Dr. Camille Parmesan, Assistant Professor of Integrative Biology at
University of Texas at Austin, has worked extensively in researching the effects of global warming and weather changes on biological systems. Her
works extend from studying the population distribution ranges of butterflies as associated to changing weather patterns, to being a contributor on the
Working Group II of the Intergovernmental Panel on Climate Change (IPCC). Dr. Parmesan’s observations and conclusions are informative, intriguing and
alarming. This article serves as a summary to a few of her works in preface to an upcoming ATSNN interview with Dr. Parmesan.
Dr. Parmesan’s body of works reveals four important points in the global warming trend we currently live within, and contribute to:
* As anyone who attempts to stay knowledgeable of the body of research concerning global warming will already know, there is a gradually increasing
trend in the mean temperature for most of the globe.
* The changing weather patterns of the world are producing detectable changes in biological societies from insects, to birds, to humans, and in some
instances, in entire eco-systems.
* Though the increasing mean temperature trend is of concern, along with the causal increase of carbon dioxide, and will adversely affect the globe
as a whole, “extreme” weather events, those falling outside the normal ranges for a given parameter (i.e. temperature, precipitation, storms, floods,
landslides, etc.) are having instantaneous, severe, and sometimes permanent effects on biological systems.
* The occurrence of extreme weather events is increasing.
As is common knowledge for anyone attempting to stay knowledgeable of the research concerning global warming trends, the global mean surface
temperature has exhibited a significant increasing trend since the onset of the industrial age. Figure 1 illustrates the temperature trends over the
past 140 years, as well as over the past 1000 years. (1)
That this increasing trend in surface temperature is due to substantial increases in levels of greenhouse gases (GHGs) in the atmosphere due to
emissions inherent to the industrialization of the modern world has been born out by a preponderance of research work and evidence. And though the
industrialized processes that are creating the perilous trend we must now acknowledge and attempt to remedy are not the subject of this review, to
write an article on any research connected with global warming and not review this fundamental point would be remiss. Figure 2 reflects the increases
in GHGs over the past 1000 years. (2)
In 2001 the Intergovernmental Panel on Climate Change (IPCC) met in Geneva, Switzerland. This meeting constitutes the culmination of 3 years of
meetings, writings, multiple review periods (by experts as well as governments) and multiple revisions. The IPCC consisted of two working groups.
Working Group I focused on the observed changes in the global climate, the causes for these changes, and forecast for the future based on historical
data and global warming models. This group concluded that the mean global surface temperature had increased by 0.6 C over the past 100 years and
based on projected models would warm an additional 1.4 to 5.8 C by 2100 with an accompanying average global sea level change of 0.09 to 0.88 m (0.3 to
Effects of Global Weather Changes on Biological Systems
Working Group II of the IPCC focused on the analysis of impacts, adaptation and vulnerability of the earth’s biological systems to the changing
weather patterns associated with global warming. Dr. Parmesan participated in the work of this group. The report issued by this group points out the
examples of changes in biological systems to date:
Examples of observed changes include shrinkage of glaciers, thawing of permafrost, later freezing and earlier break-up of ice on rivers and
lakes, lengthening of mid- to high-latitude growing seasons, poleward and altitudinal shifts of plant and animal ranges, declines of some plant and
animal populations, and earlier flowering of trees, emergence of insects, and egg-laying in birds. Associations between changes in regional
temperatures and observed changes in physical and biological systems have been documented in many aquatic, terrestrial, and marine environments.
As pointed out in the group’s report, the observed changes to biological or physical systems have been in the direction that logic would assume if the
known climate changes are known. The juxtaposition of these two trends bares out a situation that odds would tend to eliminate as sheer chance. Dr.
Parmesan has extensively studied the geographic distribution range of various species of butterflies and has found evidence within the change of
boundaries of their geographic distribution that global warming is affecting where they live. 57 species of butterflies were studied in various
countries and it was found that 67% of these species have had their northern boundaries extend northward. In other words, for the range of areas in
which they inhabit, the geographic location of their most northerly locations have extended toward the north. For almost all these species, when the
northern boundary shifted north, the southern boundary either remained stable, or also moved toward the north (i.e. retracted). For these, their
range sizes actually increased as they shifted northward. The rest had their entire geographic distribution shift toward the north with no change in
overall range size. Several of these species have extended their northern boundaries even though this required habitation of heavily cultivated
landscapes less conducive to the species. This seems to preclude that land usage is the reason for the shift in boundaries, since an analysis of
development of land by humans would tend to shift the boundaries southward if it were the driving factor. (4)
What the data does point toward as the driving factor is a shift in isotherms. An isotherm is a series of points of similar temperatures which
creates a temperature band around the globe. As global warming increases, the isotherms are shifting to the north. Europe, which has warmed by 0.8 C
in the past century, had its isotherms shift to the north by 120 km. In North America, the isotherms shifted to the north by 105 km. In both these
cases, the species studied in the region shifted in their northern boundaries to the north by a similar distance. This agreement between isotherm
shifts and northern boundary shifts is consistent across continents and species in the northern hemisphere. (5)
Similar shifts have been detected in the historical record of the Pleistocene glaciation period. The record shows that species shifted their
distribution ranges with the changing climate. However, in the modern, industrialized world the landscape now presents barriers, due to human
activity, that can prevent similar dynamics from occurring. Fragmentation of populations is increasing, creating smaller and more isolated
communities. This can lead to reduced genetic variation which can then result in less ability to adapt to changes. Also, the distance between
fragments of a population is increasing, working against the species’ ability to intercommunicate between communities. If a single community is hit
with a catastrophic disturbance, it is less likely to be regenerated by the interaction with a healthier, non-affected community. (6)
The irreversibility of some of the adverse effects to natural systems, whether they be physical or biological, cannot be denied.
