Image: “Global Warming” Hits London
All indications are that the upcoming solar minimum may be even quieter than the last one which was the deepest in nearly a century.
Daily observations of the number of sunspots since 1 January 1900 according to Solar Influences Data Analysis Center (SIDC). The thin blue line indicates the daily sunspot number, while the dark blue line indicates the running annual average. The recent low sunspot activity is clearly reflected in the recent low values for the total solar irradiance. Data source: WDC-SILSO, Royal Observatory of Belgium, Brussels. Last day shown: 31 March 2019. Last diagram update: 3 April 2019.
The sun continues to be very quiet and it has been without sunspots this year more than half the time as we approach what is likely to be a deep solar minimum. In fact, all indications are that the upcoming solar minimum which is expected to begin later this year may be even quieter than the last one which was the deepest in nearly a century. Solar cycle 24 has been the weakest sunspot cycle with the fewest sunspots since cycle 14 peaked in February 1906. Solar cycle 24 continues a recent trend of weakening solar cycles which began with solar cycle 21 that peaked around 1980. The last time the sun was this blank in a given year on a percentage basis was 2009 during the last solar minimum when 71% of the time was spotless. That last solar minimum actually reached a nadir in 2008 when an astounding 73% of the year featured a spotless sun – the most spotless days in a given year since 1913. One of the natural impacts of decreasing solar activity is the weakening of the ambient solar wind and its magnetic field which, in turn, allows more and more cosmic rays to penetrate the solar system. The intensification of cosmic rays can have important consequences on such things as Earth’s cloud cover and climate, the safety of air travelers and as a possible trigger mechanism for lightning.
Galactic cosmic rays are high-energy particles originating from outside the solar system that can impact the Earth’s atmosphere. Our first line of defense from cosmic rays comes from the sun as its magnetic field and the solar wind combine to create a ‘shield’ that fends off cosmic rays attempting to enter the solar system. The shielding action of the sun is strongest during Solar Maximum and weakest during Solar Minimum with the weakening magnetic field and solar wind. The intensity of cosmic rays varies globally by about 15% over a solar cycle because of changes in the strength of the solar wind, which carries a weak magnetic field into the heliosphere, partially shielding Earth from low-energy galactic charged particles.
Spaceweather.com has sponsored the launching of space weather balloons to the stratosphere almost weekly since 2015. Sensors onboard those balloons show an increase in radiation (X-rays and gamma-rays) penetrating our planet’s atmosphere:. Above: Four years of overlapping data from neutron monitors and cosmic ray balloons.
Evidence of an increase in stratospheric radiation
One way to monitor cosmic ray penetration into the Earth’s upper atmosphere is to measure stratospheric radiation over an extended period of time. “Spaceweather.com” has led an effort for nearly four years to monitor radiation levels in the stratosphere over California with frequent high-altitude helium balloon flights. These balloons contain sensors which detect X-rays and gamma-rays in the energy range 10 keV to 20 MeV and are produced by the crash of primary cosmic rays into Earth’s atmosphere. These energies span the range of medical X-ray machines and airport security scanners. The findings confirm the notion that indeed cosmic rays have been steadily increasing over California as solar cycle 24 heads towards the next solar minimum.
During the last solar minimum in 2009, radiation peppering Earth from deep space reached a 50-year high at levels never before seen during the satellite era – and we’re getting close to those same levels and a new record is certainly on the table. Ground-based neutron monitors and high-altitude cosmic ray balloons are registering a new increase in cosmic rays. The Oulu neutron monitor in Finland, which has been making measurements since 1964, reports levels measured in April 2019 are now only percentage points below the satellite era maximum reached in 2009.
Source: The Sodankyla Geophysical Observatory in Oulu, Finland.
Consequences of increasing cosmic rays: cloud cover/climate
The correlation between cosmic rays and cloud cover over a solar cycle was first reported by Svensmark and Friis-Christensen in 1997. A more recent study by Svensmark published in the August 2016 issue of Journal of Geophysical Research: Space Physics continues to support the idea of an important connection between cosmic rays and clouds.
In this publication, the authors found that “the observed variation of 3–4% of the global cloud cover during the recent solar cycle is strongly correlated with the cosmic ray flux. This, in turn, is inversely correlated with the solar activity. The effect is larger at higher latitudes in agreement with the shielding effect of the Earth’s magnetic field on high-energy charged particles. The above relation between cosmic ray flux and cloud cover should also be of importance in an explanation of the correlation between solar cycle length and global temperature that has been found”.
