# Does the sun have cycles causing temperature changes on Earth?

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Can the Sun go through seasons or cycles to cause a temperature change?

Could the Sun have to go through any kind of thermal cycle to change the climate on Earth and by how much?

The Sun's magnetic field is way too weak to have any measurable effect on the Earth's orbit. The sunspot cycle does produce a small but detectable signature in the global average temperature (about $$0.2sideset{^{circ}}{}{mathrm{C}}$$). Over a billion-year timescale the Sun is getting hotter as helium builds up in its core.

The Sun is gradually increasing in brightness by 1% every hundred million years. This increase in solar output will, over the long term, cause a gradual warming of the Earth's surface.

In roughly 1 billion years, which is long before it becomes a red giant, the combination of the Sun's gradual increase in output and the "moist greenhouse effect" will make the Earth's surface too hot for liquid water to exist.

For more details see my blog post The Future of humanity

## 100,000-Year Climate Pattern Linked To Sun's Magnetic Cycles

HANOVER, N.H. &ndash Thanks to new calculations by a Dartmouth geochemist, scientists are now looking at the earth's climate history in a new light. Mukul Sharma, Assistant Professor of Earth Sciences at Dartmouth, examined existing sets of geophysical data and noticed something remarkable: the sun's magnetic activity is varying in 100,000-year cycles, a much longer time span than previously thought, and this solar activity, in turn, may likely cause the 100,000-year climate cycles on earth. This research helps scientists understand past climate trends and prepare for future ones.

Published in the June 10 issue of Earth and Planetary Science Letters (Elsevier, volume 199, issues 3-4), Sharma's study combined data on the varying production rates of beryllium 10, an isotope found on earth produced when high-energy galactic cosmic rays bombard our atmosphere, and data on the past variations in the earth's magnetic field intensity. With this information, Sharma calculated variations in solar magnetic activity going back 200,000 years, and he noticed a pattern.

Over the last 1 million years, the earth's climate record has revealed a 100,000-year cycle oscillating between relatively cold and warm conditions, and Sharma's data on the sun's magnetic activity corresponded to the earth's ice age history.

"Surprisingly, it looks like solar activity is varying in longer time spans than we realized," says Sharma. "We knew about the shorter cycles of solar activity, so maybe these are just little cycles within a larger cycle. Even more surprising is the fact that the glacial and interglacial periods on earth during the last 200,000 years appear to be strongly linked to solar activity."

Sharma's calculations suggest that when the sun is magnetically more active, the earth experiences a warmer climate, and vice versa, when the sun is magnetically less active, there is a glacial period. Right now, the earth is in an interglacial period (in between ice ages) that began about 11,000 years ago, and as expected, this is also a time when the estimated solar activity appears to be high.

Beryllium 10 is useful for studying the geology from hundreds of thousands of years ago mainly because it has a half-life of about one and a half million years. In addition, there are two key factors that have affected beryllium 10 production over the last 200,000 years: the earth's magnetic field and the sun's magnetic activity. When there are high-intensity solar magnetic storms, more charged particles are interacting with cosmic rays, and less beryllium 10 is produced. Likewise, the earth's magnetic field changes the flux of cosmic rays into and out of the atmosphere.

Since the production rate of beryllium 10 and earth's magnetic field intensity are known for the last 200,000 years, Sharma could calculate solar magnetic activity for this time period.

"I took sets of existing, independent data and made new comparisons and calculations," says Sharma. Then he went a step further to make a connection with the history of ice ages by looking at oxygen isotopes in the oceans, which reveal the history of how much ice was at the poles and are therefore a measure of average global surface temperature.

"I compared the estimated past variations in the solar activity with those of the oxygen isotopes in the ocean. Although there is a strong relationship between solar activity and oxygen isotopic variations, it is too early to say exactly what is the mechanism though which the sun is influencing the terrestrial climate."

