
Earth Temperature Timeline - alanfranz
https://xkcd.com/1732/
======
0-_-0
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...](https://dotearth.blogs.nytimes.com/2013/03/31/fresh-thoughts-
from-authors-of-a-paper-on-11300-years-of-global-temperature-changes/?_r=0)

~~~
DoctorOetker
Unfortunately, your stance is deceptive:

Assuming a resolution period of ~120 years (full cycle) or halfcycle (assuming
an effective sample every ~120 years, hence a full cycle period of ~240
years), then the recent excursion can be roughly approximated as a step
function. If one lowpasses a step function, you get visible ringing. In the
low resolution part of the record there is no ~120 year nor ~240 year ringing
at all, so the probability of a similar Heaviside step function theta in
temperature having been present but filtered out is nearly zero...

~~~
0-_-0
It's not literally a low pass filter with a sinc function of course, that was
an analogy. It's more like a gaussian smoothing. You're not going to get
ringing in the temperature record...

Here's the direct quote again if you missed it above:

 _" We showed that no temperature variability is preserved in our
reconstruction at cycles shorter than 300 years"_

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toomuchlove
Please label 2016

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dogwhistle
Hug of death . Alternate links please?

