The Bogotá Basin, home to over 11 million people and situated in the eastern branch of the Andes, serves as a natural laboratory for examining terrestrial climate history. The basin’s geological record preserves sediments dating back to the Pliocene epoch, roughly 5.2 to 2.5 million years ago—the last interval in Earth’s history when atmospheric CO₂ concentrations matched contemporary levels. This temporal parallel provides a unique analog for projecting future climate scenarios, especially in regions where the interaction between land elevation and climate drivers remains poorly understood.

Utilizing an extensive 585-meter sediment core extracted decades ago but newly analyzed with advanced modern techniques, the team harnessed state-of-the-art uranium-lead zircon geochronology to refine the temporal framework of sediment deposition. Zircons—robust minerals capable of encapsulating uranium—offer reliable radiometric ages, marking the chronology of stratified volcanic ash layers interspersed within the sedimentary sequence. This precise dating enabled reconstruction of temperature dynamics spanning approximately 3.7 million years, embedding a continuous terrestrial climate record within a well-constrained geological timeline.

Thermometric reconstructions relied on brGDGTs (branched glycerol dialkyl glycerol tetraethers), bacterial membrane lipids whose molecular structures chemically adapt to ambient temperatures. These biomarkers, preserved across epochs in anaerobic depositional environments, function as proxies to infer paleotemperatures with high temporal resolution. Analysis revealed a startling finding: Pliocene terrestrial temperatures in the Bogotá Basin averaged 4.8 degrees Celsius warmer than those of the subsequent Pleistocene epoch, a difference substantially exceeding prior theoretical expectations derived from oceanic temperature proxies.

This marked amplification of terrestrial warming diverges from conventional climate models, which typically predict a proportional relationship between sea surface temperature increases and overlying land warming in tropical latitudes, with a factor around 1.4. However, the findings indicate that terrestrial air temperatures in this high-altitude tropical environment increased by nearly twice the magnitude suggested by sea surface temperature shifts. Such pronounced regional warming implies that existing climate models may inadequately account for elevation-dependent feedback mechanisms or regional ocean-atmosphere interactions that modulate terrestrial temperatures beyond oceanic signals.

The study’s authors speculate on several potential drivers for this anomalous warming trend. One hypothesis points to enhanced temperature sensitivity at high elevations: mountain regions like the Andes might exhibit non-linear warming responses under elevated greenhouse gas forcing. Yet, modeling suggests that orographic effects alone cannot fully explain the magnitude observed. Another possibility implicates persistent changes in Pacific Ocean circulation dynamics during the Pliocene, akin to prolonged or intensified El Niño-like conditions, which might have boosted regional warming through altered moisture and atmospheric circulation patterns impacting the Andes.

The amplification of terrestrial temperatures at high-altitude tropical sites revealed by this research carries far-reaching implications for predicting localized climate change impacts. Populations residing in mountainous basins such as Bogotá are directly exposed to health risks, ecological shifts, and infrastructure vulnerabilities associated with regional temperature anomalies that global or ocean-based temperature proxies fail to adequately represent. Consequently, this study underscores the urgent necessity of integrating terrestrial paleoclimate data at regional scales into climate risk assessments and adaptation planning frameworks.

Beyond its immediate climatological insights, the study demonstrates the transformative value of revisiting historic geological archives with contemporary analytical tools. The legacy sediment core, originally drilled in the late 1980s, offered an untapped reservoir of environmental data that only now, through enhanced biochemical proxies and geochronological precision, could elucidate complex terrestrial climate patterns. This exemplifies a fruitful synergy between paleontology, geochemistry, and climate science, driving advances that enrich understanding of Earth system processes and greenhouse gas feedbacks.

Importantly, the work advocates for a paradigm shift in how climate reconstructions integrate terrestrial data, emphasizing the heterogeneity of climate responses across latitudinal, elevational, and regional gradients. As atmospheric CO₂ continues its upward trajectory, the lessons gleaned from ancient climate analogs suggest more pronounced and perhaps unforeseen warming impacts on human-inhabited mountainous tropical regions than previously acknowledged by global climate models focused primarily on oceanic or polar datasets.

The implications extend to policy and public awareness, calling attention to the fact that the lived experience of climate change is inherently local and shaped by complex terrain interactions. By improving paleoclimate reconstructions at the regional and continental scales, scientists can furnish policymakers with more accurate scenarios that reflect not only global averages but also the intense variability that affects vulnerable populations in megacities such as Bogotá and comparable environments worldwide.

In a climate context increasingly dominated by uncertainties surrounding feedback loops and regional variability, this study stands as a critical reminder of the necessity to ground climate projections in data that embrace the full complexity of Earth’s environmental history. The robust application of geochemical proxies like brGDGTs, coupled with high-fidelity radiometric dating methods, establishes a promising pathway for future research aimed at unraveling the intricacies of terrestrial climate amplification particularly in equatorial mountainous realms.

As the global community confronts the accelerating pace of climate warming, studies like this illuminate the urgent need for comprehensive datasets and refined models that capture the nuanced interplay of elevation, atmospheric chemistry, and ocean-driven climate variability. The Bogotá Basin example is a compelling case illustrating that terrestrial landscapes, especially in tropical mountain zones, may warm more drastically than oceanic systems alone suggest, necessitating tailored mitigation and adaptation strategies that account for such amplified terrestrial climatic shifts.

This novel research, published in the prestigious Proceedings of the National Academy of Sciences, not only recounts Earth’s climatic past with unprecedented clarity but also serves as a clarion call highlighting the intricate vulnerabilities of tropical terrestrial environments in an era of ongoing global climate transformation. It galvanizes the scientific community to deepen efforts in regional paleoclimatology, elevating terrestrial records to a central role in understanding and combating the multifaceted challenges posed by future climate change.

