As someone who believes in Anthropomorphic Climate change, that graphic is just horrendous. Here is another XKCD to explain why: https://xkcd.com/605/
To be less punchy: Most of the data on the graph is on a scale of 500 years and the data is filled in with dashed lines. Starting the late 1800's we suddenly have real data(what is the update frequency?, how does that compare to previous data?)
Here is the note on the graphic: "Limits of this data: Short warming or cooling spikes may be 'smoothed out' by these reconstructions but only if they are small enough or brief enough"
To be less punchy: Most of the data on the graph is on a scale of 500 years and the data is filled in with dashed lines. Starting the late 1800's we suddenly have real data(what is the update frequency?, how does that compare to previous data?)
Here is the note on the graphic: "Limits of this data: Short warming or cooling spikes may be 'smoothed out' by these reconstructions but only if they are small enough or brief enough"
What is small enough? What is brief enough?