Thursday, October 31, 2013

Brit Scientist Fears Return to 'Little Ice Age'

Real risk of a Maunder minimum 'Little Ice Age' says leading scientist
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.
Hendrick Avercamp - Enjoying Ice - ca 1630
But think of the skiing and skating!  Who cares if agricultural production falls.  Let 'em eat ice.
...According to Professor Lockwood the late 20th century was a period when the sun was unusually active and a so called ‘grand maximum’ occurred around 1985. Since then the sun has been getting quieter.

By looking back at certain isotopes in ice cores, he has been able to determine how active the sun has been over thousands of years. Following analysis of the data, Professor Lockwood believes solar activity is now falling more rapidly than at any time in the last 10,000 years. He found 24 different occasions in the last 10,000 years when the sun was in exactly the same state as it is now - and the present decline is faster than any of those 24.
I take such claims, that "X is increasing (or decreasing) at an unprecedented rate" with a large grain of salt.  Our knowledge of past climate pattern is almost entirely gathered with methods that give us rather crude estimates of the rate of change, low pass filters that tend to damp the rapidity of the signal.

Based on his findings he’s raised the risk of a new Maunder minimum from less than 10% just a few years ago to 25-30%. And a repeat of the Dalton solar minimum which occurred in the early 1800s, which also had its fair share of cold winters and poor summers, is, according to him, ‘more likely than not’ to happen.

Andreas Scheffelhout - Winter Landscape - ca 1840
Still, it's worth continuing research into the sun-climate connections.  We have historical evidence that periods of low solar activity (as defined by sunspot cycles), but we don't yet understand the causal connection.  The change in total solar irradiance is insufficient to account for more than a fraction of the observed climate swings, leading us to infer other mechanisms.  At this point, the leading contender would have to be the Svensmark Hypothesis, in which the solar magnetic field, which varies with the solar cycle, shields the earth from cosmic rays less during periods of low solar activity.  The cosmic rays, in turn, produce ions in the atmosphere that aid cloud formation, and cool the climate.  Preliminary tests of the hypothesis in cloud chambers confirm that it could be a factor.

Damn that Pleistocene; just when you get used to the climate, it changes again.

Previous posts on the solar activity/climate connection:

Solar Magnetic Activity Linked to Climate Via Cosmic Rays
Solar Breakdown - AAS Predicts Solar Minimum
CERN Head Censors Scientific Thinking
Dalton or Maunder?

No comments:

Post a Comment