Two things can be true at the same time.

It can be difficult to understand that the Earth is warming at all when dangerously cold temperatures are currently threatening our wellbeing. But a day or two or even a week below zero in Iowa is just a fraction of the year and a small point on a big map. When we talk about Earth or even the United States, a year-to-year analysis shows a stark warming trend. This is ultimately the difference between weather and climate. Weather is the day-to-day atmospheric conditions for one particular location, while climate is a trend over longer periods of time.

Record-high temperatures from nearly 100 years ago can also make this distinction difficult to understand. 1934 is the eighth warmest year on record for the United States and the fifth warmest year on record for Iowa. In Des Moines, 1934 still holds 16 high temperature records in which temperatures reached over 100°. Why? Exceptional drought during the summer. It takes more energy to heat water than it does land, so when there is no water in the ground, the land heats up faster. 

You may notice in recent years there haven’t been many 100° high temperatures across central Iowa. Why? There is also about 4% more water vapor in the atmosphere now than there used to be in the late 1800s. As described above, if the air has more moisture in it, it can’t heat up as fast as it can when it’s drier. That doesn’t mean we can’t or won’t see 100° days in the future, they’re just becoming less common. In 2021, Des Moines set a new record high of 101° on June 16, but central Iowa was in its worst drought stage since 2013. This is one of only three 100° highs Des Moines has seen since 2014. 

Going back to 1934, while Iowa and the U.S. experienced one of their top 10 warmest years, globally it was nowhere near the top 10 warmest. It was a cooler-than-average year.  Below you’ll see how temperatures in 1934 and 2021 compared on the global scale. If you move the divider all the way to the right you’ll notice that in 1934, the United States did experience a warmer-than-average year, but most of Earth actually experienced cooler-than-average temperatures. Now swipe the divider all the way to the left. You’ll see nearly all of Earth experienced above average temperatures in 2021.

Left: Global temperatures in 1934 vs Right: Global temperatures in 2021

What you’re looking at is the global temperature of the Earth compared to average over an entire year. By looking at several years and how they stack up against one another we can see different trends, but one is quite clear. Dr. Katherine Hayhoe, a climate scientist, describes this trend in her book, Saving Us, “The truth is that no matter how cold or hot it is today, no matter what season it is, each successive decade is breaking new ground as the warmest on record at the global scale.” Below is a video that shows the global temperature difference from 1884 to 2021.

Globally, 2021 was the sixth warmest on record, falling behind #1 2016, #2 2020, #3 2019, #4 2015, and #5 2017. The U.S.’ top 5 warmest years are (1) 2012, (2) 2016 , (3) 2017, (4) 2015, and (5) 2020. Iowa’s top 5 warmest years are (1) 1931, (2) 1921 , (3) 1987 and 2012, and (5) 1934.