"Something is happening to our Sun. It has to do with sunspots, or rather the activity cycle their coming and going signifies. After a period of exceptionally high activity in the 20th century, our Sun has suddenly gone exceptionally quiet. Months have passed with no spots visible on its disc. We are at the end of one cycle of activity and astronomers are waiting for the sunspots to return and mark the start of the next, the so-called cycle 24. They have been waiting for a while now with no sign it's on its way any time soon."
He's right you know. Look at the decreasing sunspot count here (click the "sunspots" trend chart). Apparently Cycle 24 hasn't kicked off yet and is a year overdue.
"Looking back through sunspot records reveals many periods when the Sun's activity was high and low and in general they are related to warm and cool climatic periods. As well as the Little Ice Age, there was the weak Sun and the cold Iron Age, the active sun and the warm Bronze Age. Scientists cannot readily explain how the Sun's activity affects the Earth but it is an observational correlation that the Sun's moods have a climatic effect on the Earth."
Stand by for a Little Ice Age ? Bring back the Frost Fairs !
There seem to have been 18 sunspot minima periods in the last 8,000 years; studies indicate that the Sun currently spends up to a quarter of its time in these minima.
Oort Solar Minimum
(1010-1050) – temperature on Earth is colder than average.
Medieval Solar Maximum
(1075–1240) – coincides with Medieval Warm Period. Vikings from Norway and Iceland found settlements in Greenland and North America.
Wolf Solar Minimum
(1280–1340) – climate deterioration begins. Life gets harder in Greenland.
Spörer Solar Minimum
(1420-1530) – discovered by the analysis of radioactive carbon in tree rings that correlate with solar activity – colder weather. Greenland settlements abandoned.
Maunder Solar Minimum
(1645–1715) – coincident with the 'Little Ice Age'.
Dalton Solar Minimum
(1790–1820) – global temperatures are lower than average.
Modern Climate Optimum
(1890–2000) – the world is getting warmer. Concentrations of greenhouse gas increase. Solar activity increases.
2000- onwards - heat death or big freeze ?
While looking for more on sunspots I found this well-written Harry Eagar report in a Hawaii paper of a lecture by Jeff Kuhn.
IfA solar session out of this world
By HARRY EAGAR, Staff Writer
PUKALANI – Over decades of scanning changes in the sun, solar astronomers noticed that when there were few sunspots, the Earth was cold; and when there were many, the Earth was warmer.
Today is a time of many sunspots, so that might explain global warming.
Not so fast, says University of Hawaii solar astronomer Jeff Kuhn. You can also find a correlation between sunspots and the number of Republicans elected to the U.S. Senate.
“Ask to see the rest of the data,” Kuhn told an audience of about two dozen people Friday at the Advanced Technology Research Center of the Institute for Astronomy, where he is associate director.
The lecture, the second of a monthly series planned at the IfA’s new home at Kulamalu, was titled, “Why we really need to know how the sun works.”
The University of Hawaii’s Institute for Astronomy has been studying the sun from Mees Observatory for a long time, but why sunspots wax and wane on a fairly regular cycle of about 11 years; or why they sometimes disappear almost entirely are still mysteries.
Kuhn presented a capsule review of Earth’s climate history – which he said is not really known except for the past 2,000 years or so. Thanks to dust from Mongolia, which obscured the sun enough to let Chinese astronomers look at it with their naked eyes, we have a pretty good record of sunspots for the last 1,000 years, and they do correlate well with the ups and downs of Earth’s climate in recent centuries.
“Does the sun affect climate?” Kuhn asked. “Statistics aren’t enough.”
He also gave a capsule history of what is known about the sun’s behavior, the essence of which is that the sun has been getting hotter since the Earth formed – it is about 30 percent more luminous now that it was then.
Run that movie backward, and it becomes evident that so little warmth was reaching the Earth a long time ago that it should have iced up. But if it did do so, the increase intensity of solar radiation that occurred since those early millennia would not have been enough to melt the ice, Kuhn said.
The early history of Earth’s climate remains uncertain, but ice cores indicate that the last 10,000 years have been the most stable ever. In the previous interglacial (warm) period, temperatures swung wildly from hot to cold within less than a century.
The reasons for the dampening of climate swings are not understood, but the factors that affect the Earth-sun physical system are known: the luminosity of the sun, the albedo or reflectivity of the Earth, the emissivity (radiation) of the Earth’s atmosphere and the geometry of the Earth’s path around the sun.
The latter varies on time scales from a year to 100,000 years.
“We have to understand all of these,” said Kuhn.
Emissivity can be affected by ocean currents, which change as continents drift around on a time scale of tens of millions of years; or by the concentration of greenhouse gases in the atmosphere, which can change on long and short time scales.
The concentration of carbon dioxide has been increased by burning fossil fuels, although the added load was small until after World War II, Kuhn said. But the concentration has been higher in the past – maybe a thousand times higher. It has also been much lower during ice ages.
So the question is: What drives climate – those subtle changes in the geometry of the Earth’s relationship to the sun, or the small increase in carbon dioxide?
The GCMs (Global Circulation Models) used by the United Nations Intergovernmental Panel on Climate Change “do not reproduce these long-term changes” in the Earth-sun geometry, Kuhn said.
He was one of the advisers on a panel of the latest report (IPCC-4) who requested that the report take account of solar variance. The panel was controlled by two men, Kuhn said, who were committed to the view that carbon dioxide is the important component of temperature change, and IPCC-4 leaves out solar components.
“Does carbon dioxide explain temperature change?” Kuhn said. He said the short answer is no.
Glaciers are in retreat, and this is often cited (for example, by former Vice President Al Gore in “An Inconvenient Truth”) as evidence for the impact of carbon on climate.
Kuhn, however, has a pair of graphs that bring that theory into question. One shows when the glaciers began melting, and the other when the carbon dioxide began rising.
The melting began at least 80 years before the carbon buildup.
“It’s not caused by the carbon dioxide,” said Kuhn.
He said carbon dioxide levels have changed by 50 percent over 20,000 years, but climate has been remarkably stable, far more stable than during the previous interglacial period. The Earth is now in a warm interlude in a long Ice Age.
“This change (the warmer Earth era that coincides with the beginning of human civilization 10,000 years ago) wasn’t caused by carbon dioxide,” Kuhn said.
“It was caused by insolation.”
Insolation is the amount of solar radiation or energy received by the Earth.
Kuhn said a study of sea level changes reaches the same conclusion, that climate changes observed now are part of a long-term cycle in the relationship between sun and Earth. The models relied upon by the IPCC “should not be used to predict future climate changes,” he said.
“To change our economy on that basis would be wrong.”