Download Global Warming: Basic Definitions

Global Warming
Answer the following questions without looking up the answers:
1. Describe in your own words what global warming means.
2. How does the greenhouse effect fit into global warming?
3. You've seen that science can sometimes be misrepresented in the media. List some reasons
why this can happen.
4. Do you think it's a problem when science is misrepresented in the media? Why or why not?
Does your answer depend on what the consequences might be?
5. Before you proceed to the following lessons, write a brief paragraph explaining your
thoughts on global warming. What did you know about it before you started this lesson? Do
you feel you have good information? Where did you learn what you know? It's okay if you don't
know much, that's important to write, too.
Global Warming Part 2: Climate Change
Lessons from the Past
As a detective investigating global warming, the first thing you'll set out to do is learn what it
is you're really dealing with. What is global climate change, exactly? Without understanding
how climate has changed on Earth over millennia, it's impossible to have any basis for
comparison when trying to understand current climate patterns.
To truly understand climate change, you'll do what many scientists have already done
and continue to do — find out all you can about the history of earth's climate. Does earth have
natural fluctuations in its climate? If so, over what time span do these fluctuations occur?
Without understanding how climate has changed on earth over millennia, it's impossible to
have any basis for comparison when trying to understand current climate patterns.
Follow the link to “NOAA's Paleoclimatic Data Before 1000 Years Ago.” to find out
about the earth's climate and climate change prior to 1000 years ago. Be sure to read the
linked summaries to “commonly cited periods of warmth.”
Next find out about climate over the last 1000 years by following the link to “NOAA's
Paleoclimatic Data of the Last 1000 Years.” Pay particular attention to the paragraphs and
graphs below the “Summary of Studies” heading.
You'll use the information you've just read to answer the questions
NOAA's Paleoclimatic Data Before 1000 Years Ago
NOAA's Paleoclimatic Data of the Last 1000 Years
1. How do you go about estimating ancient temperatures? Is there more than one way?
2. How would you determine whether climate was changing (consider that the earth has
different seasons, so how would you know whether climate was changing?)?
3. When estimating ancient temperatures, do different estimates tend to agree with each
other, or disagree? In other words, for a given period in earth's history, do different
researchers and different climate measures give similar results?do they agree with one
another?
4. Is there evidence that the earth has warmed or cooled in the past 1000 years?
5. Is there evidence that it has warmed or cooled before 1000 years ago?
6. What are some explanations for why the earth's climate changed in the ancient past?
7. When the earth's climate shifted in the ancient past, do we know how long it took?
8. Why do scientists look at climate both prior to 1000 years ago, and over the last 1000
years? Does this level of scrutiny provide us a better grasp of how global climate works?
Comparing Current to Ancient Climate
Now that you've learned about earth's ancient climate patterns, you'll want to do some
further sleuthing to understand more about current global climate patterns. How would decide
whether climate has changed over the last 100 years. Also, how would you know whether
recent climate change is fundamentally different than it was prior to the industrial revolution?
In other words, what evidence would you need to show that humans might be having an
impact on current climate patterns (HINT: would comparing the rate of climate change in the
ancient past to present day help answer the question?)?
Find out more about relatively recent climate change (over about the last 140 years) by
following the link to “NOAA's Instrumental Record of Past Global Temperatures”.
You'll use the information presented there and the information from what you've
already read at “NOAA's Paleoclimatic Data of the Last 100 Years” to answer the
questions.
NOAA's Instrumental Record of Past Global Temperatures
NOAA's Paleoclimatic Data of the Last 1000 Years
1. Do scientists use different methods to estimate climate over the last 100 years, than they
do for measuring ancient climate patterns? If so, would this affect the reliability of the data in
either scenario?
2. Do measurements using human-made instruments (like satellites and thermometers)
suggest that global climate has been warming over the last century?
3. Is there anything different about warming over the last 100 years compared to ancient
global climate change?
4. Does the rate of warming differ over the last 100 years compared to the rates of warming
further in the past?
5. Even if warming has been dramatically different over the last 100 years, does that provide
definitive evidence that human-related activities are the cause? (We'll discuss this question at
more length in subsequent sessions. What other things would you need to know — besides
temperature change — to be able to say whether humans are partly responsible for current
warming trends?)
