Even temporary global warming above 2°C will affect life in the oceans for centuries

Subject: Environment

Section: Protected Areas in news

Context:

There is growing consensus that our planet is likely to pass the 1.5 degrees Celsius warming threshold. Research even suggests global warming will temporarily exceed the 2℃ threshold, if atmospheric carbon dioxide (CO₂) peaks at levels beyond what was anticipated.

Climate overshoot:

The period of time in which warming is increasing past the 1.5°C mark and then cooling back down is called a climate overshoot. About 90 percent of climate models predict a period of climate overshoot, with years if not decades of higher global temperatures, before stabilizing at 1.5°C.
These changes include sea-level rise, less functional ecosystems, higher risks of species extinction, and glacier and permafrost loss.
Research found that humanity will continue to feel its impacts long after atmospheric CO₂ levels have peaked and declined.

What are the impacts of climate overshoot?

Long periods of higher global temperatures could result in many different damaging outcomes for a wide variety of ecosystems, including increased coastal flooding and forced human migration, greater devastation and frequency of forest fires, and loss of biodiversity.
The conversion of new land for agricultural use may put additional stress on animal habitats, and when temperatures level off and cool, we may see animals migrating in search of habitats that no longer exist. Focusing on limiting the end-of-century warming at 1.5°C—rather than what global temperatures may peak at before that point—puts people and nature at risk.

Coupled Model Intercomparison Project (CMIP6):

The project underpins the latest assessment reports by the Intergovernmental Panel on Climate Change (IPCC).
Carbon Dioxide Model Intercomparison Project (CDRMIP): Designed to explore the reversibility of a climate overshoot and how this impacts the Earth system.
In viable ecosystems the supply of oxygen needs to exceed their demand. The closer supply is to demand, the more precarious ecosystems become, until demand exceeds supply and these ecosystems are no longer viable.
The changing ocean temperatures impact the long-term viability of different marine species and their habitats.

What did the study find?

Across all climate overshoot experiments and all models, the findings show the water volumes that can provide viable habitats will decrease. This decrease persisted on the scale of centuries – well after global average temperature recovers from the overshoot.
The study findings raise concerns about shrinking habitats.

What are the implications of shrinking marine habitats?

The combination of temperature and deoxygenation shows warming may harm marine ecosystems for hundreds of years after global mean temperatures have peaked.
There will be a need for resource management to avoid compromising species abundance and food security.
Climate overshoots not only matter in terms of their peak value but also in terms of how long temperature remains above the target. It is better to return from an overshoot than staying at the higher level, but a lot worse than not overshooting in the first place.

Source: DownToEarth