In my opinion, the primary driver of the climate, needless to say is the Sun. In short, when someone tells me that humans are the primary driver, I respond by saying this:
“We got this big ball of fire in the sky called the Sun. When you tell me that humans are causing all this warming, that is like you sitting at a bonfire while someone lights up a cigarette and you tell them “hey, put out that cigarette (referring to CO2), it is getting too hot in here!”
-Larry The Cable Guy
It is utter nonsense…
THE EARTH-SUN CONNECTION
As we stated in the beginning of The Atmosphere section,
“…The Sun gives out energy to the planets in the solar system. This energy comes from TSI (Total Solar Irradiance) and sunspot count. The energy is given out by the Sun is energy in motion, otherwise known as kinetic energy. Temperature is a measurement of the amount of kinetic energy possessed by the particles of an object. The more energy that is given out by the Sun means that Earth will be warmer. The less energy given out by the Sun means that Earth will cool…”
“If there was no Sun, the atmosphere would freeze and collapse to Earth, which would then lead to harmful UV radiation as the Earth moved in a straight line through outer space. Global temperatures would plunge to absolute zero within a couple of weeks…”
Simplified, this means that the primary source of energy on Earth comes from the big ball of fire in the sky, the Sun! The radiation heats the atmosphere and the surface, while also assisting in atmospheric circulations.
The amount of energy given out by the Sun changes on an 11-year cycle known as the “solar cycle.” You may be familiar with sunspots, which come and go on the surface of the Sun on the same cycle. Solar influence only changes the amount of energy the Earth receives by about 0.1%, sometimes a little more. This small decrease in the energy given out by the Sun has small direct effects on the climate.
It is a hard question for many to answer, but there is debate as to how such a small change in energy output could have large scale effects on the global climate system.
Though direct effects on the global climate system from solar cycles is really nothing, there are indirect effects, which have been theorized to have a much larger effect on the climate system. During solar maximums (high sunspot count), such slight warming of the lower and mid atmosphere due to changes in intensity of ultraviolet radiation by geomagnetic activity AND more importantly solar radiative forcing, can have large effects on the climate. The 0.1% increase in solar activity blocks out cosmic rays from the inner planets in the solar system, which affects cloud formation. With less cosmic rays coming into the Earth’s atmosphere, less cloud nucleation will occur. Less cloud cover results in an overall increase in global temperatures.
SOLAR EFFECTS ON THE CLIMATE
Despite there being an 11-year solar cycle, there are others that vary from 27 days, to 11, 22, 80, 180 years or more (Figure 1). The more active the Sun is, the brighter it is, due to faculae surrounding the cooler sunspots. The increased solar activity results in more radiation received by Earth, than during low sunspot activity periods.
The change in total solar irradiance varies by 0.1% during the 11-year cycle (Willson and Hudson 1988). The short variance in solar activity has led to the conclusion among many scientists, that solar effects are irrelevant to climate change. However, they seem to forget about long-term cycles such as the Grand Solar Minimum cycle, which can result in 0.4% reduction in solar activity (Hoyt and Schatten (1993), Lean et al. (1995), Lean (2000), Lockwood and Stamper (1999), and Fligge and Solanki (2000)).
On the other hand, the solar activity we referred to above did not account for eruptional activity, such as solar flares and solar wind. These outbursts of activity have been theorized to have enhanced effect alongside solar cycles. Since 1901, the total magnetic flux emitted from the Sun has increased by a factor of 2.3 (Figure 2), which has likely contributed to some of the warming we have been seeing by ultraviolet radiation inducing chemical reactions in the upper atmosphere (Lockwood et al. 1999).
Studies have shown that direct total solar irradiance accounted for 52% of the warming which took place from 1910 to 1960, but only 31% of the warming from 1970 to 1999 (Lockwood and Stamper (GRL 1999)). N. Scafetta and B. J. West of Duke University validated Lockwood and Stamper’s assessment in 2006 (GRL 2006 and b0) by doing a reconstruction of the temperatures for the last 400 years for the Northern Hemisphere. Their findings lined up with what Lockwood and Stamper found; 50% of the warming since 1900 was solar influenced, while 25% to 35% of the warming between 1980 and 2006 was solar influenced.
So the question to ask would be why the solar effect accounts for less warming of the Earth in recent decades than it did in the early 20th century?
According to the 2006 report released by Scafetta and West, the main reason why solar influence has had less impact on the climate, is because the temperatures in and around urban areas have seen bias due to the urban heat island effect and/or land use changes, as documented in Pielke et al., 2002, and Kalnay and Cai, 2003. It is also worth noting that in their temperature reconstruction, the instrumental temperature record (~1880 – Present) was reconstructed using global databases, mainly based on the global weather stations. It is worth noting that many of these stations closed during the 1990s and early 2000s, especially the rural ones, which aren’t biased, in which many actually show a cooling trend since the 1940s; this was also documented in their report. A follow-up paper was released by Scafetta and West in 2007, in which they stated that the Sun could actually account for 69% of the warming since 1900, had the instrumental temperature data been reliable.
Meteorologist Joseph D’Aleo noted that had they used the USHCN data in their temperature reconstruction, they would have been better off, thus the solar correlation to temperature would be more justified, despite the USHCN data only accounting for the United States. This is because USHCN data is much more reliable because there is less missing data, and a better scheme for adjusting for missing data, as well as adjustments for urbanization.