Global Warming Part 3: Nuts and Bolts
How the Science Gets Done
The next part of your detective work is to gain a working knowledge of how the science
of studying climate change gets done. If you see exactly how and why scientists say what they
do about climate, and if you understand the nuts and bolts behind how the science gets done,
then you'll be a better equipped detective — you'll be far more confident about judging the
validity of information you find regarding climate change.
Recall that some of the tools scientists use to examine past climate patterns include ice
cores, tree rings, satellites, and thermometers. There are actually two main approaches to
measuring climate. One way is through direct measurements. The other is by using indirect, or
“proxy” measurements. Proxy measurements are critical to scientists interested in the earth's
past climate record. Without proxies, we'd have no idea of what earth's climate was like in the
past. Some tools are like time machines — they provide scientists surprisingly detailed views of
what the earth's climate and atmospheric composition were like in the past. Can you think of
some ways you could measure climate directly versus indirectly?
Weather Stations
Various instruments come under the umbrella heading of “weather station.” In fact, any
weather station may or may not contain all of these instruments. If you have an outdoor
thermometer that tracks temperature change, you have a sort of weather station. But for
climate researchers, tracking these measurements must be a long-term project. Climate
researchers keep records of temperature, humidity, barometric pressure, wind speed and
velocity, cloud cover and rainfall from all over the world — from both land and sea. In addition,
many sites have climate data that are archived for many years — so researchers can compare
measurements from decades ago to current weather patterns. These measurements are mainly
recent, however. The ability to measure weather patterns this way has only been around for
the last couple of centuries.
Satellites
Satellites can measure the temperature of the earth's lower atmosphere (troposphere).
These measurements have been recorded for only about the last twenty years. But the
measurements of temperature in the troposphere tend to agree with the surface temperature
recordings, though by a slightly lesser degree.
Greenhouse Gases
Special equipment can precisely measure the amount of different greenhouse gases
currently in the atmosphere. The records for these kinds of measurements are, by necessity,
recent — they only go back as far as when the technology became available to measure them.
But scientists can see short-term changes in atmospheric gases like carbon dioxide, nitrates,
methane, and others. And they can compare ice core measurements (see below) of some of
these gases from the more distant past. For more information on measuring greenhouse gases
follow the link to “EPA's Climate Change and Greenhouse Gases”.
http://web.archive.org/web/20130510201015/http://www.epa.gov/outreach/scientific.html
The Climate Change Toolbox
Proxy Measurements
Tree Rings
Chances are good you've had the chance to count tree rings — you look at a crosswise slab of
wood and pick out the lines spanning from the center to the bark's edge. You can read much
more than the age of a tree with these lines, however. Scientists who specialize in reading tree
rings are called “dendrochronologists.” And they can look at changes to each ring and make
accurate predictions about what the climate was like when they tree laid down a particular
ring. That's because each ring corresponds to a year of growth, and good years with favorable
temperature and precipitation correspond to relatively large rings. When the climate was less
favorable for a particular tree's growth the rings are smaller — showing that the tree didn't
grow as well in a given year. To use tree ring data, scientists have to have trees. They can look
at tree rings from trees recently cut down, or they can use a bore to study rings from live trees
without cutting them down. They can also use long dead trees from ancient structures or
shipwrecks. Wood that has been well preserved over the centuries works particularly well.
Pollen
“Paleobotanists” are scientists who specialize in understanding ancient plant life and pollen.
Pollen can provide very good evidence of what regional climate was like for a given area. To
find pollen that corresponds with ancient times, scientists take cores from lakes and
sediments. Then they analyze the pollen grains at different levels in the core that correspond
to different time periods — the oldest pollen can be found at the bottom of the core, while the
most recent is found near the top. For every species of pollen, there is a suite of habitat
conditions that would have been necessary for that species to survive and thrive. So if certain
pollen grains turn up in a sample, scientists can make accurate predictions about what regional
climate conditions were probably like at the time.
