The media is full of stories about human-caused global warming.
But did you know there are large areas of the planet where humans are causing cooling?
Importantly, Washington is a prime example of our ability to massively cool the surface.
We do this by irrigating vast areas of eastern Washington and northern Oregon.
Consider a recent satellite image of our region (below).
The Columbia Basin should be a desert. Instead of desert or arid rangeland, we have irrigated vast areas, with the evidence being all the green dots and squares covering much of the basin.
Spraying water for irrigation causes massive cooling by evaporation. Or evaporation from a wet ground or wet plants results in strong cooling.
When the sun's rays hit the surface, much of that energy goes into evaporating water rather than warming the surface.
You can see the impacts of irrigation on temperatures quite easily. Below are some satellite images (so you can see where the irrigation is taking place) and high temperatures on a recent day (May 9) over a portion of the Columbia Basin (you can see the Columbia River). Generally, in the 70s over irrigated areas and low-80s over the nearby desert lands.
Here is a blow-up of the next day. Much cooler over the irrigated area.
The amount of irrigation in the Columbia Basin was rapidly increased in the late 1940s into the 1950s... and it had a profound impact on the temperature trends. Typically, irrigation results in 2-5 F cooling. Sometimes more.
At Othello, the mean high temperatures during summer actually DECLINED during the mid-century and stayed down.
Similar lack of warming in Ritzville.
So perhaps you can understand why fewer folks in Eastern Washington are concerned about global warming.😊
If you aren't impressed with the massive temperature experiment in eastern Washington, imagine the profound cooling impacts of the irrigation of large areas of the central valley of CA (see below).
Looking at a station there (Denar 3), you can see a similar lack of warming during the past century. Cooling due to the effects of irrigation played a role in this.