Global warming

[shunyadragon]

Source: https://scitechdaily.com/1000-plus-years-of-tree-rings-confirm-unprecedented-nature-of-2021-western-north-america-heat-wave/

1,000-Plus Years of Tree Rings Confirm Unprecedented Nature of 2021 Western North America Heat Wave

By COLUMBIA CLIMATE SCHOOL MARCH 29, 2023

Lead author Karen Heeter takes a core sample from an old mountain hemlock near Crater Lake, Oregon, where at least one tree dated to the 1300s. Credit: Grant Harley/University of Idaho
The historic extremity of the event serves as a warning for other regions.

During the summer of 2021, an unprecendented heatwave swept across western North America, affecting regions from British Columbia to Washington, Oregon, and beyond into other interior areas that typically experience a mild climate. Temperatures shattered records in many locations, resulting in widespread wildfires and the tragic loss of at least 1,400 lives. While scientists have attributed this event primarily to human-caused climate change, labeling it as unprecedented, it is difficult to determine with certainty if it truly had no prior occurrence due to limited weather data that only dates back to the last century.

According to a recent study, based on the analysis of tree rings from the region, the 2021 heatwave was almost certainly the most severe in the past thousand years. The findings, which were published in the journal Climate and Atmospheric Science, established a yearly record of summer average temperatures starting from 950 AD. The research revealed numerous summers with abnormal high temperatures, many of which occurred in multi-year warm spells. However, the study highlights that the last 40 years, due to human-induced global warming, have been the hottest, with the summer of 2021 being the warmest of all.

“It’s not that the Pacific Northwest has never before experienced waves of high temperature. But with climate change, their magnitude is much hotter, and they have a much greater impact on the community,” said lead author Karen Heeter, a postdoctoral researcher at Columbia University’s Lamont-Doherty Earth Observatory. “Being able to look at the past and compare that with climate models, and come to similar conclusions, there’s a lot of power in that.”

Summer seasonal temperature anomalies revealed by tree rings and modern weather data, 1950-2021. Credit: Modified from Heeter et al., Climate and Atmospheric Science, 2023

The tree-ring reconstruction and modern temperature readings show that 1979-2021 saw a sustained period of hot summers unrivaled for the last 1,000-plus years. Most of the hottest years have occurred since 2000. The second-warmest period, indicated by the tree rings, was 1028-1096—at the height of the so-called Medieval Climate Anomaly, when a natural warming trend is thought to have taken hold across large parts of the planet. Another notable hot span during the Medieval Climate Anomaly ran from 1319 to 1307. But even these periods were considerably cooler than temperatures in recent decades.

The 2021 heat wave spanned a several weeks from late June to mid-July. While the researchers did not try to pick out such short periods in the rings, they say average seasonal temperatures are a good proxy for such events. Summer 2021 held the annual record, at 18.9 degrees Centigrade, or about 66 degrees Fahrenheit. By contrast, the hottest summer in prehistoric times was in 1080, at 16.9 degrees C, or 62.4 F.

This perhaps does not sound very impressive—until you consider that due in part to the near-complete human destruction of ancient trees in the lowlands, the researchers used mainly samples collected at mountain elevations above 10,000 feet. Here, temperatures are drastically lower than in the populous lowlands; there is often still snow cover in June. “You have to think about it in the broader context,” said Heeter; one can reasonably add a few tens of degrees for places like Seattle and Portland, she noted. According to the tree rings, the 2021 seasonal temperature spike was nearly 3 degrees F greater than any annual spike shown by tree rings during the Medieval period.

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[Roy]

NASA must have changed how trees grow.

[shunyadragon]

NASA must have changed how trees grow.

Huh?!?!?! Sarcasm?

I worked in forestry evaluation sampling surveys in West Virginia as a soil scientists. The nature and composition of the tree rings is a response to the environment the tree was growing.