<p>Measuring long-term temperature trends from satellites is possible, but difficult due to a variety of reasons.</p>

<p>This is ongoing research.</p>

<p>In short: the satellites that have been around long enough were built for measuring weather, not climate, and the standards to which instruments need to be built to measure one are entirely different from the other.</p>

<p>We have had satellite measurements of the atmosphere since the 1960s, and operationally since the late 1970s.  Those have always included infrared radiometer measurements, which means that, in principle, we can construct a record of surface (both land and sea) and atmospheric temperatures for the past 40 years at least.  The sensors themselves aren't very complicated — but to determine a trend we would need to be very confident about their uncertainty, stability, and inter-satellite variability.  </p>

<p>If you were to simply take 40 years of HIRS infrared measurements and plot them, you don't know if the changes are due to atmospheric or instrumental changes.</p>

<p>From 2015 to 2019, I was part of the <a href="http://www.fiduceo.eu/" rel="nofollow noreferrer">FIDUCEO</a> project which aimed to bring the science of metrology (science of measurement) to satellite observations.  Taking 40 years of AVHRR (for sea surface temperature) or HIRS (for atmospheric temperature and humidity) measurements, with 16 different editions of the instrument over a period of 40 years.  But AVHRR was built to look at pictures of clouds.  If you look at pictures of clouds, the user doesn't care if one satellite has its pictures 0.5% brighter than the previous one.  They just tweak their monitor a bit!  But if you take the global climate system, then that corresponds to more than 1K temperature difference, which for the oceans, would be huge.  In FIDUCEO, we aimed to:</p>

<ul>
<li>Develop a metrology of Earth Observation</li>
<li>Produce <em>Fundamental Climate Data Records</em> (FCDRs) for various operational meteorological instruments in visible, infrared, and microwave, meaning:

<ul>
<li>Per-datum metrologically traceable uncertainty characterisation;</li>
<li>Per-datum information on correlation structures: which component of the error estimate cancels out when averaging and which component remains;</li>
<li>Harmonisation between the various satellite sensors.</li>
</ul></li>
</ul>

<p>Here are 40 years of <a href="https://www.wmo-sat.info/oscar/instruments/view/183" rel="nofollow noreferrer">HIRS</a> (versions 2, 3, and 4), on which we tried to do some harmonisation.  The top panel shows global average brightness temperature per 24-hour period, as measured by channel 2 which IIRC peaks somewhere in the stratosphere, so this would correspond roughly to an atmospheric temperature somewhere up in the stratosphere (which, incidentally, is cooling as the Earth's surface is warming):</p>

<p><a href="https://i.sstatic.net/8VVFZ.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/8VVFZ.png" alt="40 years of HIRS"></a></p>

<p>The different colours indicate different satellites.  As you can see, there are both jumps between satellites, and trends within one satellite.  Some of this is expected, as polar-orbiting sun-synchronous satellites have a drifting local equator crossing time, but some of it is due to instrumental problems.  Some of those problems are captured by the structured uncertainty in the bottom panel, but not all of it.  The data only go back to the mid-1980s, because before that, there weren't enough overlaps to constrain the differences between subsequent pairs of satellites based on simultaneous nadir overpasses (SNOs).  For satellites in the early 1980s and late 1970s, the coefficients to calibration the thermometres measuring the temperature of the on-board calibration target appear to have been lost.  For the earliest satellites the header data does not match available documentation.  Software to produce this figure is <a href="https://github.com/fiduceo/FCDR_HIRS" rel="nofollow noreferrer">on Github</a>, raw source data are available <a href="https://www.bou.class.noaa.gov/saa/products/welcome" rel="nofollow noreferrer">from NOAA CLASS</a>, some processed data from <a href="http://www.fiduceo.eu/" rel="nofollow noreferrer">FIDUCEO</a>.</p>

<p>This is for a global average.  To do this regionally would add additional complications.</p>

<p>The <a href="https://www.wmo-sat.info/oscar/satelliteprogrammes/view/21" rel="nofollow noreferrer">CLARREO</a> programme is proposed to be the first in-orbit SI reference for accurate calibration.  Had we had that for the past 40 years, our job would be easier.  But CLARREO is still waiting for funding.</p>

<p>So the answer to your question is: with what we have now — not good enough — yet.</p>

<p>But if you are contemplating a career in satellite techno-archeology, I recommend it.  It's great fun.</p>

