...no one is predicting that the rain--or the rise--will last.
In fact, most scientists are still warning that the Great Lakes will continue a general shrinking, in volume and surface area, if global-warming trends evaporate more lake water.
One federal report, for example, suggests that Lake Erie water levels could drop by 33 inches over the next 70 years, leading to a 15 percent decrease in lake surface area and significantly altering shorelines.
While the majority of climate models show the Great Lakes dropping, a few show the opposite. Rather than acknowledge this, the article only gives us worst case numbers from one of the worst case reports. That's pathetic reporting.
"If it does get warmer as atmospheric scientists say it will, we'll see lower lake levels over time," said Thomas Croley, a hydrologist for the federal Great Lakes Environmental Research Laboratory in Michigan. "So just because they're going up now after a season of rain and snow doesn't mean they'll stay that way.
"And it certainly doesn't mean that climate change isn't real."
One of the reasons that several climate models show higher levels for the Great Lakes is that one cannot automatically make the assumption that warmer weather means lower lake levels. There's almost a century-and-a-half of data for the Great Lakes region which helps highlight that fact. For instance...
- Why have any record low lake levels survived from 1864, during which time the globe was coming out of the Little Ice Age?
- Why were all-time record high levels for Lakes Michigan and Huron set in both 1886 and 1986? Et cetera.
It's always a red flag when scientists offer flimsy explanations at best (including dismissing such events as anomalies) and then retreat behind the prognostications of climate models. Also note that we don't have a good handle on how much man's activities--both in terms of water usage and increasing the drainage of the lakes--have impacted water levels.
And speaking of dredging, though in this case regarding ports...
"Everything is not fine now just because of a little rain," said Glen Nekvasil, vice president of the Lake Carriers Association. "We have been able to load up to 12 inches deeper for now, but we can't go any lower because so many of the harbors still need dredging."
The difference between the average and record low lake levels in Lake Superior is less than two feet, and for Lakes Huron and Michigan it's just over three feet. Every inch makes a difference in how much cargo the big ships can load, whether it be lake levels or increasing muck on the bottom.
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