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Monarchs, Cold Summers, Jet Streams, Volcanoes, and More
By Chip Taylor and Janis Lentz
Chip Taylor directs Monarch Watch at the University of Kansas
The topic for our first discussion will be the effect of cold summers on the development of monarch populations, in the heart of the monarch breeding area (Figure 1).
Figure 1. Natal origins of monarchs at overwintering colonies in Mexico.
As you will see, this topic will lead us into a discussion of the factors that contribute to lower than normal summer temperatures including changes in the position of the jet stream and volcanic eruptions. (Volcanoes are associated with many of the cold summers in the northern hemisphere over the last 120 years).
Scientific pursuits should start with well-defined questions, preferably ones that can be answered with available data, from new data obtained with a protocol appropriate for the question, or from carefully controlled experiments.
Let’s start with two questions:
First, what is the effect of cold summer temperatures on monarch populations? To be more specific, we are really asking what is the impact of colder than normal summer temperatures on the size of the fall migratory population?
Secondly, what is the underlying explanation for colder than normal summers?
Before we determine how to answer the questions, let’s ask where the questions came from. I have yet to encounter a question that can’t be traced to an observation and sometimes, as in this case, the juxtaposition of two observations. In this instance, I have for several months been contemplating the impact of what appeared to me to be a cooler than normal summer in the monarch’s northern breeding areas on the development of this year’s fall migratory population. Coincidentally, I had been reading a book by Simon Winchester about Krakatoa, a volcano between Sumatra and Java that explosively erupted on the 27th of August, 1883. This eruption had a profound impact on the world’s climate for several years. I’ll get back to Krakatoa, but before I do, let’s examine the first question in detail.
Most questions of this type are based on assumptions and we should examine the assumption (or assumptions) to be sure they are justified. What is the assumption in this case?
The assumption is that the initial observation was correct and that this past summer was colder than normal. This observation is based on my experience in Kansas, where we had what I call a Minnesota summer, one more typical of the summers I experienced while growing up in Minnesota. In addition, supporting observations about the weather were related to us by Monarch Watchers throughout the critical breeding area of the upper Midwest and Ontario. However, general impressions are often wrong and to determine if the assumption is valid we need data. Further, even if it was colder than normal, it is useful to know how cold it was relative to other years, since we are trying to determine if a cold summer has an impact on monarchs. The main breeding ground for summer monarchs covers a large area between 40-50 degrees north latitude in eastern United States and Canada, roughly the area from St Joseph, MO to Winnipeg, MB in the west and Philadelphia northward in the east. If climates are regional, we should be able to check the records from two or three localities to see if they recorded similar deviations from normal. If we see the same pattern in two or more widespread locations, it would support the idea that the climate is regional. A check of the mean summer temperatures for Kearney, Nebraska
and Central Wisconsin
shows that the pattern of high and low mean temperatures over many years are similar with both showing lower than normal temperatures for 2004. A further search of the NOAA web site confirms that the overall pattern for the 40-50 degree north zone for 2004 was also one of low temperatures.
So, our assumption, based on the general observation that the summer was cooler, is correct. But, what is the explanation for this pattern? The colder summer has been attributed to a shift in the position of the jet stream
The jet stream is an upper level wind pattern that has a strong influence on the climate. Normally, the jet stream moves northward in the summer months and doesn’t strongly influence the temperatures and weather patterns in the middle of the continent. This year the jet stream was positioned much further south over the middle of North America, preventing warm air masses from the Gulf Coast, southwest and west from penetrating into the middle of the continent while bringing in cooler air masses from Canada.
So, How Cold Was It?
So, how cold was it this summer? Actually, the summer of 2004 was colder than any summer since 1992 and before that 1950 and 1951. I will have something to say about these two previous cold periods, but let’s first determine how the cold weather this year might have affected the monarch population.