CC BY-SA 4.0
2019-11-14T19:25:35.843Z
Nicely addressed! I figured if you were going to *start* this measurement with modern instruments, as the original poster seemed to imply, you'd still have to wait 30+ years to get a good enough time series.
jeffronicus
CC BY-SA 4.0
2019-11-14T20:57:58.443Z
@jeffronicus Oh yes, lots of scientists can't wait to start measuring with actual SI-calibrated instruments.  But who will pay for this, in particular considering that it should be essentially forever?  The best candidate would IMO be Copernicus Climate Change Services (C3S), maybe.
gerrit
CC BY-SA 4.0
2019-11-15T06:07:58.303Z
This is a very supportive answer. I wish it would be supplemented with xls tables. Then one could take, say, a 1000 days average, and compare 1987-1990 period with 2015-18 average. Then the error bar can be roughly assumed to be ~0.2C. I somehow feel that you will see no difference over 30 years, and all your data don't support the hockey stick - no warming, no cooling, just as expected. Thanks for the honest data.
Ale..chenski
CC BY-SA 4.0
2019-11-15T09:04:38.843Z
@Ale..chenski The y-axis on my graph has a range of 50 K (brightness temperature) and covers 40 years, the [Hockey stick graph](https://en.wikipedia.org/wiki/Hockey_stick_graph) has a y-axis range of less than 2°C and covers 1000 years.  They show different things.  You can calculate this yourself by downloading 40 years of HIRS data (around 2 TB), follow the FIDUCEO link in my answer for more information. Software is [on github](https://github.com/fiduceo/FCDR_HIRS) (link added to answer).
gerrit
CC BY-SA 4.0
2019-11-14T14:08:50.740Z
2019-11-15T09:12:26.693Z
2019-11-15T09:12:26.693Z
gerrit
<p>You seem to conflate several things in your question.</p>

<p>First, AGH skeptics don't deny "climate change". They don't even deny that anthropogenic activity does have some impact on thermal balance of Earth. They just don't think this impact has any significance, since the same climate scientists already have established that CO2 was 10-fold higher in the Earth past, and no water-amplified "runaway" effects (aka "feedbacks") have lead to any terrible effects to life on Earth. It short, there was no "point of no return", historically speaking. </p>

<p>Second, you confuse "global change in average surface temperature" with "global heating". Since the Earth is round and suffers very different insolation levels (equatorial areas are hot and radiate back quite a lot, polar areas are cold and emit much less, all in proportion to 4-th degree of absolute temperature in accord with <a href="https://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law" rel="nofollow noreferrer">Stefan-Boltzmann law</a>), it is easy to construct simple examples when lower "average temperature" leads to higher thermal emission, and higher average temperature leads to lower emission to outer space. In other words, there is no correlation between "average surface temperature" of the globe with global "radiative imbalance" (aka "global heating").</p>

<p>Therefore obtaining thermal images from distance might show ANY type of correlation with statistical averages of surface temperatures. And I don't even mention technical difficulties related to long-term stability and calibration of remote sensors, and with necessity to get these observations for at least 100 years to see any effect. And as I noted above, the effect can be anything and prove nothing. </p>