Historical and Biological Records
Like pollen, other species of organism can yield clues to scientists about ancient climate
patterns. For instance, entomologists (scientists who study insects) can determine what the
regional climate was based on which insects show up in different areas of a sediment core. The
same is true for marine animals. Tiny bivalves and crustaceans from sea sediment cores can
yield clues about what the marine environment was like at a particular time in history.
Ice Cores
Ice cores are like a window to the past. When you drill a core of ice from a place it has
lain untouched for thousands of years, you get not only frozen water, but also a frozen record
of past atmospheric data. Ice cores contain dust, different concentrations of gases, different
forms of oxygen, and other pieces of data — all of which help scientists to draw a very detailed
picture of what climate was like for a give region in ancient history.
Here you'll take a few minutes to do a little more in-depth exploration of how ice forms,
how cores are collected, why they are important to climate research. Though we don't have
time to review all of the climate change tools in this depth (but see the list of references if you
want to learn more about the other tools), it is helpful to you as a detective to learn more
about at least one of these tools. And ice cores are particularly valuable to climate researchers.
Let's find out why...
Take a few minutes to visit the link found at the bottom of this page, “Secrets of the
Ice,” a Web site developed by the Museum of Science in Boston.
http://web.archive.org/web/20120621213010/http://www.mos.org/soti/
Ice Core Review Questions
Ice Formation and Flow
1. What is “firn?”
2. How is “pure ice” formed?
3. How long may it take for pure ice to form?
4. What happens to air trapped in the snow as it is transformed into pure ice?
5. The oldest ice is at the ____________ of the ice core.
6. What are some factors that scientists consider when deciding from what location they should
try to remove an ice core?
7. About how long does it take to drill and remove about 200 feet of ice?
8. When the cores are brought to the surface, scientists try to place them into a general time
frame. They look at the light and dark banding of the cores to estimate time — much like
scientists use tree rings to count backwards in time. The light areas represent what? And the
dark areas represent what?
9. What is insolation?
10. Milankovitch cycles can account for some changes in the earth's climate in the past. Why?
11. How does dust in the earth's atmosphere affect climate? Why do scientists who study ice
cores look at calcium dust, in particular?
12. How do atmospheric gases get trapped in ice? Can scientists see what greenhouse gases
were present in ancient times by examining ice cores?
Ice Cores: Interpreting the Data
Now that you've learned about ice cores, imagine that you're a scientist who's going to
interpret some data from a recently removed hunk of ice. Follow the link at the bottom of the
page to “Interpreting Ice Core Data” and complete the “Secrets of the Ice” activity.
1. Does there seem to be a correlation between each of the variables and temperature? Are they
proportional or inversely proportional?
2. Is the timing between a change in any variable and a corresponding change in temperature
immediate or is there a delay? Why do you think a delay might exist?
3. Describe how any part of the graph, for any of the variables, could be used to determine past or
future climatic conditions.
4. If you overlay two or more graphs would your answers be the same?
Predicting the Future
Climate Models and Predictions
Most climate scientists agree that the earth's climate is warming. It has, in fact, warmed by
about 0.6 - 1.2° F since the late 19th century. But will it continue to warm into the future?
Climate models are what researchers use to try to answer that question. Researchers design
mathematical models that take into account a wide range of climate variables recorded from
the direct and indirect measurements we discussed above — including cloud cover, presence of
greenhouse gases, temperature, precipitation, and many others. Then they allow large and
sophisticated super-computers running sophisticated climate models to come up with
predictions. These mathematical models are the best attempt scientists can make at predicting
the future of climate. But that doesn't mean that they will come true. By making many
predictions, and taking into account many variables from all over the country and the world,
scientists hope that these models provide people with the most likely kinds of climate scenarios
that they can expect.
Global Warming Part 4: The Science Behind
the Climate Change Story
Now that you know how scientists use direct and indirect measurements to study climate
change, the next step in your detective's journey is to find out what the results of these
studies are. Exactly what have the tools in the climate change toolbox told us?
To find out, you'll read about three major areas of research on climate change:

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the weather
biological and ecological systems
the climate itself
What Is the Science Telling Us?
