Pulling back from the brink (Hothouse Earth)

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Pulling back from the brink (Hothouse Earth)

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• Hothouse Earth pathway, a point of no return: Today’s Earth has a temperature that is “just right” for life to have evolved and flourished. Homo Sapiens did well in the Holocene epoch (since 12000 years ago) through agriculture, etc. Finally, we are here today as a modern race.
• Global warming: That progress is the curse that led to CO2 and GHG emissions, causing global warming. This time is now called “Anthropocene”. There is a delicate equilibrium in our environment, and processes that increase or decrease warming are the core of it.
• Examples of processes and feedbacks:  

1. Melting of Greenland ice releases more water, so more sunlight gets absorbed, so more warming, so more melting of ice. (A positive feedback)
2. When CO2 increases, chemical weathering increases. That removes CO2 from environment over thousands of years. (A negative feedback)
3. The key is: If positive feedbacks > Negative feedbacks, the system equilibrium is disturbed.
4. Over millions of years, the Earth has shifted between these two states! We may be close to a threshold.
5. Next 20 years to decide the next lakhs of years! What mankind decides now, will decide the route taken by Earth over many millennia.

• Geophysical tipping point: It is a threshold beyond which a system moves from one stable state to another. The moment we touch 2oC warming (over pre-industrial levels), a domino effect of change will arrive. Regional climate tipping points have arrived. If it continues, we will reach hothouse Earth.

• Clusters of tipping-points cascades:

1. Today, CO2 concentrations in atmosphere are > 400 ppm. In mid-Miocene era (1.5 cr y.a.) sea levels were 10-60 m higher than today’s and CO2 was 300-500 ppm. We may be headed to this now.
2. To reverse any disaster, we have to globally coordinate and take major decisions – decreasing emissions, increasing carbon sinks, removing CO2 from atmosphere, even deflecting solar radiation, etc. Seems tough, as it needs more than mere technology. It needs social change.

• Summary : The tipping point in global warming, leading to a hothouse Earth, may have arrived.

Read more on - Polity | Economy | Schemes | S&T | Environment

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