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Our Changing Climate: Assessing the Risks to California

31 July 2006

A new report from the state of California warns that climate change could have a significant impact on the state's economy and the health of its residents. 

The report, Our Changing Climate: Assessing the Risks to California, [see full report - pdf file 1.9mb] says that the state climate is expected to become considerably warmer before the end of the century, the degree to which depends on the rate at which humans continue to burn fossil fuels. It looks at three potential scenarios: lower warming range with projected temperature rises between 3 and 5.5°F, medium warming range with projected temperature rises between 5.5 and 8°F, and higher warming range with projected temperature rises between 8 and 10.5°F.

The report says that the three projections show little change, on average, in total annual precipitation for the state but warns that even modest declines in precipitation levels "would have a significant impact because California ecosystems are conditioned to historical precipitation levels and water resources are nearly fully utilized”.

The report warns that while total precipitation is by affected much over the course of the century, rising temperatures may cause more precipitation to "fall as rain instead of snow, and the snow that does fall will melt earlier, reducing the Sierra Nevada spring snowpack by as much as 70 to 90 percent" increasing the risk of summer water shortages, reducing hydropower generation by as much as 30 percent, and diminishing skiing and other snow-related recreational activities. Rising sea levels could further damage the state's water supplies by flooding groundwater aquifers and the Sacramento/San Joaquin River Delta

Our Changing Climate warns that the expected impact of global warming on public health is of even greater concern.

"Continued global warming will affect Californians’ health by exacerbating air pollution, intensifying heat waves, and expanding the range of infectious diseases," reads the report. "Higher temperatures are expected to increase the frequency, duration, and intensity of conditions conducive to air pollution formation."

The report says that health problems including asthma and other acute respiratory and cardiovascular diseases will likely worsen due to the effects of increased air pollution. Further, a projected increase in the number of wildfires could produce higher levels of fine particulate matter, contributing to still worse air quality. Heat waves will likely increase mortality from "dehydration, heat stroke/exhaustion, heart attack, stroke, and respiratory distress."

Beyond health, climate change will have a significant impact on the state's $30 billion agriculture industry that employs more than one million workers.

"Increased heat-trapping emissions are expected to cause widespread changes to this industry, reducing the quantity and quality of agricultural products statewide," the report says. "Although higher carbon dioxide levels can stimulate plant production and increase plant water-use efficiency, California farmers will face greater water demand for crops and a less reliable water supply as temperatures rise. Crop growth and development will change, as will the intensity and frequency of pest and disease outbreaks. Rising temperatures will likely aggravate ozone pollution, which makes plants more susceptible to disease and pests and interferes with plant growth."

The report says that higher temperatures may result in less-than-optimal development for many crops worsening the quantity and quality of yield for agricultural products like wine grapes, dairy products, and fruits and nuts. Milk production may fall by as much as 20 percent if temperatures rise to the higher warming range by the end of the century. The report warns that agricultural weeds and pests will likely thrive under warmer conditions, further damaging agricultural production.

The report says that higher temperatures and shifts in precipitation could alter the state's ecological communities, affecting biodiversity and reducing the productivity of commercial forests. The risk of large wildfires could rise by as much as 55 percent according to medium range forecasts. Ecosystems -- estuaries and wetlands -- providing important ecological services like flood control and water filtration could be degraded by higher sea levels.

Climate change is expected to worsen storm damage in coastal areas and along rivers. Sea levels are projected to 22 to 35 inches by the end of the century, threatening to "inundate coastal areas with salt water, accelerate coastal erosion, threaten vital levees and inland water systems, and disrupt wetlands and natural habitats." Low elevation areas like Santa Cruz and the San Francisco Bay Delta region could be particularly affected. Beach erosion could destroy some of the state's most popular tourist destinations.

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