The relationship between the solar constant and climate change

The solar constant is a fixed value. The solar constant also changes periodically, ranging from 1% to 2%, which may be related to the activity cycle of sunspots.

Impact on Earth’s climate

By establishing an important connection between the solar activity cycle and the Earth’s global climate, a scientific study led by scientists from the National Center for Atmospheric Research found that Peaks of solar activity and their aftermath can affect the Earth, causing phenomena similar to La Ni?a and El Ni?o in the Earth's Pacific tropics. The new research results are expected to pave the way for humans to predict temperatures and rainfall. The activity cycle of a sunspot is 11 years. During the entire cycle, the total energy from the sun reaching the earth changes by only 0.1%. For decades, scientists have been trying to correlate changes in the amount of solar energy reaching Earth with changes in the Earth's natural weather and climate, while also distinguishing the effects of changes in solar energy on Earth's climate from the effects of human activities on climate.

Based on past research work, scientists from the National Center for Atmospheric Research used global climate computer models and more than a century of ocean temperature data to establish an inherent relationship between the solar activity cycle and the Earth's climate. connect. The relevant article was published in this month's issue of the Journal of Climate. Girod Mir, the first author of the article and a scientist at the National Center for Atmospheric Research, believes that the new mechanism established by their research can help understand the impact of peak solar activity on the tropical Pacific. In fact, when the energy released by the sun is at its peak, it has subtle but long-term effects on rainfall in the tropics and weather systems in many parts of the world.

Research shows that during peak solar activity, the sun heats the cloudless Pacific Ocean, causing increased seawater evaporation, which intensifies tropical rainfall and winds while causing cooling in the eastern Pacific. Although the 1 to 2 degrees Fahrenheit cooling occurs far away in the eastern Pacific, the evaporation of seawater, rain, wind, and cooling produce the same results as a La Ni?a event, although its intensity is only typical. half of the La Ni?a phenomenon.

In addition, La Ni?a-like phenomena caused by peak solar activity occur one to two years after a La Ni?a-like phenomenon occurs, as slow-moving ocean currents replace cold water in the eastern tropical Pacific with warmer water. will evolve into an El Ni?o-like phenomenon. Likewise, the ocean response is only 50% as strong as a typical El Ni?o. Researchers also need to conduct more studies on the impact of solar activity on weather. The study found that La Ni?a trends, caused by solar activity, cause relatively warm and dry weather in parts of western North America. Based on their understanding of solar cycle activity, Mir said, they can link these effects to weather probabilities and add them to long-term forecasts.

The sunspot activity cycle is 11 years, and the number of sunspots goes through peak years and valley years from maximum to minimum. The activity level is related to the earth's climate. British researchers have confirmed that the regularity of sunspot cycle activity affects the Earth's climate. During periods of inactive sunspots, parts of North America and Europe often experience extreme weather.

Extension:

1. The solar constant refers to the solar radiation received per minute by the unit area of ??the top of the atmosphere perpendicular to the sun's rays at the average distance between the sun and the earth (D=1.496x108km). .

The solar constant is measured outside the Earth's atmosphere, on a plane perpendicular to the incident light. The value measured by artificial satellites is approximately 1366 watts per square meter. The cross-sectional area of ??the earth is 127,400,000 square kilometers, so the power received by the entire earth is 1.740×10^17 watts. Because there are often sunspots and other solar activities on the sun's surface, the solar constant is not fixed and varies by about 1% in a year.

2. Basic Principles

Day and night are caused by the rotation of the earth, and the seasons are caused by the rotation axis of the earth’s rotation axis being 23°27′ with the axis of the earth’s orbit around the sun. caused by the angle. The Earth rotates once a day from west to east on its "axis" passing through its South and North Pole. Each revolution is one day and night, so the Earth rotates 15° per hour. In addition to its rotation, the Earth also moves around the sun once a year in an elliptical orbit with a very small eccentricity. The normal line between the earth's rotation axis and the orbital plane is always 23.5°. As the Earth revolves, the direction of its axis of rotation remains unchanged and always points toward the Earth's North Pole. Therefore, when the earth is at different positions in its orbit, the direction of sunlight projected onto the earth is also different, thus forming the seasonal changes on the earth. At noon every day, the sun is always at its highest. In tropical low latitudes (that is, in the area between 23°27′ north and south latitudes of the equator), the sun is vertically incident twice a year. In higher latitudes, the sun is always closer to the equator. In the Arctic and Antarctic regions (greater than 90°~23°27′ in the northern and southern hemispheres), the sun spends a long time below the horizon in winter, while it spends a long time above the horizon in summer.

Since the earth moves around the sun in an elliptical orbit, the distance between the sun and the earth is not a constant, and the distance between the sun and the earth is different every day of the year. It is known that the intensity of radiation at a certain point is inversely proportional to the square of the distance from the source of the radiation, which means that the intensity of solar radiation above the Earth's atmosphere varies with the distance between the Sun and the Earth.

However, because the distance between the sun and the earth is so large (the average distance is 1.5 x 108km), the intensity of solar radiation outside the Earth's atmosphere is almost constant. Therefore, people use the so-called "solar constant" to describe the intensity of solar radiation above the Earth's atmosphere. It refers to the solar radiation energy received by the unit surface area perpendicular to the solar radiation at the upper boundary of the earth's atmosphere at the average distance between the sun and the earth. The standard value of the solar constant measured by various advanced means in recent years is 1353w/m2. The change in solar radiation intensity due to changes in the distance between the sun and the earth does not exceed 3.4% in a year.