Archive for the ‘Nature’ Category

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Climate change in North Dakota

April 7, 2009
This post is in response to Darin, who left a good comment on my previous post concerning flooding in North Dakota.  Darin said:

Something is going on. I have lived here all my life and experienced two of the record level floods prior to the 1997 flood. That was the flood of 1975 and 1979.

Since then we’ve had 97-2001-2006-2009 that have each bumped all other years in the previous 110 years of record keeping down the list.

Now 7 of the top 10 flood levels come in the last 25 years.

You don’t have to have a masters in statistics to see a correlation to SOMETHING? I don’t know if it is global warming changing weather patterns, but they are changing.

Darin’s observations are legitimate and he has asked some good questions.  I would say that perhaps a master’s in statistics would, in fact, be useful in this situation.  But references to paleoclimatological records would be even more useful.  Why?  Because the real question is whether or not the climate in North Dakota and surrounding areas in the last several decades (while CO2 levels have gone up significantly) has varied in an obvious way from the magnitude of fluctuations seen during the “normal times” over the last several millennia (before CO2 levels rose).   

Consider recent history first. 

Pre-industrial CO2 levels are typically pegged at 280 ppm (parts per million).    Levels rose slowly during the 19th century and reached about 290 ppm by around 1930 and 310 ppm around 1950.   Today the number is at about 385 ppm, as shown below.  So I think that we can agree that the CO2 level started rapidly increasing when the world started becoming highly industrialized in the 40s and 50s. 

mauna-loa-co2

So when did the most extreme measured temperatures occur in North Dakota?  Answer: in the 1930s (-60 and +121 degrees F), when CO2 levels were much closer the pre-industrial levels.  When was the previous measured record crest of the Red River?  Answer: 1897, at 40.1 feet, when atmospheric CO2 levels were almost at pre-industrial  levels.

Paleoclimatological history

Drought is the most commonly sited risk of CO2 induced anthropogenic global warming for North Dakota.  For example, the Center for Integrative Environmental Research at the University of Maryland reports in their paper “Economic Impacts of Climate Change on North Dakota”:

“Atmospheric models predict that North Dakota will become drier in the future, with drought patterns becoming more intense as a consequence of global warming.”

Additionally the argument is made that rising levels of atmospheric CO2 will result in “climate change,” as opposed simple “global warming,” with greater extremes in temperature, precipitation, etc.  Using this terminology any changing climate conditions can be attributed to anthropogenic CO2, right?  Well, no.  This argument only works if it can be shown that the range of weather extremes in the era of increasing CO2 is statistically greater than the range of weather extremes during at least several thousand years while CO2 held steady at about 280 ppm.   What does the paleoclimatological record say about North Dakota climate for the last several thousand years?

In 1999, in the Proceedings of the North Dakota Academy of Sciences, Allan Ashworth pointed out that:

North Dakotan’s know only too well the effects of climate change. From 1988 to 1992 the State experienced drought conditions but since then North Dakota has been in a wet cycle. North Dakotans are stoical when it comes to weather but even so there is a concern about what the future will bring. Most of our knowledge of climate change comes from an instrumental record that is only 100 years in length. This record has been extended by dendroclimatology and by high resolution paleontologic and geochemical studies of lake sediments. What these studies are showing is that 100 years is far to short a time to show the variability in the climate record. (emphasis added)
 

 Ashworth points out some interesting details.  For example, at Rice Lake “maximum drought conditions during the mid-Holocene occurred between 7-6″ thousand years ago.  Similarly, “maximum drought conditions at Elk Lake, Itasca Park, Minnesota, occurred between 6.2 to 6″ thousand years ago.  At Moon Lake the presence of Iva pollen (which at the present “does not extend north of Nebraska…is thought to represent warmer conditions”  in the mid-Holocene.  Ashworth gives details of lake salinity and level changes during the mid-Holocene and notes “The general assumption is that significant changes in the lake levels are the result of climate change” during the last several thousand years, before CO2 levels rose.  He further notes:

“Individual records show a lot of variation, but there appears to be a cyclicity to drought, with intense droughts occurring on a frequency of 40 – 60 years. What is particularly striking is the Moon Lake salinity record is the magnitude of a series of droughts prior to AD 1200: at AD 200-370, AD 700-850 and AD 1000 -1200. These droughts were all of a greater magnitude than the intense drought of the 1930’s.”

