David Archibald has an interesting post at Watts Up With That titled: Premonitions of the Fall (in temperature). The part that most intrigued me was the discussion of the research by Libby and Pandolfi who based their forecast of long term cooling on Kings Canyon tree rings. David suggests it was the most successful current predictions of a potential long term cooling period.
The most successful prediction of the current minimum, in terms of lead time and detail, was made by two researchers in the US later that decade. Using tree ring data from redwoods in Kings Canyon in California, in 1979 Libby and Pandolfi forecast that, “by running this function into the future we have made a prediction of the climate to be expected in King’s Canyon; the prediction is that the climate will continue to deteriorate on the average, but that after our present cooling-off of more than the average decay in climate, there will be a temporary warming up followed by a greater rate of cooling-off.”
In a Los Angeles Times interview, Libby and Pandolfi gave a more detailed forecast:
“The forecast is for continued cool weather all over the Earth through the mid-1980s, with a global warming trend setting in thereafter for the rest of the century – followed by a severe cold snap that might well last through the first half of the 21st century.”
“Both the isotope record and the thermometer record show neat agreement for the cold decades at the ends of the 17th and 18th centuries, when temperatures fell by 1-10th to 2-10ths of a degree.”
“More recently, the world has enjoyed an agricultural boom during the past 70 years or so. The Earth’s annual average temperature has risen by about 1 to 1½ degrees, about as much of an increase as the decrease during the Little Ice Ages, during this interval.
When she and Pandolfi project their curves into the future, they show lower average temperatures from now thorugh the mid-1980s. “Then,” Dr. Libby added, “we see a warming trend (by about a quarter of 1 degree Fahrenheit) globally to around the year 2000. And then it will get really cold – if we believe our projections. This has to be tested.”
How cold? “Easily one or two degrees,” she replied, “and maybe even three or four degrees.”
The remarkable thing about the Libby and Pandolfi prediction is that they got the fine detail right, up to the current day, which gives a lot of credence to their projection for the next fifty years.
You can read the rest of the article HERE. It has some other interesting projections, including this one:
A Finnish tree ring study (http://lustiag.pp.fi/holocene_trends1000_INQUA.pdf) followed in 2007 – Timonen et al. This is a portion of a figure from that study showing a forecast cold period starting about 2015 that is deeper and broader than any cold period in the previous 500 years: