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“Rivers of Rain” Could Wreck China, Unless We Reduce CO2 Emissions

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Guest essay by Eric Worrall

According to an AGU study, this might be our last chance to save the Chinese Communists from a climate catastrophe.

Climate Change Could Open Up ‘Rivers in The Sky’ Over East Asia 

DAVID NIELD 23 JANUARY 2022 

We know that the climate crisis is already having a profound effect on global weather systems, altering temperatures, rainfall, wind patterns, and more – and a new study predicts likely deluges over the mountainous parts of East Asia in the future.

The pouring rain will be brought on by atmospheric rivers, scientists predict. These narrow corridors of concentrated moisture can quickly cause flooding when they hit a barrier such as a mountain range, releasing vast amounts of water in a short space of time.

According to the researchers’ models, rainfall events in East Asia will be more frequent and more severe in the coming decades as the planet warms up. More water will be transported through the air, and more precipitation will land on the ground.

“We find that both the atmospheric river-related water vapor transport and rainfall intensify over the southern and western slopes of mountains over East Asia in a warmer climate,” write the researchers in their published paper.

“Atmospheric rivers will bring unprecedented extreme rainfall over East Asia under global warming.”

Read more: https://www.sciencealert.com/climate-change-could-open-up-rivers-in-the-sky-over-east-asia

The abstract of the study;

Atmospheric Rivers Bring More Frequent and Intense Extreme Rainfall Events Over East Asia Under Global Warming

Y. KamaeY. ImadaH. KawaseW. Mei
First published: 01 December 2021

Portions of East Asia often experienced extremely heavy rainfall events over the last decade. Intense atmospheric rivers (ARs), eddy transports of moisture over the middle latitudes, contributed significantly to these events. Although previous studies pointed out that landfalling ARs will become more frequent under global warming, the extent to which ARs produce extreme rainfall over East Asia in a warmer climate remains unclear. Here we evaluate changes in the frequency and intensity of AR-related extreme heavy rainfall under global warming using a set of high-resolution global and regional atmospheric simulations. We find that both the AR-related water vapor transport and rainfall intensify over the southern and western slopes of mountains over East Asia in a warmer climate. ARs are responsible for a large fraction of the increase in the occurrence of extreme rainfall in boreal spring and summer. ARs will bring unprecedented extreme rainfall over East Asia under global warming.

Read more: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021GL096030

Naturally the study embraces RCP 8.5.

The study authors predict increased water vapour transport and concluded that will lead to increased rainfall. “Increased water vapor in the warmer air alone can lead to increased AR [Atmospheric River] occurrence“. But where does the power come from, to evaporate and transport all that additional water vapour?

The following is one of the few studies I have read which questions the assumption that warmer temperatures automatically lead to a significantly intensified water cycle.

Constrained work output of the moist atmospheric heat engine in a warming climate

Incoming and outgoing solar radiation couple with heat exchange at Earth’s surface to drive weather patterns that redistribute heat and moisture around the globe, creating an atmospheric heat engine. Here, we investigate the engine’s work output using thermodynamic diagrams computed from reanalyzed observations and from a climate model simulation with anthropogenic forcing. We show that the work output is always less than that of an equivalent Carnot cycle and that it is constrained by the power necessary to maintain the hydrological cycle. In the climate simulation, the hydrological cycle increases more rapidly than the equivalent Carnot cycle. We conclude that the intensification of the hydrological cycle in warmer climates might limit the heat engine’s ability to generate work.

Read more (requires registration): http://science.sciencemag.org/content/347/6221/540.full

The point is, climate intensity is not related to surface temperature, it is related to how quickly solar energy passes through the climate system. This is nothing to do with the debate about whether CO2 or solar variations drives global warming, because I’m not talking about variations in surface temperature.

What I am talking about is the energy flow, from sunlit daytime to interstellar space, which drives the entire global weather system.

You can have more storms, or more intense rainfall, but not both. If water vapour transport and rainfall does intensify, the energy to power that rainfall intensification has to come at the cost to the intensity of another atmospheric phenomenon, to keep the thermodynamic books balanced. Climate change could redistribute the intensity of extreme weather – but any rise in extreme weather intensity in one location has to be more or less counterbalanced by a reduction in intensity elsewhere.

Let’s just say I’m not going to lose any sleep over the predictions of this study.

via Watts Up With That?

January 26, 2022

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