Climate change to decrease average number of mild weather days


3599894522_06f3bbf307_o
Residents enjoy pleasant weather at Noelridge Park in Cedar Rapids, Iowa. (Louis/flickr)
Jenna Ladd | January 24, 2017

The first of its kind, a recent study found that climate change is likely to decrease the number of “nice weather” days worldwide.

The authors of the study, scientists from the National Oceanic and Atmospheric Association and Princeton University, define “nice” or “mild” days as those days when temperatures are between 64 and 86 degrees Fahrenheit, dew points are below 68 degrees Fahrenheit and less than half of an inch of rain falls. Currently there are an average of 74 nice days globally per year, but that number is likely to drop to 70 in the next twenty years and to 64 by 2081.

Karin van der Wiel is a postdoctoral researcher at Princeton University and lead author of the study. She said,

“We used a climate model to simulate the current climate. In that simulation we counted the number of mild days. Then, we increased greenhouse gases in the climate model to simulate the future effects of climate change. This leads to increasing temperatures, changes in humidity, changes in precipitation over the whole world and with very specific patterns. In this new, future climate, we counted the number of mild days again. We could then calculate the change — increase or decrease — of mild weather days for each location globally.”

Not all corners of the Earth will be affected equally, however. Tropical regions are expected to lose the most nice days, with some areas losing up to 50 per year by the end of this century. Meanwhile, London is expected to gain 24 nice days each year.

Predictions for Cedar Rapids, Iowa mirror global averages. Eastern Iowa currently enjoys 76 nice days annually; researchers say that number is expected to drop to an average of 72 between 2016 and 2035 and to 66 each year between 2081 through 2100.

Frequent high humidity makes it tough for Iowa to meet the pleasant weather criteria outlined in the study. Absolute humidity has risen by 13 percent during the summer months in Des Moines since 1970, according to Iowa State climate scientist Gene Takle. Increased humidity also contributes to the extreme rain events that have plagued Iowa in recent years.

van der Wiel said, “Mild weather is something everyone knows, experiences, and has memories of,” she continued, “Our study shows that human-caused climate change is going to lead to changes in mild weather all over… The changes are happening now, and where people live.”

Iowa sees the “humidity effect” this week


Image
Photo by Pentax_clic; Flickr

This week’s climate in some Iowa cities has been notably warm. However, the warmer than usual climate is not due to abnormally high temperatures, but rather high humidity levels.

Image
Photo by Iowa State University Department of Agronomy

The chart above shows the difference between temperature and heat index at an 80 or above degree level. Continue reading