Degree Days and Monarch Growing Season
As you may know, the rate of development of monarchs through all life stages is temperature dependent. To understand how to relate daily temperatures to the rate of growth of monarchs, we need to understand two simple concepts, developmental zero and degree-days. Developmental zero (DZ) refers to the fact that there are both low (DZmin) and high (DZmax) temperatures at which all stages of the monarch will not grow. The metabolic machinery slows down and development stops. At the low end of the scale, monarch eggs, larvae and pupae will not grow or develop if the temperature is lower than 52.7F(11.5C). At the higher end, larvae fail to survive when the temperatures remain at 91.4F (33C). The measurement of degree days is a way to calculate the amount of growth, or physiological, time that occurs in a 24 hour period. To calculate how each day contributes to the development of the monarch population at a specific location, we need to know the maximum and minimum temperatures for each day and whether the temperature was lower than 52.7 F (11.5C) or higher than 91.4F (33C) degrees. There are several formulas for calculating degree days (DD) but the easiest one to use is as follows:
DD = (Tmax + Tmin) ÷ 2 DZmin
where DD = degree days; Tmax = maximum temperature; Tmin = minimum temperature; and DZmin = temperature below which monarchs will not grow (52.7F). In performing this calculation you may also use DZmax = temperature above which monarchs will not grow (91.4F).
There are two rules to follow in calculating degree days using this formula:
if Tmax > DZmax, set Tmax = DZmax
if Tmin < DZmin, set Tmin = DZmin
if for a typical summer day Tmax = 88 and Tmin = 60, the equation is
DD = (88 + 60) ÷ 2 - 52.7 or DD = 74 - 52.7 = 21.3
On the other hand, if Tmax = 95 (greater than DZmax) and Tmin = 50 (less than DZmin) by substituting the DZ values for the for the temperature values, the equation becomes
DD = (91.4 + 52.7) ÷ 2 - 52.7 or DD = 72.05 - 52.7 = 19.3
We should note here that there are two special cases to consider, both of which result in zero monarch development (though DD is not the same in both instances):
if Tmax and Tmin are both > Dmax, then DD = Dmax - Dmin
if Tmax and Tmin are both < Dmin, then DD = 0
Metabolic rate and growth is not linear over the range of 52.7F to 91.4F degrees, but rises slowly as temperature increases above 52.7F, peaking at 84.2F (29C) degrees and then declining to reach a basal or maintenance level at 91.4F. At 91.4 F degrees caterpillars do not grow and eventually die (Zalucki 1982). Graphically, representations of metabolic rates, or growth, relative to temperature, are a bit like a J that has been tilted 140 degrees to the left. Because the formula for degree days doesn’t account for the non-linear development over the range of temperatures at which growth occurs, it only provides an approximation of developmental rate. However, it is pretty close.
The total number of degree days (DD) required for monarchs to develop from the time an egg is laid to the time at which an adult female lays her first egg is 397C degree days. The egg requires 45C degree days, the larval stages 187, the pupa 120 and the adult female 45C degree days from emergence to egg laying (Zalucki 1982, Zalucki and Rochester 2004). For convenience we will round off the egg to egg period to 400C DD. Since all the calculations by Zalucki for DD were made in Celsius (centigrade) and the data from our weather service comes in Fahrenheit we need to convert 400 DD to the Fahrenheit equivalent, 720 DD.
The minimum developmental time from egg to adult is 24 days and to this we need to add 3 days to account for the time after emergence until a female is mated and laying eggs. Thus, a monarch maturing at the maximum rate (i.e., in 27 days) averages 26.7F (14.81C) degree days per day. The interval from egg to egg is often used as a measure of the length of a generation. If we wanted to know the number of degree days - and therefore potential number of generations of monarchs for a summer for a specific location - all we have to do is apply the above formula for degree days for each day of the “monarch growing season.” Degree days are then summed until a total of 720 has been accumulated for a generation. The “monarch growing season” is simply the interval from the date of the arrival of the first monarchs at a given location to the midpoint of the migration. Because we usually don’t see the first monarch arrive in the spring, we will use the average date of first arrival to mark the beginning of the monarch growing season at each latitude. Since some monarchs are still larvae and pupae when the fall migration starts, we will use the midpoint of the migration as the end of the growing season. The average dates of arrival in the spring and the midpoints for the migration are summarized in Table 1.
