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| Florida's Mammoth Oak (the 2nd largest live oak in Florida) is ~400 years old. Will it and other very old trees survive more warming? Photographed on a very hot day in early May, 2021. Temperature 97°F 36°C. Photo: Phillip Lott |
NOAA unveils new U.S. climate ‘normals’ that are warmer than ever
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| U.S. temperatures from 1991 to 2020 compared with 20th-century average |
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A Warming World Psychological research shows that climate change can alter an individual's mental health both directly and indirectly, impacting how we respond to this crisis |
“You can see that there’s a huge difference in temperature over time as we go from cooler climates in the early part of the 20th century to ubiquitously warmer climates here in the last two sets of normals,” Palecki said.
While the normal U.S. temperature is on the rise, some regions have warmed more than others and, over short time periods, some smaller areas haven’t warmed at all.
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| Mammoth Oak, Lake Griffin State Park Photo: Phillip Lott |
Temperatures actually dropped slightly for 1991-2020 compared with 1981-2010 across a part of the north-central United States extending into south-central Canada. Such departures can happen even amid longer-term warming if the decade being added (the 2010s) happens to be slightly cooler in a particular location than the decade being dropped (the 1980s).
The increase in temperature observed in Alaska reflected in the latest normals means that Fairbanks is “no longer a sub-Arctic climate in the widely used Köppen classification” for climate zones according to Rick Thoman, a climate specialist at the University of Alaska-Fairbanks. Instead, it resides within a “warm summer continental” zone, he tweeted.
It's official: just-released @NOAANCEIclimate 1991-2020 normals, Fairbanks Aiport no longer a sub-Arctic climate in the widely used Köppen classification. Now a "warm summer continental" climate. Change because the May normal temp went above 50F (10C). #akwx @Climatologist49 pic.twitter.com/tFPo1fCnUq
— Rick Thoman (@AlaskaWx) May 4, 2021
The new normals reveal that the U.S. climate is not only becoming warmer but also wetter. Preliminary data showed a national precipitation average of 31.31 inches for 1991-2020, up by 0.34 inches over the 1981-2010 value of 30.97 inches. The 20th-century average was 29.94 inches.
However, precipitation trends vary by region. Between 1981-2010 and 1991-2020, it turned wetter across much of the eastern two-thirds of the nation but drier across most of the Southwest.
The impact of climate change on precipitation is more complex than on temperature. Many parts of the United States are projected to get wetter over time, especially toward the northern states. However, rainfall and snowfall appear to be trending toward clusters of intensified precipitation, separated in some cases by longer dry periods, particularly in California. There are also signs that a multi-decade megadrought may have already set in over the southwest United States and northwest Mexico.
The landscape-drying influence of hotter temperatures will tend to increase the effects of drought even where average precipitation doesn’t change.
“It’s not surprising that precipitation maps don’t show the same unmistakable fingerprint of climate change that the temperature maps do,” noted Rebecca Lindsey at Climate.gov. “And yet, it’s probably not a coincidence that the last four maps in the series [shown below] … are nationally the four wettest-looking maps in the collection.”
“What we’re trying to do with climate normals is to put today’s weather in a proper context so we understand whether we’re above normal or below normal and also we’re trying to understand today’s climate so people know what to expect,” Palecki said.
The great challenge in depicting “normal” climate is that U.S. climate is no longer stationary, as increases in greenhouse gases push temperatures ever upward. That means even a recent 30-year average may not capture the true likelihood of a given temperature right now, especially as a set of climate norms approaches the end of its useful life.
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| Climate Normals for Central Florida, Sanford Airport reporting station |
Some resource managers are looking as much toward future change as they are toward the recent past, according to University of Oklahoma’s Renee McPherson. An associate professor of geography and environmental sustainability, McPherson also serves as university director for the South Central Climate Adaptation Science Center of the U.S. Geological Survey.
“It used to be that the normals would give a great idea of what the climate has been like for someone’s 30-year career, so new resource managers could get up to speed quickly on how and why a more senior manager made the choices they did based on past climate,” McPherson said in an email.
“Now we’re seeing enough change from one decade to the next that we need to prepare managers differently. They need to understand these are not static, so the direction of change is as important, or more important, as the values of the normals themselves.”
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| The global surface temperature departure of +0.85°C (+1.53°F) in March 2021 was the smallest March temperature departure since 2014 and was the eighth highest for March in the 142-year record. March 2021 also marked the 45th consecutive March and the 435th consecutive month with temperatures, at least nominally, above the 20th-century average. |
Other nations around the world are also updating their climate norms to reflect the 1991-2020 period, as mandated by the World Meteorological Organization (WMO). Until recently, the WMO recommended such updates each decade but required them only every 30 years. Thus, the last full worldwide update of national and local climate norms was for 1961-1990, a metaphorical lifetime ago in a world whose climate is rapidly changing.
* NOAA notes that while the new normals approximate climate averages, they involve complex statistical methods and processing to calculate.
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