Consequences of increasing cosmic rays: threat to air travelers
Not only can an increase of cosmic rays have an impact on Earth’s cloud cover and climate, it is of special interest to air travelers. Cosmic radiation at aviation altitudes is typically 50 times that of natural sources at sea level. Cosmic rays cause “air showers” of secondary particles when they hit Earth’s atmosphere. Indeed, this is what neutron monitors and cosmic ray balloons are measuring–the secondary spray of cosmic rays that rains down on Earth. Secondary cosmic rays penetrate the hulls of commercial aircraft, dosing passengers with the whole body equivalent of a dental X-ray even on ordinary mid-latitude flights across the USA. International travelers receive even greater doses (source). The International Commission on Radiological Protection has classified pilots as occupational radiation workers because of accumulated cosmic ray doses they receive while flying. Moreover, a recent study by researchers at the Harvard School of Public Health shows that flight attendants face an elevated risk of cancer compared to members of the general population. They listed cosmic rays as one of several risk factors.
Consequences of increasing cosmic rays: possible lightning trigger
Finally, there has been some research suggesting there is a connection between cosmic rays and lightning (paper 1, paper 2). When cosmic rays smash into molecules in our atmosphere, the collisions create showers of subatomic particles, including electrons, positrons, and other electrically charged particles. This shower of electrons would collide into still more air molecules, generating more electrons. All in all, cosmic rays could each set off an avalanche of electrons and trigger lightning.
While the frequency of solar storm activity generally lessens during periods of low solar activity (e.g., during solar minimum phases), there is actually some evidence that suggests the severity does not diminish. In fact, the most famous solar storm of all now known as “The Carrington Event” took place in 1859 during an overall weak solar cycle (#10). In addition, other solar activity, such as coronal holes that unleash streams of solar material out into space, can amplify the auroras at Earth’s poles. The bottom line, a lack of sunspots does not mean the sun’s activity stops altogether and it needs to be constantly monitored – even during periods of a blank sun.
Meteorologist Paul Dorian
From last year ..
Solar minimum may bring 50 years of global cooling
Grand Minimum May Usher In 50 Years Of Global Cooling
By Paul Homewood
Reduced sunspot activity has been observed and indicates the sun is heading into a 50 year reduced solar activity similar to what happened in the mid-17th century.
Comparison to similar stars indicates the reduced activity will cause 0.25% less UV for 50 years.
Modelling indicates that this will cause a few tenths of a degree of cooling.
This will counteract global warming for 50 years.
The cooldown would be the result of what scientists call a grand minimum, a periodic event during which the Sun’s magnetism diminishes, sunspots form infrequently, and less ultraviolet radiation makes it to the surface of the planet. Scientists believe that the event is triggered at irregular intervals by random fluctuations related to the Sun’s magnetic field.
Scientists have used reconstructions based on geological and historical data to attribute a cold period in Europe in the mid-17th Century to such an event, named the “Maunder Minimum.” Temperatures were low enough to freeze the Thames River on a regular basis and freeze the Baltic Sea to such an extent that a Swedish army was able to invade Denmark in 1658 on foot by marching across the sea ice.
A team of scientists led by research physicist Dan Lubin at Scripps Institution of Oceanography at the University of California San Diego has created for the first time an estimate of how much dimmer the Sun should be when the next minimum takes place.
There is a well-known 11-year cycle in which the Sun’s ultraviolet radiation peaks and declines as a result of sunspot activity. During a grand minimum, Lubin estimates that ultraviolet radiation diminishes an additional seven percent beyond the lowest point of that cycle. His team’s study, “Ultraviolet Flux Decrease Under a Grand Minimum from IUE Short-wavelength Observation of Solar Analogs,” appears in the publication Astrophysical Journal Letters and was funded by the state of California.
“Now we have a benchmark from which we can perform better climate model simulations,” Lubin said. “We can therefore have a better idea of how changes in solar UV radiation affect climate change.”
Lubin and colleagues David Tytler and Carl Melis of UC San Diego’s Center for Astrophysics and Space Sciences arrived at their estimate of a grand minimum’s intensity by reviewing nearly 20 years of data gathered by the International Ultraviolet Explorer satellite mission. They compared radiation from stars that are analogous to the Sun and identified those that were experiencing minima.
The reduced energy from the Sun sets into motion a sequence of events on Earth beginning with a thinning of the stratospheric ozone layer. That thinning, in turn, changes the temperature structure of the stratosphere, which then changes the dynamics of the lower atmosphere, especially wind and weather patterns. The cooling is not uniform. While areas of Europe chilled during the Maunder Minimum, other areas such as Alaska and southern Greenland warmed correspondingly.
Lubin and other scientists predict a significant probability of a near-future grand minimum because the downward sunspot pattern in recent solar cycles resembles the run-ups to past grand minimum events.