Table 1. Average arrival dates for spring monarchs, midpoints and peaks of the fall migration by latitude.
To determine if the number of degree days differs between a warm year and a cold year, we have calculated the number of degree days for Lawrence, KS from 28 April until 22 September for 2003 and 2004 in Appendix 1. The number of degree days for this period in 2004 was 2858 or 4.1% less than that of 2003 (2980.2). This difference isn’t very great but if we look at the length of the generations for each year (Table 2) we can see how the lower temperatures in 2004 extended the length of the mid summer generations.
Table 2. Duration of monarch generations in days in Lawrence, KS*
*The assumption here is that the first generation starts on the average date of first arrival. If monarchs arrive late, the effect is to shorten the number of days for the first generation because temperatures increase as the season progresses. However, late arrivals can also have the effect of reducing the number of generations or contributing to the late development of the last generation putting them at risk of not being able to complete development in sufficient time to join the migration.
This analysis shows that, even in Lawrence, KS, an area at the southern end of the monarch’s summer breeding range, a cool summer can have a significant impact on the length of each generation as well as the potential production of monarchs. Such an impact is likely to be greater in the northern portions of the monarch breeding area, such as MN, WI and MI, where the monarch growing season is shorter and the summer temperatures even lower than in KS. To test this possibility, we examined the degree days for Minneapolis, MN for 2003 and 2004 (Appendix 2). At this latitude (45N) the growing season extends from 22 May to 10 September (112 days). Note that due to the shorter season and lower temperatures, the number of generations in Minneapolis is effectively limited to only two, whereas in KS four generations are generally the rule. In total degree days, the 20.3% difference between 2003 (2006.55) and 2004 (1601.15) in MN is greater than that in KS (4.1%). Thus, it would appear that the cold summer of 2004 had a greater impact on monarch development in Minneapolis (Table 3) than it did in Lawrence.
Table 3. Duration of monarch generations in days in Minneapolis, MN*.
*This analysis suggests a partial third generation of monarchs for Minneapolis in 2003 assuming an arrival date of 22 May. On the other hand, a late arrival in 2004 would seem to put some of the second generation monarchs at risk of not completing develop in time to join the migration.
As mentioned above, the cause of the cold summer in 2004 was a change in the position of the jet stream that brought its path lower over the mid-portion of the continent than is the case in most summers.
Going back through the temperature records the most recent cold summer was 1992 (Figure 2)
Figure 2. Mean summer (June- August) temperatures for the East North Central Region of the United States.
The cold summer of 1992 was followed by a slightly warmer summer in 1993, one that was noteworthy for mid-summer flooding in many parts of the Midwest. These two events were clearly associated with the “dust veil” cast into the lower stratosphere by the June 1991 eruption of Mount Pinatubo in the Philippines. Going back a bit further, the next notably cold summer occurred in 1950. The summer of 1951 produced record rainfall in eastern KS and the worst mid-summer flooding recorded in this part of the Midwest. (If these two cold periods are an indication, 2005 could be a wet year in the lower Midwest.) The cold summer of 1950 was presumably associated with the position of the jet stream. However, the effect of the jet stream was not understood at that time and its position wasn’t recorded. [1950 was also a La Niña year, an event associated with lower temperatures and higher rainfall - see below] The “dust veil index” was low and there was no volcanic activity to account for this cold period, nor for the coldest summer (1915) in the last century. The “dust veil index” (DVI) is a measure of the dust cast into the stratosphere by volcanoes. The dust serves as a shield to incoming radiation from the sun and has the effect of reducing the amount of the sun’s energy that reaches the earth’s surface and the lower atmosphere, thereby reducing the mean temperature of the earth. The DVI has been calculated from the year 1500 to the present. Note that there are periods of volcanic activity and other times when volcanic eruptions are few and the DVI drops to near zero. We haven’t found a temperature record back to 1500 but there are records for the earth’s mean temperature back to 1867. We have combined these two sets of data in Figure 3 and divided the period from 1867 into three sections, a volcanic period from 1867 to 1917 (Fig 4), a period with no major volcanic eruptions (1918-1966), and a second volcanic interval from 19672001 (Fig 5).