Natural systems at risk include glaciers, coral reefs and atolls, mangroves, boreal and tropical forests, polar and alpine ecosystems, prairie
wetlands, and remnant native grasslands. While some species may increase in abundance or range, climate change will increase existing risks of
extinction of some more vulnerable species and loss of biodiversity. It is well-established that the geographical extent of the damage or
loss, and the number of systems affected, will increase with the magnitude and rate of climate change. (7)
Northerly movement of domains is not the only behavioral change observed in animals. Map turtles are a good example of how the changing weather
patterns can effect the sex distribution in a species. As is the case in many reptiles, an individual map turtle’s sex “is determined by the maximum
temperature experienced during a critical phase of embryonic development.” If the maximum temperature during this period is below 28 C, only males
will be produced. If the maximum temperature exceeds this level, only females will be produced. So for a given nest, a single-sex is produced
according to the maximum incubation temperature experienced. Equilibrium of the sexes is achieved through population mixing across different nests.
However, due to fragmentation of the overall distribution range due to development by humans, the map turtle communities are tending to be smaller,
and more isolated. This could lead to less sex dispersal across nesting communities. In addition to effects on embryonic development, breeding
habits of certain animals are affected by the weather. In the Galapagos mockingbird, the birds become more polygamous during wet years. And for the
African elephant, for which breeding is year-round, the hierarchy of breeding can be affected by variations in the duration of the rainy season which
can lead to genetic make-up changes in the entire population.(8)
In British bird species, 31% since 1971, and 53% since 1939 have shown long-term shifts toward earlier onset of breeding season. Five species of
British amphibians, out of a group of 6 species observed, are breeding earlier than they were in 1978. These shifts are significant. For the bird
species observed, the shift has been approximately 9 days earlier while the amphibian shift has been up to 7 weeks earlier. (9)
Human systems are vulnerable to changing weather patterns as well.
Human systems that are sensitive to climate change include mainly water resources; agriculture (especially food security) and forestry; coastal
zones and marine systems (fisheries); human settlements, energy, and industry; insurance and other financial services; and human health.
Modeled projections of adverse impacts to humans include:
· A general reduction in potential crop yields in tropical and sub-tropical regions; as well as in mid-latitudes.
· Decreased water availability in already water-scarce regions including the sub-tropics.
· Increased numbers of affected people from vector-borne (malaria, etc.) and water-borne (cholera, etc.) diseases as well as increases in heat stress
· Increased flooding for developed communities (both from increased precipitation and increased sea levels).
· Increased energy demands for summer cooling. (11)
But as important and concerning as the general trends are, the extreme weather events observed over recent years that have resulted in excessive loss
of life and astronomical financial losses have led to concerns and analysis of extreme event impacts. That the above increasing trends in average
temperatures is associated more with an increase in the minimum daily temperature, rather than maximum temperature, is even more concerning. In
addition to temperature increases, precipitation has also increased over the same period of time analyzed. Furthermore, there is a growing body of
evidence that suggests extreme events (i.e. weather events that fall outside the ranges of what is considered normal weather ranges) are not only
increasing in frequency, but in impact to biological systems. (12)
Extreme Temperature Events
Studies conducted within the United States show different temperature trends for different regions of the country, but the overall trend has shown a
mean temperature increase for the country as a whole (with the southeastern portion of the U.S. actually showing a cooling trend). At the same time,
the number of days that temperature extremes are exceeded (either as a temperature event falling below the range’s minimum or falling above the
range’s maximum) have decreased. Temperature trends have been detected in other parts of the world as well. In Australia and New Zealand, as in the
U.S. the number of days the minimum temperature extreme is exceeded is decreasing indicating an increase in the minimum temperatures. In addition, in
New Zealand, the number of days the maximum temperature extreme is exceeded is increasing, causing a shift upwards in the mean daily temperature. In
Europe, a decrease in frost days since the 1930s has indicated an increase in the minimum winter temperatures. For the U.S., Russia and China, the
maximum temperature extreme has either held steady or actually decreased in the case of China. However, over the same period of time the minimum
temperature extreme has increased, thereby shifting the mean temperature upwards. But more importantly, for every country examined, the number of
frost days has decreased and the minimum temperature extreme increased. (13)
Extreme Precipitation Events
An increase in heavy precipitation events has been detected in the U.S. and other countries. Furthermore, countries showing a decreasing or
increasing monthly or seasonal precipitation level also see a significant portion of that change attributed to heavy or extreme precipitation events
