This story is part of , CNET’s series on how we’re preparing now for what could come next.
California is aflame. Nearly 700,000 acres are burning from over 370 distinct wildfires that have forced tens of thousands of residents to evacuate. The deadliest and most damaging conflagrations are the result of over 10,000 lightning strikes in the San Francisco Bay Area alone, driven by a week of extreme heat that climbed into the triple digits and culminated in a 130-degree record in the hottest part of the state (and the third-hottest recorded temperature ever, if verified).
“The hots are getting hotter. The dries are getting drier. Climate change is real. If you are in denial about climate change, come to California,” said Governor Gavin Newsom, speaking at the Democratic National Convention through a short, self-shot video captured in a redwood forest about a mile from a wildfire. But are the dots between climate change and California’s wildfires really that easy to connect?
First, the facts: Natural disasters are — statistically speaking — getting both worse and more frequent. Wildfire season is longer and more destructive than at any time in recorded history. In the US, flood zones encompass more homes than ever before. And than in years past. That much is indisputable.
But teasing out what’s responsible for making natural disasters worse, and specifically to what extent climate change plays a role, can get muddled pretty quickly. For example, even as fires have become more destructive, some studies have shown a net decrease in wildfire burn area over the last 20 years. And while more people live in flood zones today than ever before, it’s partly because there are simply more people than ever before that need housing.
With a topic as politically charged as climate change, any disparity in the data runs the risk of derailing the conversation. So I’m going to stick to the facts, and that means admitting some key concessions that climate scientists have identified as crucial to keeping the discussion on track.
First, that “natural disaster” is something of a misnomer. A hurricane that lands on an uninhabited strip of coastline isn’t a “disaster” no matter how strong its storm surge. It takes civilization and human development to create conditions conducive to a disaster. Secondly, that climate change is only one among multiple factors that influence the frequency and severity of wildfires, severe floods, hurricanes and the like. There’s simply no magic bullet.
With that in mind, let’s look at what experts in the field — climate scientists, meteorologists, statisticians — have to say about climate change’s impact on natural disasters.
What are the most common natural disasters?
Floods and storms (such as hurricanes and tornadoes) are by far the most common, accounting for as much as 70% of the world’s total natural disasters, according to the World Economic Forum. Rounding out that list are earthquakes (8%), extreme hot and cold temperatures (6%), landslides (5%), drought (5%), wildfire (4%) and volcanic activity (2%). Combined, these events result in an average 60,000 deaths per year, or about 0.1% of global deaths overall.
Isn’t there a difference between climate and weather?
Yes, but they’re still closely linked. Weather refers to events occurring in Earth’s atmosphere on a day-to-day basis. Weather concerns the short-term changes we experience, like the difference between rain and sunshine, or snow and sleet. Climate describes overall weather patterns across a much longer period of time — like years and decades — and over a specific area or region, like, for example, North America.
Changes to climate, like the overall increase in average temperature observed over the last century — a net gain of about two degrees Fahrenheit — can affect weather patterns. Likewise, weather can be used to calculate broader changes in climate — higher average rainfall makes for a more humid climate, for example.
How can climate change influence both floods and droughts? And extreme hot and cold temperatures?
Water evaporates faster as temperatures warm, which means global warming causes more water to evaporate. This has changed the way water, both as rain and in the form of humidity, is distributed around the globe, meaning some areas have started having less rain than usual during certain times of the year (leading to drought), and other areas have experienced more (leading to flooding).
And while it may seem obvious that global warming could lead to extreme heat, climate change can also intensify extreme cold temperatures by reducing the air pressure that keeps cold weather at the Earth’s poles, allowing them to drift farther toward the equator than usual.
How does climate change influence natural disasters?
Climate change might affect each of the eight most common natural disasters in a few ways:
Floods: According to the National Resources Defense Council, though our warming world may not induce floods directly, it exacerbates many of the factors that can lead to flooding, which include excessive rainfall and snowmelt.
Storms: Scientists expect that as global temperatures go up, extreme precipitation will likely increase as well (like I mentioned above about evaporation). This creates conditions conducive to .
Earthquakes: No, the weather doesn’t cause earthquakes, but there are several theories for how climate change might provoke them. Reduced atmospheric pressure might allow fault lines to shift more easily, increased rainfall following hurricanes may result in more erosion and reduces the weight on fault lines so they might shift more easily. They increased rainfall itself also might lubricate fault lines and lead to more slippage.
Extreme Temperatures: Fluctuations in temperature are ultimately a consequence of unusual changes to atmospheric pressure. Normally, what’s called a “polar vortex” encircles Earth’s two poles and blocks frigid air from drifting too far toward the equator. However, as air pressure fluctuates around the globe — more wildly as a result of climate change — those polar vortexes can become unstable, which may allow cold air to drift into typically much warmer climes, and vice versa.
Landslides: Climate change leads to more extreme precipitation, which erodes more of Earth’s topsoil and may trigger more frequent and more deadly landslides.
Drought: Higher average temperatures cause more water to evaporate, which can intensify droughts.
Wildfire: The same conditions that lead to drought — hotter, drier air and the drier vegetation that results from them — also fuel increased wildfire activity across the globe.
Volcanic activity: The same factors that could influence earthquakes — decreased atmospheric pressure, increased rainfall — have also been linked to upticks in volcanic activity.