Figure 3. Yearly worldwide average temperature and Dust Veil Index (DVI).
Globally averaged temperatures were obtained from
Dust Veil Index was obtained from
Figure 4. Yearly worldwide temperatures and Dust Veil Index (DVI) 1867-1917.
This graph shows that worldwide temperatures usually decrease following major volcanic eruptions such as Krakatoa (1883) and Soufriere & Pelee (1902). The exception here is the increase in temperature in 1878 associated with a strong El Niño (http://www.ngdc.noaa.gov/paleo/ei/ei_reconsb.html).
Figure 5. Yearly worldwide temperatures and Dust Veil Index (DVI) 1967-2001.
The two major volcanic eruptions in this period were El Chichon (1983) and Mt Pinatubo (1991). Note that Mt St Helens (1980) did not contribute substantially to the DVI.
There are two striking things to note about this analysis; the mean temperature of the earth is more variable during volcanic intervals and the mean temperature rose progressively through time and increased substantially (.425 C or about 3%) from the second to the most recent period (Figure 6).
Figure 6. Mean and variance of worldwide temperatures.
The error bars indicate a greater variance in temperatures during periods of volcanic activity, 1867-1917 and 1967-2001 than a non-volcanic period 1918-1966. The El Niño-La Niña cycle evidently contributes to the variance as well. There have been 7 strong El Niño-La Niña events since 1967. Such events were evidently less common prior to the 1950s.
Clearly, the earth is much warmer now than it was in the first quarter of the 20th century, and through much of the 19th century, suggesting that monarchs in those time periods had less of an opportunity to develop substantial populations than has been the case in the last 80 years. This statement is supported by the temperature records over the last 600 yrs; see http://www.ngdc.noaa.gov/paleo/ei/ei_reconsa.html.
The impact of dust from volcanoes in the stratosphere (DVI) is shown in Figure 4. One of the largest volcanic eruptions was Krakatoa, which occurred on the 27th of August 1883. The volume of dust cast into the atmosphere by this volcano was sufficient to reduce the earth’s temperature for the following four years. Interestingly, summer temperature records for the upper Midwest (Minneapolis) during this interval were not exceptionally cold. Chicago, on the other hand, had 4 cold summers in a row starting in 1884. Extreme cold temperatures at the end of August in 1885 and 1887 in Minneapolis (http://home.att.net/~minn_climo/MSP1885.gif) certainly must have delayed the emergence of the last monarchs and disrupted or delayed the migration.
The Year Without a Summer
In this context, it is also interesting to contemplate the impact of Tambora, a volcano in Indonesia. Tambora explosively erupted in April 1815. It’s characterized as the largest volcanic eruption of the 19th century and of recorded history. The dust canopy that enveloped the earth after the Tambora eruption cooled the atmosphere, resulting in an extremely cold summer in the northern hemisphere in 1816. Crop failures due to the short growing seasons and midsummer frosts led to starvation and political unrest in parts of Europe and emigration in the United States. 1816 was characterized as the “year without a summer” and the effect in New England was so harsh that many residents left the region in the next few years for the frontiers in the eastern portion of the Midwest. Tambora therefore seems to have had the effect of accelerating the colonization of the Midwest. Given the impact of our relatively cold summer in 2004 on monarchs (the lowest recorded number of monarchs since monitoring began in 1992 at Cape May (http://www.concord.org/~dick/mmp02.html), imagine the impact of the summer temperatures of 1816 on monarch reproduction throughout it’s range. It seems likely that Tambora had a severe impact on monarch populations as well as those of many other species (see below).
Factors Influencing Summer Weather
The factors, and interactions among them, that influence summer weather patterns are complex and not thoroughly understood. Some of the possible interactions are summarized in Table 4.