One explanation of the 100,000-year cycle was offered by the Milankovitch Theory of Ice Ages in the 1940s, which suggested that the cyclical variations in the earth's orbit around the sun result in the earth receiving varying amounts of solar radiation that, in turn, control the climate. This explanation is under dispute because the variations of the solar energy in relation to the changes in orbit are very small. Other current research focuses on past variations in the sun's irradiance, or heat intensity (as opposed to the magnetic activity).

Sharma notes that more analysis is needed to test his theory. "I've only looked at 200,000 years. My calculations need to be verified for a million years, for instance. Plus, regarding the current global warming debate, it still needs to be examined if the role of solar activity will exacerbate the rising temperatures that result from carbon dioxide buildup in the atmosphere."

This work was supported by Dartmouth College, the Max Planck Institute and by a grant from the National Science Foundation.

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Materials provided by Dartmouth College. Note: Content may be edited for style and length.

## Tiny Solar Activity Changes Affect Earth's Climate

Even small changes in solar activity can impact Earth's climate in significant and surprisingly complex ways, researchers say.

The sun is a constant star when compared with many others in the galaxy. Some stars pulsate dramatically, varying wildly in size and brightness and even exploding. In comparison, the sun varies in the amount of light it emits by only 0.1 percent over the course of a relatively stable 11-year-long pattern known as the solar cycle.

Still, "the light reaching the top of the Earth's atmosphere provides about 2,500 times as much energy as the total of all other sources combined," solar physicist Greg Kopp at the University of Colorado told SPACE.com. As such, even 0.1 percent of the amount of light the sun emits exceeds all other energy sources the Earth's atmosphere sees combined, such as the radioactivity naturally emitted from Earth's core, Kopp explained.

To learn more about how such tiny variations in solar energy might impact terrestrial climate, the National Research Council (NRC) convened dozens of experts in many fields, such as plasma physics, solar activity, atmospheric chemistry, fluid dynamics and energetic particle physics.

Sun's role in Earth's climate

Many of the ways the scientists proposed these fluctuations in solar activity could influence Earth were complicated in nature. For instance, solar energetic particles and cosmic rays could reduce ozone levels in the stratosphere. This in turn alters the behavior of the atmosphere below it, perhaps even pushing storms on the surface off course. [Sun's Wrath: Worst Solar Storms Ever]

"In the lower stratosphere, the presence of ozone causes a local warming because of the breakup of ozone molecules by ultraviolet light," climate scientist Jerry North at Texas A&M University told SPACE.com.

When the ozone is removed, "the stratosphere there becomes cooler, increasing the temperature contrast between the tropics and the polar region. The contrast in temperatures in the stratosphere and the upper troposphere leads to instabilities in the atmospheric flow west to east. The instabilities make for eddies or irregular motions."

These eddies feed the strength of jet streams, ultimately altering flows in the upper troposphere, the layer of atmosphere closest to Earth's surface. "The geographical positioning of the jets aloft can alter the distribution of storms over the middle latitudes," North said. "So the sun might have a role to play in this kind of process. I would have to say this would be a very difficult mechanism to prove in climate models. That does not mean it may not exist &mdash just hard to prove."

In addition, climate scientist Gerald Meehl at the National Center for Atmospheric Research and his colleagues suggest that solar variability is leaving a definite imprint on climate, especially in the Pacific Ocean.

When researchers look at sea surface temperature data during sunspot peak years, the tropical Pacific showed a pattern very much like that expected with La Niña, a cyclical cooling of the Pacific Ocean that regularly affects climate worldwide, with sunspot peak years leading to a cooling of almost 1 degree Celsius (1.8 degrees Fahrenheit) in the equatorial eastern Pacific. In addition, peaks in the sunspot cycle were linked with increased precipitation in a number of areas across the globe, as well as above-normal sea-level pressure in the mid-latitude North and South Pacific.

"The Pacific is particularly sensitive to small variations in the trade winds," Meehl said. Solar activity may influence processes linked with trade wind strength.

