Why We Cannot Claim Human Impact on Long-Term Climate Trends in the Sonoran Desert

The Sonoran Desert is one of the most biologically diverse and ecologically unique deserts in the world. Spanning parts of Arizona, California, and northwestern Mexico, it has been shaped by millions of years of geological, climatic, and ecological forces. Yet today, many scientists and policymakers claim that this ancient desert is being fundamentally altered by human-driven climate change. This article challenges that assumption and argues that we simply do not possess the data or scientific foundation to make such a definitive claim.

Our direct observations of weather and climate in the Sonoran Desert only date back about 120 years. This is a blink of an eye in geological terms. Since the late 19th century, agencies like the National Weather Service have collected temperature, precipitation, and wind data. However, these records are far too recent to be used as the basis for evaluating long-term climate trends. A century of data cannot meaningfully characterize the climatic evolution of a region that has developed over millions of years. Any fluctuations observed in this short time span could just as easily be part of a natural oscillation as they could be evidence of human influence.

In the absence of long-term instrumental data, scientists often turn to paleoclimatic proxies such as tree rings, sediment cores, and pollen analysis to reconstruct ancient climates. While these methods can provide useful insights, they are inherently limited. Proxy data offers only fragmented snapshots of past conditions and is often localized, meaning it may not reflect broader regional or global patterns. Additionally, interpreting these records is subject to considerable uncertainty and debate within the scientific community. Even our most advanced dating methods—such as radiometric techniques—rarely allow precise resolution beyond one million years, and they cannot provide a continuous, high-resolution account of the Sonoran Desert’s full climatic history.

The truth is, we do not fully understand how the Sonoran Desert formed, how many climate regimes it has endured, or how often its ecological balance has shifted due to natural factors like solar cycles, oceanic currents, volcanic activity, or tectonic shifts. Over tens of thousands of years, this region has likely experienced extreme variability—periods of wetter and drier conditions, hotter and cooler temperatures, and even episodes of dramatic ecosystem transformation. Without a comprehensive and unbroken record of these natural changes, we cannot accurately define what a “normal” or “stable” climate trend for the Sonoran Desert even looks like.

Despite this uncertainty, some researchers continue to assert that recent temperature or rainfall changes in the region are largely attributable to human influence, particularly through greenhouse gas emissions. This attribution, however, rests on assumptions that are not empirically supported. It assumes that we know what the long-term climate baseline is, that current changes are outside the bounds of natural variability, and that we can isolate anthropogenic signals from natural ones. In reality, none of these conditions are met, especially not in a region as complex and poorly understood as the Sonoran Desert.

Ultimately, our capacity to understand long-term climate dynamics is constrained by the scope of our data, the limits of our tools, and the vast timescales over which Earth’s systems operate. It is not anti-scientific to acknowledge these limits—it is, in fact, the essence of scientific humility. We cannot impose certainty where it does not exist. Until we achieve a more complete picture of the Sonoran Desert’s natural climate history, we must refrain from drawing bold conclusions about human impact on its long-term trends. Doing otherwise risks misrepresenting the science and politicizing a subject that demands honest inquiry above all.