This table provides a summary of the world temperatures in relation to the strong El Niño and La Niña events recorded since 1950. The mean world temperature is given for the year before the start of the event, for the year of the event, and for the year following the event. Because of the size of the earth’s atmosphere relative to regional events, such as volcanic eruptions and heating or cooling of the mid pacific, there is a time lag before the effects of such events are seen, hence the emphasis on the year after the event. Note that the mean world temperature was lower for each year after a La Niña event and higher for each of the El Niño events, except for 1991-1992.
Table 4. Relationship of Strong El Niños and La Niñas to Mean World Temperature (C).
The El Niño and La Niña years were chosen from a consensus list found at http://ggweather.com/enso/years.htm.
Globally averaged temperatures were obtained from http://www.ldeo.columbia.edu/edu/dees/ees/climate/labs/globaltemp/globaltemp.html.
* El Chichon, Mexico, erupted March-April 1982
In June of 1991 Mt Pinatubo erupted in the Philippines, an event which lowered world temperatures dramatically. It is interesting to consider that the impact of Pinatubo might have been even greater were it not for the strong El Niño which occurred in the same time frame. The strong El Niño of 1982-1983 may have had the effect of blunting the impact of eruption of El Chichon (1982) in Mexico as well. Scientists disagree strongly as to whether there is any connection between volcanic eruptions and El Niño events. One analysis suggests that volcanoes trigger the occurrence of El Niños:
while another maintains that El Niños have occurred coincidentally with volcanic eruptions (http://www.grida.no/climate/ipcc_tar/wg1/449.htm). Whether the relationship between volcanic eruptions and El Niños is causal or coincidental is still unclear however, it is evident that El Niños and La Niñas occur independently of volcanic activity. An example of the latter is the strong El Niño of 1997-1998 that may have contributed significantly to the elevated mean world temperature in 1998, the highest mean temperature (15.242C) recorded for the planet to date. Less clear are the factors that contribute to the position of the jet stream in mid summer and the occasional sudden drop in the world’s temperature as was the case in 1917. Volcanic eruptions are not associated with this year and studies of jet streams and El Niños did not begin until the late 1940s. One retrospective analysis attributes the drop in temperature in 1917 to the effect of a strong La Niña in 1916. The summer of 1915 was the coldest in North America in over 105 years but we have been unable to attribute this unusual summer to any particular cause.
In summary, temperatures during the monarch breeding season, especially in the Upper Midwest and Ontario, appear to have a strong influence on the size of the monarch’s fall migratory population. However, other factors such as droughts in the spring in Texas, predation by fire ants and other predators and parasites, the survival rates of the overwintering population during the winter and as they move northward through Mexico in the spring, and the distribution, abundance and condition of milkweeds, have a significant role in determining the numbers of monarchs in the annual cycle.
We would like to thank Jim Lovett and Sarah Schmidt, Monarch Watch Program Assistants, for their assistance in creating materials included in this article and for their proofreading and revision of the text. Without their input the publication of this article would not have been possible.
Notes, Lessons, Background Information and Web Sites
Growing Season and Migration Window
The average arrival dates for spring monarchs in Table 1 is used as the start of the growing season. In the fall, the “migration window” at each latitude, that is the interval from the start of the migration until it ends (except for a small percentage of stragglers) is approximately 26 days. Therefore, to estimate the end of the growing season for your latitude, you need to know the midpoint of the migration. As an example, the average date of arrival of the first monarchs in Lawrence, KS (39N) is 28 April. In the fall, the average date for the arrival of migrants from the north is 9 September. Therefore, the midpoint of the migration is 22 September for a potential growing season of 148 days. Using these same criteria, the potential growing season for Minneapolis, MN (45N) is 112 days.
Because development peaks at 84.2F (29C) degrees it seems logical to expect that the maximum growth rate could be achieved at a constant temperature at this level. If this were the case, the length of a monarch generation would be a little over 24 days rather than 28. However, there are constraints on the rate of growth. Increasing temperature is not like pressing your foot on the gas pedal of a car, the organism must rest, food needs to be processed, etc. Monarch larvae actually mature faster under fluctuating rather than constant temperatures.
