- Solar cycles
The magnetic field of the Sun changes every 11 years: a period of increasing brightness of the star is followed by a period of dimming. Usually such fluctuations do not have a strong effect on the Earth’s climate, but there are more significant cycles.
“Large solar minima” are decadal periods of decreasing solar activity. They are quite frequent: over the past 11,000 years, such activity decreases have occurred 25 times. One such minimum, the Maunder minimum, occurred between 1645 and 1715 and resulted in a 0.04-0.08 percent drop in solar energy levels from today.
Over the last half century, the Sun has dimmed, while the Earth, on the contrary, has warmed. And global warming has nothing to do with it at all.
- Short term climate fluctuations
Precipitation and temperature are influenced not only by seasonal weather patterns, but also by other short-term cycles. For example, the El Niño effect causes changes in the circulation of the waters of the tropical Pacific Ocean over a period of two to seven years. Such fluctuations result in warm and very wet weather conditions from December through February on the northern coast of Peru and Ecuador. - Volcanic Sulfur.
Powerful volcanic eruptions cause sulfuric acid particles to enter the stratosphere, which shield sunlight, cooling the climate. The result is more sea ice, which in turn reflects sunlight. Global cooling is thus prolonged and intensified.
For example, the eruption of the Ilopango volcano in El Salvador between A.D. 539 and 540 caused a climate cooling of about 2 °C that lasted 20 years. The recent Pinatubo eruption in the Philippines in 1991 cooled the global climate by 0.6 °C for 15 months.
- plate tectonics
The shifting of tectonic plates can slowly change the Earth’s climate. Tectonic collisions set chemically reactive rocks like basalt and volcanic ash in motion, increasing the rate of reactions that “attract” carbon dioxide. Carbon dioxide is a major regulator of Earth’s climate because it blocks heat from trying to rise from the planet. - Orbital oscillations.
The Earth’s orbit oscillates when the Sun, Moon, or other planets change their positions relative to it. These cyclical oscillations – called Milankovitch cycles – cause the amount of sunlight to change at mid-latitudes. Consequently, the climate changes as well.
About 11,700 years ago, Milankovitch cycles caused ice ages on Earth or, conversely, brought the planet back from them. When the fluctuations in the Earth’s orbit made summers warmer in the north, huge ice sheets melted in North America, Europe, and Asia. Then northern summers became cold again, and the ice sheets grew again.