In a 1997 Quaternary Research paper concerning climate variability, as measured by a variety of markers at Moon Lake, North Dakota,  Blas L. Valero-Garces, et al. wrote:

Seismic stratigraphy, sedimentary facies, pollen stratigraphy, diatom-inferred salinity, stable isotope (δ18O and δ13C), and chemical composition (Sr/Ca and Mg/Ca) of authigeniccarbonates from Moon Lake cores provide a congruent Holocene record of effective moisture for the eastern Northern Great Plains. … A change at about 710014C yr B.P. inaugurated the most arid period during the Holocene. Between 7100 and 400014C yr B.P., three arid phases occurred at 6600–620014C yr B.P., 5400–520014C yr B.P., and 4800–460014C yr B.P. Effective moisture generally increased after 400014C yr B.P., but periods of low effective moisture occurred between 2900–280014C yr B.P. and 1200–80014C yr B.P. The data also suggest high climatic variability during the last few centuries.  (emphasis added)

 If Valero-Garces, et. al., are correct then is seems that recent variability in North Dakota is not unusual, and cannot be blamed on anthropogenic CO2.

Sherilyn C. Fritz of the University of Nebraska – Lincoln Department of Geosciences and her co-authors considered the “Hydrologic Variation in the Northern Great Plains During the Last Two Millennia“, and claim that

“The data show that the last 2,000 years have been characterized by frequent shifts between high and low salinity, suggesting shifts between dry and moist periods. Long intervals of high salinity suggest periods of multiple decades when droughts were intense and frequent, thus indicating times when drought was more persistent than in the 20th century. ..[T]he climate of the last 2000 years was hydrologically complex, with large oscillations between low-salinity wet phases and high-salinity dry phases.” (emphasis added)

Fritz gives details from three North Dakota lake sites showing constant variation…

“All records show an interval of prolonged drought between ca. A.D. 40 and 130, followed by a wetter period, and also a dry period about A.D. 250, which two of the records (Moon [Lake]and Rice [Lake]) suggest was sustained for more than a century. Shorter periods of drought are evident at ca. A.D. 400 and 530, and the data suggest a period of major and sustained drought from ca. A.D. 620 to 790. The time from A.D. 1020 to 1150 was also characterized by major drought and was followed by a distinct wet interval to at least A.D. 1300. …. All sites show intervals of very fresh conditions, suggesting high precipitation, sometime between A.D. 1330 and 1430 and in the early decades of the 1800s. The data also suggest periods of drought in the decades surrounding A.D. 1500, 1600, and 1800, and in the latter decades of the 19th century.”

Kathleen Laird of the Department of Ecology at the University of Minnesota writes in Nature  that

“Extreme large-scale droughts in North America, such as the “Dust Bowl” of the 1930s, have been infrequent events within the documented history of the past few hundred years, yet this record may not be representative of long-term patterns of natural variation of drought intensity and frequency. .. Here we present a reconstruction of drought intensity and  frequency over the past 2,300 years in the Northern Great Plains…” (emphasis added)

Laird studied the salinity record of Moon Lake, North Dakota, as an indicator changing hydrological conditions and said…

“Our working assumption is that periods of positive water balance (precipitation > evapotranspiration) are reflected by higher lake levels and lower salinities, whereas when the water balance is negative, lake levels are lower and salinity higher …”

and found the following fluctuating signal:

Figure 2.  Salinity of Moon Lake, North Dakota, from Laird, et. al., Nature

Figure 2. Salinity of Moon Lake, North Dakota, from Laird, et. al., Nature

My conclusion is that the precipitation variation seen over the last 100 years in North Dakota is not unusual when compared to previous centuries, when CO2 levels remained near 280 ppm

 
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Comments on “An Exchange on Climate Science and Alarm” between Lindzen and Rahmstorf

March 10, 2008

Lubos Motl’s blog recently highlighted an exchange between Stefan Rahmstorf and Ricbard Lindzen.  this peaked my interest because I have already picked apart another paper by Rahmstorf.  Rahmstorf’s part of the exchange is from chapter 3 (which he wrote) of the book Global Warming: Looking Beyond Kyoto,published in paperback in December of 2007.  You can see Rahmstorf’s chapter here.

