[cogitator]

1. First they say it's the hottest it has been in 400 years which doesn't seem to agree with your charts which show that it was hotter in the medieval warm period around 1200 AD.

1200 AD was 800 years ago.

They say surface temps only rose 1 degree in 20th century. Is a 1 degree increase that significant and how much of that 1 degree do they estimate is caused by humans vs natural causes?

Note that's 1 deg F, 0.6 deg C. That change is attributed 33-50% to human activities. This is due to the fact that early 20th century temperature increase (1900-1930s) is considered to be about 50% solar driven, 50% human activities. There was a cooler period mid-century (about 0.2 C) attributed to natural variability and perhaps to sulfate aerosols. Since the mid-1970s, the 0.4-0.6 C rise is considered to be primarily due to human activities.

[VeniVidiVici]

This is due to the fact that early 20th century temperature increase (1900-1930s) is considered to be about 50% solar driven, 50% human activities.

Wow! So, how did they arrive at this figure? And why couldn't it be 90/10? And what exactly caused the lack of heat from sunlight for the entire period of the Little Ice Age?