säteilymuutokset

Säteilymuutokset refers to changes in the amount of radiation received by Earth from the Sun. These fluctuations are a natural phenomenon that can influence Earth's climate over long geological timescales. The primary drivers of these changes are variations in Earth's orbit around the Sun and the Sun's own activity cycles.

Orbital variations, often referred to as Milankovitch cycles, include changes in the eccentricity of Earth's orbit (how elliptical it is), the tilt of Earth's axis (obliquity), and the wobble of Earth's axis (precession). These orbital parameters affect the distribution and intensity of solar radiation reaching different parts of Earth at different times of the year. For example, a greater axial tilt leads to more extreme seasons, with hotter summers and colder winters.

Solar activity, such as sunspot cycles, also plays a role. While the total solar irradiance (the amount of solar energy reaching Earth's atmosphere) varies by only a small fraction over a typical 11-year sunspot cycle, these small changes can still have a cumulative effect on climate over millennia. Periods of significantly lower solar activity, like the Maunder Minimum in the 17th century, have been correlated with cooler periods on Earth, such as the Little Ice Age.

These natural säteilymuutokset are distinct from anthropogenic climate change, which is driven by human emissions of greenhouse gases. However, understanding the Earth's response to natural radiative forcing is crucial for accurately modeling and predicting future climate scenarios. Paleoclimate data, derived from ice cores, ocean sediments, and other geological records, provides evidence for past climate shifts that align with predictions based on variations in solar radiation.