CC BY-SA 4.0
2019-11-12T00:41:20.510Z
"no water-amplified "runaway" effects (aka "feedbacks") have lead to any terrible effects to life on Earth." I think that the five mass extinctions would probably count as: "terrible effects to life on Earth".
polcott
CC BY-SA 4.0
2019-11-12T01:00:19.933Z
"Second, you confuse "global change in average surface temperature" with "global heating"." In other words you are saying then when the Earth is measured to be hotter, the Earth is not really hotter at all. You could only be correct if the increase in heat measured on the surface was offset by a loss of heat somewhere else such as the Oceans.
polcott
CC BY-SA 4.0
2019-11-12T01:21:37.143Z
@polcott, this is a very sensitive topic, so you better try to use accurate terminology.I am saying that some surface spots on Earth are getting "hotter" over, say, 100-years trend, and some spots are getting colder, all in accord with global NOAA network data. The trends are not uniform across the globe. I am stating that the same change in "average surface temperature" (aka "warming") can produce positive or negative "global radiative imbalance", depending on particular distribution of trends and affected areas.This is a simple mathematical consequence of sigma*T^4 emission law.
Ale..chenski
CC BY-SA 4.0
2019-11-12T01:40:30.293Z
@polcott, the major premise of AGW is an alleged increase of surface temperatures with growth in atmospheric CO2 concentration. The chart you appended clearly indicates the absence of this cause-effect relation:  450MBC the CO2 is at 4000 ppm level and increasing, while the temps drop; 350MBC- Co2 drops, but temps stays flat; 140MBC - Co2 drops, but temps are sharply up and stays flat for ~40M years, while CO2 continues to drop from 2000 ppm to 1000 ppm. Correlation between alleged mass extinctions and CO2 levels is also a clear imagination at most.
Ale..chenski
CC BY-SA 4.0
2019-11-12T02:01:24.833Z
The errorbars for CO2 back then are very wide. Much more recent data shows a very strong linear correlation between CO2 and temperatures that is predominantly caused by a third factor. We can know for sure that the green house effect is real because it is the only reason why the Earth is warmer than the Moon.
polcott
CC BY-SA 4.0
2019-11-12T02:50:47.727Z
@polcott, no, you are mistaken. the correlation is not "linear". Accurate mathematical studies by Hansen et al. indicate that there is indeed a fine-scale correlation, but the increase in CO2 *lags* temperature increases by ~800 years. So the most obvious and unbiased interpretation of ice core data is that CO2 is just a delayed function of surface temperature, and not the cause.
Ale..chenski
CC BY-SA 4.0
2019-11-12T03:35:54.453Z
The lag has been refuted and even with a lag it is still linear and thus not logarithmic or exponential. https://skepticalscience.com/skakun-co2-temp-lag.html?fbclid=IwAR2A_wvpTcWfdMjZsY_64JELzKt592FpXX8Q1UtIopgvoq3t8TqaThBGyxc "approximately 7% of the overall glacial-interglacial global temperature increase occurred before the CO2 rise, whereas 93% of the global warming followed the CO2 increase."
polcott
CC BY-SA 4.0
2019-11-12T11:07:25.720Z
Regarding extinction events, we are near the start of one which began a few  hundred years ago and will probably take a few thousand years to run its course. It has nothing to do with climate change, but everything to do with human activity.
Michael Walsby
CC BY-SA 4.0
2019-11-13T05:16:51.040Z
@polcott, the time lag in ice core data cannot be refuted. Even a bold correlation over entire Vostok data set in analysis by J.Hansen et al. shows a peak of 92.5% with shift by 700 years. This cannot be "refuted". Despite some assumptions about discrepancy between age of air bubbles and surrounding ice, the Vostok record has an advantage of having "synchronous sampling" of Co2 and Temps, so there can be no mistakes or stretching like if you try to put into a bucket many individual uncorrelated proxies as "Shakun et al." did. "Hide the lag" :-)
Ale..chenski
CC BY-SA 4.0
2019-11-13T06:09:24.350Z
"he time lag in ice core data cannot be refuted." It already has been refuted go look at the linked source.
polcott
CC BY-SA 4.0
2019-11-15T04:56:39.470Z
I really hate the "it was higher in earth's history" mentality. we also had jungles in the arctic, a desert larger than all the current ones combined, and dinosaurs running around. no one thinks we are going to wipe out life on earth, we are worried about screwing our civilization over to the point of collapse or regression by damaging our infrastructure and major food sources. Human civilization is delicate, life as a whole is not.
John
CC BY-SA 4.0
2019-11-15T06:16:46.717Z
@john, how it is that "human civilization is delicate"? Animals can't migrate over the edges of lands when climate zones shift, they stay and die. But modern human can. What could be wrong if Russians will supply you with bananas and pineapples from Siberia? And you can comfortably live in Northern Canada...
Ale..chenski
CC BY-SA 4.0
2019-11-15T15:12:49.653Z
@Ale..chenski because humans civilization is built around producing large amounts of cereal crops in highly fertile areas with existing infrastructure, ares which cease to be fertile as rainfall patterns and temprature change. land is not interchangeable, soils vary widely in quality.  Worse we are driving our pollinators extinct which will make soil fertility moot. disruption of food production is hte single biggest cause of civilization collapse in history, and out current civilization is so interconnected such collapse will not stay isolated.
John
CC BY-SA 4.0
2019-11-12T00:17:19.987Z
2019-11-12T00:17:19.987Z
Ale..chenski
<p>Some anthropogenic global heating (AGH) skeptics deny that any global heating is occurring. I figured out a way that could be used to refute them. A weighted average of all of the thermal points on the Earth could be computed on a daily basis. These thermal points are obtained from thermal images. </p>

