If You Thought Last Week Was Hot . . .

Higher temperatures, rising ocean, loss of snowpack forecast for state 

JANE KAY / San Francisco Chronicle 1aug2006

[Full Report at state portal]

California will become significantly hotter and drier by the end of the century, causing severe air pollution, a drop in the water supply, the melting of 90 percent of the Sierra snowpack and up to six times more heat-related deaths in major urban centers, according to a sweeping study compiled with help from respected scientists around the country.

Graphic from report

The weather — up to 10.5 degrees warmer by 2100 — would make last month's heat wave look average. If industrial and vehicle emissions continue unabated, there could be up to 100 more days a year when temperatures hit 90 degrees or above in Los Angeles and 95 degrees or above in Sacramento, the report states. Both cities have about 20 days of such extreme heat now.

The report's good news: If emissions of carbon dioxide and other greenhouse gases are significantly curtailed, the number of extremely hot days might increase by only half those figures.

The report, released today by the California Environmental Protection Agency, was prepared by the California Climate Change Center, established three years ago by the California Energy Commission. Scripps Institution of Oceanography and UC Berkeley are responsible for the core research, and about 75 scientists from universities, government agencies and nonprofit groups contributed to the study.

The report is the first under an executive order signed in June 2005 by Gov. Arnold Schwarzenegger that calls for biennial studies on the potential impact on the state of continued global warming.

"What we wanted to do with the document is summarize the scientific reports so regular citizens can understand the grave concerns that we believe are facing California,'' said Claudia Chandler, assistant executive director of the Energy Commission.

Climate experts have faith in the reliability of global climate models and their ability to forecast what will happen to the planet as the heat-trapping greenhouse gases continue to build in the atmosphere. However, some scientists have been reluctant to say how global warming might affect specific regions, including areas the size of California. That's because there is debate over whether models are good enough to zoom in on possible local effects of planetary climate change.

But Chandler said the state was depending on the core of scientists who prepared the report to use the best models available to help the state prepare for problems in the not-too-distant future. "We probably won't know until 10 years from now. But that will be too late. We cannot turn our backs on trying to address this very serious situation.''

Highlights of the report:

• Hotter weather would increase the risk of death from dehydration, heat stroke, heart attack, stroke and respiratory distress. Under the most extreme scenario, heat-related deaths could increase by four or six times.
  
  
• The snowpack, the state's major source of fresh drinking water, could nearly disappear.
  
  
• Power demand could go up as much as 20 percent, but hydropower supplies would drop.
  
  
• Heat could put stress on dairy cows, which could produce up to 20 percent less milk. Fruit and nut trees could produce smaller, inferior-quality crops. Wine grape quality could be severely affected in all but the coolest growing regions.
  
  
• Sea levels would rise, with the possibility of inundating the Sacramento-San Joaquin River Delta, a source of two-thirds of the state's drinking water.

"We looked at agriculture, one of the state's most important sectors, and the increased potential of wildfires,'' said Chandler.

"We looked at public health from the standpoint of deteriorating air quality and the reduced water from the Sierra Nevada snowpack. We looked at what rising sea levels would mean to the delta's water pumps and levees and to the coastal cities of Los Angeles, San Francisco, Oakland and San Diego.''

The study authors based their assessments on what would happen in California under three different emissions scenarios. The amount of emissions would determine the amount of temperature rise over the century as greenhouse gases trapped excess heat that would otherwise radiate into space. These scenarios — which contain varying assumptions on economic and population growth, use of new efficient technologies and shifts away from the use of fossil fuels — have been adopted by the United Nations Intergovernmental Panel on Climate Change, a collaboration of 2,000 scientists from 100 countries.

With continued higher emissions, temperature increases are projected between 8 and 10.5 degrees; with medium emissions, temperatures would increase between 5.5 and 8 degrees; with lower emissions, the temperature is projected to rise between 3 and 5.5 degrees.

How the state manages emissions could have a significant impact on how global warming affects California, the report said. For example, if temperatures rise as much as 5.5 degrees, there will be 75 to 85 percent more days of weather conducive to production of unhealthful smog in Los Angeles and the San Joaquin Valley, it said. The days could be cut if emissions stayed at the lower scenario.

Sea levels have already risen about 7 inches along the California coast in the past century. If greenhouse gases continue and temperatures rise into the upper range, the ocean is expected to rise 22 to 35 inches by the end of the century.

A mix of increasingly severe winter storms and high tides is expected to cause more frequent and severe flooding, erosion and damage to coastal structures, the report said.

The report concludes that California policy alone cannot significantly affect the warming planet.

"California alone cannot stabilize the planet. However, the state's actions can drive global progress," the report concludes. If other states and nation's follow California's example of limiting emissions of greenhouse gases, "we would be on track to keep temperatures from rising ... and thus avoid the most severe consequences of global warming."

Projecting future climate

    Summary of projected global warming impact, 2070-2099 (as compared with 1961-1990):

                                                    Heat wave days    Heat related 
                                                    in major urban    deaths in major 
                                                    centers           urban centers 
                       Loss of           Sea level  (Number of        (Number of  
                       Sierra snowpack   rise        times as         times as 
    Warming range     (In percent)      (In Inches)  many)            many)         .
    
    LOWER (3-5.5°F)   30-60%             6-14        2-2.5             2-3 
    MEDIUM (5.5-8°F)  70-80%            14-22        2.5-4             2-6 
    HIGHER (8-10.5°F)    90%            22-35        3-4               4-6  


                       Critically  
                       dry years        Increase in
                      (Number of        electricity
                       times as        demand 
    Warming range         many)       (In percent) 
    LOWER (3-5.5°F)       1.5           3-6% 
    MEDIUM (5.5-8°F)    2-2.5            10%   
    HIGHER (8-10.5°F)     2.5            20% 
    
    * Average global mean temperature, 
1961-1990 
    ** Emissions scenarios characterize 
different assumptions based on 
patterns of economic and population growth, 
use of more efficient technologies 
and shifts in uses of fossil fuels.

source: http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2006/08/01/MNGDAK90EK1.DTL&type=printable 1aug2006