The intensity of the Sun continuously changes, but there were no direct measurements of the size of these shifts before 1979. Since then, the Sun's variations have been very small. Indirect evidence suggests that the Sun's variations in the past may have been large enough over the course of centuries to affect Earth's climate significantly. However, several recent studies indicate that the warming effect of solar variations since the late 19th century, and particularly in the past 50 years, has been considerably smaller than the warming effect of the greenhouse gas buildup. Climate and weather are different.
Weather refers to temperatures, precipitation, and storms on a given day at a particular place.
Climate reflects a long-term average, sometimes over a very large area, like a continent or even the entire Earth. Averages over large areas and periods of time are easier to estimate than the specific characteristics of weather. Nevertheless, scenarios for global warming always recognize a large range of uncertainty.