Skip to main content
Menu

Main navigation

  • About
    • Annual Reports
    • Leadership
    • Jobs
    • Student Programs
    • Media Information
    • Store
    • Contact
    LOADING...
  • Experts
    • Policy Scholars
    • Adjunct Scholars
    • Fellows
  • Events
    • Upcoming
    • Past
    • Event FAQs
    • Sphere Summit
    LOADING...
  • Publications
    • Studies
    • Commentary
    • Books
    • Reviews and Journals
    • Public Filings
    LOADING...
  • Blog
  • Donate
    • Sponsorship Benefits
    • Ways to Give
    • Planned Giving

Issues

  • Constitution and Law
    • Constitutional Law
    • Criminal Justice
    • Free Speech and Civil Liberties
  • Economics
    • Banking and Finance
    • Monetary Policy
    • Regulation
    • Tax and Budget Policy
  • Politics and Society
    • Education
    • Government and Politics
    • Health Care
    • Poverty and Social Welfare
    • Technology and Privacy
  • International
    • Defense and Foreign Policy
    • Global Freedom
    • Immigration
    • Trade Policy
Live Now

Cato at Liberty


  • Blog Home
  • RSS

Email Signup

Sign up to have blog posts delivered straight to your inbox!

Topics
  • Banking and Finance
  • Constitutional Law
  • Criminal Justice
  • Defense and Foreign Policy
  • Education
  • Free Speech and Civil Liberties
  • Global Freedom
  • Government and Politics
  • Health Care
  • Immigration
  • Monetary Policy
  • Poverty and Social Welfare
  • Regulation
  • Tax and Budget Policy
  • Technology and Privacy
  • Trade Policy
Archives
  • April 2021
  • March 2021
  • February 2021
  • January 2021
  • December 2020
  • November 2020
  • October 2020
  • September 2020
  • August 2020
  • July 2020
  • June 2020
  • May 2020
  • April 2020
  • March 2020
  • February 2020
  • January 2020
  • December 2019
  • November 2019
  • October 2019
  • September 2019
  • August 2019
  • July 2019
  • June 2019
  • May 2019
  • April 2019
  • March 2019
  • February 2019
  • January 2019
  • December 2018
  • November 2018
  • October 2018
  • September 2018
  • August 2018
  • July 2018
  • June 2018
  • May 2018
  • April 2018
  • March 2018
  • February 2018
  • January 2018
  • December 2017
  • November 2017
  • October 2017
  • September 2017
  • August 2017
  • July 2017
  • June 2017
  • May 2017
  • April 2017
  • March 2017
  • February 2017
  • January 2017
  • December 2016
  • November 2016
  • October 2016
  • September 2016
  • August 2016
  • July 2016
  • June 2016
  • May 2016
  • April 2016
  • March 2016
  • February 2016
  • January 2016
  • December 2015
  • November 2015
  • October 2015
  • September 2015
  • August 2015
  • July 2015
  • June 2015
  • May 2015
  • April 2015
  • March 2015
  • February 2015
  • January 2015
  • December 2014
  • November 2014
  • October 2014
  • September 2014
  • August 2014
  • July 2014
  • June 2014
  • May 2014
  • April 2014
  • March 2014
  • February 2014
  • January 2014
  • December 2013
  • November 2013
  • October 2013
  • September 2013
  • August 2013
  • July 2013
  • June 2013
  • May 2013
  • April 2013
  • March 2013
  • February 2013
  • January 2013
  • December 2012
  • November 2012
  • October 2012
  • September 2012
  • August 2012
  • July 2012
  • June 2012
  • May 2012
  • April 2012
  • March 2012
  • February 2012
  • January 2012
  • December 2011
  • November 2011
  • October 2011
  • September 2011
  • August 2011
  • July 2011
  • June 2011
  • May 2011
  • April 2011
  • March 2011
  • February 2011
  • January 2011
  • December 2010
  • November 2010
  • October 2010
  • September 2010
  • August 2010
  • July 2010
  • June 2010
  • May 2010
  • April 2010
  • March 2010
  • February 2010
  • January 2010
  • December 2009
  • November 2009
  • October 2009
  • September 2009
  • August 2009
  • July 2009
  • June 2009
  • May 2009
  • April 2009
  • March 2009
  • February 2009
  • January 2009
  • December 2008
  • November 2008
  • October 2008
  • September 2008
  • August 2008
  • July 2008
  • June 2008
  • May 2008
  • April 2008
  • March 2008
  • February 2008
  • January 2008
  • December 2007
  • November 2007
  • October 2007
  • September 2007
  • August 2007
  • July 2007
  • June 2007
  • May 2007
  • April 2007
  • March 2007
  • February 2007
  • January 2007
  • December 2006
  • November 2006
  • October 2006
  • September 2006
  • August 2006
  • July 2006
  • June 2006
  • May 2006
  • April 2006
  • Show More
July 28, 2015 4:40PM

The Progressive Increase of the Urban Heat Island’s Influence on Temperature Records

By Craig D. Idso

SHARE

Global Science Report is a feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our monthly “Current Wisdom.”

