Jinho Ahn, from Seoul National University, explains how the study of ice core from the past 800,000 years informs us about todays climate change.
Here is a summary of the video we invite you to watch, if you were not able to attend our 24-hours online event, 5 June 2023.
The global temperature has been relatively stable for the last 2,000 years. The temperature increase during the 20th century looks very unusual. Human activities, especially greenhouse gases emissions (carbon dioxyde, methane and nitrous oxydes), are the primary drivers of temperature increase. Our future projections for temperature and sea level raises depend on scenarios about greenhouse gases emissions.
Precise measurements of the CO2 atmospheric concentration have been made from the early 1960s: it evolved from 315 ppm then, to over 400 ppm today. And the increase rate itself is increasing. But, for a better understanding of the interactions between CO2 atmospheric concentration and Earth climate, we need much longer records.
The past in ice cores
Ice cores from Antarctica and Greenland provide valuable information about greenhouse gas concentrations and their origins, as the ice trapped small bubbles of air at the time it formed. The analysis of the greenhouse gases in these bubbles provides valuable information about the origins and fate of these gases. It helps understand the behavior and the control mechanism of these green house gases.
The records of the past 800,000 years show that there have been cycles in greenhouse gases concentrations, as well as in Antarctic temperatures and ice formation volumes. The coincidence of these cycles indicated the important role of CO2 in regulating temperatures.
These records show also that today’s levels of CO2 and methane atmospheric concentrations are at levels unprecedented in the past 800,000 years. The speed of the rise is also amazing: the faster variations have been of 10 ppm/century, but in the past century is has been more around 100 ppm/century.
This rapid increase in greenhouse gas concentrations is primarily attributed to human activities such as fossil fuel emissions, land use changes, and agricultural practices. Today, 55% of our emissions are absorbed by the ocean, but the efficiency of carbon uptake by land and oceans may decrease in the future, leading to a higher concentration of CO2 in the atmosphere and accelerated global warming.
More knowledge needed
Even if we manage to reach net zero emission by 2100, sea level will continue to rise, even though the temperature doesn’t increase too much. There is a possibility of significant sea level rise, with some models projecting a rise of more than 15 meters in certain regions, posing a major challenge for the future.
More scientific knowledge is needed:
- about the possible feedbacks in the carbon cycle, that would increase temperatures and sea level even more;
- about tipping points : non linear changes that may happen on the planet, and that won’t be reversible;
- to understand why the climate cycles period changed in the past from 41,000 years to 100,000 years, the ice core community if looking for ice older than 800,000 years.