<p>The reality is that we don’t know how reliable proxies are.  All of them have shown deficiencies.  Corals have shown they don’t fix <sup>18</sup>O like a time capsule, ice cores show that they’re not static (things migrate through the ice) and tree rings show a cooling trend in the late 20th century.  Aggregating a bunch of proxies on the assumption that these errors cancel is unproven and a huge leap of faith.  Anyone who claims proxies can detect global temperature to anything near what a thermometer can detect is either crazy or lying to you.  I wish it weren’t so, but that’s reality. There are too many unknown errors and since we don’t actually have a record of temperature prior to 1850, we have nothing to compare it against.</p>

CC BY-SA 4.0
2021-08-12T06:38:04.413Z
References\evidence for some of your claims might help you to convince :-)
JeopardyTempest
CC BY-SA 4.0
2021-08-11T10:22:05.027Z
2021-08-11T10:47:54.100Z
2021-08-11T10:47:54.100Z
Captain climate
<p>Overall, any individual proxy is not a reliable indicator.  It's the combination of multiple proxies that provides a clearer picture. </p>

<p>For example, tree ring growth has been correlated with temperatures.  However, it's not without it's anomalies:</p>

<blockquote>
  <p>...from the middle of the 20th century tree ring growth was less than might have been expected from the temperature record... ([source]</p>
</blockquote>

<p>(<a href="http://www.climatedata.info/Proxy/Proxy/treerings_introduction.html">http://www.climatedata.info/Proxy/Proxy/treerings_introduction.html</a>)) </p>

<p>If we were to only look at tree-rings, we could not possibly trust on them as a reliable source, since they have known problems.</p>

<p>We can also use coral as a indicator of past climate.  However, it's also somewhat questionable:</p>

<blockquote>
  <p>However, long (multi-centure) records are rare, and the possible influence of non-climatic influences has not yet been confidently established.
  <a href="http://www.meteo.psu.edu/holocene/public_html/shared/articles/MannPersp2002.pdf">source</a></p>
</blockquote>

<p>Ice-cores are not immune to skepticism:</p>

<blockquote>
  <p>An indisputable interpretation of ice-core oxygen isotopes in terms of
  atmospheric temperature variability, moreover, remains elusive, and
  precise annual dating can be difficult.</p>
</blockquote>

<p>However, if we can combine these three indicates along with other indicators (pollen, earth bores, etc), we can increase the reliability of our understanding.  For example, if most indicators show a cold year, we can more reliability say it was a cold year.  </p>

<p>Combining these proxies together helps us to gain a clearer picture of the past environment.</p>

<p><strong>Overall Reliability</strong></p>

<p>However, with that said, the amount of uncertainty with the multi-proxy method is not small.</p>

<p>At the Workshop on Mathematics in the Geosciences, Blake McShane presented a new algorithm for estimating paleoclimate.  This algorithm provided a more reliable estimate by <em>increasing the uncertainty</em> of the predictions.  That's an important point that I will restate:</p>

<p>Through his talk, he showed that his method was <em>more reliable</em> because it was <em>less certain</em>.</p>

<p>Even that wide uncertainty level, he questioned:</p>

<blockquote>
  <p>Indeed, this should make us <em>increase</em> our level of uncertainty (indeed perhaps 
  our wide intervals are in fact optimistically too narrow)!</p>
  
  <p><a href="http://www.earth.northwestern.edu/people/seth/Mathgeo/mcshane.pdf">source</a></p>
</blockquote>

<p>In the end, we can look at proxies for guidelines and trends, but they cannot be used for reliable readings.</p>

CC BY-SA 3.0
2014-05-06T21:39:55.410Z
2014-05-07T07:15:57.290Z
2014-05-07T07:15:57.290Z
Richard
<p>Since reliable modern records of climate only began in the 1880s, proxies provide a means for scientists to determine climatic patterns before record-keeping began, though it appears that the the distribution of <a href="http://en.wikipedia.org/wiki/Proxy_%28climate%29">proxy records</a> for global average temperatures, just like the instrumental record, is <a href="http://en.wikipedia.org/wiki/File:2000_Year_Temperature_Comparison.png">strongly non-uniform</a>, with more records in the northern hemisphere.</p>

<p>How accurate are climate proxies in giving us a clear picture of global average temperatures throughout Earth history?</p>

CC BY-SA 3.0
2014-05-06T17:37:03.167Z
What's the source for the distribution of proxy records being non-uniform? That would surprise me...
Semidiurnal Simon
CC BY-SA 3.0
2014-05-06T17:41:47.980Z
@SimonW: Added a source.
blunders
CC BY-SA 3.0
2014-05-06T18:13:12.097Z
How could we know? That is, we've only got the proxies, so what could we validate them against?
410 gone
CC BY-SA 3.0
2014-05-06T18:17:49.140Z
@EnergyNumbers Historical records since 1880.  Meaning, compare the proxies to the records as a baseline.
Richard
CC BY-SA 3.0
2014-05-06T18:22:10.400Z
@Richard: Correct, otherwise it's unclear what the baseline would be, right?
blunders
CC BY-SA 3.0
2014-05-06T18:24:19.953Z
To @EnergyNumbers point, though, we *only* have historical data back to the late 1900s.  We can't easily validate measurements beyond that barrier.
Richard
CC BY-SA 3.0
2014-05-06T18:25:17.753Z
@Richard aren't those the data that the proxies are **calibrated** with?
410 gone
CC BY-SA 3.0
2014-05-06T18:25:57.657Z
But climate's been really stable over the past 120 years - compared with the timescale we're looking at proxies over - so cross-calibration is of pretty limited use...
kaberett
CC BY-SA 3.0
2014-05-06T18:26:40.897Z
So the question stands.  And I, for one, am very interested in the answer.
Richard
CC BY-SA 3.0
2014-05-06T19:36:42.847Z
The limits of my understanding of this area are "crap, forams are probably not as good a record as we've been hoping for the past thirty years", but that doesn't count as an answer ;)
kaberett
<meteorology><climate><temperature><paleoclimatology>
How accurate are climate proxies in giving us a clear picture of global average temperatures throughout Earth history?
blunders
# How accurate are climate proxies in giving us a clear picture of global average temperatures throughout Earth history?

