"Temp variation" refers to changes or fluctuations in temperature, indicating that the temperature can go up or down from its normal or average level. Full definition
Solar forcing varies by about 1w / m2 during the 11 year solar cycle and causes 0.1 deg of temp variation. (climate-skeptic.com)
So if I look at the spectral graph of the sunspots and temp anomalies (in my case East England) and I see spikes close to temp variations and sunspot activity, I think it would be reasonable to look if there was a correlation. (realclimate.org)
Or that the temp variation was confined to the NH? (judithcurry.com)