Tucson Standard

University of Arizona issued the following announcement on Nov. 10.

A University of Arizona-led effort to reconstruct Earth's climate since the last ice age, about 24,000 years ago, highlights the main drivers of climate change and how far out of bounds human activity has pushed the climate system.

The study, published Wednesday in Nature, has three main findings: 

• It verifies that the main drivers of climate change since the last ice age are rising greenhouse gas concentrations and the retreat of the ice sheets.
• It suggests a general warming trend over the last 10,000 years, settling a decade-long debate the paleoclimatology community about whether this period trended warmer or cooler.
• The magnitude and rate warming over the last 150 years far surpasses the magnitude and rate of changes over the last 24,000 years.

"This reconstruction suggests that current temperatures are unprecedented in 24,000 years, and also suggests that the speed of human-caused global warming is faster than anything we've seen in that same time," said Jessica Tierney, a UArizona geosciences associate professor and co-author of the study.

Tierney, who heads the lab in which this research was conducted, is also known for her contributions to the Intergovernmental Panel on Climate Change reports and climate briefings for the U.S. Congress.

"The fact that we're today so far out of bounds of what we might consider normal is cause for alarm and should be surprising to everybody," said lead study author Matthew Osman, a geosciences postdoctoral researcher at UArizona.

An online search of "global temperature change since the last ice age" returns a graph of global temperature change over time that was created eight years ago.

"Our team's reconstruction improves on that curve by adding a spatial dimension," Tierney said.

Global average surface temperature since the last ice age 24,000 years ago. Time is stretched for the past 1000 years to visualize recent changes.Matthew Osman

The team created maps of global temperature changes for every 200-year interval going back 24,000 years.

"These maps are really powerful," Osman said. "With them, it's possible for anyone to explore how temperatures have changed across Earth, on a very personal level. For me, being able to visualize the 24,000-year evolution of temperatures at the exact location I'm sitting today, or where I grew up, really helped ingrain a sense of just how severe climate change is."

Original source can be found here.