Climate skeptics have a new favourite argument - 'global warming
has stopped'. It's been popping up online for a while, and formed
the central point of
a fairly misleading article in the Mail on Sunday a week
ago.
Over the weekend the Sunday Times ran an effort to get to the
bottom of the meme, written by their Science and Environment Editor
Jonathan Leake. As well as concluding that global warming hasn't
'stopped', the piece is also interesting in providing an insight
into where these kind of Mail stories about global warming having
'stopped' are coming from.
Leake's article is titled '
So, do we freeze or fry?". He writes:
"Research based on Met Office figures
pointed to temperatures having been flat since 1997.
It was the kind of admission that those who doubt climate science
pounce on. "Forget global warming," trumpeted The Mail on Sunday,
because "the planet has not warmed in 15 years". It then cited
other research, into the declining energy output of the sun, to
suggest the real danger was from a big freeze"
And continues:
"Some scientists appear to be warning we
will fry, while other sources fear we will freeze. For the public
the outcome is, increasingly, confusion. Where might the truth
lie?"
It's worth pointing out that the Met Office responded to the
Mail on Sunday piece by David Rose on the day that it was written,
noting that it made 'numerous errors', and we wrote about it
here.
Temperature records show we're still
warming
Climate scientists agree that the global warming trend
continues, as a group of experts explained last week in a
letter to the Wall Street Journal:
"Climate experts know that the long-term
warming trend has not abated in the past decade. In fact, it was
the warmest decade on record. Observations show unequivocally that
our planet is getting hotter. And computer models have recently
shown that during periods when there is a smaller increase of
surface temperatures, warming is occurring elsewhere in the climate
system, typically in the deep ocean. Such periods are a relatively
common climate phenomenon, are consistent with our physical
understanding of how the climate system works, and certainly do not
invalidate our understanding of human-induced warming or the models
used to simulate that warming."
For his article Leake consults three records of global
temperature - the Met Office's HadCRUT3 dataset, NOAA's NCDC
dataset, and satellite data compiled by John Christie at the
University of Huntsville, Alabama.
It is Christie's satellite record that has shown the largest
increase this century, Leake notes:
"Oddly, given [Christie's] reputation as
a climate sceptic, he found the biggest rise of all.
'From 1997-2011 our data show a global temperature rise of 0.15C,'
he said
'What's more, our satellites have been taking this data since
1979, and over that period [the] global temperature has risen
0.46C, so the world has been getting warmer.'"
All three of these records show a small rise in temperature over
the last decade or so, leading Leake to the inevitable conclusion
that the world is warming. He concludes:
"Overall, then, the world has got
slightly warmer since 1997."
But, he asks,
"why has it warmed so much less than was
predicted by the climate models?"
This is a slightly odd question, as the current behaviour of
global temperatures is within expectations of many climate
modellers. Scientists explain that this is down to natural climate
variability masking the long-term warming trend, a point made in
the article by Peter Stott of the Met Office:
"For most climate scientists the answer
is simple. 'Fifteen years is just too short a period over which to
measure climate change,' said Peter Stott, head of climate
monitoring at the Met Office. 'The world undergoes natural
temperature changes on all kinds of time scales from daily
variations to seasonal ones. It also varies naturally from year to
year and decade to decade.'"
The research behind 'warming has stopped'
claims
Leake reveals that it was David Whitehouse, science editor at
the Global Warming Policy Foundation, who provided the analysis of
Met Office data which underpinned Rose's suggestion that 'the
planet has not warmed for the past 15 years'.
"Research based on Met Office figures
pointed to temperatures having been flat since 1997... [Dr
Whitehouse], it turns out, was a source of the research that
sparked the whole row.
'We set out to see how long it had been since the temperature had
risen, and 15 years was what emerged from the data set,' [Dr
Whitehouse] said. 'It raises serious questions about how the Met
Office models future climate.'"
This source of the analysis wasn't noted in the Mail article -
of which the Met Office said:
"This article includes numerous errors
in the reporting of published peer reviewed science undertaken by
the Met Office Hadley Centre and for Mr. Rose to suggest that the
latest global temperatures available show no warming in the last 15
years is entirely misleading."
As we have noted, looking at temperatures since only 1997 is the
kind of cherrypicking
that considers only a relatively short time period, over which
temperatures are known to be dominated by natural variation. This
can mask the overall global warming trend.
The Sunday Times article does appear to show that Dr Whitehouse
accepts that global warming has not 'stopped' -
"'The records do show that global
temperatures have risen by about 0.4C over the past three decades,
most of it in the 1990s,' [Whitehouse] said.
'I accept that CO2 is a greenhouse gas that might warm the world
but the key issue is how strong the effect is and how the data
compare with the models used to predict the future.'"
Leake writes:
"This is an interesting admission,
turning what had appeared to be an attack on the keystones of
climate science - that greenhouse gases cause global warming - into
a 'shades of grey' debate over whether global warming will happen
slowly and steadily or in jerks, accelerating in some decades but
then slowing or even reversing a little in others."
It's also worth pointing out that this admission rather
undermines the introductory headline to the Mail on Sunday piece,
which read: 'As the Met Office releases new figures which show no
warming in 15 years...', and also the line in the third paragraph
which states that the Met Office data 'confirms that the rising
trend in world temperatures ended in 1997.'
False balance on how sun will affect
climate
Leake's article also addresses how the sun might affect the
climate in the future in the context of man-made climate
change.
It's worth noting here that whilst there is ongoing research
into the sun's effect on climate, there is general agreement that
its impact will only be a small fraction compared to projected
man-made climate change.
Interestingly, the Sunday Times has
done a poor job on accurately representing the impact of
solar activity on climate change before. A 2010
review of the peer-reviewed research summarised the current
scientific understanding on the topic, concluding:
"...The predicted solar cycle‐related
surface temperature change is small relative to [man-made]
changes."
Since then two
more
peer-reviewed research papers have been published, both supporting
this conclusion. So although the Sunday Times presents this as an
area of great contention:
"...one of the key unresolved issues
lies in the behaviour of the sun, whose output appears to be
undergoing a steady but small decline. Most scientists accept that
this will reduce global warming. The debate is over just how strong
this effect will be, with people such as [Judith] Curry suggesting
it could be powerful while others see it as small."
...the considered scientific opinion appears considerably less
doubtful.