Context for Controversy
In most of the great political, social, and environmental challenges
of our age, controversy and disagreement are key features of the
public dialogue. A good rule of thumb is that the intensity of the debate
tends to be inversely proportional to the available knowledge on the subject.
However, there are spectacular exceptions to this rule of thumb. Consider
the pro-life versus pro-choice abortion debate. Here the debates are prolonged
and vociferous, even though the science of reproduction and its prevention
are rather well understood. Obviously, the continually improving scientific
understanding of reproductive science will have little to do with changing
the tone of this debate. The abortion debate is about legitimate clashes
of value systems that new scientific understanding is unlikely to diminish.
This extreme example provides an instructive context for understanding
the character of the intense controversies and disagreements concerning
human-caused greenhouse warming. There would not be much of a global
warming controversy if increasing greenhouse gases in the atmosphere
were perceived to produce an effect of theoretical curiosity- but an effect
deemed irrelevant for serious changes in the climate. I can visualize scientists
disagreeing, as they typically do, in scientific conferences on points
of correct or incorrect explanations of various phenomena. A few might
get passionate about their own viewpoint, but the disagreements would not
normally prevent the key players from going out later for coffee, beer,
or dinner together.
Interestingly, this is a reasonable characterization of what happens at
climate conferences, even now. Things change, however, when a member of
the scientific community is arguing for a political position "in the
name of science." Even in this case, the mood is generally polite,
but the questions to the speaker are typically pointed and sometimes emotional.
My interpretation is that working climate scientists are not comfortable
dealing with the unfamiliar science/ nonscience interface. Our instincts
are to continue to fight scientifically fair and to openly admit uncertainty,
even when unscientific weapons are employed. In effect, serious scientists
are trying to find the scientific truth, whereas advocates typically appeal
to science to advance their personal agendas. This mismatch often leads
to an amplified sense of "scientific" controversy,
at least to an uninformed observer.
Genuine
Scientific Uncertainty and Disagreement
The above observations are not offered to assert that scientists should
not argue. On the contrary, the whole culture of physical science is about
disagreements and alternative explanations. But the discipline of science
is about settling disagreements using the scientific method. The very ethic
of science is designed to get to the truth through hypothesis testing by
careful experimentation.
A good test for determining whether or not the scientific method is being
used to evaluate assertions about the science of the problem is whether
or not previous assertions are altered in the face of contrary evidence.
Many instructive examples of legitimate scientific disagreement have energized
new understanding in the light of improved information.
The example of the physical explanation of the spectacularly large Antarctic
"ozone hole" phenomenon is especially instructive in this context.
The new information on the ozone hole discovery changed within about 2
years the way establishment science understood ozone depletion. My own
small part in that story was in advancing a testable hypothesis on whether
the ozone hole was a natural phenomenon (11).
Our hypothesis (the only identified plausible "natural" alternative)
was indeed tested and was found to be physically consistent; however, it
failed by nearly a factor of 10 as an explanation of the sharp ozone decreases.
In real science, if the numbers are off the hypothesis fails. There are
self-proclaimed "scientists" who still use terms such as "ozone-hole
hoax" to describe the state of ozone science. Clearly, such "scientists"
are ignoring compellingly large and convincing ozone decreases, as well
as the strong scientific evidence available to explain the decreases.
It is important to recognize that scientific disagreement is a cornerstone
of the scientific ethic. Contrary to our legal traditions, all theory,
all models, and all data are, in effect, "guilty until proven innocent."
Moreover, the proof of innocence in science is inevitably relative. Einstein,
in principle, "shot down" Newton's laws of motion. In practice,
however, we live our daily lives implicitly assuming the virtual correctness
of Newton's laws without fear that the departures from the "true physics"
could cause us any observable problems. Thus, we are comfortable with scientific
understanding that is "good enough" for application to the purposes
at hand.
