# Changing U.S. Extreme Temperature Statistics

## TL;DR

This study introduces a nonparametric metric to analyze extreme temperature changes, revealing fewer all-time lows but no significant trend in record highs across US weather stations, aiding understanding of climate extremes.

## Contribution

It presents a novel nonparametric statistic for assessing local temperature extremes and compares historic data with climate models to evaluate extreme temperature behavior.

## Key findings

- Fewer all-time lows than expected under no climate change.
- No significant trend in record high temperatures.
- The metric is validated through Monte Carlo simulations.

## Abstract

The rise in global mean temperature is an incomplete description of warming. For many purposes, including agriculture and human life, temperature extremes may be more important than temperature means and changes in local extremes may be more important than mean global changes. We define a nonparametric statistic to describe extreme temperature behavior by quantifying the frequency of local daily all-time highs and lows, normalized by their frequency in the null hypothesis of no climate change. We average this metric over 1218 weather stations in the 48 contiguous United States, and find significantly fewer all-time lows than for the null hypothesis of unchanging climate. Record highs, by contrast, exhibit no significant trend. The metric is evaluated by Monte Carlo simulation for stationary and warming temperature distributions, permitting comparison of the statistics of historic temperature records with those of modeled behavior.