Although the Sun provides almost all the energy needed to warm the planet, its contribution to climate change remains widely disputed. Many empirically based studies claim that it has a significant impact on climate, while others (often based on computer simulations of global climate) claim that it has a small impact. The Intergovernmental Panel on Climate Change (IPCC) supports the latter view, estimating that almost 100 % of the observed warming of the Earth's surface between 1850–1900 and 2020 was due to human-caused emissions. This is known as the anthropogenic global warming theory (AGWT). (Nicola Scafetta, PHYSORG)