Mark Fife writes:
This is my eighth post in this series where I am examining long term temperature records for the period 1900 to 2011 contained in the Global Historical Climatology Network daily temperature records. I would encourage anyone to start at the first post and go forward. However, this post will serve as a standalone document. In this post I have taken my experience in exploring the history of Australia and applied it forward to cover North America and Europe.
The way to view this study is literally a statistic-based survey of the data. Meaning I have created a statistic to quantify, rank, and categorize the data. My statistic is very straight forward; it is simply the net change in temperature between the first and last 10 years of 1900 through 2011 for each station.
Below is a list of countries showing the lowest net change, the highest net change, and the number of stations per country.
This is an old-fashioned histogram showing how the stations ranked in terms of overall temperature change. This shows the data falls in a bell-shaped curve. The underlying distribution is very close to normal. This means analysis using normal techniques will yield very reasonable estimates. This is significant to a statistician. However, you don’t need any statistical knowledge to understand this.
The mid line value is between -0.5° and 0.5°. The number of stations showing an overall drop in temperature is 40%. Slightly less than 60% of the stations show an increase. The absolute change is statistically insignificant in 74.6% of the stations.
The following graph shows a normalized look at each category: No significant change, significant warming, and significant cooling. The graph is of rolling 10-year averages. Each plot has been normalized to show the 1900 – 1910 average as zero.
You will note, though the overall slope of each plot is significantly different, the shape of the plots is nearly identical. A random sampling of individual station data shows that condition remains true for each station in the range. For example, Denmark’s Greenland station shows the 1990 – 2000 average is the same as the 1930 – 1940 average.
Short term changes, such as the warming into the 1930’s, hold true for the clear majority of stations. Other examples of this would be the 1940’s temperature jump, the post 1950 temperature drop, and the late 1990’s temperature jump.
Long term changes vary significantly.
There are several conclusions to be drawn from this analysis.
- There is no statistically significant difference between North America and Europe. Those stations showing significant cooling are just 8% of the total. By that statistic, the expected number of the 17 European stations to show cooling would be just one. The number expected to show significant warming would be three. From a statistical sampling standpoint, 17 is just not a robust enough sample size to yield accurate estimates.
- Short term changes which appear in the vast number of stations from Canada to the US to Europe are probably hemispheric changes. However, there is no indication these are global changes as there is no evidence of similar changes in Australia. Australia did not experience a 1930’s warming trend for example. In fact, the overall pattern in Australia is obviously different from what we see here.
- The evidence strongly suggests the large variation in overall temperature trends is due to either regional or local factors. As shown in the data table at the beginning, the extremes in variation all come from the US. As noted before, there just aren’t enough samples from Europe to form accurate estimates for low percentage conditions.
- Further evidence suggests most of the differences in overall temperature change are due to local factors. What we see from the US is extreme warming is generally limited to areas with high population growth or high levels of development. Large cities such as San Diego, Washington DC, and Phoenix follow the pattern of significant change. Airports also follow this pattern. However, cities like New Orleans, St Louis, El Paso, and Charleston follow the pattern of no significant change.
In Conclusion, based upon the available long-term temperature data the case for global warming is very weak. There is evidence to suggest a hemispheric pattern exists. The evidence further suggests this is a cyclical pattern which is evident in localized temperature peaks in the 1930’s and the 1990’s. However, changes in local site conditions due to human development appear to be the most important factor affecting overall temperature changes. Extreme warming trends are almost certainly due to human induced local changes.
What is unclear at this point is the significance of lower levels of human induced local changes. Assessing this would require examining individual sites to identify a significant sample of sites with no changes. Unfortunately, the US, Canada, and Europe are not nearly as obliging on that kind of information as the Aussies are. I must admit the Australians have done an excellent job of making site information available. Having the actual coordinates to where the actual testing station resides made that easy. I literally pulled them up on Google Maps and was able to survey the site and surrounding areas.
It appears this is about as far down the rabbit hole as I am going to get, at least, not without a lot of work which at this point doesn’t appear warranted.
For more, visit me at http://bubbaspossumranch.blogspot.com/
Mark Fife holds a BS in mathematics and has worked as a Quality Engineer in manufacturing for the past 30 years.