Scientists have also often speculated whether the Maunder Minimum, a 70-year dearth of sunspots in the late 17th to early 18th century, was linked with the coldest part of the Little Ice Age, during which Europe and North America experienced bitterly cold winters. This regional cooling might be linked with a drop in the sun's extreme ultraviolet radiation. In fact, the sun could currently be on the cusp of a miniature version of the Maunder Minimum, since the current solar cycle is the weakest in more than 50 years.

"If the sun really is entering an unfamiliar phase of the solar cycle, then we must redouble our efforts to understand the sun-climate link," said researcher Lika Guhathakurta at NASA's Living with a Star Program, which helped fund the NRC study.

Although the sun is the main source of heat for Earth, the researchers note that solar variability may have more of a regional effect than a global one. As such, solar variability is not the cause of the global warming seen in recent times.

"While the sun is by far the dominant energy source powering our climate system, do not assume that it is causing much of recent climate changes. It's pretty stable," Kopp said. "Think of it as an 800-pound gorilla in climate &mdash it has the weight to cause enormous changes, but luckily for us, it's pretty placidly lazy. While solar changes have historically caused climate changes, the sun is mostly likely responsible for less than 15 percent of the global temperature increases we've seen over the last century, during which human-caused changes such as increased greenhouse gases caused the majority of warming."

Tracking the sun

In the future, researchers suggested that to better understand how solar variability might affect the Earth, a future space observatory might include a radiometric imager. Such a device could essentially map the surface of the sun and reveal the contributions of each of its surface features to the sun's luminosity.

The solar disk is dotted by dark sunspots and bright magnetic areas known as faculae. Sunspots tend to vanish during low points in the solar cycle, and a radiometric imager could help reveal the links between prolonged spotlessness on the sun and Earth's climate.

Ancient signals of climate such as tree rings and ice cores might also help shed light on the link between the sun and climate. Since variations in Earth's magnetic field and atmospheric circulation might disrupt this evidence on Earth, a better long-term record of solar radiation might lie in the rocks and sediments of the moon or Mars, researchers added.

The scientists detailed their findings Jan. 8 in a report, "The Effects of Solar Variability on Earth's Climate," issued by the National Research Council.

## Global Warming Natural Cycle

Is global warming a natural cycle? Or is global warming affected by human influence? What does the science say? Both are true. In the natural cycle, the world can warm, and cool, without any human interference. For the past million years this has occurred over and over again at approximately 100,000 year intervals. About 80-90,000 years of ice age with about 10-20,000 years of warm period, give or take some thousands of years.

The difference is that in the natural cycle CO2 lags behind the warming because it is mainly due to the Milankovitch cycles. Now CO2 is leading the warming. Current warming is clearly not natural cycle.

Where are we currently in the natural cycle (Milankovitch cycle)? The warmest point of the last cycle was around 10,000 years ago, at the peak of the Holocene. Since then, there has been an overall cooling trend, consistent with a continuation of the natural cycle, and this cooling would continue for thousands of years into the future if all else remained the same. But since 1750 however, the CO2 content of the atmosphere has deviated from the natural cycle. Instead of decreasing, it has increased because of the fossil-fuel burning. Methane and nitrous oxide have also increased unnaturally because of agricultural practices and other factors. The world has also warmed unnaturally. We are now deviating from the natural cycle.

The natural cycle is understood by examining the paleo records. The fact that the earth goes in and out of ice ages distinctly outlines the natural cycles of Earth's climate. This occurs about every 100,000 years. We are currently in a warm period. Generally, Earth spends about 80-90,000 years in an ice age and around 10-20,000 years (or so) in a warm period.

## Does the Sun Affect our Weather and Climate?

There have many arguments about whether or not variations in the Sun’s activity affect our weather and climate. The Old Farmer’s Almanac’s long-range forecasts are based predominantly upon solar activity, with their basis being that changes in activity on the Sun do indeed directly cause changes in weather patterns on Earth.

