Unfortunately, this is deceptive. The point of it seems to be to show how the recent sudden increase in temperature is unprecedented in the last 22000 years. The problem is that the data for different intervals comes from different sources. The last part showing the rapid rise comes from very accurate, yearly measurements. Historical data comes from reconstructions with much lower resolution. In a signal processing sense that means that the historical data is "low pass filtered". In other words, it lacks high frequency variation. You could say that the information you need to decide whether the recent rapid temperature rise is unprecedented or not is missing from the vast majority of the chart, but it's present in the last segment of the chart.
Authors of the Marcott et. al. (2013) [1] paper that the XKCD chart uses state:
Q: "Is the rate of global temperature rise over the last 100 years faster than at any time during the past 11,300 years?"
A: "Our study did not directly address this question because the paleotemperature records used in our study have a temporal resolution of ~120 years on average, which precludes us from examining variations in rates of change occurring within a century. Other factors also contribute to smoothing the proxy temperature signals contained in many of the records we used, such as organisms burrowing through deep-sea mud, and chronological uncertainties in the proxy records that tend to smooth the signals when compositing them into a globally averaged reconstruction. We showed that no temperature variability is preserved in our reconstruction at cycles shorter than 300 years, 50% is preserved at 1000-year time scales, and nearly all is preserved at 2000-year periods and longer. Our Monte-Carlo analysis accounts for these sources of uncertainty to yield a robust (albeit smoothed) global record. Any small “upticks” or “downticks” in temperature that last less than several hundred years in our compilation of paleoclimate data are probably not robust, as stated in the paper."
[1]: https://dotearth.blogs.nytimes.com/2013/03/31/fresh-thoughts...
Authors of the Marcott et. al. (2013) [1] paper that the XKCD chart uses state:
Q: "Is the rate of global temperature rise over the last 100 years faster than at any time during the past 11,300 years?"
A: "Our study did not directly address this question because the paleotemperature records used in our study have a temporal resolution of ~120 years on average, which precludes us from examining variations in rates of change occurring within a century. Other factors also contribute to smoothing the proxy temperature signals contained in many of the records we used, such as organisms burrowing through deep-sea mud, and chronological uncertainties in the proxy records that tend to smooth the signals when compositing them into a globally averaged reconstruction. We showed that no temperature variability is preserved in our reconstruction at cycles shorter than 300 years, 50% is preserved at 1000-year time scales, and nearly all is preserved at 2000-year periods and longer. Our Monte-Carlo analysis accounts for these sources of uncertainty to yield a robust (albeit smoothed) global record. Any small “upticks” or “downticks” in temperature that last less than several hundred years in our compilation of paleoclimate data are probably not robust, as stated in the paper."
[1]: https://dotearth.blogs.nytimes.com/2013/03/31/fresh-thoughts...