Environmental Science Chapter 2
great debate over scientists resulted in multiple hypothesizes:
A possible explanation for what we have observed that is based on some previous knowledge.
testable:
A possible explanation that generates predictions for which empirical evidence can be collected to verify or refute the hypothesis.
Solomon's journals went through a peer review:
A process where researchers submit a report of their work to outside experts who evaluate the study's design and results to determine if it is of a high-enough quality to publish.
theory:
A widely accepted explanation of a natural phenomenon that has been extensively and rigorously tested scientifically.
precautionary principle:
Acting in a way that leaves a safety margin when the data is uncertain or severe consequences are possible.
Policy has been described
as translating our values into action
chemicals seemed to increase
at a rate matching the disappearance of ozone.
correlation between the presence of CFCs and ozone depletion—
both occurred together It suggested that CFCs may be related to ozone decline
The observation of a decrease in ozone did not come from just a few readings,
but represented data collected at two different sites over more than a dozen seasons
Phenomena that are not objectively observable (What is my dog thinking? Do ghosts exist?) and ethical or religious questions (Is the death penalty wrong? What is the meaning of life?)
cannot be empirically studied, and therefore are not under the purview of science.
The lowest level, the troposphere
STARTS AT THE GROUND AND extends about 7 miles up. This level is familiar to us—it is the air we breathe and where our weather occurs.
ultraviolet (UV) radiation:
Short-wavelength electromagnetic energy emitted by the Sun
experimental
cause and effect
Scientists generally require a
high probability (at least 95%)
Scientists can gather empirical evidence about the environment and living things using a wide variety of tools
including natural tools, such as their eyes, ears, and other senses.
On both of her trips to the Antarctic, her team raised balloons into the air which measured the composition of the atmosphere where the ozone hole was found
and simultaneously analyzed light reaching the ground to determine whether it was changing in the region with less ozone and more ClO.
Scientific investigation, in both the natural and social sciences
is based on data gathered through empirical evidence, or observations.
Science
is both a body of knowledge (facts and explanations) and the process used to get that knowledge.
Solomon and the team had decide to fly to the other end of the world
scientific paper published the year before since the late 1970s, the ozone layer had thinned by about a third during the Antarctic spring.
Susan Solomon became a scientist because
she was curious about the natural world around her
This prediction was falsifiable,
since Solomon might not find high levels of ClO.
Understanding the process is more important than the "facts,"
since facts may change as more information is collected through the scientific process. This process is a powerful tool that allows us to gather evidence to test our ideas, and to evaluate the quality of that evidence.
As evidence mounts from replicate studies and from multiple predictions
we become more confident in our data and conclusions
BAD OZONE
we convert oxygen to ozone
GOOD OZONE
we convert ozone to oxygen
Replication
within a study is a hallmark of good science—in this case, multiple data points collected at more than one testing site
Scott Menzies testing the prediction that mice exposed to high UV-B
would develop more skin cancer than mice exposed to normal levels of UV-B
These isolated chlorine atoms destroyed ozone
—particularly in the Antarctic spring, when sunlight streamed in.
UV- B
-10% reaches ground -ozone is stopping most of -can cause DNA damage
Precautionary principle
-better safe than sorry
UV- C
-does not reach earth's surface
Adaptive management
-employee this law, see how it goes, and as we find out more information if we need to tweak it, we will fix it
UV-A
-reaches earths surface -causes skin cancer and sunburn -50% of it reaches ground
5. How is this data similar to and/or different from the data collected by Susan Solomon's team? And what does this data mean for the hypothesis that Solomon proposed?
...
6. How does this research study support the idea that science is a community enterprise?
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Mesosphere
...
Thermosphere
...
Solomon's OBSERVATIONAL STUDY
1- weather balloons to see if CLO 2-Monitored amount of light reaching the ground ****looking for UVB reaching ground ****if more= less ozone
In 1974, they proposed that CFCs were not entirely harmless in the atmosphere
And once in the stratosphere, the molecules would be exposed to UV light so intense that it would break them apart. The process would release solitary chlorine atoms, which previous research had shown could chemically react with—and destroy—ozone
ozone prevents most of the UV-B from reaching
Earth's surface, where it can harm organisms.
EPA-
Environmental Protection Agency enforce and regulate
CFCs contain atoms of carbon, fluorine, and chlorine
For example, CFC12, a common refrigerant, has the molecular formula CCL2FL2—one carbon atom (C) is bound to two chlorine (Cl) and two fluorine (Fl) atoms
experimental study:
Research that manipulates a variable in a test group and compares the response to that of a control group that was not exposed to the same variable. cause and effect hypothesis
This stratospheric (good) ozone should not be confused with ground-level (bad) ozone found in the troposphere.
Ground-level ozone is a component of smog and is harmful to living things
We manipulate the independent variable (in this case, the amount of UV-B radiation), and measure the dependent variable (the incidence of skin cancer) to see if it is affected.
