The recent assertion that one day in July 2023 was the hottest in over 100,000 years has been dismissed as scientifically unfounded. This claim hinges on temperature estimates from a time before thermometers existed, using techniques called “Palaeo Proxies” that are unable to provide daily temperature data.
Understanding Palaeo Proxies
Palaeo Proxies, also known as paleoclimate or paleoenvironmental proxies, are tools scientists employ to reconstruct past climate and environmental conditions. Stemming from physical, biological, or chemical processes responsive to temperature fluctuations or other climatic factors, proxies act as surrogates for direct measurements of ancient climates.
Examples of Palaeo Proxies
Here are some examples of proxies:
1. Ice Cores: Drilled from glaciers and polar ice sheets, they encompass trapped air bubbles and isotopic compositions that shed light on previous atmospheric conditions, such as temperature and Greenhouse Gas concentrations.
2. Tree Rings: Past climate variations and tree growth conditions can be decoded from the width, density, and isotopic composition of tree rings. These serve as key indicators of temperature and rainfall changes.
3. Coral Records: Growth patterns and isotopic compositions of corals provide clues about past sea surface temperatures and oceanic conditions.
4. Pollen Records: The presence and abundance of specific pollen types in sediment cores reflects past vegetation changes and climate trends.
Limitations of Palaeo Proxies
Despite their usefulness, these proxies do have their limitations. One of the primary assumptions is that the processes behind these proxies operated the same in the past as they do now. However, proxies buried in ocean and lake sediments can only record temperature anomalies over centuries or thousands of years. Therefore, daily temperature estimates are impossible. Moreover, they only provide local or regional estimates of historical temperature discrepancies with considerable uncertainties. Global estimates, derived by averaging all local proxies, harbor even larger uncertainties, making claims about daily temperatures on a global scale unreliable.
Other Methods to Estimate Historical Temperatures
Scientists can also estimate temperature changes over longer timescales using isotopes with known radioactive decay rates, such as during the Holocene Epoch – a geological period that commenced approximately 11,650 years ago and persists today. Carbon or lead isotopes with half-lives ranging from 5,000 to over 10 million years can be used for estimating past temperatures. Despite their potential, these methods also fall short when it comes to providing daily temperature data, being limited to longer timescales.
