Climate change

Temperatures of the past 24,000 years find unprecedented global warming


The study reveals that greenhouse gas concentrations have been increasing since the last ice age.

A University of Arizona study looked at Earth’s climate since the last Ice Age around 24,000 years ago, highlighting the main drivers of climate change and how far human activity has pushed the climate system out of bounds. The research has been published in the ‘Nature Journal’.

The study had three main conclusions:

1. He verified that the main drivers of climate change since the last ice age are increasing greenhouse gas concentrations and retreating ice caps.

2. He suggested a general warming trend over the past 10,000 years, settling a debate that has spanned decades as to whether this period tends to warm or cool in the paleoclimatic community.

3. The magnitude and rate of warming over the past 150 years far exceeds the magnitude and rate of change over the past 24,000 years.

“This reconstruction suggests that current temperatures are unprecedented for 24,000 years, and also suggests that the rate of man-made global warming is faster than anything we’ve seen in the same time period,” Jessica said. Tierney, Arizona Associate Professor of Geosciences and co. -author of the study.

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

“The fact that we are now so far from the limits of what we might consider normal is a cause for concern and should surprise everyone,” said lead author of the study, Matthew Osman, researcher. postdoctoral fellowship in geosciences at UArizona.

An online search of “the change in global temperature since the last ice age” would produce a graph of the change in global temperature over time that was created eight years ago.

“Our team’s reconstruction improves this curve by adding a spatial dimension,” Tierney said.

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

“These maps are really powerful. With them it is possible for anyone to explore how temperatures have changed across the Earth, on a very personal level. For me, being able to visualize changing temperatures on 24,000 years ago in the exact spot where I sit today, or where I grew up, really helped me understand just how bad climate change is today, ”Osman said.

There are different methods to reconstruct past temperatures. The team combined two independent datasets – temperature data from marine sediments and computer simulations of the climate – to create a more complete picture of the past.

The researchers looked at the chemical signatures of marine sediments to gain information about past temperatures. Because changes in temperature over time can affect the shell chemistry of a long-dead animal, paleoclimatologists can use these measurements to estimate the temperature in an area. It wasn’t the perfect thermometer, but it’s a starting point.

On the other hand, computer-simulated climate models have provided temperature information based on scientists’ best understanding of the physics of the climate system, which is also not perfect.

The team decided to combine methods to harness each other’s strengths. This is called data assimilation and is also commonly used in weather forecasting.

“To forecast the weather, meteorologists start with a model that reflects the current weather, then add observations such as temperature, pressure, humidity, wind direction, etc. to create an updated forecast,” Tierney said.

The team applied this same idea to the past climate.

“With this method, we are able to exploit the relative merits of each of these unique data sets to generate observational-constrained, dynamically consistent, and spatially complete reconstructions of past climate change,” said Osman.

Now the team is working on using their method to study climate change even further into the past.

“We are excited to apply this approach to ancient climates that were warmer than today, as these times are essentially windows to our future as greenhouse gas emissions increase,” Tierney said.