The Climate in Emergency

A weekly blog on science, news, and ideas related to climate change

Dry Heat

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This is an article I posted some years ago about an earlier horrible drought and heat wave after heat wave. I’m re-posting an edited version of it in preparation for a few articles about this year’s horrible droughts and heat waves.

The word “drought” just sounds hot and uncomfortable, doesn’t it? A lot of people speak about heat waves and droughts together, almost as though they are the same thing.

They aren’t the same thing at all. Hot weather can be rainy and droughts can and do happen in the winter. Parts of Antarctica are among the driest deserts in the world. But drought and heat are connected; they each make the other worse.

 

First, many animals and plants, humans included, need more water when it’s hot out. Animals pant or, in our case, sweat, using evaporation to stay cool. The hotter the weather, the more water we use panting or sweating. Plants neither sweat nor pant, but in order to photosynthesize they have to open pores in their leaves so they can breathe. But they also lose water through their pores, a process called transpiration. The hotter the weather, the faster plants transpire. If they cannot draw enough water up from their roots to keep up, and cannot shut down photosynthesis, they wilt or even die.

A drought during a heat wave is like losing your job when the rent is due; the loss is not actually bigger, but it seems bigger because you really need the money.

But heat does not just make drought seem worse, higher temperatures actually dry out the land. More heat means rivers and lakes evaporate faster. The soil surface dries out, too (and, once dry, the soil heats up, baking the air above it and making the heat wave even worse). Meanwhile, all the plants that have not died or gone dormant are sucking huge amounts of water up from deep underground in order to keep up with transpiration.  A drought is a gap between the amount of water the land needs and the amount of water the land actually gets, so a heat wave can create a drought, even if rainfall itself remains normal.

But rainfall is not going to remain normal. Global warming does not just mean more heat, it also means changed weather patterns so that some areas get more rain (or even snow) than previously, while others get less.  Some areas, such as the Mediterranean countries and the central areas of the United States and Mexico, simply must adapt to a new, dryer reality. New England is one of the regions that will likely get more rain, but if a greater proportion of that rain falls in a couple of very heavy storms there could still be more drought in between the storms. Heavy rains also do not recharge aquifers very well because the water flows away before most of it can soak in. Even snow that melts early can cause drought, because the water is lot available later in the year when the land needs it.

So heat makes us need more water at the same time that it drives more water away through evaporation and transpiration, on top of weather pattern changes that give some places less water and other places a lot of water they cannot really use.

This dreary prediction is fairly well locked in for the next few decades, because there is a time delay in how the atmosphere responds to what we do to it. We are now dealing with the consequences of our parents’ and grandparents’ mistakes. The fact that our grandparents didn’t know any better, and our parents were busy dealing with a lot of seemingly more pressing problems (like raising us, for example) is important emotionally, but it doesn’t actually make the weather any less messed up.

The fact that we are likewise busy dealing with our own other pressing problems will not make our legacy any easier for our children and grandchildren to deal with—but we do have some choice over what burdens they will have to bear.

The time-lag means that many of us alive today will not see the consequences of what we do to the climate. If we push the sky past a tipping point beyond which life as we know it is no longer possible, we will be safely dead by the time things really fall apart. If we work and sacrifice and bend our minds towards solving the most important puzzle our species has ever faced, we will not live to see the fruits of our labor.

The big question then is are we the sort of people who will put ourselves out for future generations or not?

Ideas and plans, like trees and vegetables, grow if they are fed and watered and die if they are not. With a limited amount of time and money, and against a backdrop of climatological principles we cannot simply wish away, we still have some choice over which of the seeds we have planted will get water.

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Author: Caroline Ailanthus

I am a creative science writer. That is, most of my writing is creative rather than technical, but my topic is usually science. I enjoy explaining things and exploring ideas. I have one published novel and another on the way. I have a master's degree in Conservation Biology and I work full-time as a writer.

3 thoughts on “Dry Heat

  1. Pingback: The Climate Emergency

  2. Pingback: On Natural Gas | The Climate Emergency

  3. Pingback: How Normal Is this Abnormality? | The Climate in Emergency

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