What is causing global climate change?
Drought ranks second in terms of national weather-related economic impacts, with annual losses nearing $9 billion per year in the U.S. [1] Beyond direct economic impacts, drought can threaten drinking water supplies and ecosystems, and can even contribute to increased food prices.
Within the last decade, drought conditions have hit the Southeastern U.S., the Midwest, and the Western U.S. In 2011, Texas had the driest year since 1895. In 2013, California had the driest year on record.
There are different types of drought
Drought can call to mind images of dry, cracked earth; low reservoir levels; and barren fields, yet these are actually examples of different types of drought, each of which is measured differently.
We most often think about drought in relation to precipitation, assessing the degree of dryness (in comparison to a local or regional average) and the duration of the dry period. This is known as a meteorological drought, which is highly specific to a region as average precipitation may vary considerably spatially.
We can also think about hydrological drought, or how decreased precipitation affects streamflow, soil moisture, reservoir and lake levels, and groundwater recharge.
Farmers are most concerned with agricultural drought when available water supplies are not able to meet crop water demands. Agricultural droughts can occur for a variety of reasons, including low precipitation, the timing of water availability, or decreased access to water supplies. For instance, earlier snowmelt may not change the total quantity of water available but can lead to earlier runoff that is out of phase with peak water demand in the summer. Thus, it is possible to suffer an agricultural drought in the absence of a meteorological drought.
Climate change affects a variety of factors associated with drought
When considering the relationship of drought to climate change, it is important to make the distinction between weather and climate. Weather is a description of atmospheric conditions over a short period of time, while climate is how the atmosphere behaves over relatively long periods of time.
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