How long have solar output variations been observed to affect climate?

Solar output variations affecting climate have been observed over several centuries, primarily due to historical records and scientific studies that trace changes in climate to fluctuations in solar activity. Historical evidence suggests that significant changes in solar output, such as the Maunder Minimum—a period from about 1645 to 1715 with very low solar activity—corresponded with notably cooler temperatures in Europe, illustrating the impact of solar variations on climate over a prolonged period.

Research into past climate conditions also supports the understanding that solar irradiance has natural cycles, which can lead to climate changes over decades to centuries. By analyzing ice cores, tree rings, and other climate proxies, scientists have been able to identify patterns that correlate solar activity with climate shifts throughout history.

This understanding is essential in recognizing that while modern climate change, particularly since the Industrial Revolution, can be attributed mainly to anthropogenic factors, natural variations in solar output have historically played a role in shaping Earth's climate over a much longer time frame.