Climate scientists don’t think we’re heading for another "Little Ice Age"
- 29 Oct 2013, 17:00
- Roz Pidcock
From time to time, we're told by parts of the media that earth
is headed for another 'little ice age'. Today was the turn of The
Daily Express, in an
article urging us to "get ready" for erratic and extreme
weather in the UK.
The paper claims experts warn Britain "faces a new mini-Ice Age
with decades of severe Siberian winters and washout summers". But
the scientist the paper cites tells us he feels "very
The piece is loosely based on comments made by Professor Mike
Lockwood from the University of Reading to BBC weatherman Paul
Hudson for last night's
Inside Out programme.
The BBC programme looks back over recent cold winters in the UK
and opens with the claim, "Scientists are warning that we could be
heading towards a mini-ice age".
Hudson wrote up his take on the interview
"It's known by climatologists as the
'Little Ice Age', a period in the 1600s when harsh winters across
the UK and Europe were often severe. The severe cold went hand
in hand with an exceptionally inactive sun, and was called the
Maunder solar minimum.
Now a leading scientist from Reading University has told me that
the current rate of decline in solar activity is such that there's
a real risk of seeing a return of such conditions."
Having spoken with Professor Lockwood, it's clear he isn't
warning of a "new mini-ice age." He tells us a decline in solar
activity would have "nothing more than a minor effect" on
Both the BBC programme and the Express focus on a period
beginning in the late 17th Century in which the sun went through a
period of prolonged low
solar activity - known as the Maunder Minimum.
This period of low solar activity lasted for around 70 years,
and coincided with the beginning of what's known as the
Little Ice Age (LIA), when parts of the northern hemisphere
cooled by as much as two
25 to 30 per cent chance
Could we see another period of particularly low solar activity?
As well as rising and falling on an 11-year cycle,
scientists know the sun's activity has been in
decline since about 1985.
paper from 2010, Lockwood put the chances of seeing a return to
a Maunder Minimum-style low in solar activity in the next 50 years
eight per cent. But a particularly fast decline in solar output
in the last few years means he now thinks it's more like a 25 to 30
per cent chance, he told the BBC's Inside Out programme.
Does this mean we're on course for a return to Little Ice Age
conditions? Lockwood tells us he "could not have been clearer" in
the interview that the answer is a resounding no.
Nevertheless, to varying degrees, this is something both the BBC
blog post and The Express suggest. Warning of an imminent ice age
perennial story. But there are two reasons why it isn't really
on the cards.
The sun is not the only factor
The latest IPCC report, published last month,
explains that the Maunder Minimum was only
one factor in bringing about the LIA.
It may turn out that the onset of the LIA was more
closely linked to unusually intense volcanic activity and
interactions between sea ice and ocean currents during the
At a recent
conference, scientists explained how a major atmospheric
circulation known as the North Atlantic Oscillation (NAO)
was in a negative phase at the onset of the LIA, which amplified
the cooling effect of a reduction
in solar irradiance and volcanic activity.
This, in turn, affected the distribution of sea ice in the
Arctic and disrupted a major ocean circulation that distributes
heat across the globe, known as the Atlantic Meridional Overturning
So a fall in temperature to rival the LIA would need more than a
drop in solar activity.
Bigger human influence
Perhaps more importantly, even if we did see a return to a
Maunder-style low in solar activity, earth's climate is very
different now from how it was in the 17th century.
In a paper
from 2012, Lockwood and colleagues modelled the expected
temperature drop over the 21st century due to waning solar activity
- and they found that the change is likely to be dwarfed by the
much bigger warming effect of greenhouse gases in the
The paper says:
"[T]he likely reduction in the warming
by 2100 is found to be between 0.06 and 0.1 [degrees Celsius], a
very small fraction of the projected anthropogenic warming."
paper from 2010 by Stefan Rahmstorf and Georg Feulner comes up
with a slightly higher estimate, but still "no more than [a drop
of] 0.3 degrees Celsius in the year 2100".
That would be significant, but on the other hand we've already
seen 0.85 degrees of human-caused warming over the industrial
period, with more to come.
recent report [Chp 8, page 34] says:
"[E]ven if there is such decrease in the
solar activity, there is a high confidence that the Total Solar
Irradiance (TSI) variations will be much smaller in magnitude than
the projected increased forcing due to GHG."
So a less active sun could have a small but noticeable cooling
effect on earth's temperature - but only if greenhouse gases
weren't having a much bigger warming influence.
The BBC piece includes the caveat that "most scientists believe
long term global warming hasn't gone away. Any global cooling
caused by this natural phenomenon would ultimately be temporary,
and if projections are correct, the long term warming caused by
carbon dioxide and other greenhouse gases would eventually swamp
this solar-driven cooling."
But it also claims that "global temperatures may fall enough,
albeit temporarily, to eliminate much of the warming which has
occurred since the 1950s."
While we're not on course to see a return to Little Ice Age
conditions globally, there is some evidence of a regional effect of
low solar activity in the UK.
Research by Lockwood and colleagues suggests colder than
average winters in the UK occur more commonly during low solar
activity. He tells the BBC programme:
"We think lower solar activity does seem
to tie up with more cold winters in central Europe and the UK."
Lockwood's paper proposed a few possible mechanisms, but the
authors are careful to stress that "this is a regional and seasonal
effect relating to European winters and not a global effect."
Lockwood describes the effect as a "redistribution of
temperature around the Northern hemisphere, not a global
The weather we get in the UK and northern Europe is already
influenced by a number of factors. So the effect of a drop in solar
activity could be hard to disentangle from the natural swings in
temperature from one year to the next. It's a very complicated
picture - take
emerging research suggesting Arctic sea ice loss could be
increasing the chances of cold winters, for example.
Irrespective, it's clear from speaking to Professor Lockwood
that he doesn't think a decline in solar activity would push us
into a mini ice age, given the current backdrop of human-induced