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Much of the raw data behind the various datasets reporting the average temperature of the world are now available. So it is possible to look for strange patterns in the daily or monthly temperature data. The reported "average temperature of the world" is, ultimately, derived from these datasets by various corrections, normalisations and regional aggregations.

Recently I came across a claim that the temperature anomalies are remarkably concentrated geographically. The hypothesis suggested, tentatively, by the author (Clive Best, blog on topic here) suggested that this might reflect contamination of the raw data by rapid urbanisation. NB his argument is very different from the idea that US data is corrupted by the urban heat island effect which is addressed here: https://skeptics.stackexchange.com/questions/10341/has-the-urban-heat-island-effect-on-the-us-temperature-record-been-underestimate)

He reports (my emphasis):

The anomalies from ~4000 stations all over the globe are then combined to give one global anomaly, yielding the familiar graph we know and love which shows ~0.6 deg.C rise since 1850. Looking in more detail however we discover that some parts of the world are not warming at all and some are even cooling.

His argument develops:

It immediately becomes obvious that the bulk of observed warming is concentrated in the Northern Hemisphere : Eastern Europe, Russia, central Asia, India, China, Japan, Middle East, North Africa. These are all areas of rapid population increase, development and industrialisation. There is essentially no warming at all in the Southern Hemisphere. Bolivia, Peru, Paraguay and Argentina all appear to be cooling. Even Australia and Zealand are static or cooling. The US is evenly divided and the UK shows essentially no signal at all.

...Could much of the observed temperature rise over the last 6 decades be simply due to increasing urbanisation and development since ~1960 ?

Climate models don't produce even warming across the world so there could be explanations perfectly consistent with the observations of major regional differences. So my question is: does the large variation in regional temperature anomalies have a straightforward explanation in mainstream warming theory or is it a sign that some regional records are contaminated by urban development?

NB Best used the data from HADCRUT3 released by the UK Met Office, but it is also obvious in the NOAA GSOD dataset which is conveniently available to 2010 in Google's BigQuery as a sample dataset (you can also download it if you have the capacity process it).

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migrated from skeptics.stackexchange.com Sep 22 '15 at 9:23

This question came from our site for scientific skepticism.

  • $\begingroup$ BTW, I think there is no notable claim here, this is just a rehash of similar arguments that have already been answered here, e.g. skeptics.stackexchange.com/questions/22086/… and skeptics.stackexchange.com/questions/22379/… and skeptics.stackexchange.com/questions/19291/…, it is just a new combination of the same mistakes in analysis. $\endgroup$ – Dikran Marsupial Sep 22 '15 at 7:05
  • $\begingroup$ @DikranMarsupial I think this question is distinct because, I suspect, it questions whether homogenisation is uniformly effective across the globe. I don't think there is much of an issue any more with the US data which is where the previous UHI argument mostly occurred. $\endgroup$ – matt_black Sep 22 '15 at 7:59
  • $\begingroup$ No, that is purely your own inference AFAICS. Best points out a North/South hemispheric difference, but that can be explained (rather obviosuly) by the difference in distribution of land masses. $\endgroup$ – Dikran Marsupial Sep 22 '15 at 8:02
  • $\begingroup$ If you want to raise questions that your feel are implied by the original claim, then skepticsSE is not the place for it (as the question raised won't fit the definition of a notable claim). Try the earth sciences SE (which is probably a better place for most of these questions anyway). $\endgroup$ – Dikran Marsupial Sep 22 '15 at 8:09
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The blog article suggests that the increase in "waste heat" from growing urbanisation is biasing the temperature observations. The problem with this argument is that the heat generated directly from burning fossil fuels is far too small to make a difference, compared to the change in the Earths energy balance due to increasing greenhouse gasses. See:

Integrating anthropogenic heat flux with global climate models Authors

Mark G. Flanner

Atmospheric Science, Volume 36, Issue 2, January 2009. DOI:10.1029/2008GL036465

Abstract 1 Nearly all energy used for human purposes is dissipated as heat within Earth's land–atmosphere system. Thermal energy released from non-renewable sources is therefore a climate forcing term. Averaged globally, this forcing is only +0.028 W m−2, but over the continental United States and western Europe, it is +0.39 and +0.68 W m−2, respectively. Here, present and future global inventories of anthropogenic heat flux (AHF) are developed, and parameterizations derived for seasonal and diurnal flux cycles. Equilibrium climate experiments show statistically-significant continental-scale surface warming (0.4–0.9°C) produced by one 2100 AHF scenario, but not by current or 2040 estimates. However, significant increases in annual-mean temperature and planetary boundary layer (PBL) height occur over gridcells where present-day AHF exceeds 3.0 W m−2. PBL expansion leads to a slight, but significant increase in atmospheric residence time of aerosols emitted from large-AHF regions. Hence, AHF may influence regional climate projections and contemporary chemistry-climate studies.

The blog article says:

My guess is that 80% of this energy ends up as heat (2nd law thermodynamics). Assuming that energy consumption is concentrated mostly in urban areas then the net “anthropogenic” heating in those areas works out at around 5 watts/m2. This then leads to an average 1.4 degreeC. rise in temperature for urban areas. Anyone who has lived in the city knows from experience that the surrounding countryside is indeed some 1-2 degrees colder.

Indeed the climatologists know that as well, they are not stupid, and hence "homogenise" the observations to remove these sorts of biases. Note that if the bias were due to increasing urbanisation, this would be easily detectable by comparison with the observations from rural stations in the same region. This is not rocket science (see my answer here for links on homogenization)!

Note also that increasing urbanisation would not necessarily cause an increase in local forcing, because as you increase the fossil fuel use, you also increase the area over which it is dissapated, which the author of the blog post also appears to have missed.

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  • $\begingroup$ I think this is a good summary of the conventional position and a good answer. I have two concerns (though they might not be addressable here). The first is the basic one of verifying the effect Best claims in multiple un-homogenised datasets (I've tested it myself but I'd like to hope it has been addressed properly in the academic literature). If the effect is really there then the issue might be whether homogenisation works well in places like Russia (I think the USA isn't an issue). $\endgroup$ – matt_black Sep 22 '15 at 7:50
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    $\begingroup$ @matt_black, there is a huge amount of work done on homogenisation (i.e. dealing with these sorts of drifts, disocntinuities and biases) AND in evaluating how well they work (e.g. surfacetemperatures.org/home). Now just looking at individual un-homogenised station records will not tell you whether this is happening as there is no way of telling climate change from any posited UHI growth change. To do that you need to do things like compare with nearby rural stations. See onlinelibrary.wiley.com/doi/10.1002/wcc.46/abstract for introductory paper. $\endgroup$ – Dikran Marsupial Sep 22 '15 at 7:59

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