I suggest that this "good enough" principle provides useful guidance
for viewing the human-caused greenhouse warming problem. Obviously, anything
as complex and interactive as climate offers plenty of opportunity for
legitimate scientific disagreement. My own view is that the climate science
community has been straightforward in acknowledging the significant remaining
uncertain-ties in the projections of possible future climate changes. Most
importantly, we still acknowledge a factor of three (1.5°-4.5°C)
range of uncertainty in the equilibrium global-mean surface temperature
response to a doubling of CO2 (12).
In addition, I have asserted that there is a greater than 90% chance that
a doubling of CO2 would produce a warming
within that range (13). We scientists
acknowledge that adding the effects of sulfate particles (a result of fossil
fuel burning) produces an uncertain cooling offset effect. We also freely
acknowledge that the aerosol cooling effect was given insufficient attention
in the 1990 IPCC Report (14).
These observations strongly indicate that the great controversy about greenhouse
warming is not really about the uncertain state of the science. In the
scientific community, the uncertainty is widely acknowledged. We do, however,
frequently argue about the significance and validity of new claims and
new results. The path to sharpened scientific truth is always a rocky one.
The Misuse of
Scientific Information
The current, highly energized greenhouse warming debates go well beyond
scientific controversy. They are driven by arguments that are not scientific,
at least in the sense that practicing scientists use the term. The arguments
are frequently, and legitimately, centered around clashes in values and
priorities. Unfortunately, however, assertions are being made about climate
change "in the name of science" that are not based on fundamental,
quantifiable climate science. How is this so? There are many techniques
available to use or misuse scientific knowledge to support one's personal
viewpoint, which may or may not have much to do with the lessons from the
science itself. Actually, it is easy to "mine" the lore of climate
facts to justify a particular, preset point of view.
The most obvious misuse of climate knowledge comes from the openly stated
uncertainties in the predicted global-mean surface temperature increase
for doubled atmospheric CO2. The widely
accepted range of 1.5°- 4.5°C leads to some intriguing arguments.
Those who are legitimately afraid of the economic consequences of CO2
mitigation (who I call "Ostriches," with their heads in the sand),
almost independent of the scientific evidence, tend to appeal to the information
that buttresses the case for the numbers to be at or below the low end
of the range. "I just know the real result will be on the low side
because...." Those who are legitimately concerned about the environmental
consequences of high CO2 levels (who I
call "Chicken Littles," who see the sky falling), almost independent
of the scientific evidence, tend to appeal to the information that buttresses
the case for the warming numbers to be at or above the high end of the
range. "I just know that the real results will be on the high side
because...."
Like it or not, the truth is that we do not know the truth about where
the final answer will lie. The inconvenient reality is that uncertainty
"just is." If we knew that our previous best estimate was, say,
on the high side, the scientific community would most assuredly lower the
best guess. It would be unscientific to do otherwise. It is clear that
well-meaning, but agenda-driven, people will still legitimately disagree
for nonscientific reasons. In effect, these are values-driven positions
that have little to do with the true state of scientific understanding.
People who use such "science" to reinforce their personal opinions
are not interpreting science as scientists understand it.
Intriguingly, in the greenhouse warming debates, the natural variability
of the climate system is frequently misused in a manner surprisingly analogous
to the misuse of scientific uncertainty, as explained above. In this case,
Ostriches say that the unforced natural variability of climate is so large
that the observed warming trends over the past century are explainable
by appeals to the natural variability of, say, global-mean surface air
temperature. Thus, for the observed, roughly 0.6°C warming over the
past 130 years, Ostriches can properly argue that this might be a natural
warming cycle that has nothing to do with the in-creasing greenhouse gases.
However, Chicken Littles can point out that we might have been in a natural
cooling cycle over the past 130 years, and thus the greenhouse effect is
probably larger than it currently appears from the data. The problem with
both these arguments is there is no evidence to confirm either of them.
That is one of the reasons it is very difficult to appeal to the temperature
record to lower the uncertainty limits on greenhouse warming projections
very much. Natural variability, like uncertainty, "just is."
No values-driven debating tricks will make this reality disappear. When
either uncertainty or natural variability is systematically used to push
a prestated position, be wary. Science may just have been misused, to the
net loss of a more rational effort to establish what is really going on
in the science of this daunting problem.