GS Paper III

News Excerpt:

According to the paleo-thermometry study, it was estimated that the Earth’s surface has already warmed more than 1.5°C on average over pre-industrial levels.

Why has the threshold been set at 1.5°C?

• 1.5 degrees C is not a scientific threshold. 
• It became enshrined in the Paris Agreement after intense negotiations by member countries of the U.N. Framework Convention on Climate Change (UNFCCC).
• It comes from a figure of ‘– 2°C’, which was decided by European countries to set as an aim (threshold) in the 1990s. 

Key points about the study:

• Recently published in Nature magazine, this study is based on a technique called paleothermometry.
• According to this study earth’s surface has already warmed by more than 1.5°C on average over pre-industrial levels.
• The major drawback of the study is that the scientists have collected warming data from only one location and have extrapolated it to be indicative of the global mean temperature trend.

The methodology adopted in the study:

• Paleo proxies (don’t directly measure the temperature, we call them proxies of past temperature deviations, palaeo means past) constitute a technique that uses chemical evidence stored in various organic matter, such as corals, stalactites, and stalagmites, to approximate the temperature at some point in the past. 
• However, it is still only indirect evidence of temperature change concerning a baseline temperature. The evidence can’t measure the actual overall temperatures.
• Under this technique, researchers calibrate the various chemical compounds assimilated by some species into their biogenic materials, such as calcium carbonate or chalk, in modernity to establish the relationships between those chemicals and the prevailing local temperature.
• When such a biogenic material from the past is found, scientists can piece together when the biogenic material was deposited (using the quantity of certain isotopes that decay at a steady rate over time). 
• They then study the assimilated chemicals to deduce the temperature deviations during that time period. 
• The results are very local temperature anomalies (estimates from the past), so they can’t be the basis for any scientifically robust claims about tiny deviations of past temperatures from instrumental records.

Impact of the study:

• The 1.5°C exceedance claim does not offer any clear explanation of why such exceptional warming occurred or how it can explain some location-specific disasters or, in fact, the pattern of any level of global warming. 
• This is important because warming patterns matter the most for our ability to manage the disasters associated with global warming.
• From India’s perspective, the amount and the distribution of the 2023 monsoons have not been explained yet, and it is unclear how the combination of El Niño, its unusual pattern, and global warming together produced the monsoons that India experienced. 

El Nino as a warming paradigm:

• The tropical Pacific Ocean absorbs the heat during normal and La Niña years and throws it out in an El Niño year, causing a mini global warming.
  • This mini-global warming has consequences at distant locations (also called teleconnections). 
  • These El Niño teleconnections themselves also modify the warming pattern. As a result, droughts can have a stronger feedback that affects temperature than floods in many instances. 
  • Depending on whether warming due to an El Niño is in the eastern Pacific Ocean or closer to the international dateline, the impacts on the monsoon and the other parts of the world can be very different.
• These same processes work in the global warming regime as well. As human-made greenhouse gases initiate the warming, the warming pattern is amplified in the Arctic and over the desert regions of the Middle East but damped over the eastern Pacific and the northern Atlantic oceans. 
  • These local warmings and coolings and their magnitudes determine the net effect of natural variability and global warming in a particular locality.

• From the above cases it becomes clear that the pattern of warming really matters, not the threshold crossing. 

Need for accurate predictions:

• They play a vital role in managing and curbing climate change.
• These are needed to adapt to the changing seasons and the unavoidable harm they are rendering to lives, livelihoods, and economies.

Conclusion: 

Prioritizing the understanding of global warming patterns over arbitrary temperature thresholds is crucial. Regional variations and phenomena like El Niño significantly influence warming impacts. Accurate predictions are essential for effective climate management, emphasizing the need for comprehensive approaches to address the complex challenges of climate change.