The Little Ice Age is pretty much attributable to a decrease in solar activity (the Maunder Minimum), and natural variability, particularly ocean circulation. The earlier warmth was more of a "normal" climate setting. Now we're in a period at least as warm as back in the Medieval period, and we're adding a factor (CO2 to the atmosphere) that should, if you believe basic physics, augment Earth's temperature. There are obviously variables in the climate system, but what the study shows (on top of other studies showing essentially the same thing, in different ways) is that the currently observed warming trend can't be attributed to solar variability. Thus there isn't much else to blame it on except increasing concentrations of atmospheric CO2.
Why do you reject the effect of cosmic rays on cloud cover since we have seen a clear correlation with cosmic ray flux and cloud cover and also with cosmic rays and high altitude temperature?
I have a friend who is a world renown climatologist/geophysicist.
He agrees with you.
I suppose I should've added a sarcasm tag.
If the sun's energy output has barely changed over the last 1000 years, then it didn't cause any other climate change over this period either.
So the warming period prior to the little ice age was caused by CO2 AND the little ice age itself was caused by CO2, if you follow the logic of the article.