---

Perhaps no other climatic variable receives more attention in the debate over CO2-induced global warming than temperature. Its forecast change over time in response to rising atmospheric CO2 concentrations is the typical measure by which climate models are compared. It is also the standard by which the climate model projections tend to be judged; right or wrong, the correctness of global warming theory is most often adjudicated by comparing model projections of temperature against real-world measurements. And in such comparisons, it is critical to have a proper baseline of good data; but that is easier acknowledged than accomplished, as multiple problems and potential inaccuracies have been identified in even the best of temperature datasets.

One particular issue in this regard is the urban heat island effect, a phenomenon by which urban structures artificially warm background air temperatures above what they normally would be in a non-urbanized environment. The urban influence on a given station’s temperature record can be quite profound. In large cities, for example, urban-induced heating can be as great as Tokyo’s 10°C, making it all the more difficult to detect and discern a CO2-induced global warming signal in the temperature record, especially since the putative warming of non-urbanized areas of the planet over the past century is believed to be less than 1°C.  Yet, because nearly all long-term temperature records have been obtained from sensors initially located in towns and cities that have experienced significant growth over the past century, it is extremely important that urbanization-induced warming -- which can be a full order of magnitude greater than the background trend being sought -- be removed from the original temperature records when attempting to accurately assess the true warming (or cooling!) of the natural non-urban environment. A new study by Founda et al. (2015) suggests this may not be so simple or straightforward a task.



Working with temperature records in and around the metropolitan area of Athens, Greece, Founda et al. set out to examine the interdecadal variability of the urban heat island (UHI) effect, since “few studies focus on the temporal variability of UHI intensity over long periods.” Yet, as they note, “knowledge of the temporal variability and trends of UHI intensity is very important in climate change studies, since [the] urban effect has an additive effect on long term air temperature trends.”

To complete their objective the four Greek researchers compared long-term air temperature data from two urban, two suburban and two rural stations over the period 1970-2004. The UHI was calculated as the difference between the urban and suburban (or rural) stations for monthly, seasonal and annual means of air temperature (max, min, and mean).

Among their several findings, the authors report notable differences in the UHI’s intensity across the seasons and in comparing the UHI when calculated using maximum, minimum, or mean temperatures. Of significance to the discussion at hand, however, the authors note “the warming rate of the air temperature in Athens is particularly large during [the] last decades,” such that the “difference of the annual mean air temperature between urban and rural stations exhibited a progressively statistically significant increase over the studied period.” Indeed, as shown in the figure below for the stations (a) National Observatory of Athens (NOA) in the center of Athens and Tanagra (TAN), approximately 50 km north of the city, as well as for (b) the coastal urban station of Hellinikon (HEL) and again the rural station of Tanagra, the anthropogenic influence of urbanization on temperatures at these two urban stations is growing in magnitude with time such that “the mean values of UHI magnitude [calculated across the entire record] are not quite representative of the more recent period.”


Media Name: gsr_072815_fig1.jpg

 



Interdecadal variation and annual trends of the Athens, Greece UHI calculated between two urban and one rural station using mean annual temperatures over the period 1970-2004. The two urban stations were the National Observatory of Athens (NOA) in the center of Athens and Hellinikon (HEL), located near the urbanized coast. The rural station Tanagra (TAN), was located approximately 50 km north of the city. Adapted from Founda et al. (2015).

Such findings as these are of significant relevance in climate change studies, for they clearly indicate the UHI influence on a temperature record is not static. It changes over time and is likely inducing an ever-increasing warming bias on the temperature record, a bias that will only increase as the world’s population continues to urbanize in the years and decades ahead. Consequently, unless researchers routinely identify and remove this growing UHI influence from the various temperature data bases used in global change studies, there will likely be a progressive overestimation of the influence of the radiative effects of rising CO2 on the temperature record.

 

Reference

Founda, D., et al. 2015. Interdecadal variations and trends of the Urban Heat Island in Athens (Greece) and its response to heat waves. Atmospheric Research, 161-162, 1-13.

Related Tags
Energy and Environment

Stay Connected to Cato

Sign up for the newsletter to receive periodic updates on Cato research, events, and publications.

View All Newsletters

1000 Massachusetts Ave. NW
Washington, DC 20001-5403
202-842-0200
Contact Us
Privacy

Footer 1

  • About
    • Annual Reports
    • Leadership
    • Jobs
    • Student Programs
    • Media Information
    • Store
    • Contact
  • Podcasts

Footer 2

  • Experts
    • Policy Scholars
    • Adjunct Scholars
    • Fellows
  • Events
    • Upcoming
    • Past
    • Event FAQs
    • Sphere Summit

Footer 3

  • Publications
    • Books
    • Cato Journal
    • Regulation
    • Cato Policy Report
    • Cato Supreme Court Review
    • Cato’s Letter
    • Human Freedom Index
    • Economic Freedom of the World
    • Cato Handbook for Policymakers

Footer 4

  • Blog
  • Donate
    • Sponsorship Benefits
    • Ways to Give
    • Planned Giving
Also from Cato Institute:
Libertarianism.org
|
Humanprogress.org
|
Downsizinggovernment.org