Possible irreversible changes to subsystems before reaching the point of climate change

Recently, some researchers at the University of Copenhagen published an article in the Proceedings of the National Academy of Sciences describe their work investigating the possibility of changes to the Atlantic Meridional Overturning Circulation (AMOC) and the circumstances that could lead to such changes. In their paper, Johannes Lohmann and Peter Ditlevsen noted that climate models show that irreversible changes to subsystems such as the AMOC, one of the world’s global subsystems, can occur before a tipping point if changes occur rapidly.

They further noted that fresh water flowing through the melting ice in the Atlantic Ocean could cause just as much irreversible change. More recently, an international team of climate scientists has published a piece of Perspectives, also in PNAS, the damage of the damage that can result if irreversible changes occur before the tipping points, and also what models suggest, will happen when the earth begins to reach certain tipping points.

In climate science, tipping points are climate poles that occur when changes are made to the global ecosystem that result in other permanent changes. If too much carbon dioxide is injected into the atmosphere, for example, it would become too hot for animals to survive. Climate models indicate that under such scenarios there are no more times. Once a tipping point is reached, we cannot solve the problem by stopping carbon emissions. More recent research has suggested that there may be some tipping points that may cause climate change on a smaller scale, but which will still be irreversible. Fresh, cold water penetrating the North Atlantic Ocean, for example, could result in permanent changes to the AMOC. The AMOC is particularly responsible for the mild temperatures in Europe.

In their paper, the authors of the Perspectives piece describe the likely outcomes of different scenarios that could lead to changes in the subsystem before the tipping point. They note, for example, that the world’s oceans contain subsystems. In addition to rising water levels, the oceans around the world are experiencing carbon dioxide being absorbed by the atmosphere. Acidification harms marine life. In addition, previous research has shown that the upper part of the ocean absorbs heat into the atmosphere much higher than lower regions. The lower regions are only now beginning to experience the effects of warming, a protracted event that could change the entire ecosystem under water – a change that would be irreversible.

The good news is that the researchers of the AMOC study and the authors of the Perspectives piece agree that it is not too late to prevent such scenarios from unfolding. All that is needed to stop greenhouse gas emissions, and then for scientists to focus their energy on the parts of the planet that have already been harmed.

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