Bird Migration
Biology
Biologists and ecologists are discovering significant changes in bird and other animals' habits
and patterns. This kind of evidence does not directly show shifts in climate like the research
highlighted later in the section on Climate. But it does provide compelling indirect evidence
that the climate may be changing — and it provides information on how climate change can
and will affect populations of organisms. If biologists have studied particular organisms and
their habits for a number of years, and those habits begin to change in what seems to be a
response to shifts in temperature, or other climate-related factors — then a possible
explanation for those changes in habits would be based on shifts in climate.
Let's take a closer look at a couple of these kinds of studies.
Climate Shifts: Bird and Mammal Habits
Climate change affects lower altitude environments differently than higher altitude ones. And
that can confuse animals that use those environments. A recently published study by Dr. David
Inouye, a professor at the University of Maryland, and his colleagues, documents changes in
bird and mammal behavior at the Rocky Mountain Biological Laboratory, in Gothic, Colorado.
The Lab, nestled at about 9,500 feet above sea level, is still covered with snow in the spring
even though temperatures are a little warmer. At the same time, over the last 25 years, spring
has arrived earlier and earlier in areas of lower altitude. As a result, American Robins that
migrate from low altitude wintering grounds to high-altitude summer breeding grounds in the
Rockies, are arriving earlier in the spring (14 days earlier over the past 19 years), and must
wait longer for snow to melt before they can feed and nest. This puts them at risk of starvation
since not much food is available when snow still coats the ground.
Hibernation Patterns
What's more, yellow-bellied marmots (close relatives of woodchucks) usually hibernate for
eight months during the long mountain winters. But now they are emerging earlier — 38 days
earlier over the past 23 years — from their winter's dens in anticipation of early springs.
Inouye thinks that the marmots emerge because of the warmer spring temperatures, and that
they anticipate an early snowmelt. When in fact, the snow doesn't melt earlier — if anything,
it's been melting later than normal. So the marmots, too, risk starvation as they wait longer
for snow to melt before they can feed.
Researchers have documented these shifts by paying close attention to when robins arrive at
the Lab, and when marmots emerge from their dens. Says Inouye, “ A relatively simple
observation, such as the first sighting of a robin each spring, can be made almost by anyone,
and if continued for a long enough time, can provide important insights into global change.”
He's concerned that other high-altitude animals may be at risk. “There is growing evidence to
support that climate change is resulting in earlier and longer growing seasons at low altitudes,
earlier migrations by some bird species, and earlier reproduction in both plants and animals,”
says Inouye.
Climate Changes Species Behavior, Inouye article
Article by Dr. David Inouye, Climate change is affecting altitudinal
migrants and hibernating species.
Climate Change has affected the breeding date of Tree Swallows
Article by Dunn P.O. and D. W. Winkler, Climate change has affected the
breeding date of tree swallows throughout North America.
Climate Changes Butterfly Behavior
USA Today article, Scientists see signs of European butterflies reacting to
global warming.
Animal Biology: Correlation vs. Causation
All of these studies are quite interesting because they document significant changes in
animal biology — those changes may be in seasonal timing, in how far birds migrate north, or
even in the extinction of certain species. And each of these studies correlates the animals'
behavior changes to significant shifts in climate — warmer weather earlier, for instance, or
warmer temperatures further north than they once were.
But does a correlation absolutely prove a relationship between these animals' behavior
changes and shifts in the climate? Correlations are just that — they show that two or more
factors are related to each other. And just because they are related doesn't necessarily mean
that climate is affecting animal biology. But researchers can also examine many other factors
and show that those factors are much less likely to be causing behavior changes, than climate.
Thus, many of these kinds of studies show very strong correlations of climate change with
organisms' biology — so you can grow more confident that climate is in some way responsible.
Questions to Consider:
1. Does the research on tree swallows, robins, yellow-bellied marmots, and butterflies (in
the Biology section above) prove beyond a doubt that the animals' are changing their
seasonal habits, migration patterns, and nesting behaviors because of warmer spring
temperatures? Are there alternative explanations? If so, how likely are they?
2. Based on your reading, do you personally think that a changing climate may be
responsible for the changes in animals' habits that you read about? What if there were
ten more studies like this, or a hundred? How would that affect your answer?
