Monday 27 April 2015

STATISTICAL FALLACIES IN THE GLOBAL WARMING DEBATE

Introductory books on statistics usually start by noting some ways in which they can
used to mislead.  A popular textbook possibly still in use was called "How to lie with
statistics",  Three elementary fallacies were usually noted:  the selection of base dates
for a time series;  possible misuse or misunderstanding of averages;  and the
fact that correlation does not imply causation.  All three are widely evident in the
debate about global warming.
(1)  Selective use of base dates:  Long-run series of temperature statistics usually start
about 1850,  However this was towards the end of the Little Ice Age  (in fact, I think
the cold era could be regarded as continuing until about 1900) so that this starting
point shows figures for subsequent years rising more than they would is based on
a presumably "more normal"  one.  Even more importantly, the two or three decades
leading up to 1970 (in some cases, 1976)  were much colder than the preceding five,
so that an annual series starting then shows a much higher rise since. What would be
a "normal" year ro series of years to use as a base date?  The answer is that there
isn t one, and all that can be done is to give the raw figures for as many years as
possible and allow the reader to form a judgement.
                                  The practice, adopted by all sides in the global warming
debate, of giving annual figures as "anomolies"  also presupposes that the base date(s)
are in some sense normal.  Using a fairly long period of time as the base helps to
remedy this; for example the most recent World Bank Development Report, for 2014,
shows (Table 9, p.316)  global temperatures relative to 1951-1980.  This seems at
first sight a fairly fool-proof  procedure, but it includes three probably cold decades and only one warm one, 1970-1980.
                                  The anti-warmists, in arguing that global temperatures have not
risen since about 1997, fall into the same fallacy.  It is fairly universally agreed that
the decade of the 1990s was exceptionally warm  (there were three El Ninos, which
usually come at intervals of up to five years)  and a stable statistical series starting from
a high base date is compatible with a long-run rising trend.  (In any case, it does not seem
to be true that global temperatures have not risen since ca. 1997.  The World Bank
table just quoted shows an anomaly of 0.59 for 2001-2010, compared wirth 0.37 for
1991-2000.)
(2)  The dangers of averages  The elementary statistical textbooks often quote the
example of the non-swimmer told that a river is on average 3 feet deep, walks in and
gets drowned.  The point of course is that an river could be much deeper than three feet
in some parts if it is shallower than that in others.  .Foe many (most) purposes, differences
in temperature-  polar, temperate zones and tropics; day and night;  summer and winter,
ground level and atmosphere (lower and upper)- \are more important in tryng to elucidate
causal relationships than is the global average.  In addition it seems that there is a causal
link between opposing trends in different regions.  This may be more apparent in
rainfall than in temperature trends. For example there seems to be a link between wet
weather caused by El Nino in the Southern Hemisphere and drought in California  (though,
one of many cases where assumptions and prediction are unrelaible, the expected severe
El Nino in 2014 did not materialise, and California is suffering one of its worst droughts
on record).
(3)  Correlation does not imply causation  The textbooks in the 1950s used to quote the
example of the birth rate and the number of storks in Sweden in the 1930s- both were
falling at about the same rate. Many discussions of the link between atmospheric carbon
dioxide and global temperatures consist of little more than a juxtaposition of two
series of statistics, with little attempt to set out the physics, chemistry and meterology
of the presumed link  (this is true for example of Unit 1, "Global Warming", in an
otherwise admirable Open University course "Exploring Science",  S104 and, even more
a very close examination of  alternative  explanations.

anthropogenic.