An independent analysis was done in 1993 and later updated in 2005 by Hoyt and Schatten, where they overlayed annual TSI data and USHCN temperature. The graph below (Figure 3) shows the 11-year running mean for solar irradiance versus the 11-year running mean of the USHCN temperature dataset. The alignment below confirms the correlation between TSI and temperature, an R² of 0.59 (59%). However, if you notice, there is a three to five-year lag between the change in TSI and U.S. temperature. If we factor that into the equation, we get an R² of 0.654 (65.4%), which goes along with the Northern Hemisphere warming effect from the Sun with a correlation of 0.5 to 0.69.
Satellite missions have been able to measure and observe changes in TSI in recent decades, but there have been errors. Judith Lean and Froelich took note in their 1998 report, of how there was no measurement of TSI from the 1979 through the 1990s because the sensors did not collect data.
NASA’s Richard Willson was able to find errors in Lean and Froelich’s dataset of TSI. A better version of the data was released thereafter, which showed that there was a 0.05% increase in TSI per decade, which may be a factor in recent warming (Figure 4).
At the same time, even more studies (Willie Soon (2005) and Kärner (2004)) have shown that changes in solar activity have influence on the climate.
Willie Soon showed that 10-year running mean Arctic temperatures over the last 100 years (Polyokov) have a very strong correlation with total solar irradiance, with an R² of 0.79 (79%), while greenhouse gases only had a correlation of 0.22 (22%) (Figure 5).
My research has shown that the Sun may account for more than half of the warming through both direct and indirect effects. However, 15% of climate change alone, between 1900 and 2017 can be attributed by the Sun directly and not indirectly, which is a lot when you have so many drivers on the table (Figure 6).
We touched base a little on UV radiation having effect on the climate through the 11-year solar cycle. The UV wavelengths are known to increase by 6% to 8% or more during solar maximum, with even greater change with extremely short UV wavelengths and X-ray wavelengths (Baldwin and Dunkerton, JAS 2004).
Energetic flares may increase UV radiation by 16% in which the ozone layer in the stratosphere absorbs this energy very well, in which it will eventually be forced downward into the troposphere. In 1999, Shindell used a climate model which took into account ozone chemistry, in which it showed natural global warming during high flux (high UV) years. It has been shown and well documented in peer-reviewed scientific papers, such as Labitzke and Van Loon (1988), that high flux years produce warming in the mid and lower levels of the stratosphere during the winter, which will eventually warm the troposphere. The Northern Hemisphere winter of 2001-2002 took place during solar cycle 23’s very strong high flux (Figure 7).
This extremely high solar flux resulted in a global warming trend between 2001 and 2002 (Figure 8a), in which the polar jet stream shrunk (Figure 8b), while the subtropical jet stream broke into two centers for the first time ever. This high flux period likely had something to do with the breakup of the Larsen ice sheet in Antarctica thereafter (Figure 8c).
This example is exactly what Labitzke, Van Loon, and Shindell were referring to in their papers.
GLOBAL EFFECTS OF LOW SOLAR ACTIVITY
NASA used the model (mentioned above) to help figure out the temperature reconstruction of the Maunder Minimum (Figure 9).
To put it simply, the model showed that as the Sun was quiet in activity during the 1680s, it was also cooler than it is today, thus when sunspot activity went up during the late 1700s, Earth began to warm. However, prior to 1680, Earth had already been in a cold spell known as the Little Ice Age for about 80 or 90 years, likely called by atmospheric and oceanic circulation changes (see Figure 10). The quiet Sun likely assisted in further cooling of the Earth after 1680, in which Europe and North America had many deep freezes that lasted much of the winter. Glaciers also grew during this time, while sea ice grew south of the Arctic, and the canals in the Netherlands froze each winter, which is a rare occasion today.
Mike Lockwood showed that direct effects are apparent on the climate system due to changes in solar activity. During quiet times, the NAO tends to turn negative with North Atlantic blocking. While the NAO can have large-scale effects, when it and the Arctic Oscillation (AO) are connected, the effects are larger.
Despite widespread agreement that the Little Ice Age was global, there are uncertainties because Europe and North America are the only locations that have reliable data dating back that far as far as thermometer data goes (official records did not start until the 1850s for the U.S.).
TROPICAL / EQUATORIAL EFFECTS OF LOW SUNSPOT ACTIVITY
Warming near the equator can be greater because the warming of the ozone layer can be greater because it absorbs ultraviolet radiation. Through the length of a solar cycle, the amount of solar radiation varies by 10% or more. Research has shown that tropical cyclone landfalls in the U.S. can increase by three or more during solar minimums.
Low sunspot years with above-normal sea surface temperatures tend to be more conductive to tropical cyclone development (Figure 11), because low solar activity causes less UV radiation to reach the ozone, which in turn cools the troposphere below. UV radiation has been shown to influence a hurricane’s strength.
Studies have shown that ozone (O3) in the stratosphere and sea surface temperatures in the Pacific respond to solar maximum, which increases the solar effect on air patterns in the atmosphere. These changes may result in gustier winds, increased rainfall, sea surface temperatures, and cloud cover over tropical and subtropical areas. A massive team of international scientists, led by NCAR, compiled over 100 years worth of weather data and three computer models to prove this theory correct.
Because solar cycles, the stratosphere, and the ocean water in the Pacific are connected, scientists can somewhat predict what the monsoon season in India or tropical Pacific rainfall will be like up to a decade out.
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