But they ignore the fact that historical changes in carbon dioxide levels always followed changes in temperatures, so could not be the cause of such changes. The article below asserts the opposite, and talks about ‘better understanding’ while promoting a greenhouse climate theory that says one minor trace gas is all that matters.
– – –
A University of Arizona-led team has nailed down the temperature of the last ice age—the Last Glacial Maximum of 20,000 years ago—to about 46 degrees Fahrenheit (7.8 C), says Phys.org.
Their findings allow climate scientists to better understand the relationship between today’s rising levels of atmospheric carbon dioxide—a major greenhouse gas—and average global temperature.
The Last Glacial Maximum, or LGM, was a frigid period when huge glaciers covered about half of North America, Europe and South America and many parts of Asia, while flora and fauna that were adapted to the cold thrived.
“We have a lot of data about this time period because it has been studied for so long,” said Jessica Tierney, associate professor in the UArizona Department of Geosciences. “But one question science has long wanted answers to is simple: How cold was the ice age?”
Tierney is lead author of a paper published today in Nature that found that the average global temperature of the ice age was 6 degrees Celsius (11 F) cooler than today. For context, the average global temperature of the 20th century was 14 C (57 F).
“In your own personal experience that might not sound like a big difference, but, in fact, it’s a huge change,” Tierney said.
She and her team also created maps to illustrate how temperature differences varied in specific regions across the globe.
“In North America and Europe, the most northern parts were covered in ice and were extremely cold. Even here in Arizona, there was big cooling,” Tierney said. “But the biggest cooling was in high latitudes, such as the Arctic, where it was about 14 C (25 F) colder than today.”
Their findings fit with scientific understanding of how Earth’s poles react to temperature changes.
“Climate models predict that the high latitudes will get warmer faster than low latitudes,” Tierney said. “When you look at future projections, it gets really warm over the Arctic. That’s referred to as polar amplification. Similarly, during the LGM, we find the reverse pattern. Higher latitudes are just more sensitive to climate change and will remain so going forward.”
Knowing the temperature of the ice age matters because it is used to calculate climate sensitivity, meaning how much the global temperature shifts in response to atmospheric carbon.
Tierney and her team determined that for every doubling of atmospheric carbon, global temperature should increase by 3.4 C (6.1 F), which is in the middle of the range predicted by the latest generation of climate models (1.8 to 5.6 C).
Atmospheric carbon dioxide levels during the ice age were about 180 parts per million, which is very low. Before the Industrial Revolution, levels rose to about 280 parts per million, and today they’ve reached 415 parts per million.
Full article here.
via Tallbloke’s Talkshop
August 27, 2020 at 04:42AM