Developmental zero and degree days have been treated in two previous Updates:
developmental zero - http://www.monarchwatch.org/update/2002/0501.html#4 and
degree days - http://www.monarchwatch.org/update/2002/0606.html#3.
In the previous explanation of degree days, I used an example of monarch grow rates in the vicinity of Mc Allen, TX, during a period, mid March-early April, when the temperature extremes did not reach either the low of 52.7F or the high of 91F.
For more information on how to calculate degree days for insects please see: http://www.ipm.uiuc.edu/degreedays/calculation.html http://www.ipm.ucdavis.edu/WEATHER/ddconcepts.html
How Cold was it in the Summer of 2004?
The temperature extremes recorded for some selected cities can be found at: http://www.ncdc.noaa.gov/oa/climate/research/2004/aug/augustext2004.html
The following site provides many maps and figures showing the regional temperature patterns for June-August:
The figure shown at the following site shows the summer temperatures for the north central region (MN, WI, MI, IA) since 1895:
The coldest summer occurred in 1915, closely followed by 1992 and 1927, then 1967, 1950 and 2004 (the temperatures of the latter being similar to those of 1903 and 1904 which followed the volcanic eruptions of 1902). For a review of the summer of 2004 on a national scale see:
The following site shows the five coldest summers for south central Nebraska: http://www.crh.noaa.gov/gid/display.php?fname=/mischeadlines/summer04.html
Note that in this region the summer of 1992, the Mt Pinatubo summer, was the coldest on record and that 2004 is among the top five coldest summers throughout this region.
Impact of Cold Summers on Other Wildlife
While monarchs are our focus, we shouldn’t forget that other species are affected by the same conditions. While giving a talk at a local Audubon Society meeting recently, one of the members mentioned that hawk owls, snowy owls, great gray owls, cross bills, grosbeaks, and other northern birds began moving into northern Minnesota in extraordinary numbers in late November and early December. I had seen this report
but it all snapped into place when a member of the audience mentioned that such a southern migration of these boreal residents hadn’t been seen in over 50 years in the early 1950s. Do you see the connection? The summer of 1950 was one of the coldest of the century and this was followed by another relatively cold summer in 1951. What happens in the boreal forests during cold summers? We can only speculate, but it seems likely that lower temperatures reduce the growing season, limit growth rates of plants, delay maturation of fruits and seeds, etc., and that these effects create a food shortage for rodents, reducing their populations below those that can sustain the owl populations - leading to the southward migrations of these northern birds.
Ben Franklin and Volcanoes
Ben Franklin was a keen observer, an analytical thinker, and a problem solver. In 1783, Ben was in France. In June of that year, the eruption of the Laki volcano in Iceland produced a dust cloud that quickly spread over northern Europe, resulting in a dry fog that cooled the air. Franklin observed that the fog was not dissipated by the heat of the sun, as is normally the case with a fog containing moisture. He deduced that the cooling effect was due to the opacity of the dry fog that he attributed to a volcano in Iceland (Hecla Hecla) that erupted in 1776. He evidently was unaware of the massive dust cloud created by Laki in 1783. Ben Franklin’s original account can be found at: http://www.dartmouth.edu/~volcano/Fr373p77.html.
General Information on the Effects of Volcanoes on Weather
There are numerous web sites containing texts that discuss the relationships of volcanic eruptions to weather. These relationships are complex. The impact of volcanic eruptions on the earth’s temperature appears to be a function of the height to which the volcanic ash is cast into the atmosphere, the size of the particles and their composition. The eruption of Mt St Helens in 1980 had little impact since most of the ash remained in the troposphere and was quickly washed out by rainfall. If the ash particles in an eruption are small (2 microns), incoming radiation is intercepted and the effect is to lower the earth’s temperature. On the other hand, if the particles are large (5 microns), incoming radiation is not particularly affected but outgoing radiation is trapped creating a “greenhouse” or heating effect. Most of the particulate matter consists of sulfuric acid and deposits of the sulfuric acid “fallout” from volcanoes have been observed in ice cores from glaciers.