 Rahmstorf shows the same CO2 vs. time and temperature vs. time data overlay that Al Gore used in An Inconvenient Truth.  Figure 1, below, shows part of page 36 of Rahmstorf’s chapter in the book.  The image shown in Rahmstorf’s paper notes the source of his data as “Climate and Atmospheric History of the Past 420,000 Years from the Vostok Ice Core, Antarctica, Nature 399 (June 1999): 429-36″ by Petit, et. al.

Figure 1. Excerpt from Rahmstorf’s chapter in Global Warming: Looking Beyond Kyoto.  Rahmstorf added the points for 1959 and 2005 in a similar fashion to Al Gore.

But Rahmstorf forgot to mention that original source of his data included insolation vs. time, along with CO2 vs. time and temperature vs. time.  Figure 2, below, shows an excerpt from Petit’s original paper, in Nature, in which I have highlighed all three parameters vs. time.  Note that Rahmstorf puts the present at the right and the past at the left.  Petit has present at the left and the past at the right.  Other than that, and the fact that Rahmstorf leaves out the insolation data, they are the same.

petit-full-page-2.jpg

Figure 2.  Excerpt from Petit’s Nature paper.  This is Rahmstorf’s source, but Rahmstorf leaves out the insolation vs. time data

It is not possible for the CO2 level or the temperature to control the insolation.  It is clear that the temperature and the CO2 can only follow the insolation.  There doesn’t seem to be any likely mechanism for the insolation to directly impact the CO2 level.  Therefore, the insolation must influence the temperature, and the temperature influences the CO2 level.  There may be a small feedback to the temperature from the CO2, but it cannot be large.  This is evidenced by the fact that no matter how high the CO2 goes the temperature still follows the insolation back down. 

In figure 3, below, I have digitized the temperature, CO2 level and insolation from Petit’s data and plotted the temperature series with the CO2 series and again with the insolation series for the last 150,000 years.  Temperature obviously correlates better with insolation than with CO2

side-by-side-graphs.jpg

Figure 3.  Digitized versions of Petit’s data.  Why does Rahmstorf leave the insolation out of his presentation?

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“Warmer Oceans, Stronger Hurricanes,” Trenberth, Scientific American, July 2007

October 1, 2007

Hyperbole comes in many forms. This article in Scientific American came with a full page artist’s rendering of a “future hurricane.” I have shown a very small (to avoid copyright lawyers) copy of the picture below, with a blow up of one section. The caption for the picture in the magazine says “Future hurricanes could be more severe thanks to global warming.” The blow up shows a giant hurricane bearing down on the Caribbean and the East coast of the United States


Figure 1. The small picture at the left is a miniature version of the 8 inch by 11 inch full page artist’s rendering of a “future hurricane” form page 44 of the July 2007 Scientific American. The right side shows a blow up of part of the picture.

The very first paragraph of the article reminds the reader of the 2005 hurricane season and, of course, Katrina. So, I use a pair of pictures below to compare Katrina to the imagined “future hurricane.” The first is a satellite image of Katrina shortly before it made landfall near New Orleans. The second is a detail of the Scientific American picture. Note that the sizes of the images have been adjusted to give the same scale.

Figure 2. Detail of Scientific American picture of “future hurricane” with same scale as image of Hurricane Katrina in figure 3,below.

Figures 3. Satellite image of Hurricane Katrina just hours before making landfall at New Orleans. This image is on the same scale at the artist rendering of a “future hurricane” in figure 2, above.

Figure 4. Juxtaposition of the Scientific American “future hurricane” and the very real Katrina from the satellite image. I have removed land masses from both pictures. Both pictures are on the same scale, as in figures 2 & 3.

