Latest / The Climate Translation / Fueling the Storm

Transcript

Fueling the Storm · The Climate Translation

• 0:00
  If you live near anybody of water, such as the Gulf of Mexico or the Atlantic, you know
• 0:13
  what it feels like to watch the tropics during the summer and fall during hurricane season.
• 0:20
  You check the forecast, you will follow the tracks, you watch systems form, strengthen
• 0:26
  and sometimes turn towards you.
• 0:30
  During my time as a TV meteorologist on the Texas coast, I saw that up close.
• 0:36
  Seasons where one system after another developed in the Gulf.
• 0:40
  Storms that seemed to intensify faster than expected, and like many people who have watched
• 0:46
  hurricanes over the years, I found myself asking a simple question, is something changing?
• 0:54
  Because when we talk about climate change and hurricanes, the conversation often surrounds
• 1:00
  the connection between warmer oceans and the number of tropical systems.
• 1:06
  But the science tells a more complicated story.
• 1:10
  It's not just about how many hurricanes form, it's how they behave, how strong they become,
• 1:17
  how quickly they intensify and how much rain they produce, as well as how long they last,
• 1:24
  how much they reach land.
• 1:26
  Today we're going to take apart what a warmer world means for hurricanes, not just in numbers,
• 1:32
  but in energy.
• 1:34
  Welcome to the podcast, I'm Dr. Mac, and this is the Climate Translation.
• 1:44
  To understand what climate change might do to hurricanes, we need to start with a simple
• 1:49
  question.
• 1:51
  What does a hurricane actually need to form?
• 1:54
  At its core, a hurricane is a heat engine.
• 1:58
  It runs on warm ocean water.
• 2:02
  When the surface of the ocean reaches about 80 degrees Fahrenheit or higher, it provides
• 2:08
  the fuel storms need.
• 2:11
  Warm water evaporates into the atmosphere, and that adds moisture and energy.
• 2:16
  That warm, moist air rises, cools, and condenses into clouds, and in the process, it releases
• 2:24
  heat.
• 2:26
  That released heat is what powers the storm.
• 2:30
  It lowers pressure at the center, pulls in more air, and keeps the system going.
• 2:37
  The more heat that's released, the more the storm can organize and strengthen.
• 2:42
  So in a very real sense, a hurricane feeds on the ocean.
• 2:48
  Now there are other ingredients too.
• 2:50
  You need relatively low wind shear, meaning winds at different heights in the atmosphere
• 2:56
  aren't tearing the storm apart.
• 2:58
  You need enough rotation from the Earth's spin to help the system organize, and you need
• 3:03
  to disturbance to get things started in the first place.
• 3:07
  But without warm water, none of it works.
• 3:11
  Without the fuel, you can't have the storm.
• 3:14
  So this brings us to a key connection.
• 3:17
  The oceans are warming.
• 3:19
  Over the past several decades, the surface of the ocean, especially in regions where
• 3:24
  hurricanes form, has been steadily increasing in temperature.
• 3:29
  And more importantly, that warmth isn't just sitting at the surface, it's extending deeper
• 3:35
  into the ocean.
• 3:37
  Now that's important because hurricanes don't just interact with the very top layer
• 3:43
  of water, as they churn, they mix the ocean beneath them.
• 3:48
  In the past, that mixing could bring cooler water up to the surface and could weaken the
• 3:54
  storm.
• 3:56
  But when the water is not just warm at the surface, but several meters down, that's less of a cooling
• 4:02
  effect.
• 4:04
  The storm keeps having access to its fuel.
• 4:08
  So when we ask what human-induced climate change is doing to hurricanes, this is the first
• 4:14
  piece of the answer.
• 4:16
  We're not changing the rules about how hurricanes form.
• 4:20
  We're changing the environment they form in.
• 4:23
  We're raising the temperature of the fuel that powers the system.
• 4:28
  And when you increase available energy and a system like that, the behavior of storms
• 4:35
  start to change in ways that weren't always obvious at first glance.
• 4:41
  Now it's important to point out that while it's true that warm water fuel storms and warmer
