The Little Ice Age, following the historically warm temperatures of the Medieval Warm Period, which lasted from about AD 950 to 1250, has been attributed to natural cycles in solar activity, particularly sunspots. A period of sharply lower sunspot activity known as the Wolf Minimum began in 1280 and persisted for 70 years until 1350. That was followed by a period of even lower sunspot activity that lasted 90 years from 1460 to 1550 known as the Sporer Minimum. During the period 1645 to 1715, the low point of the Little Ice Age, the number of sunspots declined to zero for the entire time. This is known as the Maunder Minimum, named after English astronomer Walter Maunder. That was followed by the Dalton Minimum from 1790 to 1830, another period of well below normal sunspot activity.
The increase in global temperatures since the late 19th century just reflects the end of the Little Ice Age. The global temperature trends since then have followed not rising CO2 trends but the ocean temperature cycles of the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). Every 20 to 30 years, the much colder water near the bottom of the oceans cycles up to the top, where it has a slight cooling effect on global temperatures until the sun warms that water. That warmed water then contributes to slightly warmer global temperatures, until the next churning cycle.
Those ocean temperature cycles, and the continued recovery from the Little Ice Age, are primarily why global temperatures rose from 1915 until 1945, when CO2 emissions were much lower than in recent years. The change to a cold ocean temperature cycle, primarily the PDO, is the main reason that global temperatures declined from 1945 until the late 1970s, despite the soaring CO2 emissions during that time from the postwar industrialization spreading across the globe. At first the current stall out of global warming was due to the ocean cycles turning back to cold. But something much more ominous has developed over this period. Sunspots run in 11 year short term cycles, with longer cyclical trends of 90 and even 200 years. The number of sunspots declined substantially in the last 11 year cycle, after flattening out over the previous 20 years. But in the current cycle, sunspot activity has collapsed. NASA’s Science News report for January 8, 2013 states,“Indeed, the sun could be on the threshold of a mini-Maunder event right now. Ongoing Solar Cycle 24 [the current short term 11 year cycle] is the weakest in more than 50 years. Moreover, there is (controversial) evidence of a long-term weakening trend in the magnetic field strength of sunspots. Matt Penn and William Livingston of the National Solar Observatory predict that by the time Solar Cycle 25 arrives, magnetic fields on the sun will be so weak that few if any sunspots will be formed. Independent lines of research involving helioseismology and surface polar fields tend to support their conclusion.”
That is even more significant because NASA’s climate science has been controlled for years by global warming hysteric James Hansen, who recently announced his retirement. But this same concern is increasingly being echoed worldwide.
The Voice of Russia reported on April 22, 2013,
“Global warming which has been the subject of so many discussions in recent years, may give way to global cooling. According to scientists from the Pulkovo Observatory in St.Petersburg, solar activity is waning, so the average yearly temperature will begin to decline as well. Scientists from Britain and the US chime in saying that forecasts for global cooling are far from groundless.” That report quoted Yuri Nagovitsyn of the Pulkovo Observatory saying, “Evidently, solar activity is on the decrease. The 11-year cycle doesn’t bring about considerable climate change – only 1-2%. The impact of the 200-year cycle is greater – up to 50%. In this respect, we could be in for a cooling period that lasts 200-250 years.” In other words, another Little Ice Age.