Although our seasonal forecasts have been far more accurate than any others made with a similar time frame, until recently nearly all meteorologists and climatologists have not believed that it was even possible for changes in solar output to affect Earth’s weather, let alone control it to a large extent, as we believe is the case.

The reason for their skepticism has to do with the energy output from the Sun, which is known as the solar constant. Technically, it is not really a constant—it does change significantly over billions of years. It also varies over days and years, but as these variations are a tiny fraction of its value, the scientific consensus has been that any changes in solar energy on a shorter-than-geological-era scale are much too small to have any effect on Earth’s weather.

A defining feature of science that helps to make it so valuable is that as new information comes to light, scientific consensus changes, and what was once believed to be incorrect can become the new truth.

### Emerging Evidence

Several years ago, a research paper was published by some Russian meteorologists who believed that they had discovered and defined a mechanism by which tiny changes in solar output could have an effect on Earth’s weather. They postulated that these changes affected the top of Earth’s atmosphere, an area known as the thermosphere, which was thin enough for these small changes to have an effect on it—and that these changes were then enhanced by orders of magnitude as they reflected into the troposphere, the lowest portion of the atmosphere, where our weather occurs.

Recently, others have picked up on this research, and its concepts seem to be moving into the scientific mainstream.

The SABER instrumentation aboard the TIMED satellite launched 17 years ago has provided data on the infrared emissions from carbon dioxide ( CO2 ) and nitric oxide ( NO ), two substances that play a key role in the energy balance of air in the thermosphere. By measuring the infrared glow of these molecules, SABER can assess the temperature at the very top of the atmosphere.

### The Thermosphere Climate Index

Martin Mlynczak, at NASA ’s Langley Research Center, has developed something called the Thermosphere Climate Index ( TCI ), which measures the temperatures at the top of Earth’s atmosphere. Although SABER has been in orbit for only 17 years, Mlynczak and his colleagues recently calculated TCI going all the way back to the 1940s. “ SABER taught us to do this by revealing how TCI depends on other variables such as geomagnetic activity and the Sun’s UV output—things that have been measured for decades,” he explained. (See the accompanying graph of TCI data, courtesy of NASA .)

As 2019 begins, the Thermosphere Climate Index is on the verge of setting a Space Age record for cold, which reflects the historic low in solar activity in the current cycle.

So, recent data has proven that temperatures in the uppermost portion of the atmosphere vary substantially, in parallel with solar activity. Recent research proposes a mechanism by which these changes can have a significant effect on weather patterns in the lower atmosphere. While these changes in scientific consensus may not come close to the importance of the refinements of Newtonian mechanics made by Einstein early in the 20th century, they do, at the very least, add scientific credibility to the forecast methodology that we use to make your long-range forecasts here at The Old Farmer’s Almanac.

Have you picked up your copy of the 2019 Almanac? It’s available in local bookshops and retail stores and on Amazon! You can also look inside to learn more on our Web store here.

## Journal criticised for study claiming sun is causing global warming

A high profile scientific journal is investigating how it came to publish a study suggesting that global warming is down to natural solar cycles. The paper was criticised by scientists for containing “very basic errors” about how Earth moves around the sun.

The study was published online on 24 June by Scientific Reports, an open access journal run by Nature Research, which also lists the prestigious Nature journal among its titles. A spokesperson told New Scientist that it is aware of concerns raised over the paper, which was authored by four academics based at Northumbria University, the University of Bradford and the University of Hull, all in the UK, plus the Nasir al-Din al-Tusi Shamakhi Astrophysical Observatory in Azerbaijan.

The authors suggest that Earth’s 1°C temperature rise over the past two centuries could largely be explained by the distance between Earth and the sun changing over time as the sun orbits around our solar system’s barycentre, its centre of mass. The phenomenon would see temperatures rise a further 3°C by 2600, they say.

