Andrey Kamenov, Ph.D. Probability and Statistics

It seems that new U.S. President Donald Trump doesn’t believe in global warming. At least, he has made clear his intent to undo some, if not all, of President Obama’s climate change policies. But just how important is climate change? And does global warming affect the country?

Of course, the implications of any climate change go far beyond a simple change in temperature. But this change is something one can measure directly, so it should definitely be a place to start. The most complete data on the topic is provided by the PRISM climate group (see the link at the bottom of the page).

First, let’s explain what the numbers in the PRISM dataset mean. Each month, they calculate an average of daily temperature maximums as well as minimums. These are called monthly max and min respectively. Most of the time, we’ll deal with the mean, which is exactly the average of two numbers.

Average temperature in the U.S.

Let’s see how mean monthly temperatures changed in four decades. We will also find out whether the rate of change is large enough to be statistically significant. For this, we will utilize the Mann-Kendall test — see the link at the bottom of the page for details.

According to this test, the seasonally adjusted temperature data show an increase of exactly 0.6 degrees. Our test confirms that this rate of change is large enough to be statistically significant.

It also shows that climate change affects colder months more significantly. While monthly maximums have only increased by 0.3 degrees, the minimums have gone up by 0.9 degrees.

Of course, for a country so large, we cannot measure the climate change entirely by a single number (or even three numbers). Indeed, it appears that some states are virtually unaffected by a temperature increase. At the same time, the effect is much more severe in others.

Just look at the map:

Change in monthly temperature by state

There is a statistically significant positive trend in average temps almost everywhere. The only exception is the large yellow spot in the center of the map (Oklahoma and Arkansas, along with all the states to the north).

Most of the states are seeing temperatures slowly climbing at a rate from 0.2 to 0.5 degrees per decade. Especially high numbers are observed in New Jersey and Vermont in particular. Another one of the most affected states is New York at 0.4 degrees.

Source(s):

• PRISM climate group datasets provided by Oregon State University on 31 Mar 2017
• Mann-Kendall test Python implementation

About Andrey Kamenov

Andrey Kamenov, Ph.D. Probability and Statistics

Andrey Kamenov is a data scientist working for Advameg Inc. His background includes teaching statistics, stochastic processes and financial mathematics in Moscow State University and working for a hedge fund. His academic interests range from statistical data analysis to optimal stopping theory. Andrey also enjoys his hobbies of photography, reading and powerlifting.

Other posts by Andrey Kamenov:

• Are people living outside the metro areas cushioned against falling home prices?
• Owners prefer to build small homes outside of metro areas
• Exercise or sleep: which is more important for your health?
• Measuring health levels in the U.S.
• Where to be born in the U.S.