Climate vulnerability update

California’s Fourth Climate Change Assessment released in August is the latest in the state’s exemplary series of reports on the state’s vulnerability to climate change. Highlights from the summary of findings include:

  • Under a medium-low future emissions average statewide temperatures are projected to rise by 4.4°F by mid-century and 5.6° by end of century. Under a high emissions future, temperatures are projected to rise by 5.8° by mid-century and 8.8° by end of century. These changes would dwarf the temperature increases that have already occurred, of more than 1° for most of the state, with some areas exceeding 2°.
  • Increasing acreage burned by wildfire is associated with increasing air temperatures. One Fourth Assessment model suggests large wildfires (greater than 25,000 acres) could become 50% more frequent by the end of century if emissions are not reduced. The model produces more years with extremely high areas burned, even compared to the historically destructive wildfires of 2017 and 2018. By the end of the century, California could experience wildfires that burn up to a maximum of 178% more acres per year than current averages.
  • By 2050, the average water supply from snowpack is projected to decline by one-third from historical levels, with either medium-low or high continued emissions. If emissions continue unchecked, water from snowpack could fall to less than one-third of historical levels by 2100.
  • If emissions continue at current rates, total sea-level rise by 2100 is projected to be four and a half feet, almost twice the rise that would occur under the medium RCP 4.5 scenario.

The assessment website in itself is a model for making accessible the high volume of material that goes into compiling a comprehensive assessment, breaking out vulnerabilities under a broad framework (people, infrastructure, transportation, natural and working lands and waters, ocean and coast), and that is further broken down into specific impacts (increases in temperature, wildfire, sea level, etc.). Findings are presented on both a statewide and sub-regional basis.

The state of our climate

 Safeguards under attack

Some good news!