<
https://www.iflscience.com/not-only-the-hottest-on-record-summer-2023-was-hottest-for-2000-years-74214>
"The Northern Hemisphere’s summer was a scorcher, pushed off the charts by a
combination of global heating and El Niño. Given the much higher baseline
today, and how exceptional it was, some people speculated last summer may have
been the hottest for 100,000 years, if not longer. That’s not a claim that can
currently be tested, but new evidence shows summer 2023 was the hottest at
least since the time of Jesus, and the 1.5°C (2.7°F) target agreed on in Paris
nine years ago may be well behind us.
The further back we look in time, the hazier our estimates of global
temperatures become. We have less than 50 years of satellite data covering the
entire globe. There’s a bit over a century of records from widespread weather
stations, and if we extrapolate from limited parts of the planet, we can go
back to about 1850.
That doesn’t mean, however, that we have no capacity to compare modern
temperatures with those of the past. Climate proxies such as the growth rings
in trees, isotopes from air bubbles in ice, and limestone cave structures all
tell us something useful. Professor Ulf Büntgen of the University of Cambridge
is part of a team that used the summer proxies to put last year in context.
“When you look at the long sweep of history, you can see just how dramatic
recent global warming is,” Büntgen said in a statement. “2023 was an
exceptionally hot year, and this trend will continue unless we reduce
greenhouse gas emissions dramatically.”
Büntgen and colleagues relied on tree rings to reach this conclusion. Growing
conditions are reflected in the width of tree rings laid down in a specific
year. In temperate and sub-polar zones where water is usually not a limiting
factor, this generally reflects the warmth of the spring and summer. Individual
trees’ growth may be affected by specific local factors, but with a large
enough sample, it’s possible to gain an estimate of temperatures that tracks
closely with measurements since they have been available."
Via Joyce Donahue and Janet Logan.
Cheers,
*** Xanni ***
--
mailto:xanni@xanadu.net Andrew Pam
http://xanadu.com.au/ Chief Scientist, Xanadu
https://glasswings.com.au/ Partner, Glass Wings
https://sericyb.com.au/ Manager, Serious Cybernetics
