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The impacts of global warming 

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on people are going to be 
more than just 

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the average change in the temperature. 
It's like a fever. 

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If you have a fever of 104 F (40C), what you 
feel is 

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a lot more than just a couple of extra 
degrees of warmth. 

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What you feel is your head hurts, and your 
stomach hurts, and you're sick. 

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It's more than just the temperature. 

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On the Earth, the strongest climate 
impacts are likely to be 

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regional impacts, rather than a globally 
averaged change. 

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It's kind of like if you have a log 
that's on fire and you increase 

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the amount of oxygen, you can kind of 
predict overall that the log will 

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burn faster in some way. 

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But what's actually affecting a little bug 
crawling on the log

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is the flickering of the flames,

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and that's a lot harder to forecast. 

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I have my students a book by 
Mark Lynas

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called Six degrees, Our Future on a 
Warmer Planet. 

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The book is divided into chapters 

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that correspond to different amounts of 
warming. 

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And he's describing the various climate 
impacts 

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that people have predicted, scientists 
have predicted,

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as a function of the amount of warming 
where they start to kick in. 

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If you're interested, I recommend you 
have a look at that. 

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I think the most severe 
impacts are likely to have 

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to do with water availability and drought.

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It's a bit paradoxical. 

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Overall, when you make the planet warmer, 
warmer air can hold more water vapor. 

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And if you're running the air 
through the wringer of 

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the hydrological cycle, of having it go up, 
and make clouds,

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and come back down, and from that you get an 
increase in the overall amount of rainfall 

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as the earth warms. 
But as it turns out, places that are 

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dry today are predicted to get even 
drier in a global warming a world. 

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A continental interior dries 
out as the temperatures go up. 

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In continental interiors 

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there is expected to be a deficit of 
rainfall relative to the 

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pre-warming a case. 
Here is a plot of 

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a map of where the rainfall changes are 

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expected to be found, a composite from 
all of the different climate 

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models that are used in the IPCC 
scientific assessment. 

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And it's hard to predict regional climate 

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changes, which means that different models 
don't 

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always agree exactly on what they expect 
to have happen here or here or there. 

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But there is some coherence that's coming 
out from the models. 

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What you see is drying in places where 
it's actually 

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anomalously dry today. 
The American Southwest, the 

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Mediterranean, Australia; these are all 
places that are drier

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than they should be today. 

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And they are predicted to get even drier 
in a warmer world.