Our Sun today (by Diego Fdez-Sevilla)
(updated 28/07/2014. Link to met office re-established)
“We had adopted a kind of solar uniformitarianism. As people and as scientists we have always wanted the Sun to be better than other stars and better than it really is.” Eddy, Jack A. (1977). “The Case of the Missing Sunspots.”
It has been a matter of study the role that the Sun plays over the forces that move our climate. One primary impact comes from the energy that our planet receives and influences the amount of heat that our atmosphere absorbs being translated into temperature and weather patterns.
The behaviour of our Sun has been modelled into cycles describing periods of 11 years. Based on past observations, the appearance and disappearance of sunspots have been correlated with Sun’s activity. At solar maxima there are more sunspots on the Sun’s surface.
Our Sun is the primary force of the Earth’s climate system, driving atmospheric and oceanic circulation patterns. It lies behind every aspect of the Earth’s climate and is, of course, a key component feeding energy into the greenhouse effect that has allowed life to develop in our planet as we know it and now, threatens our capability for adaptation.
Studies have pointed to that when the Sun has gone quiet, it coincided with the earth cooling slightly and there is speculation that a similar thing could happen now.
Throughout the 20th century the Sun was unusually active, peaking in the 1950s and the late 1980s. Dean Pensell of NASA, says that, “since the Space Age began in the 1950s, solar activity has been generally high. Five of the ten most intense solar cycles on record have occurred in the last 50 years.”
Many scientists believe that the Sun was the major player on the Earth’s climate until the past few decades, when the greenhouse effect from increasing levels of carbon dioxide overwhelmed it.
But around the turn of the century things started to change. Within a few years of the Sun’s activity starting to decline, the rise in the Earth’s temperature began to slow and has now been constant since the turn of the century. This was at the same time that the levels of atmospheric carbon dioxide carried on rising.
Computer models suggest that of the 0.5C increase in global average temperatures over the past 30 years, only 10-20 per cent of the temperature variations observed were down to the Sun, although some said it was 50 per cent and, the debate remains about finding scientific consensus on the effect that the Sun has on climate change.
Our Sun in 2008
The year 2008 was predicted as the solar minimum of its cycle so, from 2008 forward it was expected to be seen an increase in its activity and the number of sunspots. However, the low activity of the Sun remained in 2009 making the news: NASA: In 2008-2009, sunspots almost completely disappeared for two years. Solar activity dropped to hundred-year lows; Earth’s upper atmosphere cooled and collapsed; the sun’s magnetic field weakened, allowing cosmic rays to penetrate the Solar System in record numbers. It was a big event, and solar physicists openly wondered, where have all the sunspots gone?
“This is the quietest Sun we’ve seen in almost a century,” says NASA solar scientist David Hathaway. But this is not just a scientific curiosity. It could affect everyone on Earth and force what for many is the unthinkable: a reappraisal of the science behind recent global warming. The disappearance of sunspots happens every few years, but this time it’s gone on far longer than anyone expected – and there is no sign of the Sun waking up.”
NASA Earth Observatory: Our Sun is always too bright to view with the naked eye, but it is far from unchanging. It experiences cycles of magnetic activity. Areas of strong activity manifest as visible spots—sunspots—on the Sun’s surface. The year 2008, however, earned the designation as the Sun’s “blankest year” of the space age. Our Sun experienced fewer spots in 2008 than it had since the 1957 launch of Sputnik. As of March 2009, the Sun was continuing its quiet pattern.
These images from the Solar and Heliospheric Observatory (SOHO) spacecraft compare sunspots on the Sun’s surface (top row) and ultraviolet light radiating from the solar atmosphere (bottom row) at the last solar maximum (2000, left column) and at the current solar minimum (2009, right column.) The sunspot images were captured by the Michelson Doppler Imager (MDI) using filtered visible light. On March 18, 2009, the face of the Sun was spotless.
Above image courtesy NASA
Since regular sunspot observations began, astronomers have documented 24 cycles of sunspot activity. The images acquired in July 2000 showed the Sun near the peak of Solar Cycle 23. That cycle waned in late 2007, and Solar Cycle 24 began in early 2008, but showed minimal activity through early 2009. The small changes in solar irradiance that occur during the solar cycle exert a small influence on Earth’s climate, with periods of intense magnetic activity (the solar maximum) producing slightly higher temperatures, and solar minimum periods such as that seen in 2008 and early 2009 likely to have the opposite effect.
Our Sun in 2013
Something unexpected is happening on the Sun. 2013 was supposed to be the year of “solar maximum,” the peak of the 11-year sunspot cycle. Yet 2013 has arrived and solar activity is relatively low. Sunspot numbers are well below their values from 2011, and strong solar flares have been infrequent. The quiet has led some observers to wonder if forecasters missed the mark.
Solar physicist Dean Pesnell of NASA’s Goddard Space Flight Center has a different explanation. “This is solar maximum,” he says. “But it looks different from what we expected because it is double-peaked.” Given the tepid state of solar activity now, a maximum in May seems unlikely. “We may be seeing what happens when you predict a single amplitude and the Sun responds with a double peak,” says Pesnell. He notes a similarity between Solar Cycle 24 and Solar Cycle 14, which had a double-peak during the first decade of the 20th century. If the two cycles are twins, “it would mean one peak in late 2013 and another in 2015.”
