Like I said recently, show me what the average global temperature was in 1165. Tell we what temperature proxy or combination of proxies can come up with a useful estimate with a one year temporal (time) resolution.
People focus on spatial resolution (location of the proxies) and the error margins of the data but rarely discuss the time resolution. We're used to getting thermometer and satellite readings on a daily basis forming pretty good average global temperature calculations with high spatial resolution and decent error margins. A thousand years ago and you're just guessing what it was like in any given year or span of years.
And starting with Mann in 1998, these guesses started getting lower for past temperatures trying to show 1) to be true. That's just one aspect, yet a very important skepticism of AGW. It's just one of many shaky legs of the theory.
We will never know, barring time travel or the like, if 20th century warming is *unprecedented*. What we do know is that it appears to be unusually large. From what we can tell, temperatures typically change on the order of one degree/1000 years, and to the best of my knowledge we are currently wekk on track to have a temperature increase significantly greater than 1 degree/century, in the 21st century.
And the error margins of that study suggest that we cannot be absolutely certain that curent temperatures are higher than those of 250 years ago. However, only if the true temperatures for that time were at the extreme high end of the margin of error would they equal or exceed current temperatures. This suggests that the *likeliest* answer is that current temperatures are significantly warmer than those 250 years ago.
Remember, the 95% confidence level is basically "There is a 5% chance or less that the result lies outside of this range". I'd bet if you looked for a 90% confidence level, you'd see margins of error small enough that current temperatures would lie well outside of them. It's just that 95% confidence is kind of the usual scientific standard for "we can treat this as fact rather than speculation"...
The rate of rise was unprecedented in MODERN times only, and of course it does become harder to reconstruct older temperature rises.
But at the same time according to wikipedia, the solar activity at the same time was the most intense for the last 9000 years.
3) Both
NO
or that temperature may be warmer than it was 250 years ago?
http://berkeleyearth.org/results-summary/
I'm looking for either...
1) The rate of warming in the 20th century is unprecedented.
2) The temperature today is higher than it was 250 years ago.
3) Both
