HARI SREENIVASAN: Now let's turn to the extreme heat wave baking the West and Southwest parts
of the country.
Temperatures are well above the 100-degree mark.
In California, it was 127 degrees yesterday in Death Valley, 122 in Palm Springs.
In Phoenix, the temperature is expected to top out at 118 degrees today.
In fact, it's been so hot there, more than 40 flights were canceled or delayed because
some planes can't safely lift off in that heat.
A new analysis published in the journal "Nature Climate Change" this week also said climate
change is leading to more heat waves in general.
It found that 30 percent of the world's population is exposed to potentially deadly heat for
20 days per year or more.
It's the subject of our weekly segment on the Leading Edge of science with Miles O'Brien.
Let's start with what's happening in Phoenix.
Miles, you have flown for a long time.
We have always heard of flights being delayed because it's too cold.
How can a flight not take off because it's so hot?
MILES O'BRIEN: Yes, Hari, if it weren't for the snow and ice, the winter would be the
perfect time to fly, because a wing achieves flight, it derives lift based on the number
of air molecules that surround it.
And, as the temperature heat up, those molecules command.
We know that, when you warm things up, things expand generally.
So there are fewer air molecules, so it takes greater amount of speed for that aircraft
to fly.
And if the runway isn't long enough to support that -- in other words, if the temperature
is so high that there are so few molecules there to lift the wing that you don't have
enough runway to get going fast enough, you're grounded.
HARI SREENIVASAN: All right, so this is still smaller planes that were affected.
What's the difference with the bigger planes?
MILES O'BRIEN: Well, the larger planes, the Boeing 737s, the big airliners, are designed
to operate in a wider range of circumstances, for one thing.
They are kind of a global product that has to operate in all kinds of intense conditions.
And, frankly, it just costs more to certify them to these parameters.
In addition, a 737, for example, has a lot more potential payload, so you can take off
some cargo and still fly the mission.
These smaller planes are not designed with as much versatility, and because they're smaller,
they have less capability to reduce the payload and thus take off.
And really, ultimately, they have charts in there that a pilot has to look at, and there
will be a maximum temperature, given the altitude of the field, et cetera.
And if you exceed that, you legally cannot take off.
HARI SREENIVASAN: There are lots of runways that are too short to deal with this kind
of heat.
And we talked about in Phoenix, but, say, a place like La Guardia is just as confined
or San Francisco is just constrained by a certain amount of space.
MILES O'BRIEN: Yes, so researchers looked at this.
The La Guardia runway is about 7,000 feet, runways there.
And while that's about 20 feet above sea level, and thus the air is denser there, by virtue
of where it is and it doesn't get quite as hot, nevertheless, at that length, you still
-- there are still some parameters and constraints that we have to be watching as the climate
gets warmer.
This goes into the larger subject, Hari, of how our civilization is designed.
When you're thinking about a beach house on a barrier island or a runway at La Guardia
or at Phoenix Sky Harbor, we have a finely-tuned civilization, and as the temperature goes
up, even though it has only gone up a degree Celsius over a hundred years, it does create
pockets of these heat waves.
We're not exactly sure why, probably because the jet stream is weakening and causing high-pressure
systems to park in these places.
I spoke with a climate scientist who has looked into this extensively.
He's at Columbia University -- Radley Horton is his name -- as part of a series I did for
the weather app MyRadar.
RADLEY HORTON, Columbia University: If we look at the last decade or two, we are seeing
twice as many record-breaking extreme heat events, cities that are breaking their daily
record highs for a given day, compared to the ratio compared to the number of cities
having record-breaking cold temperatures.
If you make temperatures just a couple degrees warmer on the hottest days, that means much
more demand for air conditioning, for example, which means much greater risk of the power
going out, precisely at those temperatures, those times when people are so sensitive to
just a little more warming from a public health perspective.
HARI SREENIVASAN: That goes a bit to that Goldilocks effect you are talking about, because
even our infrastructure and our systems are built for us to be within a certain range.
MILES O'BRIEN: Exactly.
And that's why we need to be really watching the effects of climate change.
It's easy to dismiss a one-degree Celsius increase and say, well, that's not a big deal,
but, in isolated locations, in specific locations, whether it's Phoenix or whether it's Miami
Beach or whether it's another city that has a sea level problem that it is dealing with,
or whether it's California dealing with wildfires, those particular pockets, those problems are
exacerbated by that overall increase in the temperature of the climate, the overall temperature
of the planet.
And it causes changes to our weather systems which we're just beginning to understand.
Researchers are just getting a handle on it.
HARI SREENIVASAN: So in the case of this news about Phoenix and the air -- do airlines,
who think about buying planes years and years out -- these are hundreds of millions of dollars'
worth of purchases -- do they think differently about what kind of jets to buy or where to
park all those jets, in a place with a long runway?
MILES O'BRIEN: Hari, I think this is something the aviation industry has not gotten out ahead
of.
I suspect there are a lot of conversations going right now as we have seen this record
heat wave.
There was a similar record heat wave last year as well which caused similar problems.
So the airlines are going to have to contend with this, the airliner makers, and airports
as well.
The longest runway at Phoenix Sky Harbor is a little more than 11,000 feet.
They might have to think about extending that runway.
What about La Guardia, though?
Is that even possible?
Is it possible to even consider that?
All these things get factored into the consequences of climate change and how we as civilization
can adapt to it.
HARI SREENIVASAN: All right, science correspondent Miles O'Brien, thanks so much.
MILES O'BRIEN: You're welcome.