Did volcanic activity trigger the Little Ice Age?

14 Apr 2012

This post can be found at http://wattsupwiththat.com/2012/04/12/trigger-for-little-ice-age-a-half-... is taken from the blog of Roger Pielke Sr and refers to a paper in the Geophysical Review Letters 39, L02708, doi:10.1029/2011 GL050168 by Miller et al. Miller and pals claim a half century of volcanism initiated a chill lasting half a millennium - is this possible?

Ice cap growth in Arctic Canada and Iceland can be used to show Little Ice Age summer cold and ice growth - and it began abruptly between 1275 and 1300AD. I intensified between 1430 to 1455AD. Intervals of sudden ice growth appear to coincide with volcanic activity - that is the basic focus of the paper. In addition, cold summer are then maintained, it is alleged, by sea-ice/ocean feedbacks long after volcanic aerosols are dissipated from the atmosphere (an assumption, it seems, and one that commenters are wary of accepting). Miller and pals claim large changes in solar irradiance are not necessary - are the CAGW advocates reacting against the likes of Scafetta? One commenter, at 8.48am, is obviously sceptical as he claims Miller gets his dates from C14 in plants from beneath receding ice margins on Baffin Island. The kill dates cluster between 1275 and 1300 and a second cluster around 1450 suggesting this region was ice free before both dates - which is not the aim of the paper. The next commenter asks, 'does this mean the Maunder and Dalton Minimums didn't happen? while at 9.00am Crispin from Johannesburg says the fact that parts of Iceland, Greenland and Newfoundland were warmer prior to 1300 also suggests the warmth had an effect on permafrost in so much as these frozen bogs are not necessarily permanent and may contain amounts of relatively recent vegetation. CAGW alarmists consistently avoid mentioning what is revealed by retreating ice and glaciers in the modern world -they want permafrost as permanent, not as something that freezes and de-freezes on ocassion (or the topmost layers). A comment at 9.15am asks - if the solar minimum across LIA was irrelevant or could it perhaps trigger the volcanism? According to the person at 9.20am Reid Bryson was saying volcanoes influenced global temperatures way back in the 1970s. No one appears to have quoted Mike Baillie or his book, New Light on the Black Death: The Cosmic Connection (Tempus:2006). Baillie has the big change soemwhat later than 1300 - a massive injection of co2 around 1320 to 1330 which may have an origin in an ocean turnover event - a release of oceanic co2? Miller and pals say the cold followed on from four volcanoes with a high sulphur content. Baillie agrees as he has a tree ring downturn between 1292 to 1295 that he says shows up in different parts of the world. This coincides with reports of fireballs, lightning and meteors. In 1297 there was a year with anomalous wide rings in California hinting at forest fire ensuring rapid growth due to tree having more space and light and fertilised by the ash and carbon of burnt vegetation. It seems that Miller et al see volcanoes whereas Baillie sees meteoric fireworks. Miller et al see volcanoes as temporary cooling events and therefore the ocean also played a role whereas Baillie is locked into the Clube and Napier model in which the orbit of the earth, during the LIA, periodically encountered cosmic dust left behind by the passage of comets (in the past) and a prolonged cold spell developed - but the LIA was not universally cold. It was intespersed by warm periods. For example, what is known as the Little Medieval Warm Period during the Tudor era.