Your Average Temperature Just Changed Because of Climate Change | The Weather Channel – Articles from The Weather Channel
- The climate averages for temperature and precipitation have just changed at many locations in the USA.
- Calculated every 10 years, the temperature normals are warming up due to climate change.
- The new data set covers the period 1991 to 2020.
The climate averages for temperature and precipitation have likely changed right where you live, and this is being influenced by climate change.
The changes are part of a once-per-decade update of the climate normals released Tuesday by NOAA.
Climate normals are generally referred to as the average temperature and precipitation for a specific period such as a day, a month or a season. These so-called “normals” help to put the actual temperature or precipitation in a historical context that corresponds to what you would expect in a given time.
More than 7,300 stations in the United States have normal data for temperature, according to NOAA. Precipitation data is available for nearly 15,000 locations.
NOAA has now updated the normal data to reflect the latest three-decade average: 1991 to 2020. For many locations, this means that the average temperature is increasing overall due to global temperature rise compared to the old 1981-2010 dataset, but there is some limitations.
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The map below shows the annual average temperature change in the new normals from 1991 to 2020 compared to the previous data set, which covered the period from 1981 to 2010. Much of the lower 48 has a warmer annual mean temperature in the new normals, as evidenced by the large expansion of the red shades.
The change in temperature in degrees Fahrenheit from the previous 30 year normals (1981-2010) to the latest version (1991-2020).
(NOAA / CISESS)
Parts of the north-central United States have the least warming in the new normal. In fact, some locations, particularly in Dakotas and Montana, have slightly cooler annual mean temperatures in the new data set.
We can break this down even further by looking at the specific data for some cities in the graph below.
As you can see, the mean annual temperatures in Boston, Chicago, Dallas-Fort Worth, Philadelphia, and Seattle have increased in the new data set. Fargo, North Dakota is an example of a city where the average temperature was slightly lower for the whole year.
The first column shows the annual average temperature for each city in the new norms from 1991 to 2020. The increase or decrease in this annual average temperature compared to the old norms from 1981-2010 is given in the second column.
The annual average temperature in each 30-year normal period has developed overall warmer over the decades compared to the longer-term average of the 20th century (1901-2000).
“The impact of long-term global warming is evident: the earliest map in the series has the most pervasive and darkest blues, and the most recent map has the most pervasive and darkest reds,” Rebecca Lindsey said in a NOAA climate blog.
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However, this warming influence in the 10 different 30-year normal periods for the annual average temperature given in the following tweet is not the same for every region of the country.
Lindsey noted, “The rate of warming is changing from decade to decade due to other natural and human climatic influences (think dust bowl and chimney pollution before the Clean Air Act).”
The annual average precipitation has also changed for some cities in the new normal.
You can see some of the regional trends, particularly a drier southwest, compared between the normal 1991-2020 and 1981-2010 datasets below. Conversely, the annual mean precipitation in the new normal for some locations in the north-central and eastern United States has increased 5% or more
As above, but for changes in precipitation, as a percentage of the average precipitation from 1981-2010.
(NOAA / CISESS)
The impact of climate change on precipitation is less clear in any normal data set over the decades compared to the longer-term average (1901-2000).
“Few places have a rainfall trend that is either steadily wetter or steadily drier than the 20th century average. Instead, drier areas and wetter areas shift back and forth with no apparent pattern,” said Lindsey.
Still, global warming is likely to still affect precipitation in the US. There is only one variability that masks the longer term expected trends.
“Some parts of the country are projected to see an increase in average annual rainfall and a decrease in others. Some parts may have wetter winters but drier summers with a small net change in mean annual rainfall – but large effects on natural ecosystems and agriculture depend on it in a particular seasonal cycle, “added Lindsey.
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