Does the BBC really have to keep presenting climate science as 'believers' versus 'skeptics'?
- 06 Jul 2012, 12:00
- Verity Payne
A couple of weeks ago Telegraph blogger and climate skeptic
James Delingpole and Friends of the Earth head of campaigns Andrew
Pendleton went
head to head on the BBC's Daily Politics show. Now, they're
debating how global surface temperature has changed over the last
couple of decades in a post on Daily Politics presenter Andrew Neil's
blog.
What to make of this? Last year's BBC Trust review of the
Corporation's science coverage concluded that as there is an agreed
factbase about climate science, this should be reflected in
reporting. BBC programmes sometimes give minority skeptic opinions
"undue place", creating "false balance", the report said, with
examples of programmes "giving equal coverage to the views of a
determined but deluded minority and to those of a united but less
insistent majority".
Andrew Neil is clearly
sympathetic to climate skeptic arguments - although he stops
short of declaring his own views. He presents the blog post as a
discussion of one of the "great claims" of climate skeptics about
climate science - that global temperatures stopped rising in
1995.
But in doing so, he frames acceptance of the existence of man-made
global warming as a matter of belief - "Those who believe in
man-made global warming, like FoE," - and presents the matter as a
tussle over two competing theories - that temperature rise has
stopped, or that it hasn't.
But scientists don't believe that global temperatures have
'stopped rising'. So is this another case of false balance? We take
a close look at what both Pendleton and Delingpole have to say on
the issue.
Pendleton: Global warming has not stopped
Pendleton starts off with a graph showing the global surface
temperature trend over the last 130 years. We provide a more up to
date version (including 2011 temperatures), that also extends a
little further back in time:
Pendleton says:
"The data in the graph is important for
three reasons.
First: it shows a long term warming
trend - and quite a dramatic one - beginning in the early 20th
century and, evidently, still underway. Second: it shows how four
separate data sets reach broadly the same conclusion. And third: it
shows how much fluctuation there is from year-to-year and, in fact,
from decade-decade."
These are fair points. The average global surface temperature
has increased by around 0.8 degrees Celsius since the start of the
20th century, and there is considerable year to year variability in
global surface temperature, caused by natural variations in things
like the ENSO cycle and solar activity along with aerosol
production from natural processes and human activity.
Pendleton then quotes UCL climate science Professor Chris
Rapley:
"No climate scientist ever stated or
expected the global average temperature to rise as a smooth curve.
If you look back over the data for the last 100 years rather than
just cherry-picking a short [in climate terms] period, the
fluctuations are very clearly evident. But so is the upward trend,
especially of the last 40 years."
Again, this is true, and is echoed by other scientists,
including Met Office scientist Professor Richard
Betts:
"No matter how many times we say that
"global warming" means a rise of average temperature across the
world, decade by decade, and not every year being consistently
warmer than the last in every place on Earth, there are still those
that get this mixed up."
Pendleton then moves on to the stats, pointing out that Bob Ward
and his team at the Grantham Research Institute on Climate Change
and the Environment have a
useful blog explaining that the current hiatus in surface
temperature warming is not unusual.
This is because there are natural variations in the climate, so to
pick out the long-term temperature increase arising from greenhouse
gas emissions we have to examine longer periods of time. The
following table (from the blog) shows that there have been many
other 15 year periods over the last four decades with no
statistically significant warming.
Researchers in the US looking at
every possible linear temperature trend (longer than two years)
for the available surface temperature record found:
"Since 1945, all periods longer than 22
years indicate warming [...] In contrast, changes shorter than a
few decades can be either positive or negative. The recent cooling
trend is evident in the global record beginning in 2001. Such
changes, however, are not statistically significant and are in fact
relatively common in the historical record."
Modelling research suggests that we will probably see similar
periods that don't
show a significant warming trend in the future, although as the
warming trend increases over the coming century, such cooling
periods will probably occur less frequently.
Pendleton goes on:
"A further complicating factor is that
while the long-term trend is clear, part of the explanation for the
fluctuations over the short term is that the energy from the sun is
stored in different places - the land, the oceans and the
atmosphere."
True. Global surface temperature is actually quite a small
component of the climate system. Global warming results from an
energy imbalance in the climate system, where more heat energy is
entering than escaping the atmosphere. The oceans account for over
90
per cent of the warming to the climate system since 1955, with
the atmosphere, the continents and melting ice accounting for the
rest.