suggesting that the general trends in precipitation in these countries are being dominated by these extreme precipitation events. Figure 3, indicates
the connection between the total precipitation trends and the extreme precipitation events in various countries. (14)
Areas around the globe affected either by drought or excessive wetness are increasing. For instance, the United States is experiencing an increase in
excessive wetness since the 1970’s, while China is experiencing an increase in areas affected by drought. (15)
Impact to Biological Systems by Extreme Events
The vulnerability of human societies and natural systems to climate extremes is demonstrated by the damage, hardship, and death caused by
events such as droughts, floods, heat waves, avalanches, and windstorms. While there are uncertanties attached to estimates of such changes, some
extreme events are projected to increase in frequency and/or severity during the 21st century due to changes in the mean and/or variability of
climate, so it can be expected that the severity of their impacts will also increase in concert with global warming. (16)
Recent documentation of systematic change across a broad range of species spread over many continents now provides convincing evidence that
20th century climate trends have impacted natural systems. (17)
Though many of the observed changes in biological systems were predicted by global warming models over a decade ago, and the affect of a gradual
increase in global mean temperatures has been established and observed, research shows clear evidence of the strong adverse affects of extreme events
on biological systems. The first recorded example of this effect was in the late 1800s. A severe winter storm over Lake Michigan was observed, by
Bumpus, to kill off both the largest and smallest swallows creating a strong natural selection based on body size. In the 1950s New Mexico suffered
an extended drought that caused the pinon/juniper forest to shift its boundaries by 2 km, and remains this way to this date. El Nino events have
caused such striking occurences as the bleaching of massive coral reefs in the 1982-1983 time period. (18)
Extreme events create changes in oceanic circulation which in turn plays a major role in changes to biological systems. 40% of the 50 amphibian
species at the Monteverde preserve in Costa Rica have become extinct since 1983. Analysis of four frog species at the preserve showed that the
population declined in dramatic steps associated with specific El Nino events. The breeding changes observed in British birds and amphibians, as
discussed previously, are believed to have been effected via events associated with the North Atlantic Oscillation (NAO). (19)
In Dr. Parmesan’s work there is a repeated call for better integration of data between ecologists and climatologists for the hope of more accurately
modeling the future events, both as general trends and toward predicting extreme events. Modeling does and will play a critical role in predicting
the dynamic changes to the globe whether we change our ways or not. Unfortunately, as the Working Group II points out, both for natural systems as
well as humankind, the weakest, the poorest, the most vulnerable are always the ones that have the least ability, or resources, for adapting to
adverse weather changes. Though correcting, or reversing, the global warming trend is paramount to the long-term survival of our globe, it is for
these creatures and these systems that live in peril that we must work collaboratively, both in gaining knowledge, and improving adaptability to
ensure they weather the coming storm.
1. Summary for Policymakers: A Report of Working Group I of the Intergovernmental Panel on Climate Change, February, 2001.
3. Summary for Policymakers: A Report of Working Group II of the Intergovernmental Panel on Climate Change, February, 2001.
4. “Poleward shifts in geographical ranges of butterfly species associated with regional warming”, Nature Magazine
; Parmesan, Ryrholm,
Stefanescu, Hill, Thomas, Descimon, Huntley, Kaila, Kullberg, Tammaru, Tennent, Thomas and Warren; June 10, 1999.
6. “Impacts of Extreme Weather and Climate on Terrestrial Biota”, Bulletin of the American Meteorological Society
; Parmesan, Root and Willig
7. Summary for Policymakers: A Report of Working Group II…
8. “Impacts of Extreme Weather and Climate on Terrestrial Biota”
9. “Climate Extremes: Observations, Modeling, and Impacts”, Science Magazine
; Easterling, Meehl, Parmesan, Changnon, Karl and Mearns;
September 22, 2000.
10. Summary for Policymakers: A Report of Working Group II…
12. “Climate Extremes: Observations…”
16. Summary for Policymakers: A Report of Working Group II…
17. “Climate Extremes: Observations…”
Dr. Camille Parmesan's Website (University of Texas)
UPDATE: Dr. Parmesan's most recent paper "A globally coherent fingerprint of climate change impacts across natural systems", Nature
Parmesan and Yohe, January 2, 2003, constitutes a major advance over the analysis methodology used during the IPCC work. In this paper, Dr. Parmesan
brings two statistical analysis methods, from two diverse disciplines, together in a global synthetic analysis of 1600 species. It was concluded that
almost half of all species analyzed have shown a response to the past 100 years of global warming. This paper became a "most highly cited" paper by
ISI Web of Science in May of this year. In order to achieve this distinction the paper must be cited among the top one-tenth of one percent (0.1%) in
a current bimonthly period. Papers selected for this distinction, tend to signal important new trends in research and "serve as leading indicators
of scientific advance."
You may read Dr. Parmesan's latest paper here: esi-topics.com...
and review the selection criteria for "most highly cited" papers here: esi-topics.com...
[edit on 9-21-2004 by Valhall]