A trend of larger, more numerous and more intense wildfires continues in California, where thousands of people have been forced to evacuate in recent weeks. Nearly 30 major fires have burned across the state, including some of the largest in its history. A four-county blaze in Northern California, called the Park Fire, spread quickly to affect about 430,000 acres before being contained in August. A newer fire in Southern California's Angeles National Forest grew last week, consuming nearly 48,000 acres. At the same time, a blaze in the San Bernardino Mountains has burned more than 34,000 acres and one in Orange County has scorched over 22,000 acres. Climate change is making the deadly situation worse, scientists say. Oregon, Washington and other Westerns states also are affected, and the national preparedness level for wildfires is now at the highest level of 5.

Fire season has been starting sooner and ending later, and the annual total of wildfire acreage burned has grown in recent years. Human-amplified climate change, which refers to an ongoing increase in global average temperature, affects weather conditions in ways that increase risks. Wildfires have always been part of the Western landscape and ecosystems, but climate change brings a new era of large, catastrophic outbreaks. Heat waves have plagued California since early May. That factor and drought leave a larger amount of dried brush, grass and trees that make natural fires of those started by people easier to spread and more difficult to fight or prevent.

Climate change also intensifies wildfires for these reasons:

• Hotter temperatures have a direct influence on fire behavior, heating the fuels and making them more likely to ignite.
• Warmer nighttime temperatures decrease the overnight humidity that once helped firefighters gain control over wildfires. As humidity levels drop, the air pulls moisture from the land -- leaving vegetation dry and prone to burning.

The steady rise in global average temperature is primarily caused by humans burning fossil fuels (coal, oil and natural gas), according to a scientific consensus. With more people and property located near wildfire-prone terrain, the risks and costs mount.

Evacuee says: "Usually you get a warning first, which is just a get-ready, and historically that means you have the day to pack and prep just in case. This went from no one being concerned to ‘Leave now.’ The wind was crazy." – Katie Grossman of Victorville, Calif. (San Bernardino County)

Journalist says: "The smoke that fills our skies every summer is a traumatic reminder of death and destruction that we only have the illusion of control over. . . . The Park Fire — and massive fires like it — are not just in California's future, they are California's future." – Robin Epley, opinion writer at The Sacramento Bee

Scholar says: "In Northern California, we are seeing really high temperatures in places like the Central Valley and in parts of the eastern Bay Area. Temperatures are rising year after year." -- Tony Marks-Block, California State University assistant professor of environmental studies