Weather
Events and Patterns
Some climate scientists are concerned that global climate change could bring about
more extreme weather events. Weather and climate are tricky things to predict. And to
attribute specific weather events to global warming is even trickier. That's because it's
impossible to link particular weather events with global warming without very long-term data.
First you must have well-kept records of temperature, rainfall, storm intensity, drought
intensity, and other weather phenomena, over large scales. To that you need to add weather
models that predict what would happen in the face of global warming. Only after many, many
years of comparison can you say for sure (with a statistically significant relationship) that
global warming is, in fact, causing severe or unusual climate or weather events.
But there are some hints that suggest recent weather events and patterns are related
to global warming. A group of researchers at the NASA Goddard Institute for Space Studies
use global climate models to try to answer these sorts of questions. Dr. James Hansen says
that global warming could lead to greater climate extremes. He even testified to Congress in
1988 and 1989 that global warming would lead to greater climate extremes.
He says, “On the one hand you might see more intense droughts, heat waves and fires,
but, on the other hand, you'd also heavier rainfall, greater floods and stronger storms. This
makes sense — increased heating of the surface increases the temperature and intensifies
drought at times and places with dry conditions. But over the ocean and places that are wet,
the increased heating of the surface increases evaporation, intensifies storms driven by latent
heat, and causes greater flooding.”
Natural Variability?
Are these extreme weather effects large enough to be noticeable — and if so, can we
positively attribute them to global warming? So far, says Dr. James Hansen, of the NASA
Goddard Institute for Space Studies, it's hard to say that an extreme weather event isn't just a
part of natural weather variability. For instance, he says that we've seen global warming of
about one degree Fahrenheit, and that, “is not large enough to cause (extreme weather)
effects as large as natural variability. So probably most 'strange weather' is just that &151;
strange workings of nature.“
However, adds Hansen, “when a really extreme event occurs, like the Chicago heat
wave of a few years ago, I have to ask myself the question 'would that extreme event have
occurred in the absence of all the human-made greenhouse gases in the atmosphere?' The
answer that I come up with frequently, including the Chicago case, is: 'probably not.'”
Extreme Events and Climate — The Link Explored
Climate scientists from NOAA, the National Center for Atmosphere Research, and other
institutions, recently published a review of the scientific literature available on climate and
extreme weather events. The paper, published in the September 22, 2000 issue of the journal
Science, discussed whether a potential change in climate (e.g. global warming) could explain
increases in extreme weather events.
The authors reviewed dozens of scientific studies, and found that in many of the areas
studied, “changes in total precipitation are amplified at the tails (meaning that where rainfall is
heavy it has gotten heavier, and where it is lightest, it has gotten even drier), and changes in
some temperature extremes have been observed.” They also reviewed various climate models
for the future and saw that the models predict changes in extreme events including increases
in extreme high and low temperatures, and increases in intense rainfall and precipitation
events.
In addition, they documented changes in biological systems that are occurring more
frequently — presumably as a result of changes in climate, and perhaps by changes in extreme
events. “Climate induced extinctions, distributional (and breeding/seasonal) changes, and
species' range shifts are being documented at an increasing rate,” wrote the authors.
They concluded with, “Although the direct link between societal and biological impacts and
climate change is often difficult to make, a growing body of evidence linking climatic and
biological changes suggests systematic global increases in both the frequency and impact of
extreme weather and climate events.”
Questions to Consider:
1. Is there evidence that global warming is affecting extreme weather events?
2. Why is it difficult to be able to say so conclusively?
3. Does the review paper published in Science strengthen or weaken your detective's
judgment on whether global warming is affecting extreme weather events? Why?
Climate
Current Trends?
From your research on the history of earth's climate in Global Warming Parts 2 and 3
you know that proxy measurements from ice cores, tree rings, pollen, and others, have shown
that the earth's climate is dynamic. It has varied from warmer to cooler and back again
throughout the distant past. You also know that recent measurements taken over the last 150
years have shown a dramatic warming trend. The rate of this warming is highly unusual when
compared to climate over the last few thousand years.
Now let's look more closely at a few recent studies on climate...
Rivers and Lakes Freeze Later and Thaw Earlier
Read the story titled “Icy Records Show Warming Trend” research on freeze and thaw
records all over the northern hemisphere from the last 150 years
Ocean Traps Heat
Check out a story showing results of another kind of record — records of the oceans'
temperatures over the last 70 years or so by following the link to “Missing Heat” below.
