Return to Excel Statistics Page

Where in the US has the Temperature Increased Most

Keith Greiner

August 9, 2020

This essay reports on temperature increases in the United States by state, between 1980 and 2017. Increases are presented as the slope of a simple linear regression of a time series, where the slope of the line is in units of degrees Fahrenheit per year.

The graph shown below, presents the January, monthly average, U. S. temperature from 1980 through 2017 and the linear regression line that describes the annual increase in temperature. While there is variation in the graph’s blue line, the linear regression trend line shows an upward trend of 0.06 degrees Fahrenheit per year. This is an increase from the 0.0176 degree per year slope when the entire series of 123 years of data is included. The entire series that is available, covers the time from 1895 through 2017. While the January temperature has variation, the regression trend line calculation returns the formula for the line that has the least amount of variation between the trend line and the blue y points on the graph.. A person can use the slope, intercept, and the x value of the year to estimate the value for some future year – knowing that there will be variations between the estimate and the actual value. However, one would want to use caution when using such a linear future estimate because the slope of historical temperature line has been increasing in recent years and can be expected to continue to increase.

Since 1980, every state has had a similar increasing trend for the month of January. The map presented below shows the relative slope for each state. States with greater slopes of the regression line are shown in darker colors. Between 1980 and 2017 all states had positive slopes, which suggests that all states experienced warming trends during the month of January.

Following is a list of the temperature values for each year of the analysis. The regression slope and intercept are shown at the bottom of the list.

Column E shows the Excel code used to calculate the trend line in column D, the slope in row 46 and the intercept in row 47.

Return to Excel Statistics Page