The following texts will give students a start on this topic:
This link is to a Google search page and does not identify any particular text:
Note Figure 1 in the following article: http://www.cru.uea.ac.uk/cru/info/volcano/. This figure shows the deviations from normal temperatures in the period before and following the eruptions of select volcanoes, e.g., Krakatoa in 1883, Pelee and Soufriere in 1902, Agung in 1963, and Mt Pinatoubo in 1991. The data in this figure indicates that the impact of eruptions can last for several years.
If you or your students want to really dig deep, here are two web sites that will lead you into the primary literature: http://climate.envsci.rutgers.edu/robock/robock_volpapers.html
Anyone with a serious interest in this topic will find something of value, such as how polar bears benefited from the Mt Pinatubo eruption or how volcanoes influenced art and literature, in a PowerPoint presentation on Volcanoes and Climate by Professor Alan Robock found at http://climate.envsci.rutgers.edu/physclim/handouts.html. See item #26.
The Year without a Summer and other Climate Changes Associated with Volcanic Eruptions
The summer of 1816 is a wow topic that should pique the interests of many students. This subject is suitable for discussions, or assignments, on climatology, volcanoes, geography, history, agriculture, anthropology, etc. Web sites on this topic include: http://www.islandnet.com/~see/weather/history/1816.htm
Another year without a summer occurred in 1783. In this case, the cold weather was linked to an eruption of the volcano Laki in Iceland. The impact of this eruption was limited to more northerly latitudes as depicted in this article: http://abob.libs.uga.edu/bobk/ccc/cc020200.html.
1816: The Year Without a Summer
Central Canada Newspaper Accounts
Manitoba Hudson Bay Company Archives
Fact of the Day
Sound clip Windows Media Player) from the Hawthorne Community Association
Climate Changes of 535-536
Were the Dark Ages Triggered by Volcano-Related Climate Changes in the 6th Century?
Major Volcanic Eruptions
A list of major volcanoes, their locations and histories of activity can be found at: http://www.gesource.ac.uk/worldguide/guide_volcanoes.html and at http://www.volcano.si.edu/world/largeeruptions.cfm.
The following site is designed with students in mind: http://geography.about.com/gi/dynamic/offsite.htm?site=http%3A%2F%2Fvolcano.und.nodak.edu%2F. To track current volcanic activity, please see: http://www.volcano.si.edu/ and http://volcano.und.nodak.edu/vwdocs/current_volcs/current.html. A list of volcano cams can be found at: http://vulcan.wr.usgs.gov/Photo/volcano_cams.html.
Krakatoa - 27 August 1883
As you will see below, the explosive eruption of Krakatoa not only affected the climate but produced a tsunami that killed 10s of thousands of people in Indonesia. A surge in sea level was recorded as far away as England and the sound produced by the explosion was heard over 2900 miles away!
The Great Explosion of the Krakatau Volcano
BBC News Krakatoa: The first modern tsunami
ABC News: Past Indonesia Disasters Altered History
The Indonesian Digest: The Explosion of Krakatoa Mountain (includes timeline)
Why the sky was red in Munch's 'The Scream'
Windows to the Universe - Krakatoa
Reading Guide to Krakatoa by Simon Winchester
Teacher’s Guide to Krakatoa aligned to National Science Education Standards.
Eisenhower National Clearinghouse: curriculum resources search for volcanoes
PBS Secrets of the Dead Catastrophe!
The Twenty-one Balloons
Du Bois, W. P. (1947). The twenty-one balloons. pp 180. Viking. NY
Dust Veil Index (DVI)
The data for the dust veil index (DVI) figures was obtained from: http://www.ngdc.noaa.gov/paleo/ei/ei_data/volcanic.dat. A general description of how the dust veil index is derived can be found at: http://gcmd.nasa.gov/records/GCMD_CDIAC_NDP13.html.
General descriptions of jet streams can be found at:
The current position of the jet stream can be found at: http://www.intellicast.com/Local/USNationalStd.asp?loc=usa&seg=LocalWeather&prodgrp=SurfaceMaps&product=JetStream&prodnav=none&pid=none.