Despite how much the Maunder Minimum might have affected Earth the last time, Lubin said that an upcoming event would not stop the current trend of planetary warming but might slow it somewhat. The cooling effect of a grand minimum is only a fraction of the warming effect caused by the increasing concentration of carbon dioxide in the atmosphere. After hundreds of thousands of years of CO2 levels never exceeding 300 parts per million in air, the concentration of the greenhouse gas is now over 400 parts per million, continuing a rise that began with the Industrial Revolution. Other researchers have used computer models to estimate what an event similar to a Maunder Minimum, if it were to occur in coming decades, might mean for our current climate, which is now rapidly warming.
One such study looked at the climate consequences of a future Maunder Minimum-type grand solar minimum, assuming a total solar irradiance reduced by 0.25 percent over a 50-year period from 2020 to 2070. The study found that after the initial decrease of solar radiation in 2020, globally averaged surface air temperature cooled by up to several tenths of a degree Celsius. By the end of the simulated grand solar minimum, however, the warming in the model with the simulated Maunder Minimum had nearly caught up to the reference simulation. Thus, a main conclusion of the study is that “a future grand solar minimum could slow down but not stop global warming.”
Read the full story here.
Paul Homewood of Not Alot of People Know That comments: “The claim that global warming will offset this cooling is, in my view, highly tendentious, as it assumes the sort of underlying warming we have not seen yet.
In any event, a global is a meaningless concept and will be of no consequence to most of the Northern Hemisphere struggling with low temperatures.
NASA’s Earth Observatory explains the Grand Minimum very well”:
Many things can change temperatures on Earth: a volcano erupts, swathing the Earth with bright haze that blocks sunlight, and temperatures drop; greenhouse gases trap heat in the atmosphere, and temperatures climb. From 1650 to 1710, temperatures across much of the Northern Hemisphere plunged when the Sun entered a quiet phase now called the Maunder Minimum. During this period, very few sunspots appeared on the surface of the Sun, and the overall brightness of the Sun decreased slightly. Already in the midst of a colder-than-average period called the Little Ice Age, Europe and North America went into a deep freeze: alpine glaciers extended over valley farmland; sea ice crept south from the Arctic; and the famous canals in the Netherlands froze regularly—an event that is rare today.
The impact of the solar minimum is clear in this image, which shows the temperature difference between 1680, a year at the center of the Maunder Minimum, and 1780, a year of normal solar activity, as calculated by a general circulation model. Deep blue across eastern and central North America and northern Eurasia illustrates where the drop in temperature was the greatest. Nearly all other land areas were also cooler in 1680, as indicated by the varying shades of blue. The few regions that appear to have been warmer in 1680 are Alaska and the eastern Pacific Ocean (left), the North Atlantic Ocean south of Greenland (left of center), and north of Iceland (top center).
If energy from the Sun decreased only slightly, why did temperatures drop so severely in the Northern Hemisphere? Climate scientist Drew Shindell and colleagues at the NASA Goddard Institute for Space Studies tackled that question by combining temperature records gleaned from tree rings, ice cores, corals, and the few measurements recorded in the historical record, with an advanced computer model of the Earth’s climate. The group first calculated the amount of energy coming from the Sun during the Maunder Minimum and entered the information into a general circulation model. The model is a mathematical representation of the way various Earth systems—ocean surface temperatures, different layers of the atmosphere, energy reflected and absorbed from land, and so forth—interact to produce the climate.
When the model started with the decreased solar energy and returned temperatures that matched the paleoclimate record, Shindell and his colleagues knew that the model was showing how the Maunder Minimum could have caused the extreme drop in temperatures. The model showed that the drop in temperature was related to ozone in the stratosphere, the layer of the atmosphere that is between 10 and 50 kilometers from the Earth’s surface. Ozone is created when high-energy ultraviolet light from the Sun interacts with oxygen. During the Maunder Minimum, the Sun emitted less strong ultraviolet light, and so less ozone formed. The decrease in ozone affected planetary waves, the giant wiggles in the jet stream that we are used to seeing on television weather reports.
The change to the planetary waves kicked the North Atlantic Oscillation (NAO)—the balance between a permanent low-pressure system near Greenland and a permanent high-pressure system to its south—into a negative phase. When the NAO is negative, both pressure systems are relatively weak. Under these conditions, winter storms crossing the Atlantic generally head eastward toward Europe, which experiences a more severe winter. (When the NAO is positive, winter storms track farther north, making winters in Europe milder.) The model results, shown above, illustrate that the NAO was more negative on average during the Maunder Minimum, and Europe remained unusually cold. These results matched the paleoclimate record.
Homewood: “Note how the Maunder Minimum resulted in much lower temperatures across virtually the whole of the NH, with the exception of Alaska and southern Greenland.
Such a sharp drop in just a few years will have dire consequences.”