Climate models dismiss the role of the Sun in climate change by only considering the tiny 0.1% variations in Total Solar Irradiance [TSI] over solar cycles, while ignoring large changes in the solar spectrum such as variations in UV forcing of up to 100% over solar cycles. High-energy solar UV penetrates the ocean to the greatest depths in comparison to other solar wavelengths, heating the oceans more efficiently than other portions of the solar spectrum. Solar UV also affects production of the radiatively-active gas ozone, which also affects surface temperatures.
Climate models also ignore other potential solar amplification mechanisms via solar energetic particles [SEPs], galactic cosmic rays [GCRs] and via modulation of ocean and atmospheric oscillations such as ENSO, the North Atlantic Oscillation [NAO] and Quasi-Biennial Oscillation [QBO]. The QBO in turn affects planetary scale waves such as Rossby Waves, the jet stream, and the polar vortex. Solar minimums have been linked to the negative phase of the NAO, which in turn causes colder winters in Europe and recovery of Arctic sea ice.
These are only a few of the solar amplification mechanisms outlined in the excellent lecture slides below from a conference on climate impacts of solar radiation, which demonstrate the solar-climate connection is far more complex than the simplistic assumptions used in climate models.