“Extreme weather” caused by global warming?

Article by Isabel Key and Mina Frost.

It’s often said that global warming causes more “extreme weather” [8] – this is a very unclear statement. Let’s dive into what’s behind it.

Droughts, floods, heatwaves, tornadoes, wildfires, etc. happen naturally from time to time. Most such extreme weather events don’t happen “just because of climate change”; it is more accurate to say that “climate change influences the risk and frequency” of these events [9].

Some types of events are more influenced by human actions than others [4], but there is a clear trend: warming makes extreme weather more intense and common [1,11]. Heatwaves, for example, have become more frequent overall [3]. The heatwave in northern Europe in 2018 was twice as likely to happen because of climate change [2].

Bonus question: WHY do drought and rainfall get more extreme in some places?

At the core of drought and rainfall is evaporation [10]. If an object is hot, it means the particles of that object wiggle and bounce around more than if it was cold [7]. This bouncing-around makes it more likely for molecules to turn from a liquid into gas (evaporate). For water, this would mean it makes it more likely to turn from liquid water into water vapor. Water evaporates even at very cold temperatures, but it happens faster when it’s warmer [6], which is why your cloths dry faster in the sun than in the shadow.

More evaporation causes more extreme weather in two ways: 1) In areas which are hot, there is lots of evaporation, so the land becomes more dry and droughts are worse [5, 10]. 2) But what goes up must come down! So, storms can have heavier rainfall [5].

References

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