<p>These points would be satellite resolution distance apart. This would provide an actual measure of global heating. We could subtract out the effects of cities and volcanoes by simply ignoring every value above a certain threshold. One example of such a threshold would be the average of all of the points for that day. </p>

<p>Would this be a reasonable way to double check the trend of global temperature anomalies? </p>

CC BY-SA 4.0
2019-11-14T14:09:57.900Z
Comments are not for extended discussion; this conversation has been [moved to chat](https://chat.stackexchange.com/rooms/101018/discussion-on-question-by-polcott-how-reliable-would-measuring-global-heating-fr).
gerrit
CC BY-SA 4.0
2019-11-14T14:11:50.183Z
Hi polcott!  I have removed the graphs from the question, because they are completely irrelevant to the question about the measurability of temperature trends from space.
gerrit
<climate-change>
How reliable would measuring global heating from satellite be?
polcott
# How reliable would measuring global heating from satellite be?

(Asked by: username_0 on 2019-11-11)

Some anthropogenic global heating (AGH) skeptics deny that any global heating is occurring. I figured out a way that could be used to refute them. A weighted average of all of the thermal points on the Earth could be computed on a daily basis. These thermal points are obtained from thermal images.

These points would be satellite resolution distance apart. This would provide an actual measure of global heating. We could subtract out the effects of cities and volcanoes by simply ignoring every value above a certain threshold. One example of such a threshold would be the average of all of the points for that day.

Would this be a reasonable way to double check the trend of global temperature anomalies?

**Tags:** climate-change

> **Comments:**
> **username_1**: Comments are not for extended discussion; this conversation has been [moved to chat](https://chat.stackexchange.com/rooms/101018/discussion-on-question-by-username_0-how-reliable-would-measuring-global-heating-fr).  
> **username_1**: Hi username_0!  I have removed the graphs from the question, because they are completely irrelevant to the question about the measurability of temperature trends from space.  

---

## 2 answers

### Answer by username_1 on 2019-11-14. Score: 5

Measuring long-term temperature trends from satellites is possible, but difficult due to a variety of reasons.

This is ongoing research.

In short: the satellites that have been around long enough were built for measuring weather, not climate, and the standards to which instruments need to be built to measure one are entirely different from the other.

We have had satellite measurements of the atmosphere since the 1960s, and operationally since the late 1970s. Those have always included infrared radiometer measurements, which means that, in principle, we can construct a record of surface (both land and sea) and atmospheric temperatures for the past 40 years at least. The sensors themselves aren't very complicated — but to determine a trend we would need to be very confident about their uncertainty, stability, and inter-satellite variability.

If you were to simply take 40 years of HIRS infrared measurements and plot them, you don't know if the changes are due to atmospheric or instrumental changes.

From 2015 to 2019, I was part of the [FIDUCEO](http://www.fiduceo.eu/) project which aimed to bring the science of metrology (science of measurement) to satellite observations. Taking 40 years of AVHRR (for sea surface temperature) or HIRS (for atmospheric temperature and humidity) measurements, with 16 different editions of the instrument over a period of 40 years. But AVHRR was built to look at pictures of clouds. If you look at pictures of clouds, the user doesn't care if one satellite has its pictures 0.5% brighter than the previous one. They just tweak their monitor a bit! But if you take the global climate system, then that corresponds to more than 1K temperature difference, which for the oceans, would be huge. In FIDUCEO, we aimed to:

* Develop a metrology of Earth Observation
* Produce *Fundamental Climate Data Records* (FCDRs) for various operational meteorological instruments in visible, infrared, and microwave, meaning:
  + Per-datum metrologically traceable uncertainty characterisation;
  + Per-datum information on correlation structures: which component of the error estimate cancels out when averaging and which component remains;
  + Harmonisation between the various satellite sensors.

