What is the 1.5 degree Celsius threshold?

• • In 2015, 195 countries signed the Paris Agreement, which pledged to limit global temperatures to well below 2 degree Celsius above pre-industrial levels by the end of the century. 

• The Agreement did not mention a particular pre-industrial period, climate scientists generally consider 1850 to 1900 as a baseline, since it is the earliest period with reliable, near-global measurements. 

• It also said countries would aim to curb warming within the safer 1.5 degree Celsius limit.
• The 1.5 degree Celsius was set as a defence line, to ensure that the world avoids the disastrous and irreversible adverse effects of climate change which would begin to unfold once the average temperature increases by 2 degree Celsius above the pre-industrial levels. For some regions, even a smaller spike will be catastrophic.

What happens when the threshold is breached?

• The 1.5 degree Celsius threshold is not a light switch which, if turned on, would trigger a climate apocalypse. 
• It is just that once this threshold is breached for a long period of time, the impact of climate change such as sea level rise, intense floods and droughts, and wildfires will significantly increase and accelerate.
• The world is already witnessing these consequences, to some extent. For instance, 
  • The severe heat wave over North and Central India in late May, which saw temperatures nearing 50 degree Celsius in Delhi and Rajasthan, was nearly 1.5 degree Celsius warmer than past heatwaves. 
  • In April, the fourth global mass coral bleaching event was triggered by extraordinarily high ocean temperatures. This could harm ocean life, and the lives of millions of people who rely on reefs for food, jobs, and coastal defence.

• • A report found that five major climate tipping points are already at risk of being crossed due to warming. 

• Climate tipping points are critical thresholds beyond which a natural system can tip into an entirely different state. They cause irreversible damage to the planet, including more warming.

• They fall into three broad categories: cryosphere (for example, melting of the Greenland ice sheet), ocean-atmosphere (change in water temperature), and biosphere (death of coral reefs).

How can the world stay within the threshold?

• Curb the emissions of heat-trapping greenhouse gases (GHG): It can be done by reducing the burning of fossil fuels like coal, oil and gas, which release GHGs into the atmosphere. In 2023, the levels of GHGs in the atmosphere reached historic highs.

Why in the news?

• The World Meteorological Organization (WMO), in a separate report published in June, said there is an 80% chance that at least one calendar year between 2024 and 2028 would see its average temperature exceed 1.5 degree Celsius above the pre-industrial levels  for the first time in history.

Additional Information

World Meteorological Organisation

• It is a specialized agency of the United Nations whose mandate covers weather, climate and water resources.
• WMO provides the framework for international cooperation to advance meteorological, climatological, hydrological, and related environmental services, to improve well-being of all. 
• WMO advocates for an Earth system approach to encompass all the weather-, climate- and water-related cycles traversing the globe, irrespective of national boundaries.
• The Secretariat is headquartered in Geneva and is headed by the Secretary-General.
• WMO has 193 Members (including India). WMO Members work together to improve the accuracy and reliability of weather forecasts, warnings, and services to protect life and property. 

Sources

• https://indianexpress.com/article/explained/explained-climate/highway-to-climate-hell-9382226/
• https://wmo.int/about-wmo/overview