What is causing these wildfires? Are they abnormal right now? And what can we expect?
ALDHOUS: Wildfires are normal in the western United States; we get them every year. However, we are in a really bad season with more fires that are likely to be more intense than normal. The reason is the drought that is here in California and much of the American West. When it’s really dry you can get big and intense wildfires.
The concern is that this is most likely a harbinger of things to come. If we look at the projections from climate models, it's going to get warmer across the whole of the country. But there's a rough split that emerges between the southwest of the country essentially getting warmer and drier and the northeast getting also warmer but wetter.
So in the western United States we will likely have, over time, longer and more intense wildfire seasons. All of the bad effects we get from those are likely to intensify in the coming decades.
You had a story yesterday about the “less visible” effects of wildfires. Can you quickly tell us about it?
ALDHOUS: It’s clearly bad if your home is in the direct path of a fire — it's disastrous. But the effects go wider than that. Wildfire smoke contains very fine particles called “PM2.5” that are damaging to health. If you're asthmatic, or have other lung or cardiovascular disease, wildfire smoke may potentially shorten your life.
I've been looking at research which suggests that globally we're talking about a significant number of premature deaths each year caused by wildfire smoke – around 340,000. It's difficult to put firm numbers on how many people in the United States are having their lives shortened by wildfire smoke. It's certainly less than from other forms of air pollution. But it can become locally very severe. In 2003 and 2007 there were big wildfires near Los Angeles and San Diego and the smoke blew right over the cities. When that happens, it is dangerous. You really want to stay indoors and have the air filtered.
Because we think wildfires are going to become more frequent and more intense in the American West, this is going to become a more serious issue as times goes by.