Research shows that the world's oceans have warmed over
the last 50 years, and probably even
since the late 19th or early 20th century. About two-thirds
of the heat going into the oceans is taken down and stored in the
deep ocean, below 700 metres depth.
"In a nutshell. the simple answer to the
question posed on the programme and to the challenge by Andrew Neil
is 'no, global warming has not stopped.'"
So while surface warming has been slower in recent years, heat
has still been going into the system - the world is still
warming.
Delingpole: No warming since 1995 is "grossly
misleading"
Delingpole sets up an interesting contradiction in his submission
to the blog. He begins by saying that arguing there's been "no
warming since 1995/1998" is "quite useful" - it's certainly an
argument he's
used
frequently
in the past.
But he then argues that you can't trust the temperature data
anyway:
"It presupposes that the temperature
data sets maintained and quoted by the climate alarmist
establishment are reliable and trustworthy. But they're not: they
have been subject to "adjustments" by scientists who, as we saw in
the Climategate emails, have political motivations and a financial
vested interest in exaggerating the extent of 'global
warming'."
In fact the adjustments made to global temperature records are
to remove any artificial bias in local temperature records from
phenomena such as the urban heat island effect - where built-up,
urban areas tend to be warmer than the surrounding
countryside.
Aside from the scientists at the University of East Anglia, three
other main groups produce independent records of surface
temperature. There are also two satellite records of lower
atmospheric temperature, which show a very similar global
temperature trend. Finally, a group of scientists reanalysed
temperature data in the
BEST study, and came to similar conclusions to all of the other
research groups.
Delingpole also argues that temperature differences over recent
years are too small to really assess:
"The differences in temperature are
often by as little as 1/100th of a degree. [...] We are in the
realm, here, of angels dancing on the head of a pin."
We can rephrase this: temperatures over the last decade are all
roughly as warm as each other. But this doesn't mean that warming
has stopped, as Betts explains:
"The last decade was the warmest on
record, followed by the 1990s and then the 1980s, so the world is
definitely warming up."
He goes on:
"Funny, isn't it, how most of the
significant "anomalous" warming "detected" by NASA in recent years
(notably 2010) were in those parts of the world where there are no
weather stations?"
Some of the biggest warming trends in recent years has been in
the Arctic - which is warming
at about twice the rate of the rest of the globe as
loss of sea ice means the Arctic ocean absorbs more heat
energy. There are fewer weather stations in the Arctic than in more
populated areas of the globe, but it
isn't true that there aren't any.
Delingpole continues:
"Since 1850 the world has been emerging
from the Little Ice Age. Of course decades at the top of that
gentle warming trend (of about 0.8 degrees C) are going to be, on
average, warmer than those at the bottom."
The suggested causes of the Little Ice Age - low solar activity
and/or pronounced volcanic activity - are not currently happening.
Solar activity has been declining since the mid 20th century whilst
the world's average surface temperature has risen. So the current
warming is not likely to be a recovery from the Little Ice
Age.
Delingpole finishes with:
"What we CAN say is this. AGW theory is
predicated on the idea that there is a strong correlation between
man-made CO2 output and global warming. But while in the last
decade - thanks largely to China - CO2 levels have continued to
rise dramatically, world temperatures most definitely have not.
This suggests that there are more, many more, things responsible
for climate than CO2 levels. Such as - duh - the activity of the
sun."
The problem with this argument is that if you remove the effects
of short-term climate drivers, such as solar activity, aerosols,
and ENSO, from the global surface temperature record, you are left
with a pretty steady warming trend over the last thirty years, as
demonstrated in
research from last year:
In summary, as you might expect, Delingpole's account bears little
relation to what the scientific community says, while Pendleton is
basically repeating things that climate scientists have
concluded.
Clearly neither Pendleton nor Delingpole are climate scientists.
Perhaps appropriately for appearing on the Daily Politics, they
both have very different views on what climate policy should be. As
the BBC Trust review points out, on climate "Where policy is
concerned, the argument is far from resolved. Science can inform
the debate, but policy implications of global warming remain a
legitimate part of the news agenda."
But this is a discussion of the science of climate change, not
politics or policies. So it leaves the question - if the Daily
Politics wants to discuss the science of climate change, why
doesn't it turn to climate scientists?