#### Read more: Seven steps to save the planet: How to take on climate change and win

Ken Rice of the University of Edinburgh, UK, criticised the paper for an “elementary” mistake about celestial mechanics. “It’s well known that the sun moves around the barycentre of the solar system due to the influence of the other solar system bodies, mainly Jupiter,” he says. “This does not mean, as the paper is claiming, that this then leads to changes in the distance between the sun and the Earth.”

“The claim that we will see warming in the coming centuries because the sun will move closer to the Earth as it moves around the solar system barycentre is very simply wrong,” adds Rice. He is urging the journal to withdraw the paper, and says it is embarrassing it was published.

Gavin Schmidt of the NASA Goddard Institute for Space Studies says the paper contains egregious errors. “The sun-Earth distance does not vary with the motion of the sun-Earth system around the barycentre of the sun-Jupiter system, nor the sun-galactic centre system or any other purely mathematical reference point,” he says. He says the journal must retract the paper if it wants to retain any credibility.

#### Read more: Climate change is happening, but how fast? This is what we really know

Following criticism of the paper, lead author Valentina Zharkova, of Northumbria University, described Rice as a “climate alarmist” in an online discussion.

“The close links between oscillations of solar baseline magnetic field, solar irradiance and temperature are established in our paper without any involvement of solar inertial motion,” Zharkova told New Scientist.

Scientific Reports says it has begun an “established process” to investigate the paper it has published. “This process is ongoing and we cannot comment further at this stage,” a spokesperson said.

## Does the sun have cycles causing temperature changes on Earth? - Astronomy

The distance between Earth and Sun is probably the least critical with respect to the average temperatures on Earth. The distance between Earth and Sun is about 92 million miles and the change in distance due to the eccentric orbit of Earth around the Sun is around 3 million miles. This is a small percent of the actual distance between the Earth and the Sun, and will hence not cause an appreciable change in the average temperature (especially when considering the actual change in temperature on account of seasons).

Further, the temperature on Earth is also dependent on other factors. If one calculates the equilibrium temperature on Earth based on energy balance, then one will find that it comes to around 0 F, which is quite cold. The reason why the Earth is warm at about 70 F is because of other factors like greenhouse effect. There is a common misconception that the greenhouse effect is something really bad. The truth is that it is because of a mild greenhouse effect that Earth is as warm as it is. It is when the greenhouse effect starts becoming a runaway process that it becomes a cause for concern, and we are moving in that direction with the burning of fossil fuels.

In addition, Earth's geological activity also affects the average temperatures. As a simple example, if there is a massive volcanic eruption that sends large amounts of volcanic ash and SO2 (Sulphur-Dioxide) into the atmosphere. The ash and aerosols created by the SO2 could block sunlight, thereby cooling the Earth, leading to a "volcanic winter". An example of this was the eruption of Mt. Pinatubo in the Philippines which caused global temperatures to drop for 2-3 years! Another factor that affects climate and temperatures on Earth are variations in the solar luminosity.

So, while large changes in the distance between Earth and Sun would of course affect the average temperature on Earth, variations that are a small percentage of the actual distance will not have any appreciable effect.

Jagadheep built a new receiver for the Arecibo radio telescope that works between 6 and 8 GHz. He studies 6.7 GHz methanol masers in our Galaxy. These masers occur at sites where massive stars are being born. He got his Ph.D from Cornell in January 2007 and was a postdoctoral fellow at the Max Planck Insitute for Radio Astronomy in Germany. After that, he worked at the Institute for Astronomy at the University of Hawaii as the Submillimeter Postdoctoral Fellow. Jagadheep is currently at the Indian Institute of Space Scence and Technology.

