Let’s embark on a thought experiment, shall we? Picture yourself as a climate scientist (it’s quite an adventure!). You're gathering data to create a statistical climate model.

To build a statistical model, we need certain components, but fundamentally, we require a specific question or variable to predict. For instance, we might ask what the levels of greenhouse gases will be in 10, 50, or even 100 years, or how average temperatures might change.

How do we arrive at these predictions? Initially, we need historical data on the variables we aim to measure, such as atmospheric greenhouse gas concentrations or historical temperature records.

Equally essential is recognizing that the variables we wish to predict are influenced by other factors, some of which might also have historical data available. Thus, we must compile this data to allow our statistical analyses to forecast outcomes based on past patterns.

Sounds straightforward, right?

Well, not necessarily. Occasionally, one variable may be missing data, which could occur for various reasons, often because we either lack the technology to gather the data or we feel confident in making an assumption about how that variable has evolved over time.

Fortunately, researchers are increasingly striving to minimize the use of assumed variables and ensure all data is accurately accounted for.

Returning to our experiment, what would your response be if I asked whether wildfires have consistently escalated over the last two centuries? I suspect many of you, myself included, would agree that they have indeed increased.

To verify this assumption, a research team decided to take a closer look and journeyed to Antarctica, one of the coldest regions on Earth.

By examining carbon monoxide (CO) trapped within Antarctic ice, researchers from the University of Cambridge and the British Antarctic Survey have reconstructed nearly two centuries of biomass burning history. Their discoveries are not just another piece of the climate puzzle; they are reshaping our comprehension of fire activity in the Southern Hemisphere and challenging some longstanding notions in climate science.

Published in the Proceedings of the National Academy of Sciences (PNAS), the research centers on carbon monoxide — a gas emitted during biomass burning, including wildfires and cooking. The scientists retrieved this gas from ice cores, which are long cylindrical samples taken from the Antarctic ice sheet.

These ice cores consist of layers formed from snow compaction over the years, with each layer trapping tiny air bubbles that provide a direct snapshot of the atmosphere at the time the snow fell.

A challenge in measuring gases like CO from more recent periods is that the ice hasn't been under pressure long enough to fully encapsulate these gases.

However, the researchers chose ice cores from areas with high snow accumulation rates. The quicker snow accumulates, the faster it compresses, allowing for the formation of crucial air bubbles. This method facilitated the gathering of a continuous atmospheric CO record spanning from 1821 to 1995, covering the preindustrial era up to the dawn of the 21st century.

So, what did their research reveal? Surprisingly, biomass burning in the Southern Hemisphere has exhibited far more variability over the last 200 years than previously understood. While one might assume that fire activity rose alongside population growth and industrialization, the data tells a different story. The research indicates that after an initial rise, fire activity began to decline around the 1920s.

This decline in fire activity correlates with significant land-use transformations in regions like southern Africa, South America, and Australia, where wildlands were swiftly converted into agricultural land. Once forests were cleared, there was little left to ignite.

Dr. Rachael Rhodes, a senior author of the study from Cambridge’s Department of Earth Sciences, remarked, “This trend underscores how land conversion and human expansion have adversely affected landscapes and ecosystems, leading to a substantial shift in the natural fire regime and altering our planet’s carbon cycle.”

However, these findings are not merely historical curiosities; they carry real implications for climate models that scientists utilize to project future changes. Why is this important?

Many models, including those employed by the Intergovernmental Panel on Climate Change (IPCC), have operated under the presumption that fire activity has consistently risen with population growth. This assumption is understandable.

Nonetheless, this research indicates that these models may need recalibrating to accurately reflect the actual variability of fire activity over the past two centuries.

Consider this: if the models predicted catastrophic outcomes based on the assumption that carbon sources originated from forest fires, how does that affect our understanding now that we recognize these fires were not contributing as significantly as we believed? In essence, we now understand that the rise in greenhouse gases we observe does not necessarily stem from increased forest fires.

The essential takeaway is that our planet's fire history is more intricate than previously thought, and a deeper understanding will aid in enhancing the tools we employ to forecast, mitigate, and adapt to climate change. By addressing gaps in our knowledge with data like this, scientists can refine their models, leading to more precise predictions and improved strategies for managing climate change impacts.

Knowledge empowers us to be more effective!

Moreover, this research highlights the interconnectedness of our environment—how changes in one region, such as land use in the Southern Hemisphere, can have extensive repercussions on the global climate system. It serves as a call to reevaluate some of the assumptions we've made about how human activities have influenced our planet's past and how they will continue to shape its future.

Published in The New Climate. Stay updated for the latest in climate action.