California, Oregon and Washington State are the 3 US states overlooking the Pacific Ocean (in addition of course to Alaska and Hawaii). These are 3 large states, whose total area exceeds 850 thousand km², inhabited by a population of about 50 million - so an average density of 60 inhabitants per km² (bear in mind that the average for the EU countries is 105 inhabitants per km²). All this to say, this is a land where nature continues to have its spaces. There are deserts (the most famous being the Mojave and Death Valley), but also large parks, like Yosemite, numerous forests and protected natural areas.
In recent weeks the territory of these 3 states, more than any other in the U.S., has been affected by a disastrous series of fires of particular intensity that to date have reduced over 20,000 km² of land to ashes, killing 24 people just last week.
Climate change and this year's fires
The governor of California, Gavin Newsom, recently said: "Come to the state of California and see for yourself. These fires show that the time for discussion about climate change is over. This is a goddamn emergency. This is real and it's happening".
Is this true? Is there a relationship between the effects of climate change and the fires in the US in recent weeks? In a piece in the MIT Technology Review the unequivocal words of David Romps, director of the Berkeley Atmospheric Sciences Center: "Let's get to the point: have the heat wave, lightning strikes and drought of vegetation been affected by global warming? Absolutely, yes. Have temperatures been made significantly warmer, lightning more numerous and vegetation drier due to global warming? Yes, probably yes, and yes".
That’s two clear yeses for heat waves and vegetation drought, and a “probably yes” for lightning.
Climate scientist Daniel Swain disagrees, stating that lightning storms in August are so rare in Northern California, that it is difficult to assess whether climate change played a role in triggering these fires. In many cases fires are ignited by lightning strikes, so in this instance there remains some doubt about the relevance of climate change.
The effects of drought
On the other hand, with heat waves and their effects on vegetation there is a greater convergence of views. "Basically the dynamics are very, very simple - explains Philip B. Duffy, president of the Woodwell Climate Research Center - warmer, drier conditions create a drier fuel and what would once have been an easily extinguishable fire is now growing very quickly and getting out of control".
Supporting this thesis, the New York Times, in an interesting analysis of the situation, pointed out that "in some ways, this year's fires in California are the result of a much longer history. A prolonged drought that ended in 2017 was one of the main causes of the deaths of 163 million trees in California forests in the last decade, according to the U.S. Forest Service. One of the fastest moving fires this year devastated the forests that had the highest concentration of dead trees south of Yosemite National Park".
The NASA scenario
In a piece of analysis on the NASA website, dated December 2018, there were "6 trends to know about the fire season in the Western United States"[5]. These trends include:
- Increasing number of fires - In the last sixty years there has been a steady increase in the number of fires in the Western United States, 61% of which have occurred since 2000.
- Increasing size of fires - The average annual amount of hectares burned has been steadily increasing since 1950.
- Burning of coniferous forests, more than any other land - Since 2000, fires have gone from burning mainly bushy areas to burning coniferous forests.
As worrying as these points are, the last of their forecasts is the one that should worry us most.
- "Fires will have a big impact on our future - Research suggests that global warming is expected to increase the number of large fires in the western United States by mid-century".
