IPCC draft report published online - suggests that the sun is not behind climate change
- 14 Dec 2012, 15:30
- Carbon Brief Staff
The argument that climate change is caused by solar activity has
been described by an Intergovernmental Panel on Climate Change
(IPCC) lead author as "completely ridiculous" and "exactly the
opposite" of what the draft IPCC report concludes, after a climate
skeptic blogger leaked a draft section of its next report onto the
internet. Climate skeptic bloggers have claimed the IPCC's new
report shows solar activity is causing global warming and the "jig
is up" on climate science. But a closer look indicates that this is
another case of cherry-picking.
The fifth version of the IPCC's report on the current state
of climate science is due to be published in 2014, but individual
parts of it are currently going through an involved
process of review. The most recent draft of Working Group 1 (WG I) -
which reports on the physical science of climate change - was
published on the internet yesterday.
WG I's reports deal with the scientific basis for climate change
- examining, for example, changing levels of greenhouse gases,
temperature changes in the atmosphere and the oceans and impacts
observed around the world, including melting glaciers, changes in
rainfall and the carbon cycle. The last version of this report had
nearly a thousand pages and the next one looks like it may be even
bigger.
The latest draft has just gone through an open
process of review. Anyone can sign up to be a reviewer, but
individuals accepted as reviewers are asked not to "cite, quote or
distribute" the draft reports. However, Alex Rawls, a climate
skeptic blogger who signed up to the process posted the draft onto his website
last night, arguing:
"...I regard [that the confidentiality
agreement is made irrelevant] by the systematic dishonesty of the
report... [in] the Second Order Draft ... the addition of one
single sentence demands the release of the whole. That sentence is
an astounding bit of honesty, a killing admission that completely
undercuts the main premise and the main conclusion of the full
report, revealing the fundamental dishonesty of the whole."
Rawls is talking about a section of the draft which discusses
the theory that solar activity is causing climate change, rather
than greenhouse gases from human activities.
Rawls has
previously written about this theory, and claims that the new
IPCC report supports it. Prominent skeptic website
Watts Up With That agrees, saying that the leak contains a
"game-changing admission".
Daily Telegraph blogger James Delingpole says "even the IPCC
admits the jig is up".
Solar down, temperature up?
The Australian website
Skeptical science has already done a good job at looking
at the argument that "it was the sun wot done it", so we'll be
brief.
A handful of scientific studies propose that high energy
particles from space, called galactic cosmic rays (GCRs), can
influence global temperature by helping to form clouds, which
reflect sunlight.
At times of low solar activity, the theory suggests that more
GCRs reach the atmosphere - causing more clouds to form, and
amplifying the cooling effect.
The theory goes that this also works the other way round - more
solar activity means less GCRs, fewer clouds and therefore even
more warming. Rawls suggests this means the increase in global
temperatures is due to GCRs, and not to human activity.
The leaked IPCC report acknowledges the studies suggesting this
link in the following paragraph:
"Many empirical relationships have been
reported between GCR or cosmogenic isotope archives and some
aspects of the climate system (e.g., Bond et al., 2001; Dengel et
al., 2009; Ram and Stolz, 1999). The forcing from changes in total
solar irradiance alone does not seem to account for these
observations, implying the existence of an amplifying mechanism
such as the hypothesized GCR-cloud link."
Rawls argues that this paragraph shows the IPCC agrees with his
belief that solar activity and GCRs play a far bigger role in the
climate than scientists previously thought.
But there are two problems with this theory. First, as Professor
Steve Sherwood, a lead author on the leaked report explained on ABC
last
night, only a small number of studies suggest the link between
solar activity and GCRs. Most other studies disagree. Professor
Sherwood told ABC:
"[T]here have been a couple of papers
suggesting that solar forcing affects climate through cosmic
ray/cloud interactions, but most of the literature on this shows
that that doesn't actually work."
What's more, this conclusion is stated in the leaked IPCC
report, just a few paragraphs later:
"Although there is some evidence that
ionization from cosmic rays may enhance aerosol nucleation in the
free troposphere, there is medium evidence and high agreement that
the cosmic ray-ionization mechanism is too weak to influence global
concentrations of CCN or their change over the last century or
during a solar cycle in any climatically significant
way."
When Sherwood was asked on ABC whether Rawls' argument was a
"case of cherry-picking a sentence", he replied:
"Yeah, it's a pretty severe case of
that, because even the sentence doesn't say what they say and
certainly if you look at the context, we're really saying the
opposite."
Second, for the theory to explain current temperature rise,
solar activity would have to be increasing now. As Skeptical
Science have noted, it isn't - solar activity has been slowly
decreasing since about 1980, and is in a period of low activity, as
the graph below shows.
Were the GCR theory right, this should be having a cooling
effect at the moment - and wouldn't explain current global
temperature rise.
Solar activity has decreased over the last three decades, as
global temperature has continued to rise. Source:
Skeptical Science
Rawls suggests that global temperatures are showing a delayed
response to an increase in solar activity in the early 20th
century. But this argument makes "no physical sense", says
Skeptical Science, since the graph above shows that fluctuations in
solar activity are reflected in global temperature fairly
quickly.
The draft IPCC report makes the point clearly that while the sun
does have a small influence on earth's climate, scientists are
confident that by comparison it is a "small fraction of the
anthropogenic forcing". This echoes the last IPCC report from 2007,
from which the chart below is taken. The bottom two bars suggest
that all known effects of solar activity are minor compared to all
human impacts (in the top box).
Source:
IPCC 4th Assessment Report (AR4) 2007
What will the media say?
As far as we can see, the leaked IPCC report doesn't show that
the "jig is up" for climate science. In fact, a quick scan of the
1000 or so pages suggests that when it is finally published next
year, many of the conclusions of the report will be fairly familiar
to those who have read the last report from 2007.
If anything, it looks like the new draft firms up many of the
top line conclusions, although there are likely to be some
important differences - that is, after all, why this process has
been repeated five times.
Of course, that the section on solar activity doesn't actually
demonstrate what skeptics have said it does might not stop stories
about the sun causing climate change. Newspapers which take a line
that global warming isn't as bad as politicians think often find
such stories too tempting to ignore.
We'll see. It is worth noting that a piece arguing that solar
activity is leading to recent global warming might be difficult to
reconcile with
stories which argue that a decrease in solar activity is
causing global cooling, and may be about to lead the world into a
mini ice age.
Here we are again
Finally,
it's not the first time that an IPCC report has been leaked.
Given the IPCC review process, which makes the draft text available
to anyone who is interested, it probably won't be the last.
Some, including
Andy Revkin at the New York Times, argue that this exposes
weaknesses in the IPCC process. It's hard to avoid the conclusion
that the slow pace of the IPCC leaves it unsuited to a media
environment where information is ever-more freely available, open
access to scientific information is a burgeoning phenomena, and
embargoes are less solid than they used to be. Professor Piers
Forster of Leeds university
sums up well in his quote to the Guardian:
"Although this may seem like a 'leak',
the draft IPCC reports are not kept secret and the review process
is open. The rationale in not disseminating the findings until the
final version is complete, is to try and iron out all the errors
and inconsistencies which might be inadvertently included.
Personally, I would be happy if the whole IPCC process were even
more open and public, and I think we as scientists need to explore
how we can best match the development of measured critical
arguments with those of the Twitter generation."
Updated 4.46pm - An earlier version incorrectly attributed
the final quote.