How many mornings are in California

SZ: The fires in California seemed to have eased somewhat in the past few weeks. Why is it burning so badly there again?

Kirsten Thonicke: The fire season in California actually goes into November, sometimes into December. We have a Mediterranean climate there, similar to that in the Mediterranean region. The fire season ends when the winter rain sets in. The fires that are now occurring there are still part of this year's fire season. The danger wasn't over yet.

What influence does climate change have on the in general Risk of forest fires?

In the case of forest fires, it is an indirect influence: the drought or extreme heat has increased the risk of fire. Both have become much more likely due to climate change, and climate change has made a statistically verifiable contribution. And when fires break out, the effects are much worse because the fires burn very intensely.

Can you say that there is more fire in the world today than it was 20 or 50 years ago?

No, you can't. If you now add up the global forest fire area, then according to the satellite data, the trend has even been downwards over the past 20 years. But this trend is interrupted by extreme years, which turn out to be even more extreme.

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Is that also showing in California?

Yes. Here the fires are due to an extreme drought. California has had a mega-drought in the past ten years that lasted for several years. Then came another relatively humid year and now it was extremely dry again. The vegetation is still or was again extremely stressed by this drought.

There was also a special constellation: that a weather system with a large number of rain clouds and thunderclouds encountered an air mass limit. That led to a lot of lightning strikes in August. They started the fires that led to this mega-fire and opened the fire season a month earlier.

Will man have to live with such violent fires in the future?

In any case. With warming, we are also dealing with stronger or more frequent climatic extremes. They cause more drought or heat waves in certain regions. These in turn lead to more fires, so that these extreme fire events can occur again and again.

Even now, with a temperature difference of less than one degree due to global warming, we are seeing an extreme change in climate variability. At 1.5 or two degrees, that will likely happen more often or worse. That is a challenge that we have to face.

What does that mean in concrete terms?

Thonicke: It is not for nothing that the United States is discussing whether there could be areas that are no longer habitable because the risk of fire is so great and the stress is enormous for people if they are constantly evacuated and their houses burn down.

There could then be areas in which one can no longer live because of the risk of fire?

Exactly. Much larger areas or regions may be affected by the increasing heat waves anyway; the high temperatures make it impossible for people to continue living there. As long as something is still growing, these areas could also be affected by fires, including mega-fires. In Death Valley, for example, 54 degrees Celsius were measured on August 16, 2020, probably the highest recorded air temperature since records began there in 1913.

These heat waves are affecting ever larger areas, for example in the south of the USA, in Pakistan, in Iran or in other tropical regions. That is one of the great challenges. We ourselves and our life system are much more vulnerable than we might have thought a few years ago.