According to a new book "Unstoppable Global Warming - Every 1500 Years", human activities are not responsible for the currently observed warming of the Earth, but a natural cycle linked to the output of the Sun, which operates over a period of 1,500 (plus or minus 500) years. We can expect the current warming trend to last for around another 200 years of the present cycle. The book by climate physicist Fred Singer and Hudson Institute economist Dennis Avery, is bound to prove controversial. I note that Fred Singer is "emeritus", which is academic speak for "retired", otherwise he might have too much to lose by voicing such heretical views in the current climate of Kyoto and targets of essential cuts in CO2 emissions that must be met (a staggering 80% by 2030) in order to "save the planet". In their "consensus" he could expect the scientific "community", on whose evidence Kyoto is based, to turn on him in fury, and that would be the end of his "peer reviewed" research funding... for good! Such things do happen in science... believe it or not. Along with other global warming "deniers" the present authors are emphatic in pointing out that reversing current trends in CO2 emissions will cost a fortune, and if there is no necessity to so act, humankind will be dealt a considerable economic dis-service by implementing wholesale nuclear power, "burying" CO2 in aquifers, in used oil-wells and at the bottom of the sea etc., along with other potentially catastrophic schemes of "geoengineering", when the money could be spent on strategies of sustainability, which, global warming or not, we must find in order to survive, certainly in those years beyond the imminent peak in world oil production. Although he didn't refer to peak oil, but voiced essentially the same argument on a cost-for-cost basis, that it may prove more expedient in terms of resources to plan for global warming, e.g. by shoring-up sea defenses, rather than making wholesale life-infrastructure changes to eliminate CO2 emissions as far as possible, in his book "The Skeptical Environmentalist: Measuring the Real State of the World", there were calls (a petition I believe) that Bjorn Lomberg should be ousted from his academic post. One is reminded of poor Galileo, who by relenting his opinions managed to preserve himself from a sentence of death, to serve a commuted life-term of house-arrest, so long as he kept quiet that the Earth was not the centre of the universe, but the Sun. Being "fired" was a more permanent affair for non-believers in the middle ages, as tied to a wooden stake. Anger has relented against Lomberg, and his book is now regarded as an acceptable work of scholarship in political science, not an anti-global warming manifesto!
Accordingly, Singer and Avery would need to garner meticulous evidence to support their claim for a 1,500 year "natural" cooling-warming cycle, and indeed it would seem they have done so. Their supporting documentation encompasses records from ancient Rome, Egypt and China; paintings housed in museums painted 12,000 years ago; tooth enamel from Viking cemeteries; analyses using the most modern technology made of ice-cores, seafloor sediments, tree rings, fossilised pollen and cave stalagmites (the ones that grow "up"!).
Singer points out that the first clue to the 1,500 year cycle came only recently, when the first cores were sampled from the Greenland ice-sheet in 1983. The cycle was too long to have been picked-up by earlier peoples without access to accurate thermometers and precise, written records. The Greenland ice-core samples show the 1,500 year cycle undulating back through a period of 250,000 years, which raises temperatures at the latitude of New York and Paris by 1 - 2 degrees C for centuries at a time, and even more at the North and South Poles, with a global average of around 0.5 degrees C. In 1987, analysis of the first Antarctic ice-core samples confirmed that the cycle extended further back, and to at least 400,000 years, spanning four ice-ages and that the effect was indeed a global phenomenon. Evidence from the undersea sediments from all six oceans, in tree ring samples taken from the northern hemisphere, in the advance and retreat of glaciers both north and south, from Greenland to New Zealand, and in stalagmites taken from every continent, including southern Africa. Pollen samples show a complete reorganisation of North America's trees and other plants over the past 14,000 years, which works out to one such change every 1,650 years. The deepest seabed sediment cores show that the cycle has been operating for at least the past million years.
So, what exactly is the cause? Observations of sunspots made over the last 400 years, along with more recent analyses of carbon and beryllium isotopes, seem to connect the cycle to variations in the Sun's radiant output (energy), as recently detected by satellite measurements. Antarctic ice samples show that there is a close correlation between temperatures and CO2 levels over the past 400,000 years, which is usually taken to imply that increased CO2 levels cause global warming. However, on closer inspection, the studies show that there is actually a lag of around 800 years between the increase in temperature and that in atmospheric CO2 concentrations. So, the heating comes first, and then the CO2 levels rise. This, say Singer and Avery, makes sense because as the oceans warm, they will release some of the CO2 which is dissolved in them into the surrounding air.
The notion of natural cycles runs counter to majority currently perceived beliefs about global warming, i.e. those that place the burden of blame squarely on the shoulders of (selfish, greedy, careless!) humankind. If the warming does indeed come first to release more CO2, we may still be in for a shock, as the greenhouse-legacy of this blanketing gas subsequently heats the Earth further still, and compounds any effects of a natural warming trend. No one knows for sure. However, such natural cycles of heating and cooling must surely be taken into account in any serious models of what the world's climate is likely to be in 50, 100 or more years hence; the predictions from which are now being used to determine or justify government policies about the future of the human race.