Scientific American’s “future hurricane” is bigger than the continent of North America. It is so big that it stretches from northern Brazil to southern Canada. It is as large as the North Atlantic Ocean. This is clearly extreme visual hyperbole, but it is also a metaphor for much of the global warming debate, where preposterous exaggerations and extrapolations abound.

Those who are convinced that we are headed for a future of giant hurricanes due to increased CO2 might consider the following journal articles to mitigate the effects of the seemingly endless fear mongering so common in the global warming debate:

1. In Low Atlantic hurricane activity in the 1970s and1980s compared to the past 270 years, Nyberg, et. al., point out that “reliable observations of hurricane activity in the North Atlantic only cover the past few decades.” It is not possible to say, based on this short set of data, if the variation that has been seen during these few decades is greater than should be expected over longer time scales. However, they developed a proxy for both sea surface temperature and vertical wind shear covering 270 years. (Vertical wind shear is inversely related to hurricane formation). The result shows that “the average frequency of major hurricanes decreased gradually from the 1760s until the early 1990s, reaching anomalously low values during the 1970s and 1980s.” It seems clear that the upswing in hurricane activity seen from the beginning of the satellite era to the present is largely a consequence of the beginning of the satellite era being at the low point of hurricane activity for the last 270 years.

2. The article in Nature, Intense hurricane activity over the past 5,000 years controlled by El Nin˜o and the West African monsoon,” by Donnelly and Woodruff of the Woods Hole Oceanographic Institution in Massachusetts echos the concern that “the instrumental record is too short and unreliable to reveal trends in intense tropical cyclone activity.” To overcome these limitations they used sediment deposits in coastal lagoons of the Caribbean to gauge hurricane activity on the century and millennial time scales over a 5000 year period. They found the frequency of intense hurricanes varied widely on these time scales during the past 5,000 years and that the frequency appears to be governed by the El Nin˜o/Southern Oscillation and the strength of the West African monsoon.” Additionally, ” sea surface temperatures as high as at present are not necessary to support intervals of frequent intense hurricanes.”

3. The short instrumental record of hurricane activity was a motivation for Miller, et. al. in their 2006 Proceedings of the National Academy of Sciences paper, “Tree-ring isotope records of tropical cyclone activity.” As trees grow, the oxygen isotope ratios of the water at that place and time are locked into their rings. It is also known that the precipitation of tropical cyclones and hurricanes have oxygen isotope ratios that are greatly different that more common causes of precipitation. Miller, et. al., examined long leaf pines (pinus pulustris) in Georgia because they have shallow roots and a distinct early season growth and late season growth in their rings. these combine to give a precise temporal fix on isotope ratio variation. Their study covered 1770 to 1990. Their analysis of the tree ring oxygen isotope data shows very close agreement with the instrumental data for the southeastern United States after 1940, verifying the efficacy of their method for earlier times. The overall results indicate “systematic, decadal- to multidecadal-scale variations” in the isotope ratios, and consequently variations in the number of hurricanes. Hurricane activity appears to have peaked in the 1770s, 1800s to 1820s, 1840s and 1850s, 1865 to 1880, and the 1940s to 1950s. The quietest decades are the 1780s through 1790s, and the 1970s. The 1970s saw the beginning of satellite tracking of hurricanes. The fact that there has been an upswing in hurricanes in the satellite record is much less alarming when you consider that the 1970s was one of the least active decades (at least for the southeastern United States) in over 200 years.

Kevin E. Trenberth, “Warmer Oceans, Stronger Hurricanes,” Scientific American, July 2007, p44-51. (Get copy here.)

Johan Nyberg, et. al., “Low Atlantic hurricane activity in the 1970s and 1980s compared to the past 270 years,” Science, Vol 447, 2007. (Get copy here.)

Jeffrey P. Donnelly & Jonathan D. Woodruff, “Intense hurricane activity over the past 5,000 years controlled by El Nin˜o and the West African monsoon,” Nature, Vol 447, 24 May 2007 (Get copy here.)

Dana L. Miller, et. al., “Tree-ring isotope records of tropical cyclone activity,” Proceedings of the National Academy of Sciences, PNAS, Vol. 103, no. 39, September 26, 2006 (Get copy here.)

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