Sunday, January 27, 2008

Ann Arbor Climate Change

A little while ago, I posted a link to the UK meteorological office which had a report with a nifty little graphic showing how average annual temperature ranges have shifted warmer over the past 100+ years. I thought I could replicate it for Ann Arbor. Luckily, the University has been keeping records of daily temperatures since 1882, meaning that I can look at temperature changes over the past 125 years!

So, what have I found? Well, to be brief, the temperature of the city has increased over the past 125 years, and five of the ten hottest years were in the period of 1997-2007. What does this all mean? Well, some of the temperature increase could be attributed to the urban heat island effect, and not to local impacts of global warming, but I don't think that all of the observed temperature increase could be. However, I don't have any good data to support this assertion. Of course, I could try and find temperature data for locations near Ann Arbor (say, within 25 miles of the University) and do a comparative analysis of the overlapping years. Of course, that is a different sort of analysis, taking more time and effort. I can do it, but right now, I'll just leave you with the pretty graph that took me about a week to complete. Enjoy!

IMPORTANT NOTICE (Feb 11, 2008): The values shown below are not for Ann Arbor. I accidentally used the wrong label for these charts. I will repost the correct charts for Ann Arbor once I fix them (don't worry, they still show positive slopes).

Ann Arbor annual mean and median temperatures have increased from roughly 45 F to roughly 54 F in the past 125 years.

The yearly mean temperature in Ann Arbor increased from roughly 46F to roughly 55F over the past 125 years. One can see an oscillating "sine-wave" function with a periodicity of roughly thirty years. This may be due to the ~30 year Great Lakes water level oscillations.

The yearly median temperature in Ann Arbor increased from roughly 46.5F to roughly 56F over the past 125 years.

The ranked mean annual temperatures for Ann Arbor from 1881 to 2006. The lowest rank (1) is given to the year with the coldest mean annual temperature (1882). The highest rank (125) was given to the year with the warmest mean annual temperature (1998). In the 10-year period of 1997-2006, five years were in the top ten warmest years (1998, 1999, 2001, 2002, 2006). There is a strong positive correlation (R2=0.72) between year and annual temperature rank. With such a high correlation, one shouldn't be surprised to see more high-rank temperatures in the years to come.

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