Based on the increase of solar activity during the twentieth century, it should account for between half to two-thirds of all climate change
If solar activity did play a significant role in recent changes in global temperatures, then those temperatures should have stayed roughly the same or even declined over the last decade. A paper from 2012 even predicted there would be a 1.0°C decrease in temperatures. Clearly this has not turned out to be the case. The hottest decade on record has coincided with the weakest solar cycle for over a century. Given this combination of factors, it is rather difficult to defend the position that solar activity is indeed responsible for present climate change without a radical shake up of the understanding of solar physics. In the graphs below we have attempted to correlate the number of sunspots with variations in global sea surface temperatures (taken from the Japan Meteorological Agency), and global surface temperatures (taken from GISTEMP data). [...] These observations of the present solar cycle make it very difficult to defend the position that solar activity is ultimately responsible for the world’s current warming trend. Instead they fit with the argument that human influences are responsible for a large amount of the recent increase in global temperatures.