And ""During the 20th century one continues to observe a significant correlation between the solar and temperature patterns: both records show an increase from 1900 to 1950, a decrease from 1950 to 1970, and again an increase from 1970 to 2000." The rest of the warming may or may not be man made. So in essence they think that about half of all observable warming can be attributed to solar activity.
And hurrah they have noticed the cosmic rays research which The Economist missed.
So exploding stars in distant galaxies bombard us with cosmic rays which help produce clouds which induce cooling. "Cloud cover increases when the intensity of cosmic rays grows and decreases when the intensity declines." And over the last century, the century of global warming, our Sun's magnetic field which shields Earth from cosmic rays more than doubled, thereby reducing the average influx of cosmic rays. The resulting reduction in cloudiness, especially of low-altitude clouds, may be a significant factor in the global warming Earth has undergone during the last century.The paper points out that this is a mechanism which has been ignored until now.
What percentage of global warming is due to the reduction of clouds caused by the reduction of cosmic rays hitting the Earth? The computer models used to estimate man's role in global warming have simply not had this information in the past. So how accurate is their estimate that what we are seeing is anthropogenic?