Archives of the patterns of the jet stream across the United States for the last three years can be found at: http://squall.sfsu.edu/crws/archive/jetstream_archive.html. A student interested in meteorology could use these archives as the basis for a study on the relationship of the position of jet streams to weather, crop production, etc.
El Niño Years
Again, this is a fascinating topic for students in that El Niños, as drivers of climate and weather patterns, manifestly affect life on earth. During the El Niño winter of 1997-1998 it became so dry at the monarch overwintering sites in Mexico that the monarch colonies moved downslope into areas where none of the residents had ever seen them before. It seems likely that the monarchs moved to more humid areas or those closer to sources of water.
The following are two extraordinary and fascinating web sites that will give students in depth information on the impact of El Niños:
To engage students in the analysis of the effects of climate on the development of monarch populations, establish the monarch growing season for your area as set out above and then visit web sites for the nearest temperature records for your area. The data you need are the maximum and minimum temperatures for each day. If you wish to simply get students to learn how to make the calculations, they could compare the temperature data and degree days for a pair of hot (1933, 1983) and cold (1915, 1992) summers for Minneapolis, MN. To obtain the complete data for these years or any others, for the last hundred years or more, visit the websites indicated below.
More climate information for Minneapolis-St. Paul and for the state of Minnesota can be found by following these links:
Preliminary Local Climatological Data - Minneapolis/St. Paul, MN
Select the month from the chart to display daily maximum and minimum temperatures. Column 1 is the day, column 2 is the maximum, and column 3 is the minimum.
Daily Weather Records for Twin Cities 1890-2003
Scroll down to Historical Climate Data Listing for the Twin Cities and select the data sets from 1890 to 2003.
Searchable Map for Minnesota climate data
Use the button at Target location to accesses the map. Click the button under the map to return to the search page to set the year and select the temperature.
How to find Temperature Data for Your location
1. Weather Underground
2. National Weather Service Southern Region Headquarters
3. NCDC National Climatic Data Center http://www.ncdc.noaa.gov/oa/about/ncdcsearch.html
4. To order historical climatological data online from the National Virtual Data System, go to
5. Additional Climate Data
Articles and books
Du Bois, W. P. (1947). The twenty-one balloons. pp 180. Viking. NY.
Hansen, J., R. Ruedy, M. Sato, M. Imhoff, W. Lawrence, D. Easterling, T. C. Peterson, and T. R. Karl (2001), A closer look at United States and global surface temperature change, J. Geophys. Res., 106(D20), 23,947-23,963.
Mann, M.E., et al. 2000. Global Temperature Patterns in Past Centuries: An Interactive Presentation, IGBP Pages/World Data Center for Paleoclimatology Data Contribution Series #2000-075. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA.
Wassenaar, L. I. and K. A. Hobson. 1998 Natal origins of migratory Monarch butterflies at wintering colonies in Mexico: New isotopic evidence. Proc. Natl. Acad. Sci. 95; 15436-15439.
Winchester, S. 2003. Krakatoa. Perennial, HarperCollins Publishers, NY, pp 416.
Zalucki, M. P. 1982. Temperature and rate of development in Danaus plexippus L. and D. chrysippus L. (Lepidoptera: Nymphalidae). Journal of the Australian Entomological Society 21: 241-246.
Zalucki, M. P. 2004. Spatial and temporal population dynamics of monarchs down-under: Lessons for North America. p219-228. In The Monarch Butterfly: Biology and Conservation, eds Oberhauser, K. S. and M. J. Solensky. Cornell University press, Ithaca.
Appendix 1. Maximum temperature, minimum temperature, and degree days for Lawrence, KS in 2003 and 2004.
|Date (2003)||Tmax||Tmin||Degree Days||Date (2004)||Tmax||Tmin||Degree Days|
|2003 Total||2980.2||2004 Total||2858|
Appendix 2. Maximum temperature, minimum temperature, and degree days for Minneapolis, MN in 2003 and 2004.
|Date (2003)||Tmax||Tmin||Degree Days||Date (2004)||Tmax||Tmin||Degree Days|
|2003 Total||2006.55||2004 Total||1601.15|
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