It's been argued that if summer in the northern hemisphere coincides with Earth being at perihelion, then it will be very warm. Vice versa for summer at aphelion. This happens every 20,000 years and may explain ice ages.

It that is significant, then maybe the gravitational pull of planets could distort the sun just enough to effect shorter-term variations in solar output. All it would take is a change in the geometry of the sun, from an oblate spheroid, to an oblate spheroid with a lobe in the direction of the solar system barycenter. Even if the total solar power output remained constant, the surface would have a bulge in the direction of a planetary conjunction. Heat might tend to be radiated perpendicular to that surface, or what passes for a surface, and if there is a bulge that direction might be parallel to the sun's polar axis, instead of isotropically. If all the gas giant planets lined up, such a bulge might last for many years, enough to change the climate on Earth slightly.

If the sun radiated mostly perpendicular to the ecliptic, then the planets would get less sunlight.

If this idea could be demonstrated, it might even form a basis for the detection of extrasolar planets.