US is becoming warmer with each decade, new numbers reveal

·7 min read

New data on the "normal" temperature and climate variables in the United States has revealed that much of the country is getting warmer and wetter each decade -- and some experts say the warming trends are on par with what would be expected from greenhouse gas-induced climate change.

"Normals," as they are referred to by meteorologists, are determined based on weather factors such as temperature and precipitation that have been tabulated by researchers over the past 30 years. Those numbers are then calculated into averages for the 30-year period.

Every 10 years, the U.S. normals are reviewed and updated by scientists from The National Oceanic and Atmospheric Administration's (NOAA) National Climatic Data Center (NCDC).

The first time normals were calculated was for the period covering 1901-1930, and at that time it was measured by the World Meteorological Organization. The U.S. eventually adopted the same 30-year system.

On Tuesday, the normals for the past decade, with data spanning from 1991 to 2020, were released by the NCDC. The last report that was released measured normals from the 1981 to 2010 period. While it's referred to as a report, it is actually a data set that people can refer back to when needed, although the NOAA also has created some explanatory web pages to help people navigate the data.

The numbers released for the last decade reveal that the U.S. is continuing to grow warmer and warmer as each decade passes, Bernadette Woods Placky, chief meteorologist and Climate Matters program director at Climate Central, told AccuWeather National Reporter Emmy Victor.

In this March 10, 2021, file photo, a woman strolls along the beach under rain clouds in Seal Beach, Calif. Rainstorms grew more erratic and droughts much longer across most of the U.S. West over the past half-century as climate change warmed the planet, according to a sweeping government study released, Tuesday, April 6, 2021, that concludes the situation in the region is worsening. (AP Photo/Jae C. Hong, File)

The eastern U.S. has also become wetter, while the West has become drier. She said rising temperatures can play a role in changing precipitation patterns, and climate change "supercharges our water cycle." As the planet heats up, the water on the surface evaporates into the atmosphere, which leads to rain coming down even harder than before.

However, as the Earth's atmosphere constantly tries to reach equilibrium, not every place faces more rainfall.

"As the Southwest gets even drier, there is less moisture to evaporate, which allows more of the sun's energy to go directly into heating the surface, which also helps to explain the rapid warming in this region," AccuWeather Senior Meteorologist Brett Anderson wrote in a recent blog post on the topic.

Woods Placky explained that in drier areas such as the West, the precipitation tends to come in stronger than ever when it finally comes.

"We're seeing a mixed signal," she said. "It's getting drier, but when it does come down, it's coming down in these downpours."

This is critical data for the work forecasters do each day, so the news is big in the meteorological community. "Tracking weather normals allows meteorologists to put today's (or this year's) weather into context versus recent history, to detect trends and rate the rarity of current weather events versus history," AccuWeather Senior Weather Editor Jesse Ferrell said.

Climate new normals

Rod Bradshaw stands in a field of wheat on his farm near Jetmore, Kan., Wednesday, Jan. 13, 2021. Bradshaw, who claims to be the last Black farmer in Hodgeman County, is concerned that systemic discrimination by government agencies, farm lenders and the courts have reduced the numbers of Black farmers in the United States from about a million in 1920 to less than 50,000 today. (AP Photo/Charlie Riedel)

In addition to the weather community, many other industries that are not directly tied to meteorology look to weather normals as well.

"We have a lot of people that rely on what happens in our weather and our climate to do their daily work," Woods Placky said. "Farmers need to know when to plant crops and what types of crops. Cities need to know how to plan for snow removal and how much snow to expect."

Beyond farmers and city planners, energy and utility companies need to understand normals so they can best prepare for different seasonal demands, construction companies need to know how often it will rain within a certain time frame while on a contracted construction project and clothing and accessory retailers need to understand how weather will shift in different regions to determine what to sell and when.

(National Centers for Environmental Information)

In addition to its functional purposes, Woods Placky said the release of the normals data each decade serves as "a moment to pause and reflect and really take a look at the bigger picture."


Michael Palecki, a physical scientist for NOAA's National Centers for Environmental Information (NCEI) and project manager for NOAA's 1991 to 2020 Climate Normals, said there were a few surprises in this year's data, particularly with how temperature normals have changed in parts of the U.S.

"When we started the process we thought that the new normal for 1991 to 2020 would be warmer everywhere compared to the 1981 to 2010 normal, but that's actually not the case," Palecki said.

(National Centers for Environmental Information)

In reality, Palecki said the north-central U.S., mainly to the northwest of Chicago, was actually cooler in this decade's data set than it was from the prior decade, particularly in the Dakotas, Minnesota and Montana.

"The whole world is not going to warm exactly the same amount," Palecki said. "It's going to vary based on atmospheric circulation and ocean circulation changes."

Other parts of the northern U.S. also experience cooler normals at different times of the year, for example in April, when compared to prior decades.

(National Centers for Environmental Information)

According to the NCEI, April is the most "dynamic" core month, core months being those in the middle of a season (January, April, July and October).

Changes in temperature normals were as much as 2 degrees Fahrenheit lower in the Dakotas in April when compared to the prior decade, while regions both west and east of the Mississippi Valley continued to see a warming trend.

Across all seasons, the NCEI reports that two-thirds of the country is now wetter than it was before and most of it is warmer.

In January, the core month for winter, most of the country experienced a rise in temperatures of 0.5 to 1.5 degrees Fahrenheit. In July, the core month for the summer season, the entire West, Texas and portions of the Rocky Mountains experienced temperature increases of up to 2 degrees.

Ken, left, and Ana Seastrom sit on the beach Tuesday, April 27, 2021, in San Diego. (AP Photo/Gregory Bull)

"The patterns that we're seeing are pretty much as expected for a greenhouse gas induced climate change," Palecki said. "Were not seeing any surprises in that sense."

The transportation sector, according to Woods Placky, is currently the largest source of emissions, and large-scale electric transportation could be a solution to cut those down in the nation. The energy sector is the second-biggest source of emissions in the U.S., and things like wind and solar-powered energy can help to curb those emissions too, Woods Placky said.

"On an individual scale, there is a lot we can do to learn and talk to others about what's going on and learn how we can factor into these bigger solutions," Woods Placky said.

"On a big scale, we do need some system changes," she said.

Reporting by Emmy Victor

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