Climate Warming Threatens Water for 2 Billion 🌍

Continued Climate Warming Can Shift the Intertropical Convergence Zone Disrupting Water for 2B Folk

Water availability for nearly 2 Billion people living in the tropics could become much more problematic as climate warming continues. Although this may take decades to happen, and although it is a fairly low probability event, the consequences if it happens would be extremely severe, so the situation is plausible and hard to assign an overall risk too.

In the tropics, the Intertropical Convergence Zone (ITCZ) can be seen as a band of clouds circling near the equator. This band shifts northward with northern hemisphere summer, and shifts southward with northern hemisphere winters. It interacts with monsoons and its location determines whether the 2 billion people living in the tropics get sufficient water, too much water, or too little water.

I chat about a new peer-reviewed paper that uses Earth System Models (ESMs) to examine the risks of an irreversible shift in the ITCZ from accelerating climate warming.

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Articles and Papers and websites mentioned in this video:

LiveScience article:
2 billion people could face chaotic and 'irreversible' shift in rainfall patterns if warming continues
By Jesse Steinmetz published May 31st
Higher global temperatures mean the intertropical convergence zone could shift south — throwing off precipitation trends for a major swath of humanity, according to new research.
https://www.livescience.com/planet-earth/climate-change/2-billion-people-could-face-chaotic-and-irreversible-shift-in-rainfall-patterns-if-warming-continues

Wikipedia: Intertropical Convergence Zone (ITCZ)
https://en.wikipedia.org/wiki/Intertropical_Convergence_Zone

Wikipedia: Thermal Equator
https://en.wikipedia.org/wiki/Thermal_equator

Wikipedia: Population density
https://en.wikipedia.org/wiki/Population_density

Peer-reviewed, open-source scientific paper in journal Earths Future:
Title: Irreversible Land Water Availability Changes From a Potential ITCZ Shift During Temperature Overshoot

Abstract
Without rapid emission reduction, it is increasingly likely that global temperatures will overshoot 1.5°C before carbon dioxide removal may help reverse warming. Such temperature overshoots affect the future hydrological cycle, with implications for land water availability. However, the hydrological response to such temperature overshoots is not well understood. Here, we investigate regional and seasonal changes of precipitation minus evaporation (P − E) in an ensemble of Earth system model simulations of temperature overshoot. Most climate models broadly show P − E reversibility after overshoot. However, models exhibiting an irreversible shift of the intertropical convergence zone (ITCZ) during the temperature overshoot experience reduced wet-season and enhanced dry-season land water availability in tropical regions, which has long-lasting effects on the amplitude of P − E seasonality after the overshoot, constituting irreversible changes on human timescales. While some regions may experience alleviating seasonal hydrological conditions, others are subject to more intense seasonality. Half a century of CO2-stabilization after the temperature overshoot only halves the legacy effects of the overshoot on land water availability on over 23% of the world population in 12% of the global land area, covering regions of various hydrological regimes. Based on the model ensemble presented here, a strong irreversible shift of the ITCZ after an overshoot is a low-probability but high-impact outcome that would entail long-lasting hydrological changes with consequences for ecosystems and human societies.

Key Points
1) A strong intertropical convergence zone (ITCZ) shift occurs in 1–2 of 8 CMIP6 models simulating overshoot, not depicting the most likely but a plausible high-impact outcome

2) The ITCZ shift drives irreversible hydrological changes, affecting wet and dry season dynamics long after a return to pre-industrial levels

3) More than 1.8 billion people may face altered water availability due to overshoot impacts, especially in vulnerable tropical regions

Link: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024EF005787

Please donate to http://PaulBeckwith.net to support my research and videos connecting the dots on abrupt climate system mayhem. Or... if you want to get a climate themed T-Shirt then please visit: https://paulbeckwithstore.com/