Credit : wmo
While the sun rises faithfully each day at an accurately predictable time, scientists have found that the sun’s energy output is not really constant, but varies by a small amount over the centuries, probably less than 1%. We have seen that the number of sunspots varies with time between sunspot maxima of around 11 years and that the maximum number of sunspots is not always the same. Considerable-evidence shows that between 1645 & 1715 the number of sunspots, even at sunspot maximum, was much lower than it is today. This area of significantly lower sunspot numbers was first observed by Gustav Spӧrer in 1887 & then by E W Maunder in 1890; now called Maunder Minimum. The variation in the number of sunspots over the past three centuries. In addition to the Maunder Minimum in the 17th century, the number of sunspots at the beginning of the 19th century was slightly lower than it is today; this period is known as the Little Maunder Minimum.
When the sunspot number is high, the sun is also active in other ways, and as we will see in several sections below, some of this activity has a direct impact on the earth. For example, There are more manifestations of auroral-displays when the number of sunspots is high. Auroras occur when energetically charged particles from the sun interact with the earth’s magnetosphere, and the sun is more likely to send out particles when it is active and sunspot numbers are high. Historical reports also indicate that aurora activity was unusually low during the several decades of the Maunder Minimum.
The Maunder Minimum was a period of exceptionally low temperatures in Europe, so low that this period is known as the Little Ice Age. This coincidence in time allows scientists to understand whether small changes in the sun will affect the Earth’s climate. There is clear evidence that Europe was unusually cold for part of the 17th century. The Thames River in London froze at least eleven times, ice appeared on the Theoceans off the coast of southeast England, and low summer temperatures resulted in short growing seasons and poor harvests. However, whether and how changes in the sun on this time scale affect the earth’s climate remains a matter of dispute among scientists.
Other small changes in climate, such as the Little Ice Age, have occurred and have had an impact on human history. For example, explorers from Norway first colonized Iceland and then arrived in Greenland in 986, from where they could repeatedly visit the north-eastern coasts. of North America, including Newfoundland, between about 1000 and 1350. (Ships of the time did not allow Norse explorers to travel directly to North America, only from Greenland, which served as a station for further exploration.)
credit: modification of work by NASA/ARC
Greenland is mostly covered with ice and the Greenland station has never been self-sufficient; rather, it relied on the import of food and other goods from Norway for its survival. When a small ice age began in the 13th century, journey became very difficult and the support of the Greenland colony was no longer possible. The last known contact with him was made by an Iceland ship that went off course in 1410. When European ships visited Greenland again in 1577, the entire colony had disappeared.
The estimated dates for these migration patterns follow what we know about solar activity. Solar activity was unusually high between 1100 & 1250, including the time when European contacts were first made with North America. Activity was low from 1280 to 1340 and there was a small ice age around the time regular contact with North America & between Greenland & Europe stopped.
However, it must be assumed that the small number of sunspots or fluctuations in the sun’s energy production caused the Little Ice Age. There is no satisfactory model that can explain how a decrease in solar activity could lead to cooler temperatures on earth. An alternative possibility is that the cold weather during the Little Ice Age is related to volcanic activity. Volcanoes can emit aerosols (small droplets or particles) into the atmosphere, which efficiently reflect sunlight. For example, observations show that the 1991 Pinatubo eruption released SO2 aerosols into the atmosphere, reducing the amount of sunlight reaching the Earth’s surface enough to lower global temperatures by 0.4. ° C.
Satellite data show that the sun’s energy out-put varies by only about 0.1% during a solar cycle. We are not aware of any physical process that explains how such a small variation could lead to changes in global temperature. However, solar activity can have other effects. For example, although Sun total energy out-put of the sun only fluctuates by 0.1% during a solar cycle, its extreme ultraviolet radiation at times of solar maximum is ten times greater than at solar minimum. This large variation can affect the chemistry & temperature structure of the upper atmosphere. One effect could be a reduction in the ozone layer and a cooling of the stratosphere near the earth’s poles. This, in turn, could change the circulation patterns of the winds in the air and thus the footprints of storms. There is some recent evidence that variations in regional rainfall correlate better with solar activity than with the Earth’s global temperature. But as you can see, the relationship between what happens on the sun and what happens to the earth’s climate in the short term is still an area. that scientists study & debate.
Regardless of the effects of solar activity on local rain-fall or temperature patterns, we would like to highlight an important idea: Our data on climate change and the models developed to take account of the data consistently show that solar variability is not the cause of global warming that has occurred. for the past 50 years.