(Asked by: username_0 on 2014-05-06)

Since reliable modern records of username_5 only began in the 1880s, proxies provide a means for scientists to determine climatic patterns before record-keeping began, though it appears that the the distribution of [proxy records](http://en.wikipedia.org/wiki/Proxy_%28climate%29) for global average temperatures, just like the instrumental record, is [strongly non-uniform](http://en.wikipedia.org/wiki/File:2000_Year_Temperature_Comparison.png), with more records in the northern hemisphere.

How accurate are username_5 proxies in giving us a clear picture of global average temperatures throughout Earth history?

**Tags:** meteorology, climate, temperature, paleoclimatology

> **Comments:**
> **username_1**: What's the source for the distribution of proxy records being non-uniform? That would surprise me...  
> **username_0**: @SimonW: Added a source.  
> **username_2**: How could we know? That is, we've only got the proxies, so what could we validate them against?  
> **username_3**: @EnergyNumbers Historical records since 1880.  Meaning, compare the proxies to the records as a baseline.  
> **username_0**: @username_3: Correct, otherwise it's unclear what the baseline would be, right?  
> **username_3**: To @EnergyNumbers point, though, we *only* have historical data back to the late 1900s.  We can't easily validate measurements beyond that barrier.  
> **username_2**: @username_3 aren't those the data that the proxies are **calibrated** with?  
> **username_4**: But username_5's been really stable over the past 120 years - compared with the timescale we're looking at proxies over - so cross-calibration is of pretty limited use...  
> **username_3**: So the question stands.  And I, for one, am very interested in the answer.  
> **username_4**: The limits of my understanding of this area are "crap, forams are probably not as good a record as we've been hoping for the past thirty years", but that doesn't count as an answer ;)  

---

## 2 answers

### Answer by username_3 on 2014-05-06. Score: 15 | Accepted answer

Overall, any individual proxy is not a reliable indicator. It's the combination of multiple proxies that provides a clearer picture.

For example, tree ring growth has been correlated with temperatures. However, it's not without it's anomalies:

> ...from the middle of the 20th century tree ring growth was less than might have been expected from the temperature record... ([source]

(<http://www.climatedata.info/Proxy/Proxy/treerings_introduction.html>))

If we were to only look at tree-rings, we could not possibly trust on them as a reliable source, since they have known problems.

We can also use coral as a indicator of past username_5. However, it's also somewhat questionable:

> However, long (multi-centure) records are rare, and the possible influence of non-climatic influences has not yet been confidently established.
> [source](http://www.meteo.psu.edu/holocene/public_html/shared/articles/MannPersp2002.pdf)

Ice-cores are not immune to skepticism:

> An indisputable interpretation of ice-core oxygen isotopes in terms of
> atmospheric temperature variability, moreover, remains elusive, and
> precise annual dating can be difficult.

However, if we can combine these three indicates along with other indicators (pollen, earth bores, etc), we can increase the reliability of our understanding. For example, if most indicators show a cold year, we can more reliability say it was a cold year.

Combining these proxies together helps us to gain a clearer picture of the past environment.

**Overall Reliability**

However, with that said, the amount of uncertainty with the multi-proxy method is not small.

At the Workshop on Mathematics in the Geosciences, Blake McShane presented a new algorithm for estimating paleoclimate. This algorithm provided a more reliable estimate by *increasing the uncertainty* of the predictions. That's an important point that I will restate:

Through his talk, he showed that his method was *more reliable* because it was *less certain*.

Even that wide uncertainty level, he questioned:

> Indeed, this should make us *increase* our level of uncertainty (indeed perhaps
> our wide intervals are in fact optimistically too narrow)!
>
> [source](http://www.earth.northwestern.edu/people/seth/Mathgeo/mcshane.pdf)

In the end, we can look at proxies for guidelines and trends, but they cannot be used for reliable readings.


---

### Answer by username_5 on 2021-08-11. Score: -3

The reality is that we don’t know how reliable proxies are. All of them have shown deficiencies. Corals have shown they don’t fix 18O like a time capsule, ice cores show that they’re not static (things migrate through the ice) and tree rings show a cooling trend in the late 20th century. Aggregating a bunch of proxies on the assumption that these errors cancel is unproven and a huge leap of faith. Anyone who claims proxies can detect global temperature to anything near what a thermometer can detect is either crazy or lying to you. I wish it weren’t so, but that’s reality. There are too many unknown errors and since we don’t actually have a record of temperature prior to 1850, we have nothing to compare it against.

> **Comments:**
> **username_6**: References\evidence for some of your claims might help you to convince :-)  

---