Here are 40 years of [HIRS](https://www.wmo-sat.info/oscar/instruments/view/183) (versions 2, 3, and 4), on which we tried to do some harmonisation. The top panel shows global average brightness temperature per 24-hour period, as measured by channel 2 which IIRC peaks somewhere in the stratosphere, so this would correspond roughly to an atmospheric temperature somewhere up in the stratosphere (which, incidentally, is cooling as the Earth's surface is warming):

[![40 years of HIRS](https://i.sstatic.net/8VVFZ.png)](https://i.sstatic.net/8VVFZ.png)

The different colours indicate different satellites. As you can see, there are both jumps between satellites, and trends within one satellite. Some of this is expected, as polar-orbiting sun-synchronous satellites have a drifting local equator crossing time, but some of it is due to instrumental problems. Some of those problems are captured by the structured uncertainty in the bottom panel, but not all of it. The data only go back to the mid-1980s, because before that, there weren't enough overlaps to constrain the differences between subsequent pairs of satellites based on simultaneous nadir overpasses (SNOs). For satellites in the early 1980s and late 1970s, the coefficients to calibration the thermometres measuring the temperature of the on-board calibration target appear to have been lost. For the earliest satellites the header data does not match available documentation. Software to produce this figure is [on Github](https://github.com/fiduceo/FCDR_HIRS), raw source data are available [from NOAA CLASS](https://www.bou.class.noaa.gov/saa/products/welcome), some processed data from [FIDUCEO](http://www.fiduceo.eu/).

This is for a global average. To do this regionally would add additional complications.

The [CLARREO](https://www.wmo-sat.info/oscar/satelliteprogrammes/view/21) programme is proposed to be the first in-orbit SI reference for accurate calibration. Had we had that for the past 40 years, our job would be easier. But CLARREO is still waiting for funding.

So the answer to your question is: with what we have now — not good enough — yet.

But if you are contemplating a career in satellite techno-archeology, I recommend it. It's great fun.

> **Comments:**
> **username_2**: Nicely addressed! I figured if you were going to *start* this measurement with modern instruments, as the original poster seemed to imply, you'd still have to wait 30+ years to get a good enough time series.  
> **username_1**: @username_2 Oh yes, lots of scientists can't wait to start measuring with actual SI-calibrated instruments.  But who will pay for this, in particular considering that it should be essentially forever?  The best candidate would IMO be Copernicus Climate Change Services (C3S), maybe.  
> **username_3**: This is a very supportive answer. I wish it would be supplemented with xls tables. Then one could take, say, a 1000 days average, and compare 1987-1990 period with 2015-18 average. Then the error bar can be roughly assumed to be ~0.2C. I somehow feel that you will see no difference over 30 years, and all your data don't support the hockey stick - no warming, no cooling, just as expected. Thanks for the honest data.  
> **username_1**: @username_3 The y-axis on my graph has a range of 50 K (brightness temperature) and covers 40 years, the [Hockey stick graph](https://en.wikipedia.org/wiki/Hockey_stick_graph) has a y-axis range of less than 2°C and covers 1000 years.  They show different things.  You can calculate this yourself by downloading 40 years of HIRS data (around 2 TB), follow the FIDUCEO link in my answer for more information. Software is [on github](https://github.com/fiduceo/FCDR_HIRS) (link added to answer).  

---

### Answer by username_3 on 2019-11-12. Score: -4

You seem to conflate several things in your question.

First, AGH skeptics don't deny "climate change". They don't even deny that anthropogenic activity does have some impact on thermal balance of Earth. They just don't think this impact has any significance, since the same climate scientists already have established that CO2 was 10-fold higher in the Earth past, and no water-amplified "runaway" effects (aka "feedbacks") have lead to any terrible effects to life on Earth. It short, there was no "point of no return", historically speaking.

Second, you confuse "global change in average surface temperature" with "global heating". Since the Earth is round and suffers very different insolation levels (equatorial areas are hot and radiate back quite a lot, polar areas are cold and emit much less, all in proportion to 4-th degree of absolute temperature in accord with [Stefan-Boltzmann law](https://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law)), it is easy to construct simple examples when lower "average temperature" leads to higher thermal emission, and higher average temperature leads to lower emission to outer space. In other words, there is no correlation between "average surface temperature" of the globe with global "radiative imbalance" (aka "global heating").

Therefore obtaining thermal images from distance might show ANY type of correlation with statistical averages of surface temperatures. And I don't even mention technical difficulties related to long-term stability and calibration of remote sensors, and with necessity to get these observations for at least 100 years to see any effect. And as I noted above, the effect can be anything and prove nothing.

