Important Facts For Prelims
Palaeo Proxies
- 04 Aug 2023
- 3 min read
Why in News?
Recently, it was proclaimed that a particular day in July 2023 as the Warmest in over 100,000 Years is scientifically unfounded.
- This claim is based on temperature estimates from before the invention of thermometers, which rely on "Palaeo Proxies" that cannot provide daily timescale temperatures.
What are Palaeo Proxies?
- About:
- Palaeo proxies, short for paleoclimate proxies or paleoenvironmental proxies, are indicators or records used by scientists to reconstruct past climate and environmental conditions.
- These proxies are typically derived from physical, biological, or chemical processes that respond to changes in temperature or other climatic factors.
- Since direct measurements of climate from the distant past are not possible, scientists rely on these proxy records to understand past climate variations and long-term trends.
- Examples:
- Ice Cores: Ice cores drilled from glaciers and polar ice sheets contain trapped air bubbles and isotopic compositions that provide information about past atmospheric conditions, including temperature and Greenhouse Gas concentrations.
- Tree Rings: The width, density, and isotopic composition of tree rings can reveal past climate variations and growth conditions of trees, serving as a valuable proxy for temperature and precipitation changes.
- Coral Records: The growth patterns and Isotopic Compositions of corals offer information about past sea surface temperatures and ocean conditions.
- Pollen Records: The presence and abundance of specific pollen types preserved in sediment cores can indicate past vegetation and climate changes.
- Limitations:
- A major assumption required to make the “paleo proxy” technique workable is that the processes that produced the proxies have operated similarly back then as they do today.
- However, proxies buried in ocean and lake sediments can only record temperature anomalies on timescales of centuries or thousands of years, making daily temperature estimations impossible.
- Temperature proxies provide only local or regional estimates of historical temperature anomalies with significant uncertainties.
- Global estimates based on averaging all local proxies have even higher uncertainties, making claims about daily temperatures at a global scale unreliable.
What are the other Methods to Estimate Temperature over longer Timescales?
- Some isotopes with known radioactive decay rates can provide estimates of temperature changes over longer timescales like Holocene Epoch.
- The Holocene Epoch is a geological times scale that began approximately 11,650 years ago and continues to the present day. It is the current and most recent epoch within the Quaternary Period.
- Carbon or lead isotopes with half-lives ranging from 5,000 to over 10 million years can be used to estimate past temperatures.
- Nonetheless, these methods are also limited to longer timescales and cannot provide daily temperature data.
