Transcript Understanding Global Warming through - SERC

Understanding Global Warming through Conceptual Understanding of Change Through Time
Ed Nuhfer, Director of Faculty Development and Professor of Geology, California State University at Channel Islands.
[email protected].
A controversy where emotions run high
Will the real issue please stand up, so that I can FEEL IT?
To the left, we find two essays from the most recent two issues of “The
Professional Geologist.” The first objects to the claims of certainty in attributing
the dominant or sole cause of currently observed global warming as
anthropogenic CO2 production. The second accuses not only the authors of bias,
but also proposes that they represent “…an agenda to undermine the
‘inconvenient’ theory of global warming.” Tiller's commentary reveals the the
rancor that results when scientists do not tow a the political party line. It uses
logical fallacies to attack both the scientists who wrote the essay, speculates
baselessly on their motives and presents a hypothetical conspiracy theory to label
and defame any person who might dare to offer a similar view.
Talk radio hosts proclaiming themselves as "conservatives" frequently state that
climate changes very slowly over millions of years, that humans cannot affect
climate very much, and that global warming is not even really happening. They
portray global warming as an issue invented to frighten citizens into allowing more
intrusive government control. Self-proclaimed "Liberals" do advocate that global
warming may be the most important crisis facing humanity today. Implicit in their
advocacy are messages that anthropogenic carbon emissions cause the warming
trends observed, and that government, through regulating emissions and
controlling individuals’ energy consumption, can reduce the emissions and stop
global warming. Both parties argue that we can have continued growth needed to
drive the world’s economy.
Presenting both essays together offers an excellent segue into illustrating the value
of conceptual thinking about change through time—”excellent” precisely because
the issue of global warming IS an emotional topic. Several events in 2007
underscored the role of the affective domain in learning in Earth Sciences. One
was a workshop on the role of the affective domain at Carleton College on
February 11-13, 2007, Carleton College, Northfield, MN, which grew from an
initiative by Arizona State University’s Dr. Steven Semken with a discussion
group of participants at the 2005 Cutting Edge Workshop on Assessment. The
second was a special pre-conference workshop on the affective domain at the
annual meeting of POD (The Professional and Organizational Developmental
Network) in Pittsburgh in October, 2007, and third was a theme session on the
affective domain at the 2007 GSA Annual Meeting in Denver. Research before any
of these endeavors shows that learning increases when the affective domain is
engaged along with the cognitive. Because both major political parties have
already used global warming as an emotional issue, they have created an interest
that students can use to learn independent thinking-- likely an outcome that
advocates for neither party intended.
What’s change through time got to do with global warming?
Unlike global warming, understanding change through time is not a hot topic of
political speechwriters, television commentators or talk radio show hosts. But what
if understanding of it allowed us to analyze their messages about global warning to
see if they carry truth or fall into the category of enlisting us into supporting their
causes? When receiving two conflicting messages on a polarizing issue, how do we
know what to believe? One way is to go to the primary evidence, examine it
carefully, and make up our own minds. Going to a compilation of data and
interpreting it means that you can come away with qualification of having looked at
the evidence. Without this basis, we only know what people tell us to believe, and
that makes us very easy to manipulate.
Understanding change through time is much more than realizing that Earth is very
old and that older strata lie underneath younger strata. To understand change
through time fully, we also need to understand age, order of events, rates,
frequencies, duration, magnitudes, and patterns.
Before we can see these qualities in a record of evidence, we need to understand
precisely what these terms mean. Otherwise, we will never be able to see the
evidence before us. Larger vocabularies remove a number of barriers to learning.
Time’s temporal temperaments
Teaching isn’t telling; learning isn’t about being told.
Look at the qualities of change through time in simple conceptual terms.
Age - How old something is expressed in some unit of time, such as “How old
are you?”
Rates - How fast something changes per-unit-time such as distance traveled per
unit time as in “I drive 60 miles-per-hour” or “My resting heart rate is 70 beatsper-minute.”
Frequencies - how often things happen per-unit-time such as “How often do
you go to the movies?” or “How frequently do you brush your teeth?” Notice
the subtle difference between frequency and number of events that are not
expressed in specific units of time such as “How many movies have you seen?”
or “How often does it rain here?”
Duration - how long something lasts in units of time such as “How long should
my dog be able to live?” or How long does it take to drive from Pocatello,
Idaho, to Boulder, Colorado?”
Magnitudes - how big an event is expressed in some specific unit in comparison
to other events as in “What was the greatest recorded Richter earthquake
magnitude in history?” or the “What was the hottest day on record in degrees
Fahrenheit in Chicago?”
Ordering of Events - placing events in chronological order, such as an ability to
place the American Revolution before the War of 1812 , the “Ice Age” before the
“Iron Age,” or the Devonian Period after the Silurian Period.
Patterns in time - The graphical form of distribution of events over a period of
time. We can see different patterns most easily in graphs (Figure 1).
Figure 1. Each geologic process has a
characteristic pattern of changethrough-time with respect to how
events occur and vary in frequency
and magnitude. Constancy (horizontal
line A) and gradual change (line with
constant slope B) typify few processes.
Cyclic patterns (C) typify many
processes such as seasonal
temperatures, tides, sunspot cycles, etc.
and lend themselves to predictability.
Most processes (floods, volcanic
eruptions, earthquakes, drought,
rainstorms) occur in fractal patterns
(D). Fractal patterns consist of many
common events, a few small events, a
few large events and very rare high
magnitude events. Fractal patterns
reveal the frequency with which we
should anticipate events of certain
magnitudes to occur.
