The Green Page:

Summer 2023 Was The Hottest In 2,000 Years:

Based on an analysis of ancient tree rings that date back to the year 1, last summer was

A new study suggests that the summer of 2023 was the hottest in the past 2,000 years. The study authors described the warmth during the summer of 2023 across much of the Northern Hemisphere as "unparalleled."

“Indeed, the climate is always changing, but when you look at the long sweep of

history, you can see just how dramatic recent global warming is,” said Jan Esper, the lead

author of the study at Johannes Gutenberg University in Germany. “2023 warming,

caused by greenhouse gases, is additionally amplified by El Niño conditions, so we end

up with longer and more severe heat waves and extended periods of drought."

Of even more concern is that the 2015 Paris Agreement to limit global warming to 1.5 degrees Celcius "has already been superseded at this limited spatial scale." The Paris Agreement seeks to keep warming below that level to stave off the worst impacts of human-caused climate change.

'Exceptional' warmth

High heat swept across much of the globe last summer, exacerbating deadly wildfires in

Canada and Hawaii and fueling intense heat waves in South America, Japan, Europe and

the U.S., while likely contributing to severe rainfall in Italy, Greece and Central Europe,

NASA reported.

It is well documented that summer 2023 was the planet's hottest summer since

instrumental records began in the 1800s. However, the new study says tree rings push it

back even further, to 2,000 years ago. How does that work?

How tree rings tell us about climate change

Tree rings are an example of "climate proxy data, as they provide indirect evidence of

past climates," according to the University Corp. for Atmospheric Research. Scientists

can use tree ring patterns to reconstruct regional patterns of climatic change, the

nonprofit consortium added.

NOAA said trees that depend heavily on temperature in the growing season have narrow

rings during cold periods and wider rings for warm periods.

Using tree-ring chronologies allows researchers to look much further back in time without

the uncertainty associated with some early instrumental measurements.

For this study, scientists used meteorological station records dating back to the mid-

1800s combined with tree rings from thousands of trees across nine sites in the Northern

Hemisphere, to recreate what annual temperatures looked like in the distant past.

Last summer, they found, was 4 degrees warmer than the estimated average

temperatures for the years 1 to 1890, based on these tree ring proxies.

Hottest in 2000 years? That may be an understatement

University of Pennsylvania meteorologist Michael Mann, who reviewed the study for USA

TODAY pointed to a study published in Nature two years ago showing that the planet's recent warming is unprecedented in more than 20,000 years.

It adds to the already-established evidence that recent warming is unprecedented not just in 2,000 years but in at least 20,000 years."

Paris Agreement breached?

According to the study, the results also demonstrate that in the Northern Hemisphere, the

2015 Paris Agreement to limit warming to 1.5 degrees Celsius above preindustrial levels has "already been breached."

Big picture

Overall, the study authors said to focus on the big picture when it comes to climate

change: "When you look at the big picture, it shows just how urgent it is that we reduce

greenhouse gas emissions immediately," said Esper.

Contributing: Reuters

This article originally appeared on USA TODAY: Hottest summer in 2,000 years: Summer

2023 shattered records