Graph of the Day: What if the Sun Goes into another Maunder Minimum?
June 16, 2011
By now, you’ve probably heard the news. The sun is going cold, and all that talk about global warming was just a fad, just like Glenn Beck always said. And by the way, scientists say we’re going into a new ice age. It’s a climate crock I’ve treated before.
Now, Fox News and others are spinning reports about recent model predictions of low solar activity.
What do the actual scientists who did the work say?
Something considerably less dramatic, according to Reuters:
“…..contrary to some media reports, this does not mean a new Ice Age is coming, Frank Hill of the National Solar Observatory said in a telephone interview.
“We have not predicted a Little Ice Age,” Hill said, speaking from an astronomical meeting in New Mexico. “We have predicted something going on with the Sun.”
Scientists are in no doubt that the sun has been acting oddly in recent years. Sunspot numbers ebb and flow in cycles lasting around 11 years but over the past three years, observable sunspots have been mostly missing.
These spots have been used by scientists to indicate the sun’s magnetic activity is diminishing, and that the sun may even be shrinking. Since 2007, visible sunspot activity has stalled, leading researchers to suggest that the next solar maximum (due in 2013) could be a long while coming. Instead, the sun could go into a prolonged lulllasting several decades.
Ordinarily, its activity varies over about 11 years, but since 2007 it seems to have stalled.
This week a string of researchers presented new data showing that the sun still isn’t perking up. That means, rather than having a solar maximum in 2013, we might not see one for a long time. Instead, the sun could go into a prolonged lull lasting several decades.
This has happened before, the most famous example being the Maunder Minimum of 1645-1715 when the sun became less luminous than normal and hardly any sunspots were seen on its surface. There is plenty of evidence that such “grand minima” cool the Earth: it’s one of the more dramatic effects the sun’s changing activity can have on our climate. The Maunder Minimum itself is widely linked to the Little Ice Age.
Here’s where the story lurches away from reality. According to the Global Warming Policy Foundation (of whom more here), the sun’s shutdown means that
The Earth – far from facing a global warming problem – is actually headed into a mini ice age.
There’s a simple problem with this claim. Let’s assume that grand minima really do cool Earth’s climate: not every climate scientist is convinced of that, but for the sake of argument let’s go with it. Now the question becomes: how much do they cool it, and for how long?
The straightforward answer is: not enough. Last year researchers modelled what would happen to global temperatures if a grand minimum started now and continued until 2100. They found that it would lower temperatures by 0.3 °C at most.
Scientists have been studying and remarking on the sun’s peculiar behavior for years, and as long ago as 2009, NASA scientists wrote:
Solar irradiance: The solar output remains low (Fig. 4), at the lowest level in the period since satellite measurements began in the late 1970s, and the time since the prior solar minimum is already 12 years, two years longer than the prior two cycles. This has led some people to speculate that we may be entering a “Maunder Minimum” situation, a period of reduced irradiance that could last for decades. Most solar physicists expect the irradiance to begin to pick up in the next several months — there are indications, from the polarity of the few recent sunspots, that the new cycle is beginning.
However, let’s assume that the solar irradiance does not recover. In that case, the negative forcing, relative to the mean solar irradiance is equivalent to seven years of CO2 increase at current growth rates. So do not look for a new “Little Ice Age” in any case.
NASA’s take was born out, as, even in the midst of the lowest solar minimum in a century, 2009, and 2010, were, respectively, the number 2, and number one warmest years in NASA’s instrumental record globally.
The possibility of imminent solar dormancy was raised by reports from the ongoing American Astronomical Society meeting of fading sunspots and dips in the sun’s magnetic patterns. Those are considered portents of solar inactivity, suggesting that the next solar minimum — a natural downturn in activity — would be especially pronounced, perhaps lasting for decades.
When that last happened, between the mid-17th and early 18th centuries, northern Europe experienced a period of unusually cold weather. Known as theMaunder Minimum, or more conversationally as the Little Ice Age, it’s a period historicized by accounts of ice skating on the Thames and seasonal inns built on Baltic Sea ice.
In fact, the meaning of the latest sunspot reports is still being debated, as Andrew Revkin at Dot Earth has chronicled. But even if they really do portend a decades-long solar lull, studies already point to a minimal effect on climate.
Most Little Ice Age cooling appears to have been the result of coincidentally high volcanic activity that cloaked Earth in sunlight-blocking soot. As for the sun, a study published in 2001 in Science found that reduced solar activity produced a cooling effect of about 0.5 degrees Fahrenheit. In other estimates, the cooling is even more insignificant.
The Wired piece quotes Mike Mann of Penn State, comparing the sun’s fluctuations to greenhouse warming.
“The example I like to use is that greenhouse warming right now is the equivalent of 2 watts of power illuminating every square meter of the Earth’s surface. It’s like a Christmas tree light over every square meter. By mid-century, it will be closer to 4 watts,….the maximum impact factor of the sun is 0.2 watts per meter squared.”
A recent paper by Georg Fulner and Stefan Rahmstorf asked what might happen to earth’s climate in the event of a new solar minimum. That paper’s key graph is adapted above. The paper’s conclusion:
In summary, global mean temperatures in the year 2100 would most likely be diminished by about 0.1°C. Even taking into account all uncertainties in the temperature re- construction, the forcings, and the model physics, the overall uncertainty is estimated to be at most a factor of 3, so the offset should not be larger than 0.3°C. Comparing this to the 3.7°C and 4.5°C temperature rise relative to 1961–1990 until the end of the century under the IPCC A1B and A2 emission scenarios, respectively, a new Maunder‐type solar activity minimum cannot offset the global warming caused by human greenhouse gas emissions.