Glacier Gives Clues to Climatic Past
Also, read a USA Today article highlighting recent research published in the journal Science:
“Tibetan glacier yields evidence of warming”
Icy Records Show Warming Trend: November, 2000
Missing Heat Found in World Oceans: August, 2000
Tibetan Glacier Yields Evidence of Warming
Climate
Questions to Consider
1. Name two proxy tools used to collect data on past climate in the above three studies.
2. Do these studies yield direct or indirect evidence that the climate is warming (for example,
compared to the studies highlighted in the Biology section above)? NOTE: It's helpful to
recognize that researchers who examine how animal biology is affected by climate change
often use studies like the ones above to document shifts in climate, and to correlate those
shifts with the biological system they are studying.
3. So, do you think that the earth's climate has warmed over the last 150 years?
4. How do the data from the oceans' temperatures support the climate models for predicted
climate change?
Global Warming Part 5: Current Climate Change — Are Humans Involved?
Based on your detective work so far, you've uncovered data that clearly document a planetary
warming trend. The question now is, what's causing the current shift in climate? You've seen
that the earth has undergone many changes in climate in the past, well before humans could
potentially affect global climate. So clearly there are a variety of natural explanations for global
climate change. But are they sufficient to explain the earth's current warming? If not, does the
impact of certain human activities help explain global warming?
But How Do You Study That?
Imagine doing an experiment. You're testing the effects of fertilizer on plant growth. So,
you've got two plants in two separate pots. To one pot, you add water enriched with a
measured amount of fertilizer. To the second pot, you add the same amount of water without
fertilizer. The pot with water only is your control. Controls are critical to any science
experiment because without them you cannot say for sure whether the experimental variable
was what caused your observed results (in this case the fertilizer causes your experimental
plant to grow more quickly).
Ideally, in science experiments there is a control. Often scientists make observations without
the benefit of a control (for example, recording the timing of robins' arrival each spring), but
these are not actual experiments — they are called observational studies.
Observational Studies
So how does this relate to studying whether humans are partly responsible for climate
change? Well, consider our earth. There is just one earth. And there is now human activity
occurring on it that might be partly responsible for climate change. But there's no control to
this experiment. There's no second earth. Hypothetically speaking, it would be ideal to have
two identical earths, each occupying the same general spot in orbit, the same distance from
the sun, and each with the exact same climatic conditions. Then, to one, we could add a hefty
population of humans that cuts and burns forests, burns fossil fuels, and releases greenhouse
gases from a variety of sources. To the other earth, we would add no humans.
Then we could measure all the important climatic variables we've learned about and see
whether the experimental earth's climate (humans added) warmed up significantly more than
the control earth's climate (no humans).
But we clearly can do no such thing. There is no non-human earth to compare our
climate to, yet we are equipped to change the chemical make-up of our atmosphere profoundly
enough that climate could shift. In effect, then, we are running an uncontrolled experiment on
earth and we don't know the outcome.
But scientists have figured out some elegant ways to make good guesses about
whether human activity is involved. The most important first step is to understand how natural
phenomena can affect climate. The question is this, can natural phenomena completely explain
current climate shifts, or are those explanations inadequate to clarify climate change? If so,
does the effect of human activity help explain current climate patterns?
Natural Explanations
First, find out more about natural processes that affect global climate. Visit the Geography
course module created by Dr. Michael J. Pidwirny, of the Department of Geography at
Okanagan University College in British Columbia. The module is an Introduction to Natural
Causes of Climate Change, and you can find it at by following the link at the bottom of the
paragraph to the “Fundamentals of Physical Geography”. Some of the reading may be a
bit advanced but if you use these questions as a guide, you can just look for the information
you need, and skim the technical details (unless you are interested of course!).
http://www.physicalgeography.net/fundamentals/7y.html
Answer the following questions, as you read through this lesson:
1. List the extraterrestrial factors that affect global climate.
2. Now list the ocean, atmosphere, and land factors that affect global climate.
3. What are the four main factors that are primarily responsible for past episodes of
climate change?
