The Sun is naturally the primary driver and energy source for atmospheric and ocean systems and the Earth's surface climate. The variations in the total irradiance over a solar cycle is only 0.1%, a number that is often used to argue that the Sun cannot explain the recent global warming. However, one should point out that it is the long term variations in the solar irradiance that is important. The latter number is estimated to have increased by 0.25-0.6% during the last 200 years.
Solar cycles charted by the total irradiance as identified by several satellites since 1978. (Time period shaded in purple from VIRGO.)
