Your Average Temperature Just Changed Because of Climate Change | The Weather Channel – Articles from The Weather Channel | weather.com – The Weather Channel
- Climate averages for temperature and precipitation just changed in many U.S. locations.
- Calculated every 10 years, temperature normals are warming due to climate change.
- The new dataset covers the 1991 to 2020 period.
Climate averages for temperature and precipitation likely just changed where you live, and that’s influenced by climate change.
The changes are a part of a once-per-decade update to climate normals that were released by NOAA on Tuesday.
Climate normals are more commonly known as your average temperature and precipitation for any given period of time, like a day, month or season. These so-called “normals” help put the actual temperature or precipitation into historical context relative to what you would expect in a given time.
More than 7,300 stations across the U.S. have normals data for temperature, NOAA says. Precipitation data is available for nearly 15,000 locations.
NOAA has now updated the normals data to include the most recent three-decade average: 1991 to 2020. For many locations, that means there is an overall increase in the average temperature when compared to the old 1981-2010 dataset because of global temperature rise, but there are some caveats.
The map below shows the annual average temperature change in the new 1991-2020 normals when compared to the previous dataset that covered the 1981-2010 period. Much of the Lower 48 has a warmer annual average temperature in the new normals, as depicted by the vast expanse of red shadings.
Portions of the north-central U.S. have the least amount of warming in the new normals. In fact, a few spots, particularly in the Dakotas and Montana, have a slightly cooler annual average temperature in the new dataset.
We can break this down even more by looking at the specific data for a few cities in the graphic below.
As you can see, the average annual temperature has crept higher in Boston, Chicago, Dallas-Fort Worth, Philadelphia and Seattle in the new dataset. Fargo, North Dakota, is an example of a city where the average temperature for the entire year trended slightly lower.
The annual average temperature in each 30-year normal period has trended warmer overall throughout the decades when compared to the longer-term 20th-century average (1901-2000).
“The influence of long-term global warming is obvious: the earliest map in the series has the most widespread and darkest blues, and the most recent map has the most widespread and darkest reds,” said Rebecca Lindsey in a NOAA climate blog.
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That said, this warming influence is not the same magnitude for each region of the country in the 10 different 30-year normal periods for annual average temperature shown in the tweet below.
Lindsey noted, “The pace of warming changes from decade to decade due to other climate influences, both natural and human (think the Dust Bowl and smokestack pollution before the Clean Air Act).”
Annual average precipitation has also changed for some cities in the new normals.
You can see some of the regional trends, particularly a drier Southwest, in the comparison between the 1991-2020 and 1981-2010 normal datasets below. Conversely, annual average precipitation has increased by 5% or more in the new normals for some locations across the north-central and eastern U.S.
The influence of climate change on precipitation, when compared to the longer-term average (1901-2000) in each normal dataset through the decades, is less clear.
“Few places exhibit a precipitation trend that is either steadily wetter or steadily drier than the 20th-century average. Instead, drier areas and wetter areas shift back and forth without an obvious pattern,” said Lindsey.
Nevertheless, global warming is still likely influencing precipitation in the U.S. There is just variability that masks the longer-term expected trends.
“Some parts of the country are projected to see increases in annual average precipitation, and others may see decreases. Some may see wetter winters but drier summers, with little net change in annual average precipitation – but big impacts on natural ecosystems and agriculture that depend on a certain seasonal cycle,” Lindsey added.
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