Subject of Research: Climatic evolution of the Bogotá Basin during the Pliocene and Pleistocene epochs and temperature amplification in tropical terrestrial environments.

Article Title: Evolution of Pliocene-Pleistocene tropical terrestrial Andean temperature amplification

News Publication Date: 2-Feb-2026

Web References: http://dx.doi.org/10.1073/pnas.2520191123

Image Credits: Lina Pérez-Ángel

Keywords: Climate change, Paleoclimatology, Earth climate, Climatology

Traditionally, scientists have inferred increased dryness in northern Africa during the Pliocene-Pleistocene transition through dust concentrations found in ocean sediment cores off the West African coast. These dust deposits, interpreted as markers for expanding desert conditions—specifically the Sahara Desert—were thought to reflect diminished summer monsoon activity and reduced precipitation. This paradigm led not only to climatic conclusions but also to evolutionary hypotheses that linked habitat drying to key developments in early hominids, including shifts in bipedal locomotion and foraging strategies.

However, the new research led by Bryce Mitsunaga employed a more direct proxy for ancient rainfall: leaf waxes produced by terrestrial plants. Leaf waxes are lipid compounds synthesized by plants during the summer growing season; critically, these waxes retain the isotopic signature of the water absorbed by the vegetation. Analyzing hydrogen isotope ratios embedded in these waxes, the study offers a direct line of evidence on precipitation patterns. Greater ratios of light hydrogen (protium) to heavy hydrogen (deuterium) within leaf waxes are indicative of sustained or increased rainfall, as heavier isotopes tend to precipitate out earlier during rain events.

Mitsunaga and colleagues examined these chemical signatures within the same sediment cores from which prior dust data had been obtained. Their findings reveal that summer rainfall across northern Africa did not undergo significant reduction during the transition from the Pliocene to Pleistocene. Instead, precipitation regimes remained fundamentally constant despite substantial global climatic cooling and the expansion of Northern Hemisphere ice sheets. This result directly contradicts interpretations that linked increased dustiness to regional drying and raises the intriguing possibility that shifting wind patterns, rather than rainfall variability, were responsible for the observed dust increases.

Such insights carry profound implications for understanding not only paleoclimate dynamics but also broader Earth systems feedbacks. The Pliocene-Pleistocene boundary coincides with atmospheric carbon dioxide levels roughly similar to contemporary concentrations, albeit trending downward at that time. By illuminating the disconnection between global temperature decreases and regional hydrological cycles in northern Africa, the research refines models predicting how present and future climate change might affect precipitation in this climatically sensitive, water-stressed region.

Moreover, these findings invite a reevaluation of hypotheses concerning early human evolution. The previously suggested narrative—that intensifying aridity drove crucial evolutionary adaptations among hominins during this interval—is complicated by evidence indicating the absence of a pronounced drying trend. Species such as Homo habilis and Paranthropus, whose fossil appearances align temporally with this boundary, may have experienced more stable environmental conditions than assumed. This prompts calls for renewed research into the timing and causes of increased aridity in Africa, as well as the ecological pressures shaping our ancestors.

The study’s approach, focusing on robust chemical proxies like leaf wax hydrogen isotopes, demonstrates the importance of multi-faceted analysis in reconstructing Earth’s climatic past. By directly measuring indicators closely tied to biological and hydrological processes, rather than solely relying on indirect sedimentary dust accumulations, scientists can gain a more nuanced understanding of past environmental conditions. This methodology underscores the role of isotopic geochemistry as a powerful tool in paleoclimatology.

Additionally, the research highlights the complexity of interpreting sedimentary records. While increased dust levels in marine cores undeniably reflect changes in continental conditions, this study argues that their cause may stem from atmospheric circulation patterns and wind strength rather than precipitation deficits. If confirmed, such insights could refine interpretations of other dust-based paleoenvironmental reconstructions worldwide.

Funding for this comprehensive study came from both the U.S. National Science Foundation and international partners, including the Natural Environment Research Council and the Royal Society. The interdisciplinary team brought together expertise from Brown University, the University of Southampton, Rice University, and Harvard University, reflecting the collaborative nature of cutting-edge climate science.

Looking forward, these findings suggest that understanding climatic influences on Africa’s hydrological regimes requires integrating isotopic data with models of atmospheric dynamics and vegetation responses. This multi-proxy strategy will enhance predictions of regional climate sensitivity to ongoing global change and help clarify the environmental contexts in which humanity evolved.

In sum, the revelation that northern African rainfall patterns remained fundamentally unchanged during a time of dramatic global cooling challenges existing paradigms and opens exciting new avenues for research. By disentangling the complex interactions between climate, wind, dust, and ecology, scientists are poised to deepen our comprehension of Earth’s history and better anticipate its future.

Subject of Research: Northern African rainfall patterns during the Plio-Pleistocene transition approximately 3.5 to 2.5 million years ago and their relation to global climate change and human evolution.

Article Title: Fundamentally unchanged northwestern African rainfall regimes across the Plio-Pleistocene transition

News Publication Date: 19-Jun-2025

Web References: http://dx.doi.org/10.1126/sciadv.ads3149

References: Mitsunaga, B., Jewell, A., Crocker, A. J., Wilson, P., Buchanan, S., Herbert, T., & Russell, J. (2025). Fundamentally unchanged northwestern African rainfall regimes across the Plio-Pleistocene transition. Science Advances. https://doi.org/10.1126/sciadv.ads3149

Keywords: Climatology, Climate change, Climate data, Precipitation, Rain