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Dr. K. H. Coats



UHI's and Droughts*

 Dave Cummins (retired, Chevron), Moraga, Ca

June 2021 

If you don't understand the significance of what you're about to read. If it doesn't make the hair on the back of your neck stand up. Then you'd better re-read it, because Houston we have a problem. And that problem is drought. The greatest peril facing mankind from Climate Change is not rising atmospheric temperatures, but drought. Mankind can survive with warmer temperatures but it cannot survive without water. Crops cannot grow without rain. And for several years now there have been stories detailing droughts, crop failures, dying trees and increasing forest fires throughout the N. Hemisphere. And forget about rain in the winter. It's irrelevant unless you have enough storage to hold it for the growing season. Plants don't grow in the winter. And if you think it's bad now, droughts are going to deepen every year for decades. And we can't do anything about it. 






And now there's this. The Canary in the coal mine. Lake Mead is at its lowest level EVER. For those unfamiliar with Lake Mead, it's the largest reservoir in the US. It was created almost 90 years ago when the Hoover Dam was built. Yes, before WW2, the atomic bomb, the jet engine and TV.  Lake Mead created Las Vegas. No Lake Mead, no Las Vegas. And it's level has been dropping since 2000!


The entire US West Coast, and California in particular, where I live, is in deep peril. California's current drought is the worst in history. The reservoirs are empty again. And this is at the end of the rainy season. The fight about what to do with diminishing water supplies in all the Western States is already on in earnest. The Utah state governor is calling for divine intervention.



Unfortunately these droughts are not acts of God. They have man's fingerprints all over them.

The immediate consequences;

-  California agriculture supplies 25% of the US food demand. Diminishing water supplies means 

   that California agriculture as it is now, is a thing of the past and require US food supply change, 

- Hydroelectric power supply in the summer will crater. It will lead to rolling blackouts in the Western states for as far as the eye can see. Las Vegas in the dark? Likely.

And these droughts were entirely predictable. And unfortunately, they are going to get increasingly severe for decades. It's unstoppable. The cause? Climate change. And not the CO2 explanation for climate change, The real explanation for Climate Change, UHI's. The precipitation process is not complicated. Before water can come down, it first has to go up. Before there can be precipitation there has to be evaporation. And there are only two sources of evaporation on Earth:

 -  Evaporation from global water surfaces, both salt and fresh. And,

 - Transpiration, evaporation from vegetation. 

If evaporation from either one of these two sources falls, droughts are inevitable. And transpiration has been falling for decades. Urban Heat Islands (UHI's) have been systematically replacing vegetation with concrete since 1900. No vegetation, no transpiration.

Since UHIs (cities) will continue to develop and expand, and vegetation will continue to be eliminated, droughts will increasingly become more severe. And calculating that lost evaporation isn't difficult. Globally since 1900, we've relandscaped 1.5 million square miles. An area so large it would take over 3 hours to fly over it. Globally, compared to 1900 we're evaporating 2.9 billion acre/ft less water annually. That's enough water to flood the entire US lower 48 to a depth of 18 inches.

Why is it affecting the US Western states and California so dramatically? The jet stream travels from West to East. Before 1995, China was a backwater. In just 25 years, China has become the second largest economy on the planet. It's poured perhaps 8 times as much concrete as the US has ever done. So ever decreasing evaporation in China, translates to increasingly less precipitation and increasingly severe drought in California and the US western states. As China goes up, Lake Mead goes down.

So as China increasingly does this: 


And Shanghai is just an example. In California it results in this.


And with China growing at 5% annually for the foreseeable future, it's effect on diminishing rainfall in the US western states will double in 13 years. Quadruple in 25. Rivers will dry up. Actually it's quite frightening. The mighty Colorado river, the river that created the Grand Canyon, will likely become a trickle in late summer in just a decade from now.

And drought begets drought. As California evaporates less water and its forests burn, less rain will fall in the midwest. Precipitation is not rocket science. If water doesn't go up, there's no way it's gonna come down. And no amount of wind turbines, electric cars, and PV panels is going to change that. Only more vegetation. And even if we start now in earnest, it will take decades for that vegetation to mature and make a significant difference.

As for the Climate scientists. On the subject of droughts these folks have been strangely silent. Their "models'' predict increasing rainfall. In their model, rainfall is a function of atmospheric temperature. So if atmospheric temperatures are increasing, so too is rainfall. Let's not confuse them with facts. Climate scientists  have yet to make the connection between transpiration and rainfall. It's just not on their radar. For them these droughts must be mystifying. Their goal is decreasing CO2 levels. How eliminating fossil fuels and decreasing atmospheric CO2 levels ever connects to increasing rainfall and reducing drought simply escapes me. But then I'm just a simple process engineer.

So the question I pose to the community is how do we change the status quo? Once the climate folks understand the connection between UHI's and droughts, it's just a small step to connecting lost evaporative cooling to increasing atmospheric temperatures. Or so I would hope. Maybe then we can ditch the absurd Greenhouse Gas doctrine and change the paradigm. Forget wind turbines and electric cars. Globally we need billions of trees beginning now. In the interim, the US desperately needs another Manhattan Project, but doesn't yet realize it. It will require investment in desalination plants, gas fired power plants, wastewater reuse and enormous agricultural greenhouses to name just a few. So the question I pose to the community, is how as a community do we raise the alarm? It's already too late. Any later and the situation becomes ever more desperate. As a community are we going to be seen sitting on our hands while Rome was burning. Ideas?

And for those not familiar with the UHI explanation for atmospheric warming. It's a 2 mins read.

And it's attached. And yes UHI's are responsible for all evidence of Climate Change. Greenhouse gases are entirely irrelevant.


* Posted by David Cummins in the AICHE Engage / Discussion Central discussion of UHI's and Droughts.

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