Friday 20 March 2015

GLOBAL WARMING:  IS THERE A SCIENTIFIC CONCENSUS?                                                        
                                                           It is frequently asserted that there is an overwhelming
concensus of expert opinion that dangerous global warming is taking place and is
caused mainly by anthropogenic carbon dioxide emissions.  This view is bolstered by
citing the number of scientfic papers which support  it.  Opponents cite the large
number of scientific papers which cast doubt on the thesis.
                                                         Assessment of the controversy requires an examination
of the procedure of scientific publication, depending heavily on "peer group review",  
and the associated research grants and academic appointments and promotion.  The
procedures have developed comparatively recently, since the huge explosion of university
teaching and research since the early 1960s.  At the risk of being accused of caricature,
it might be said that before that time academics published something only when they
had or thought they had something valuable to say;  since then it has become
necessary to publish in a peer-reviewed journal in order to qualify for a research
grant and an academic job. From a lifetime working in social science teaching and
research, I would be dubious about the validity of the procedures there. No social
science journal, as far as I know, takes the elementary precaution of reviewing
submissions "blind", to rule out the possibility of preference being given to authors
and institutions which can give reciprocal favours.   In three fields with which I have
been particularly concerned- crime, immigration into Britain, and global warming- I
believe social science research bodies have acted not merely to promote a particular
standpoint but to suppress dissenting views.
                                                   I have always believed that in physical sciences the
situation is different and that the peer-group review system works as it should, but the
global warming debate suggests that at least in this field there are grave defects.
                                                   The view that there is an large conscensus in favour
of anthropogenic CO2 as the main cause of warming ignores the long-established
and still continuing work of astrophysiocists and others who support the
Milankovitch theory of climate change- that it is due to the earth*s relationship to
the sun- and also the large number who are still examining the idea that it is due
to solar acivity, especially sunspots.  It is highly significant that several of these, in
contrast to the IPCC and other warmists, conclude that the causes of climate change
are at present unknown. For example Brian McDougall,  Frozen earth:  the once and
future story of ice ages  (University fo California Press, 2008) says that since the
general acceptance of the tehory of ice ages in the middle of the nineteenth century
"literally hundreds, perahps even thousands, of scientists have pursuded research into
the causes of ice ages.  The intellectual challenge presented by the geological event,
with its multiple possibilities, has attracted the efforts of geologists, chemists,
physicists, mathematicians, biologists and climatologists.  There is still much uncertainty
about how, and especially why, an ice age actually happens.  To be sure, there are
hypotheses, but none have yet attained the status of an accepted theory  (p.8-italics
added).
                                                    A question which can usefully be posed to all who
believe they know the causes of climate change is what caused the Little Ice Age
(about 1350 to 1850) and its ending. An authoritative study of the literature on sunspots
(Judith Broady, The enigma of susnspots,  Floris Books, Edinburgh, 2002) concludes
"The verdict at present has to remain that neither climate nor solar variability are
suffcieintly well defined, either spatially or temporarily, nor their causes adequately
understood.  Increasing solar and human activity both contribute to global warming
but in what proportion is still unknown..... At the moment all we have is surmises and
it is pretty unlikely that we shallever stumble on four- or five-hundred year-old
reliable meterological records for the whole planet". (pp.171-172).

                                                         
                                                          

Tuesday 17 March 2015

the 150-year rise in world temperature

It is agreed that world temperatures have risen by some 1.8oC since about 1850,
which is also about the time recording instruments came widely into use. I think
in fact the start of the upward trend could be more correctly put at about 1900.
From then till about 1940 temperatures especially in the Arctic rose markedly,
after which there was a 30-year pause or decline until about 1970, when the
temperature rise began which gave rise to the current widespread concern
about warming.  It is hardly necessary to say that these dates are not exact
and that the start and end dates varied between countries and regions.
                                      The rise since about 1970 can therefore be seen as a
recovery from the exceptionally cold spell of the preceding 30 years, and the rise
from 1850 or 1900 can be seen as a recovery from the exceptional cold of the
Little Ice Age.  Far from being a hockey-stick picture of 1,000 or more years
of temperature stability followed by a steep upsurge in the twentieth century, the
picture is therefore one of continuous fluctuations.
                                       Hubert Lamb  (1913-1997) for long Britain*s leading
climatologist and founder in 1972 of the University of East Anglia*s  Centre
for Climate Research (later hi-jacked by the warmists)  wrote in Climate,
history and the modern world  (Methuen, 1982):
   The cooling of the Arctic since 1950-1960 has been most marked in the very
   same regions that experienced the strongest warming in the earlier decades of
   the present century, namely the central Arctic and the northernmost parts of the
   two great continents remote from the world*s oceans but also in the Norwegian-
   East Greenland sea. In some places e.g. the Franz Josef Land archipelago near
   80oN-60oE, the long-term temperature fell by 3-4 degrees C and the ten-year
   average temperatures became 6 to 10 degrees colder in the 1960s compared with
   the preceding decades.  It is clear from Icelandic oceanographic surveys that
   changes in the ocean currents have been involved, including a greatly (in the
   extreme case, ten times) increased flow of the East Greenland Current, bringing
   polar water southwards. It has in several years, especially 1968 and 1969 but also
   1955, 1975 and 1979 brought more Arctic sea ice to the coast of Iceland than for
   fifty years.  In April-May 1968 and 1969 the island was half surrounded by ice,
   as had not occurred since 1888.
                                       His next paragraph gives an idea of why some warming is
regarded as beneficial, not only in Greenland and Iceland but also in Scandinavia,
Scotland, Canada and Russia  In the first four cold has historically been associated
with famine and emigration.
   Such ice years have always been dreaded in Iceland*s history because of the
   depression of summer temperatures and the effect on farm production. In the
   1950s the mean temperatures of the summer half-year in Iceland had been 7.7
   degrees C and the average hay yield 4.3 tonnes/hectare. In the late 1960s with mean
   temperatures of 6.8 degrees the average hay yield was only 3 tonnes/hectare despite
   the use of more fertilisers. The temperature level was dangerously close to the point
   at which grass virtually ceases to grow. The country*s yield of potatoes was
   similarly reduced.  The 1960s also saw the abandonment of attempts at corn growing
  in Iceland which had been resumed in the warmer decades of the century after a lapse
  of some hundreds of years.
     Further discussion in the author*s THE GLOBAL WARMING DEBATE-  CAN 
SCIENCE PREVAIL?  published by Farsight Research, 1 Wetheral Court, Alston Road,
London SW17 OTS on21st April, 2015, price £18.