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Someone, who does not believe climate change asked me today --

How is it possible for us to conclude that the past five years are the hottest five years since record begun, since

  1. There are only a limited number of locations where we measure temperature.
  2. There is a wide range of difference in temperature even in a small area.

How would a meteorologist answer these questions?

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    $\begingroup$ Don't judge climate change only by Temperature. Temperature is only an indicator that shows the direction of Heat which is energy. Climate change occurs because we produce more energy than the threshold of an established balance. In addition several human activities on the planet change factors such as Albedo for example. All those other factors including gas releases the only thing they do is to change the established flow of energy in this planet. $\endgroup$
    – user19169
    Dec 25 '20 at 8:25
  • $\begingroup$ The question didn’t mention “climate change”. The question is about how we measure ‘global warming’, and how we draw inferences from the respective data we collect. $\endgroup$
    – froimovi
    Jan 24 at 3:55
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Besides rising surface air temperatures other indicators of global warming include -

  • ocean surface temperatures rising
  • ocean temperature at varying depths rising
  • global average sea level rising
  • Arctic sea ice extent decreasing
  • Arctic sea ice thickness and average age decreasing
  • Glacier retreat
  • Earlier Spring snow melt
  • Borehole temperatures rising
  • Earlier budding time of various plants
  • Less new record low temperatures
  • More new record high temperatures
  • Greenland losing ice mass
  • Antarctica losing ice mass
  • and etc

Every possible way we can observe and measure the changes we should expect with global warming shows results consistent with actual global warming.

Global Average Temperature as the go to single simple measure is a statistical construct, derived mostly from about 7,000 long running and up to 30,000 current weather stations recording daily minimum and maximums. It is a way to reduce complex change to a single simple number, for convenience. That metric may be a construct but it is constructed to show the extent of change to those recorded temperatures. In one sense it isn't a direct measurement of "something", yet we can confidently expect this average to rise if the climate system is warming - and not rise if it is not.

These weather records allow other kinds of examination besides getting a global average temperature - mapping of regional changes, geographic ones and all the way down to the conditions at individual sites, including their suitability for inclusion in global temperature record calculations. Badly sited ones can be excluded, step temperature changes from changing location or changes to existing location can be adjusted for to achieve better accuracy.

These records don't exist in isolation - there is a broad understanding of climate and weather processes that goes with them. They are also supported by satellite data, such as microwave sounding that allow remote estimation of atmospheric temperatures; whilst they tend to show higher response to El Nino Southern Oscillation, the rates of warming are broadly consistent with weather station records.

It is a reliable observation that in between nearby weather stations sharing similar geography there are similar weather conditions, including similar maximum and minimum temperatures. Consistently different conditions in the spaces between would be noticed and we cannot expect such differences to be confined only in those between spaces; if there were significant variations in the temperatures and rates of change over time in the spaces between locations it would be happening at those locations as well and that would show up in the weather station records. What we find in those records is consistent with global warming.

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  • $\begingroup$ To the extensive list here, one could also add snow either not falling or not accumulating in winter in places where it used to. During my younger years a mountain I lived near was always snow covered during winter. These days it's rare to see any snow on that mountain. It's something I only noticed about 20 years ago. $\endgroup$
    – Fred
    Dec 22 '20 at 4:10
  • $\begingroup$ Nice answer. Please besides the indicators mentioned, do add that all those are the measured symptoms as we might say. All of the above have changed due to our interfering with the energy levels and paths of this planet. Not to mention the air and water pollution from material and chemical waste. Parameters such as Albedo are not even known as micro-climate parameters. $\endgroup$
    – user19169
    Dec 22 '20 at 21:48
  • $\begingroup$ global warming is measured via temperature. All the other things you mention (e.g. ice thickness) are supposed consequences of a continually warming atmosphere. $\endgroup$
    – froimovi
    Jan 24 at 4:11
  • $\begingroup$ @Fred Yeah you could add that to the list if you want to not answer the question (which is about directly measuring temperatures) — not about political propaganda statements that. $\endgroup$
    – froimovi
    Feb 26 at 6:31
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Since I asked this question, I have been reading this topic. My conclusion is that the method used in estimating global average temperature is very rigorous, and that all challenges to such estimations are very superficial. A good source of information is this website --

https://skepticalscience.com/argument.php?f=taxonomy

You can also look at NASA's recent paper on this topic.

https://pubs.giss.nasa.gov/abs/le05800h.html

Here's an FAQ by NOAA about how they global temperature data

https://www.ncdc.noaa.gov/monitoring-references/faq/anomalies.php

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  • $\begingroup$ Pssst. I love how you formulated the above. How do I PM you on this site ? $\endgroup$
    – froimovi
    Feb 24 at 4:56

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