## Changes in the Sun Can Affect Climate.

Since almost all the energy on Earth comes from the Sun, changes in the Sun can have an impact on Earth. Changes in the cycle of solar activity, called the 11-year sunspot cycle, can cause small changes in the amount of solar energy that gets to Earth. However the amount of energy only changes 0.15% over the cycle, which has a very minor impact on climate comparted with other factors. These changes in the Sun are too small to be the cause of recent climate change.

There are also larger changes in the amount of energy that comes from the Sun that occur over decades and centuries. These changes are able to affect Earth’s climate. For example, in the past few decades, Earth would have cooled slightly because of slightly less energy produced by the Sun, but the amount of that change is not noticeable because of climate warming caused by extra greenhouse gases (see below).

## Sun's impact on climate change quantified for first time

A solar flare captured by the Solar Dynamics Observatory, a satellite launched by NASA in 2010

For the first time, model calculations show a plausible way that fluctuations in solar activity could have a tangible impact on the climate. Studies funded by the Swiss National Science Foundation expect human-induced global warming to tail off slightly over the next few decades. A weaker sun could reduce temperatures by half a degree.

There is human-induced climate change, and there are natural climate fluctuations. One important factor in the unchanging rise and fall of the Earth's temperature and its different cycles is the sun. As its activity varies, so does the intensity of the sunlight that reaches us. One of the key questions facing climate researchers is whether these fluctuations have any effect at all on the Earth's climate. IPCC reports assume that recent solar activity is insignificant for climate change, and that the same will apply to activity in the near future.

Researchers from the Physical Meteorological Observatory Davos (PMOD), the Swiss Federal Institute of Aquatic Science and Technology (EAWAG), ETH Zurich and the University of Bern are now qualifying this assumption. Their elaborate model calculations are supplying a robust estimate of the contribution that the sun is expected to make to temperature change in the next 100 years. For the first time, a significant effect is apparent. They expect the Earth's temperature to fall by half a degree when solar activity reaches its next minimum.

According to project head Werner Schmutz, who is also Director of PMOD, this reduction in temperature is significant, even though it will do little to compensate for human-induced climate change. "We could win valuable time if solar activity declines and slows the pace of global warming a little. That might help us to deal with the consequences of climate change." But this will be no more than borrowed time, warns Schmutz, since the next minimum will inevitably be followed by a maximum.

Strong fluctuations could explain past climate

At the end of March, the researchers working on the project will meet in Davos for a conference to discuss the final results. The project brought together various research institutions' capabilities in terms of climate effect modelling. PMOD calculated what is known as "radiative forcing" taking account of particle as well as electromagnetic radiation, ETH Zurich worked out its further effects in the Earth's atmosphere and the University of Bern investigated the interactions between the atmosphere and oceans.

The Swiss researchers assumed a greater fluctuation in the radiation striking the Earth than previous models had done. Schmutz is convinced that "this is the only way that we can understand the natural fluctuations in our climate over the last few millennia." He says that other hypotheses, such as the effect of major volcanic eruptions, are less conclusive.

Exactly how the sun will behave over the next few years remains a matter of speculation, however, since appropriate data series have only been available for a few decades and they reveal no evidence of fluctuations during this time. "To that extent, our latest results are still a hypothesis," says Schmutz, "and it remains difficult for solar physicists to predict the next cycle." But since we have been observing a consistently strong phase since 1950, it is highly likely that we will experience another low point in 50 to 100 years' time. It could be every bit as intense as the Maunder Minimum, which brought particularly cold weather during the 17th century.

Important historical data

The research project also placed great importance on the historical perspective. The Oeschger Centre for Climate Change Research at the University of Bern compared data series on past solar activity with other specific climatic conditions. People have been recording the number of sunspots, which correlates well with solar activity levels, for some three centuries now. However, it is much more difficult to quantify exactly how cold it was on Earth back then. "We know that the winters during the last minimum were very cold, at least in northern Europe," says Schmutz. The researchers still have a fair amount of work to do before they have a detailed understanding of the relationship between solar activity and the global climate both in the past and in the future.