It looks as if this solar cycle is “double-peaked” which is not all that uncommon; however, it is somewhat rare that the second peak in sunspot number during the solar max phase is larger than the first. In fact, this solar cycle continues to rank among the weakest on record which continues the recent trend for increasingly weaker cycles.
Our Sun in 2014
July 21. The sun has gone quiet. Almost too quiet. A few weeks ago it was teeming with sunspots, as you would expect since we are supposed to be in the middle of solar maximum-the time in the sun’s 11-year cycle when it is the most active. Solar physicist Tony Phillips has named it an ‘All Quiet Event.’
“It is weird, but it’s not super weird,” said Phillips, who writes about solar activity on his website SpaceWeather.com. “To have a spotless day during solar maximum is odd, but then again, this solar maximum we are in has been very wimpy.”
Phillips notes this is the weakest solar maximum to have been observed in the space age, and it is shaking out to be the weakest one in the past 100 years, so the spotless day was not so out of left field.
“It all underlines that solar physicists really don’t know what the heck is happening on the sun,” Phillips said. “We just don’t know how to predict the sun, that is the take away message of this event.”
Whether this quiet period will be similarly short-lived or if it will last longer remains to be seen.
Similar to what Eddy, Jack A. said in 1977 about the Sun, “you just can’t predict the sun,” Phillips said about our Sun today.
Finding scientific consensus
Global mean surface temperatures rose rapidly from the 1970s, but have been relatively flat over the most recent 15 years to 2013. This has prompted speculation that human induced global warming is no longer happening, or at least will be much smaller than predicted. Others maintain that this is a temporary pause and that temperatures will again rise at rates seen previously.
Scientists do not yet fully understand the ways in which the Sun might affect the Earth’s climate. Increases in X-ray and ultraviolet radiation, or energetic particles (so-called cosmic rays) from the Sun, might change the chemical composition of the Earth’s atmosphere and so might change the rate or efficiency of cloud formation. Also, the solar wind can prevent the cosmic rays penetrating the Earth’s atmosphere.
It is part of the normal process of scientific investigation to debate ideas and to propose theories and possible explanations for the data that are recorded. There are uncertainties in any climate measurements and the computer models used to forecast the climate may not include all the physical effects present in the real atmosphere, but climate scientists make allowance for these shortcomings when they record and interpret the data.
In January 21, 2014, NOAA and NASA released in a joint press conference data for the global surface temperature for 2013. NASA in its site announced this release claiming that “NASA Finds 2013 Sustained Long-Term Climate Warming Trend” generating with it a vivid debate in digital platforms.
In July 2013, The Met Office Hadley Centre released three reports addressing the recent pause in global warming. The first paper shows that a wide range of observed climate indicators continue to show changes that are consistent with a globally warming world, and our understanding of how the climate system works. The second suggests that it is not possible to explain the recent lack of surface warming solely by reductions in the total energy received by the planet, i.e. the balance between the total solar energy entering the system and the thermal energy leaving it. Changes in the exchange of heat between the upper and deep ocean appear to have caused at least part of the pause in surface warming, and observations suggest that the Pacific Ocean may play a key role. The final paper shows that the recent pause in global surface temperature rise does not materially alter the risks of substantial warming of the Earth by the end of this century. Nor does it invalidate the fundamental physics of global warming, the scientific basis of climate models and their estimates of climate sensitivity.
“One” question remains
In the joined press released by the NASA and NOAA, in summary, they both show that the ‘pause’ in global surface temperature that began in 1997, according to some estimates, continues.
One interesting aspect of solar cycles is that the sun went through a period of sunspot inactivity from about 1645 to 1715. This period of sunspot minima is called the Maunder Minimum. The “Little Ice Age” occurred over parts of Earth during the Maunder Minimum. The NOAA in its site points to a significant question, “Do solar minimums help to create periods of cooler than normal weather, and do solar maximums help to cause drought over sections of Earth? There is evidence that some of the major ice ages Earth has experienced were caused by Earth being deviated from its “average” 23.5 degrees tilt on its axis. The Earth has tilted anywhere from near 22 degrees to 24.5 degrees on its axis. The number of sunspots alone does not alter the overall solar emissions much at all. However, the increased/decreased magnetic activity which accompanies sunspot maxima/minima directly influences the amount of ultraviolet radiation which moves through the upper atmosphere. This question is not easily answered due to the immensely complex interaction between our atmosphere, land and oceans.“
No one knows what will happen or how it will effect our understanding of climate change on Earth. If the Earth cools under a quiet Sun, then it may be an indication that the increase in the Sun’s activity since the Little Ice Age has been the dominant factor in global temperature rises. However, I wonder, if temperature has raised in the past due to the major role played by solar activity, dominating planetary feedbacks, what is keeping temperatures from dropping when our Sun is in a minimum?
A remaining theory is that the planet’s climate system could go through self-sustaining oscillations, driven predominantly by feedbacks between atmospheric, terrestrial and aquatic systems.
In both cases, either the Sun is the main driver of our climate or not, I have two questions on hold to be answered:
- how deep is connected the transformation that our systems have suffered (atmospheric, terrestrial and aquatic systems), with the ability to store the increment in temperature gained in the past (so call “pause” in global warming)? and,
- how our systems are going to react when the activity of the Sun gets reinforced towards a new maxima?