In other words, if development of skin cancer is dependent on UV-B radiation, then we should see skin cancer incidence change as UV-B exposure changes
Joe Farman got his info from observations:
Information detected with the senses—or with equipment that extends our senses
Montréal Protocol:
International treaty that laid out plans to phase out ozone depleting chemicals like CFC.
Solomon's study was observational study:
Research that gathers data in a real-world setting without intentionally manipulating any variable.
trying to understand why ozone was disappearing over the region, Solomon kept thinking about temperature
October is spring in Antarctica, and scientists knew that cold spring winds would swirl around, producing a cyclone of air in the atmosphere (a polar vortex), keeping cold air in place over the poles and leading to the formation of polar clouds in the stratosphere.
adaptive management:
Plan that allows room for altering strategies as new information comes in or the situation itself changes.
scientific method:
Procedure scientists use to empirically test a hypothesis
CFCs
The compounds were first developed in the 1930s as a commercial coolant, to replace more toxic ammonia and sulfur dioxides, and were therefore included in refrigerators, air conditioners, and other household and industrial items
test group:
The group in an experimental study that is manipulated somehow such that it differs from the control group in only one way.
control group:
The group in an experimental study that the test group's results are compared to; ideally, the control group will differ from the test group in only one way.
degrees of certainty are based on statistics:
The mathematical evaluation of experimental data to determine how likely it is that any difference observed is due to the variable being tested.
did not establish a cause-and-effect relationship
The two trends could occur together by coincidence, or something else entirely could be causing both to occur.
dependent variable:
The variable in an experiment that is evaluated to see if it changes due to the conditions of the experiment.
independent variable:
The variable in an experiment that the researcher manipulates or changes to see if it produces an effect.
correlation:
Two things occur together—but it doesn't necessarily mean that one caused the other.
3 forms of UV radiation
UV-A, UV-B, and UV-C
The Montréal Protocol, administered by the
United Nations, outlined a series of deadlines over the next decade for cutting back production of CFCs.
2 groups
This experiment compared two groups—the control group of mice was exposed to normal levels of UV-B and the test group was exposed to the same amount of UV-B received in areas where ozone depletion has been observed.
4. Does the data in this graph show a correlation or a cause-and-effect relationship? Does it support the hypothesis that chlorine is the cause of ozone depletion? Explain your responses.
cause and effect- as they hit each other it caused a change. yes the more chlorine, the less ozone.
,aligning with Farman's observations from Antarctica. The two chemists calculated that at the rate CFCs were being produced in 1972, the
chemicals could destroy 6% of the ozone layer. And manufacturers were making more CFCs every year.
Farman's group also connected their results to studies by other researchers that had shown higher concentrations of an important compound:
chlorofluorocarbons (CFCs), which in turn produce atmospheric chlorine (Cl).
used these observations to draw conclusions or make inferences
conclusion/explanations of what else might be true or what might have caused the observed phenomenon.
Farman's team inferred that the ozone depletion in the Antarctic was
connected to the increased presence of chlorine compounds in the atmosphere.
observational
correlations
Ozone molecules in the stratosphere absorb much of the UV-B, a vital service since UV-B can
damage cells and biological molecules like DNA. In humans, exposure to UV-B radiation increases the risk of cataracts, skin damage, and cancer.
Independent
factor that I change
His team collected data on the atmosphere's composition
lower than normal ozone levels
Only physical phenomena that can be objectively observed—
meaning data that could be collected by anyone in the same place, using the same equipment, etc.—are fair game for science
predictions must be falsifiable
meaning that it would be possible to produce evidence that shows the prediction is wrong. (Predictions based on untestable ideas—such as, "reincarnation exists"—are not falsifiable and therefore are not considered suitable for science.)
Science is limited to asking questions about the
natural world—not all questions are open to science.
data on a graph
on which the x-axis (horizontal axis) displays the independent variable and the y-axis (vertical axis) shows the response (dependent variable)
Notice we do not claim that the hypothesis is proven
only that it is supported (or confirmed).
Governments would have to put in place their
own plans for achieving a desired outcome, or policy, for reducing CFCs.
Solomon proposed the hypothesis that cloud particles in the polar stratospheric clouds were
providing surfaces for the reactions that would free chlorine molecules (Cl2) from CFCs. In sunlight, the chlorine molecules would then break up into chlorine atoms.
next level in the atmospheric blanket, the stratosphere
rises to 31 miles above Earth's surface. The stratosphere is much less dense than the troposphere but contains a "layer" of ozone (abbreviated as O3, because it contains 3 oxygen atoms), a region where most of the atmosphere's ozone is found
Solomon's hypothesis generated the prediction that the
stratosphere would contain high levels of chlorine monoxide, or ClO
Ozone is a key element of the atmosphere
the blanket of gases surrounding our planet that is made up of discernable layers, which differ in temperature, density, and gas composition
all conclusions in science are considered tentative
the scientific opinion about CFCs didn't change overnight—because they are open to revision (because our understanding of a concept or process will change as scientists learn more)
If polar clouds and sunlight were causing chlorine to react with ozone
then the atmosphere should contain many molecules of chlorine bound to individual oxygen atoms.
