Annual Temperature Plots
Histograms Tab

Most presentations of global temperature data either deal with some type of average or display the info on a global map. Both of these presentations can be extremely useful and/or extremely misleading.

The info provided via the GHCN Temperature Plotter's Histogram tab is intended to help you understand what the data actually says.

There are so many options and configurations that using this can be a little confusing. (ok, extremely confusing.) The info on this page should help.

Main options | Bin size | Multiple plots | Raw vs Adjusted comparisons | Other Controls | Comparison of different time periods | Comment

Main options

The Histogram tab displays the number of selected sites verses the selected parameter. These examples use the raw data for the entire planet and the default baseline.

To save copies of these plots, simply right click the chart and select Save image as... or Copy image (the exact text depends on your browser). Chrome saves these as 180h x 360w *.png files.

Bin size

The application allows you to set the bin sizes. The defaults provide what I think are reasonable values. This example demonstrates the effect of this parameter - The default is in blue.

Multiple plots

There are a number of reasons to place similar plots on the same chart. Perhaps you want to compare the trend from 1900 to 1930 with the trend from 1980 to 2010. Or Europe to North America. etc.

There are 2 buttons that support comparing multiple datasets.

These buttons were used to produce the multi-bin image in the previous section.

Raw vs Adjusted comparisons

It is possible to compare the raw and adjusted data using the Plot and Add buttons described in the previous section. However, I use this feature often enough that I added a checkbox to make it automatic.

The application provides 4 datasets

For this to work, both the raw (unadjusted) and associated adjusted data must be loaded. It does not matter which of the 2 related datasets are selected.

For a good comparison, make sure that the selection criteria are the same for both datasets - normally, you will want the same countries and/or same time periods. Since the number of sites is different, you may want to use the Raw vs Adj Filters tab to refine your selection.

From that graph, it should be obvious that a major part of the warming signal is produced by the data adjustment process - a process which is poorly documented and is very difficult to review. This particular graph suggests that a major part of the warming signal is produced by simply dropping those sites which are cooling. Of course, it is not that simple.

The ocean data is identical in the 2 associated datasets and provided as only an "anomaly" temperature - meaning that the actual ocean temperatures are NOT provided, only an offset from some unspecified "average" value. A general overview of that data, and an explanation of why I think it is mostly worthless, is provided here.

Other Controls

Comparison of different time periods

It is often claimed that "temperatures are increasing faster now than in the past". In my opinion, the histograms simplify this type of analysis.

These plots use all of the default filters to get only the 523 stations with the longest records.

It appears that globally, there has been a major increase in warming between the 2 periods, but not so much for just the USA. When the USA is removed from the global data (lower left), the shift in the slopes becomes more obvious. For a comparison, I have included the global adjusted data (also minus the USA) - 187 stations. In my opinion, the major difference between the USA and the rest of the globe indicates a serious data problem.

A better comparison might be a couple of 20 year periods - 1900-1920 vs 1990-2010. Using just the raw USA data with all the filters turned on shows no significant increase in warming. Because the spread of the data increased, the Trend bin size was set to 0.05 (the default is 0.01) to produce a smoother plot.

Just for comparison, the next two plots use all 4561 adjusted global sites that meet the most basic baseline requirements. The first plot shows the trends from 1900 to 1960 - of the 4561 selected sites, 767 did not have enough data points to compute a trend, and several sites had trends larger than ±2°C/decade indicating obvious bad data. The trend histogram for the full 1900 to 2014 period is shown on the right for comparison.

Remember, these plots are included just to indicate how to use the tools and to suggest questions than can be asked. It is up to you to decide which questions are appropriate and to help you decide if claims made in various sources make sense.

One of my primary complaints with respect to climate reporting is a complete lack of information on the data spreads (standard deviations). Hopefully, this tool will bring some sanity to the discussion.


You will often hear that "the United States is not the entire planet", or something to that effect. However, it has the best long term temperature record and, no matter how you cut it, an average of more than 300 stations spread over an entire continent has to be a better proxy for world climate than 12 trees in Yamal. (According to the article, out of 252 Yamal specimens, 12 showed temperature increases, 34 showed warmer temperatures in the Middle Ages.)

Author: Robert Clemenzi
URL: http:// / Science_Facts / Annual_Temperature_Plots / Histograms_tab.html