> **Comments:**
> **username_0**: "no water-amplified "runaway" effects (aka "feedbacks") have lead to any terrible effects to life on Earth." I think that the five mass extinctions would probably count as: "terrible effects to life on Earth".  
> **username_0**: "Second, you confuse "global change in average surface temperature" with "global heating"." In other words you are saying then when the Earth is measured to be hotter, the Earth is not really hotter at all. You could only be correct if the increase in heat measured on the surface was offset by a loss of heat somewhere else such as the Oceans.  
> **username_3**: @username_0, this is a very sensitive topic, so you better try to use accurate terminology.I am saying that some surface spots on Earth are getting "hotter" over, say, 100-years trend, and some spots are getting colder, all in accord with global NOAA network data. The trends are not uniform across the globe. I am stating that the same change in "average surface temperature" (aka "warming") can produce positive or negative "global radiative imbalance", depending on particular distribution of trends and affected areas.This is a simple mathematical consequence of sigma*T^4 emission law.  
> **username_3**: @username_0, the major premise of AGW is an alleged increase of surface temperatures with growth in atmospheric CO2 concentration. The chart you appended clearly indicates the absence of this cause-effect relation:  450MBC the CO2 is at 4000 ppm level and increasing, while the temps drop; 350MBC- Co2 drops, but temps stays flat; 140MBC - Co2 drops, but temps are sharply up and stays flat for ~40M years, while CO2 continues to drop from 2000 ppm to 1000 ppm. Correlation between alleged mass extinctions and CO2 levels is also a clear imagination at most.  
> **username_0**: The errorbars for CO2 back then are very wide. Much more recent data shows a very strong linear correlation between CO2 and temperatures that is predominantly caused by a third factor. We can know for sure that the green house effect is real because it is the only reason why the Earth is warmer than the Moon.  
> **username_3**: @username_0, no, you are mistaken. the correlation is not "linear". Accurate mathematical studies by Hansen et al. indicate that there is indeed a fine-scale correlation, but the increase in CO2 *lags* temperature increases by ~800 years. So the most obvious and unbiased interpretation of ice core data is that CO2 is just a delayed function of surface temperature, and not the cause.  
> **username_0**: The lag has been refuted and even with a lag it is still linear and thus not logarithmic or exponential. https://skepticalscience.com/skakun-co2-temp-lag.html?fbclid=IwAR2A_wvpTcWfdMjZsY_64JELzKt592FpXX8Q1UtIopgvoq3t8TqaThBGyxc "approximately 7% of the overall glacial-interglacial global temperature increase occurred before the CO2 rise, whereas 93% of the global warming followed the CO2 increase."  
> **username_4**: Regarding extinction events, we are near the start of one which began a few  hundred years ago and will probably take a few thousand years to run its course. It has nothing to do with climate change, but everything to do with human activity.  
> **username_3**: @username_0, the time lag in ice core data cannot be refuted. Even a bold correlation over entire Vostok data set in analysis by J.Hansen et al. shows a peak of 92.5% with shift by 700 years. This cannot be "refuted". Despite some assumptions about discrepancy between age of air bubbles and surrounding ice, the Vostok record has an advantage of having "synchronous sampling" of Co2 and Temps, so there can be no mistakes or stretching like if you try to put into a bucket many individual uncorrelated proxies as "Shakun et al." did. "Hide the lag" :-)  
> **username_0**: "he time lag in ice core data cannot be refuted." It already has been refuted go look at the linked source.  
> **username_5**: I really hate the "it was higher in earth's history" mentality. we also had jungles in the arctic, a desert larger than all the current ones combined, and dinosaurs running around. no one thinks we are going to wipe out life on earth, we are worried about screwing our civilization over to the point of collapse or regression by damaging our infrastructure and major food sources. Human civilization is delicate, life as a whole is not.  
> **username_3**: @username_5, how it is that "human civilization is delicate"? Animals can't migrate over the edges of lands when climate zones shift, they stay and die. But modern human can. What could be wrong if Russians will supply you with bananas and pineapples from Siberia? And you can comfortably live in Northern Canada...  
> **username_5**: @username_3 because humans civilization is built around producing large amounts of cereal crops in highly fertile areas with existing infrastructure, ares which cease to be fertile as rainfall patterns and temprature change. land is not interchangeable, soils vary widely in quality.  Worse we are driving our pollinators extinct which will make soil fertility moot. disruption of food production is hte single biggest cause of civilization collapse in history, and out current civilization is so interconnected such collapse will not stay isolated.  

---

