Paleo-climatologists have only recently begun to address the Holocene temperature conundrum. The multifaceted nature of this issue is a perfect showcase for the mismatch between climate model projections and paleoclimatic proxy records from nature. Yuntao Bao, a postdoctoral scholar in geography at The Ohio State University, is the study’s first author. It uses empirical data from ice cores in polar regions and tropical mountains to inform and improve the sophistication of global climate models. Published today in the journal Communications Earth & Environment, the research sheds light on important qualifiers that affect climate predictions.
The Holocene epoch, the one we’re now in, has lasted for about 11,700 years. Climate models convincingly indicate that it is punctuated by a long-term warming trend. Recent science from tropical ice cores suggests a more rapid shift toward extreme conditions. This measure of cooling can range from 0.8 to 1.8 degrees Celsius over this time frame. This divergence leads to some key questions about the current state of climate models and their ability to project climate reality years into the future.
Discrepancies Between Models and Proxy Records
This new study provides evidence that ice core data from Greenland and Antarctica are consistent with climate model simulations of the Holocene. Tropical ice cores show the opposite signal. Ice cores from Kilimanjaro in Tanzania and Huascarán in Peru show an ongoing cooling period. This important discovery complicates what we had come to think of as the settled understanding of global temperatures during this time.
Yuntao Bao noted the fundamental issue at hand: “All models have different kinds of uncertainties.” This recognition underscores the value of routinely stressing testing the climate models. We need to hone them to correctly reflect the intricacies of Earth’s complex climate past.
Lonnie Thompson, a co-author of the study, emphasized the significance of collaboration among disciplines. As an internationally-recognized professor of Earth sciences at Ohio State, he knows that innovation comes from collaboration. He stated, “Big breakthroughs in science are going to come along the boundaries of collaboration.” This optimism portrays a larger realization that cross disciplinary methods can provide a fuller picture of what is actually happening in the climate.
The Role of Orbital Forcing
One focal point of the study is the role of orbital forcing—variations in Earth’s orbit around the sun—which has historically driven climate changes throughout the Holocene. Additionally, most climate simulations continue to ignore important features such as vegetation changes and land use. All of these factors played a huge role in driving the extreme temperature extremes during this time.
Thompson remarked on the complexity of modeling these natural variabilities, saying, “The natural world is very complex, so when you try to capture this and put it into a model, that’s a big job.” This complexity underscores the time-sensitive need for continued study. We’re going to have to address our basic knowledge of how different forces interact in the climate system.
This new research brings attention to the differences between models and the historical record of nature. It further offers easily digestible and actionable data we can all use to create better climate projections going forward. Bao underscored that the improvement of these models is important to make more accurate predictions about future climate conditions.
Implications for Future Climate Projections
The results from this study have broad implications for climate research. These corrections help shine a light on flaws in current models, allowing scientists to improve them for more accurate projections in the future. The new study calls for a stronger coordinated effort across the paleoclimate community to accomplish these objectives.
“We can work together to tackle these issues,” Thompson stated, underlining the importance of collective effort in advancing knowledge about past climates and their relevance to contemporary climate challenges.