[assblaster]

They didn't have records before 1880 according to the article. So, it could have been warmer, but there is no record of it.

[itcrowd]

There have been many reconstructions of global temperatures before 1880 using a variety of temperature proxies. A nice summary in one image is given on Wikipedia [1].

[1] https://en.wikipedia.org/wiki/Paleoclimatology#/media/File:A...

[assblaster]

They also mix proxies but superimpose temperature records from the last 150 years. A better curve would be using one set of proxy data to maintain consistency.