Climate change

NY Times - In just a few decades, summers in California will not only be much hotter, but will also stretch for months longer. Floods will become more widespread and extreme. Exposure to wildfire smoke will kill thousands more people every year.

Those are the dire projections of California’s Fifth Climate Change Assessment, a report produced by California every few years that analyzes the impacts of changing weather patterns on the nation’s most-populous state.

The future laid out in the report, which was published on Monday, touches on familiar warnings: more wildfires, bigger storms, longer droughts. But it illustrates in unsettling detail just how quickly the climate is being reshaped, and reveals what is likely to be major upheaval to long-established ways of life in California.

According to the report, average temperatures are likely to increase in California by about 4 degrees Fahrenheit by the middle of the century. Current warming in California is unprecedented compared with the past century and estimates for the past millennium, the report shows.

More and more, warm weather will arrive in California earlier in the year and persist later, with summer conditions lasting for 135 days on average by the middle of the century, compared with an average of 90 days between 1981 and 2010, according to the report. That prolonged summer will have widespread impacts, including on fire risk, tourism, agriculture and wildlife.

The warmer conditions will also mean a 40 percent reduction by midcentury in California’s snowpack in the Sierra Nevada, which feeds the state’s reservoirs. What once fell as snow will instead fall as rain and immediately become runoff. This will lead to more severe droughts, according to the report.

Many Californians have already lived through the beginnings of these trends. The state this year logged its warmest August on record. And several of the most destructive fires in state history have happened in the last decade, including the wildfires last year in Los Angeles that were among the costliest disasters in U.S. history.

Abby Edwards, senior deputy director for the Governor’s Office of Land Use and Climate Innovation, which produced the assessment, said she hoped the report would alert communities and decision makers about where to focus their efforts as the climate continues to change.