When we know how to see these qualities of time within a climate record, we can
truly start to understand many aspects of claims made about global warming. To
see whether carbon emissions from human technology can explain all climate
change, we need a record of climate that includes both human history and some
time before humans had an industrial age (age and order of events). If climate
changes, we would like to know when it changed (age) and how long conditions
lasted before they changed again (duration). We’d like to know how great these
changes were (magnitude), if they happened and how fast change occurred from
one climate to another (rate). If climates have changed more than once, we want
to know how often they change (frequency) relative to human history. If we know
this, then in our own minds we can decide whether climate remains constant,
whether its pattern of change is predictable, whether it changes gradually and, in
short, how Earth’s climate seems to behave. If climate has changed without
human intervention, can government edicts prevent change, and, if not, how
might we live best on a planet characterized by changes?
What we have below is primary information. It is simply a summary of what was
found—evidence. Learning from primary information does not depend on your
believing what others say that you should believe about climate change. All you
need to do to interpret the evidence is to look carefully for the qualities of time
found in this record and gain your own understanding. Spend some time and
study Figure 2 closely for learning the other qualities of change.
Using change through time to evaluate global warming.
The climate interpretations from the data of Figure 2 are straightforward. Wind
blows pollen into the lake, which reveals the vegetation that existed in the area
each year. Knowing the vegetation reveals the climate. Varves consist mostly of
endogenic materials (materials precipitated from within the water column), but
arid conditions allow more clastic wind-blown dust to enter the lake, which
thickens the varves. Rain falling on ground with sparse vegetation allows runoff
to carry even more sediment into the lake, so changes in varve thickness (Figure
2) are indicative of climate change. In addition, isotope data from the core served
as an additional basis to know the air temperatures that existed at any time.
Answer the questions together with one or more classmates. It takes more time to
understand climate change by interpreting evidence, than it does to simply be
told what to believe. However, doing the work from primary information always
yields superior understanding.
Using concepts of change-through-time to understand global
warming in the context of climate
Figure 2. (From Bradbury and Dean, 1993) Data from a 20-meter core of
varved sediments from Elk Lake, Minnesota. Photos show representative
varve types from each part of the varve sequence.
We have detailed evidence about climate change provided from the sediments of
Elk Lake, Minnesota (Figure 2). This high-resolution record of about 10,000
years in Figure 1 is possible because Elk Lake is a rare type of lake that
precipitates distinct couplets of thin sediment each year called varves. Each
couplet contains a white calcite-rich layer deposited in summer and a dark
organic-rich layer in winter. The lake is extant, and the annual process of
depositing of couplets is still occurring. Although radiometric dating confirms the
ages, there is no real need for it in this high-resolution record; one only need
count the couplets downward to know the ages of sediments labeled as Ka
(thousands of years) on Figure 2. In this 20 m long core, we have about 10,000
years of record. In terms of recorded human history, this is sufficient to cover the
time forward from the Stone Age (Figure 3.). Earth's population now doubles
about every 38 years. Ability to support the present population depends on food,
which depends on stable climate. Minnesota lies in the Midwest, the
"breadbasket" of North America that feeds much of the world. A climate change
that reduced agricultural capacity of this region would likely bring huge hardship.
Figure 3. Population change through major events in human history.
1. Ages and ordering of events. Use your own knowledge and Figures 2 and 3
to locate approximate positions of the following events in the varve
record of Figure 2: (a) start of the industrial revolution, (b) Columbus
landing on the "New World," (c) birth of Christ, (d) beginning of Iron
Age, (e) transition of Neolithic Stone Age to Bronze Age, (f) receding of
last continental glacier from the site.
2. Rates. (a) When did the fastest rate of sedimentation occur? What
conditions might explain that event? (b) When did the slowest rate of
sedimentation occur? What conditions explain that event? © What is the
average rate of fill of the lake with sediment since the lake was created?
3. Number of events. How many major climate changes have occurred in the
Midwest since the last ice age?
4. Frequency. Since the last ice age, about how frequently have major climate
changes occurred per 10,000 years?
5. Duration. (a) About how long did climates remain stable after a change?
(b) How long has the climate corresponding to human recorded history
persisted? We cannot predict when the next change will occur, but based
on the patterns revealed here, about when would you anticipate the next
major climate shift might be due to occur?
6. Rate. When a major climate change occurred, how long did the transition
take?
7. Order of events. Which of these major changes is attributable to
anthropogenic causes?
8. Patterns. (Honors Question!) The varve record of the past 10,000 years in
Figure 2 reveals cyclic patterns, gradual patterns, and fractal patterns.
Can you find these and label them? Figure 3 also contains a pattern of
events in time. It is not one that we see in Figure 2. What is that pattern?
After answering the above let us use our new awareness to return to consider
the concerns and arguments over global warming.
1. Importance. Global warming is climate change. If the Minnesota area reverted
from mesic forest back to warm dry prairie, why would this be a concern.? If
humans could prevent this, why might it be worth the cost and effort?
2. Government capabilities. Based on the evidence in Figures 2 and 3, if we
reduced all carbon emissions back to Stone Age levels, could we likely prevent
climate changes that will impact human civilizations?
3. Perspectives. Imagine a future in which we have (a) halted any global
warming caused by humans and (b) grown a human population equal to Earth's
capacity to support it through agriculture. How secure are humans in that future?
4. Priorities. Consider two issues—global warming, and a high population of
advanced civilizations living on a changing planet. Which makes the second an
important issue? Why is neither political party raising this issue as a concern?
Reference: Bradbury, P. and Dean, W.E. Dean, editors, 1993, Elk Lake, Minnesota: evidence for rapid climate change in the northcentral United States: Geological Society of America Special Paper 276.