I have done what study I am going to do for the present on
the global warming issue. So as one who is not a climate scientist and lacks
the training to critique some of the more esoteric analysis involved, what
conclusions have I come to?
The consensus on global warming is not as uniform as green
advocacy groups, the media or the Obama administration would like us to think.
There is general agreement among most climate scientists that warming has
occurred, and broad agreement that the warming is probably due, at least in
part, to human activity. There is much less agreement about how much this
effect is, or what contributes to it, or what the long-term prospects are, or
what the best policy response would be.
Global warming predictions are much more tenuous and
uncertain than the media or the IPCC (intergovernmental Panel on Climate Change)
or the more active green groups would have you believe. Nor it that so surprising,
really, if one thinks about it. With all our weather satellites and Doppler radar
and closely-spaced weather stations on the ground we still only have moderate
success predicting the local weather in our city more than a week ahead. Predicting global climate decades ahead is
far, far, far more complex. There are thousands or perhaps even hundreds of
thousands of processes involved, many probably not yet identified, all interacting
with each other in very complex ways. Moreover the whole system is chaotic in
the formal sense, meaning that very slight changes in initial conditions can
produce wildly different outcomes. So it is not unreasonable to be skeptical
about such predictions.
It seems to me fairly likely, but not absolutely certain,
that the global climate has warmed over recent decades. The problem with being
certain of this is that temperature data has a lot of noise (day to day variability),
and there is a great deal of variability from place to place, so discerning a
long-term global trend requires some complex time series analysis with a number
of embedded assumptions (including assumption when one “adjusts” or “prunes”
the raw data, as the IPCC has done with some of the data), and if one or more
of these assumptions are wrong the result may be wrong. However, there do seem
to be visible effects like melting permafrost and retreating glaciers and
changing growing seasons that also seem to support a warming trend, so most
likely there has been some global warming over the past century, on the order perhaps
of half a degree Celsius.
Is seems to me possible that any warming that has occurred
is at least partly due to human activity. The IPCC is fairly certain of this (always
dangerous to be certain in science, because then one stops looking) and the media
follows the IPCC. But I rate it as only “possible”
for two primary reasons:
1. There is some evidence that the parts of the climate were
as warm or warmer during the medieval warm period (~950-1250 AD), and perhaps
during the Roman Era (~0 AD) as well. These periods are of course long before
the industrial age began pouring greenhouse gases into the air, so if they were
as warm it suggests there are non-human causes of such warmings, which would challenge
the IPCC’s assertions that human activity is the primary cause. The IPCC
removed data for this period after their first (1990) report on the grounds
that the measurements (all proxy measures, like tree growth rings, since no
thermometers were around) were too uncertain.
I am not qualified to judge the validity of that decision, but it certainly
was convenient for their argument to remove this period.
2. The establishment consensus has focused on human activity
and carbon dioxide production in particular – it has become the mindset of a
large proportion of researchers. That means that few people have looked at any
other natural (non-human) possibilities. In fact, since belief in human origin global
warming has become such a liberal litmus test, proposals to study alternative
possibility have had trouble getting funding during the liberal Obama
administration, and focus on alternatives is not a particularly good career
move for a scientist in liberal academia. Or as one person put it, “you don’t
get answers to questions you don’t ask.”
None of this is to say the Donald Trump or the politicians
who don’t believe in global warming do so from any serious study of the issue,
any more than the majority of the public who do believe in global warming base
their belief on anything more than media stories and what their friends
believe. But it does suggest that the issue is far more complex than generally
portrayed, and justifies more skepticism than the public or the scientific community
seems to be displaying, especially if we are thinking about spending billions of
dollars and disrupting whole segments of the economy for remediation steps which
may well be ineffective.
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