4. Pick one of these four factors, and in one paragraph, explain how it could affect
global climate.
5. What two things are thrown into the atmosphere when a volcano erupts? Which one
of these may affect global climate? How?
6. Have any climate modifying volcanic eruptions occurred during the last century?
What were they, and how did they affect global climate?
Now follow the link to “EPA's Global Warming Climate Page” and read their description of
the Greenhouse Effect.
http://www.epa.gov/climatechange/emissions/index.html#ggo
Now answer these questions:
1. Why is the greenhouse effect important?
2. Is the greenhouse effect a natural phenomenon?
3. How does the greenhouse effect work?
Human-Related Explanations
Clearly natural processes can impact global climate. But are people now also
contributing to global affects on climate?
To wrap up what you've discovered about ancient climate and natural causes of climate
variation, and to consider some questions about whether humans are involved in current
warming trends, read “NOAA's Paleoclimatology Global Warming — The Final Word”.
Then read the “New York Times — Global Warming” article by Andrew C. Revkin.
The story not only highlights a recent study that indicates humans are partly responsible for
current climate warming, it also briefly outlines the bigger issue of trying to resolve the
different effects of natural versus human processes on climate. (You may need to register to
read the article, but there is no charge for doing so.)
NOAA's Paleoclimatology Global Warming — The Final Word
New York Times — Global Warming
Some Questions
Answer the following questions based on the article you've just read on the preceeding page:
1. What were the two main “natural processes” that Dr. Crowley examined?
2. Dr. Crowley used a climate model to see how these two natural processes predicted climate
over the last 1000 years. His results showed that the natural processes appeared to explain
climate for the last 1000 years, up until when?
3. After the mid 1800s, the relationship between natural processes and climate broke down.
What did Dr. Crowley find to be the most likely explanation for temperature increases over the
last 150 years?
4. Did other scientists agree or disagree with Crowley's findings? Why or why not?
5. Why does this study provide a good starting point for examining the issues surrounding
“natural” versus “human-caused” global climate change?
6. Does this study prove that current climate warming is due to human activity?
“Global Waffling?”
Let's start off by reading the September 10, 2000 article written by Andrew C. Revkin of the
New York Times titled “Global Waffling: When Will We Be Sure?” (You'll have to register
first if you haven't already, but it's totally free).
New York Times — Global Waffling
Now answer these questions:
1. When Revkin writes, “The bigger the idea, the harder it often is to verify with precision,”
what does he mean? Is global warming a big idea?
2. How do so-called global warming “skeptics” use scientific subtleties when debating the idea
of global warming?
3. Scientific skepticism can be and is very important to advancing our understanding of the
natural world. Do you think all skepticism is healthy? Why or why not?
4. Writes Revkin, “Somehow, many experts say, if the (global warming) threat is to be
countered, societies will have to figure out a way to act in the face of gray uncertainty, to deal
aggressively with a problem that lacks the attributes of a crisis.” What does he mean by “gray
uncertainty?”
5. Do you think people should attempt to curb greenhouse gas emissions and pollution in an
attempt to slow global warming — even if the science shows areas of gray uncertainty?
“The Contrarian View”
Now read The New York Times February 29, 2000 article titled, “Global Warming: The
Contrarian View,” which gives a more detailed synopsis of why the skeptics are skeptical.
And answer these questions:
New York Times — Global Warming: The Contrarian View
1. Explain the difference in temperature readings between ground measurements and satellite
measurements.
2. Why do some people think this discrepancy weakens the argument for global warming?
3. According to the article, is there debate among scientists (proponents and skeptics) as to
whether the climate is warming? Do proponents and skeptics agree on the amount of current
and future warming?
4a. Do the skeptics believe humans are responsible for current warming trends, or do they say
observed warming can be attributed to natural causes?
b. Does this agree with the research you've examined, or with the conclusions drawn by the
IPCC? Who should you believe? Why?
Now read this:
http://www.nwf.org/~/media/PDFs/GlobalWarming/Global%20Warming%20State%20Fact%20Sheets/Virginia.pdf?dmc=1&ts=20130221T1
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Write an essay explaining what you have learned and how it relates to your local community.