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12 | THE COLONY NEWS | JULY 2021 | COMMITTEE NEWS By Jane Payne Environmental Concepts recently published an article on CALIFORNIA'S CLIMATE CHANGE. With their permission, below is an excerpt from their article. California's climate is changing. Heat waves have become more common, and less precipitation is falling when and where it is needed the most. These changing weather patterns are impacting the state's water supply, increasing the risks of wildfires and threatening our ecosystems. Meteorologists and climatologists have identified several factors that contribute to the changes in our climate. Of major significance is an imbalance in the earth's natural cooling process, causing a warming of the earth's surface and lower atmosphere, aka troposphere. The troposphere, where clouds are formed and most of our weather occurs, has the capacity to draw moisture up from the land and surface waters through evaporation. As land, air, and water temperatures rise, the evaporation rate increases, producing a condition experts refer to as a "thirsty atmosphere." This high evaporative demand unfortunately increases the rate of soil moisture evaporation and vegetation transpiration, which leaves less water available for plants. The atmosphere can hold only a certain amount of water vapor at a given temperature before it condenses into a liquid and returns in the form of rain or snow. With warming temperatures, however, the atmosphere is capable of holding more moisture before reaching its saturation point. When warm, moist air rises and converges with the cold air above, long narrow corridors of condensed water vapor are formed known as "atmospheric rivers." They can make landfall carrying substantial volumes of moisture and producing heavy amounts of precipitation. Atmospheric rivers come in all shapes and sizes and are responsible for up to 50% of the state's annual precipitation. Numerous studies predict atmospheric rivers to increase in frequency and severity due to increasing evaporation rates and higher atmospheric water vapor levels caused by the climate changes. The majority of the precipitation that feeds California's water supply systems historically falls within a wet-seasonal period between November and March. Numerous studies, however, indicate that California will likely have a larger percentage of its annual precipitation fall within a narrower window. The effects of longer and warmer dry seasons, compounded by the narrowing of concentrated wet periods, produces an effect called "climate whiplash." The whiplash effect disrupts the seasonal balances with a late-season arrival of precipitation produced by a handful of intense storms. This late arrival, together with higher temperatures, is causing the snowpack to melt sooner, with the potential to overload the state's water supply networks and increase flood risks. The rising variability of changes in climate, due to a thirsty atmosphere, atmospheric rivers and climate whiplash, poses many obstacles for California's water managers, who already face a serious challenge in balancing the increasing needs for water against a reduction in supply. As I am looking ahead, a lot has recently been reported about a megadrought. Megadrought refers to decades-long periods of low precipitation and soil moisture, which are often associated with reduced mountain snowpacks. These periods are chronically dry, with less frequent wet years and drier dry years. A recent study in Science is referring to a megadrought which has lasted 21 years in the Southwest. It is described as "one of the worst ones of the last millennium, except that it hasn't lasted as long." It is being worsened by human-caused climate change. LANDSCAPE ADVISORY Continued on following page

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