Changing Rain
by Chris Tilley
With our earth warming up what is going to happen with precipitation? That question will again depend on where you live and the season. Another important question is will it fall as snow or rain? This article is based on the IPCC Reports.(source)
First of all average precipitation is expected to increase. Also expected to increase is the water vapor stored in the air and evaporation. These are going to vary by region.
As you can see most area see an increase in precipitation. There are some area that are going to see a decrease in precipitation most notably is the southern USA. This map is based on the A1B storyline and show the deviation from 1980 to 1999 average in 2080 to 2099.
As we can see the precipitation varies by the season. More in the winter months of DJF (December through February) and some what less in the summer(JJA). This brings up an interesting question for a lot of areas, will this precipitation fall as rain or snow? Where I live we rely of snow pack for our water. If it falls as rain we will need infrastructure to store that water.
It is also expected that the rain we do get will come in briefer more intense periods followed by longer than normal dry spells. The maps and graphs use standard deviation which is a measure of how far off of an average value we are. For more information wikipedia has a good article explaining it.(source) Most areas will will see the intense rain followed by extended dry periods. This makes me think of southern California with long dry spells and fires followed by heavy rain and mud slides. The far north will see more intense rain and more frequently.
Another interesting graphic is the map of soil moisture, with an increase in precipitation we would expect a wetter soil. However that is not necessarily the case as you can see. The reason is largely from the increased evaporation and runoffs as you can see from the other maps. Dryer soil means needing more irrigation for crops and therefore more infrastructure. The increased runoff will result in more flooding.
The end result is that water is going to be an issue in a warming earth. Everything from drinking water to water for irrigation, flooding and droughts. There is lots more in the IPCC reports sea level rises, extinctions, moving plant and animal life. We will cover those topics after chistmas when I have more time to read the reports.