• 4:48
  water can be thought of as adding more fuel to the engine, the reality is not cut and dry.
• 4:55
  A warmer ocean does give you more potential energy.
• 5:00
  But it doesn't mean every storm suddenly becomes a category 5 hurricane.
• 5:06
  And it doesn't mean every season is going to be more active than the last.
• 5:11
  The earth system is complex.
• 5:14
  There are a lot of variables at play.
• 5:17
  But what we're seeing in the data and in the observations of the tropical oceans is
• 5:23
  a potential shifting of the odds.
• 5:26
  In a warmer ocean, scientists expect that storms that do form will have a greater chance
• 5:32
  of becoming stronger.
• 5:34
  Over the past few decades, one of the clearest signals scientists have observed is an increase
• 5:40
  in the proportion of storms that reach the higher categories such as category 3, 4 and
• 5:47
  5 on the Safer Simpson scale.
• 5:50
  It's not that we're necessarily seeing more storms overall, but more of the storms that
• 5:55
  do form are reaching higher intensity.
• 5:59
  And there's another piece of this that's been getting a lot of attention in recent research,
• 6:05
  rapid intensification.
• 6:07
  This is when a storm's wind speeds increase dramatically in a short period of time, sometimes
• 6:14
  30, 40, even 50 miles per hour and less than a day.
• 6:19
  From a forecasting perspective, this is one of the most challenging scenarios.
• 6:24
  A storm that looks manageable one day can become much more dangerous than next.
• 6:30
  And warmer ocean water, that fuel for the storm, plays a key role in that process.
• 6:38
  When conditions are right, that extra heat energy can allow a storm to strengthen very
• 6:43
  quickly, especially as it approaches land, where the warm water extends even deeper.
• 6:50
  Now if this sounds familiar, it should, because it connects back to something we talked about
• 6:55
  in an earlier episode.
• 6:58
  You can think of the climate system like a set of loaded dice.
• 7:02
  Climate change is shifting the odds towards larger numbers.
• 7:06
  At any given roll, you can still get a one or a two.
• 7:10
  We will still have weaker storms and quieter seasons.
• 7:14
  But with added fuel, the odds are that a three, four, and five will come up more often
• 7:20
  than they have in the past.
• 7:23
  And when those stronger storms do develop, the impacts can be very different.
• 7:28
  Not just because of the wind, but because of what else they carry with them.
• 7:33
  And that's the next part of the story, because wind is only one piece of what makes
• 7:37
  a hurricane dangerous.
• 7:40
  The first thing that comes to mind when you think about hurricanes are their intense wind
• 7:44
  fields.
• 7:46
  We think of the structure of the storm, the category, the eye, the images of the strong
• 7:51
  gusts, bending trees, and damaging buildings.
• 7:56
  But for many storms, especially in recent years, the most dangerous part hasn't been the
• 8:02
  wind.
• 8:03
  It's the water.
• 8:05
  To understand why it's helpful to understand how air behaves at different temperatures.
• 8:11
  In the classroom, I often explain this using a balloon as an example.
• 8:16
  If I blow up a balloon just a little, you can think of it as cool air.
• 8:21
  If I blow it up a lot, you can think of it as warm air.
• 8:25
  And just like the available space in a balloon is greater when it's larger, warm air has
• 8:31
  a greater capacity to hold moisture than cool air does.
• 8:36
  In fact, for every degree Celsius the atmosphere warms, it could hold about 7% more water vapor.
• 8:45
  Now that may not sound like much, but across an entire storm system, it adds up pretty
• 8:51
  quickly.
• 8:53
  Now think about what a hurricane is doing.
• 8:55
  It's pulling in warm, moist air from the ocean, lifting it upward, and then releasing
• 9:01
  that moisture as rain.
• 9:03
  So if the atmosphere is holding more water to begin with, the storm has more to work with.
• 9:10
  More moisture in the air means the potential for heavier rainfall.
• 9:15
  And that's what we're observing.
• 9:17
  Many recent hurricanes have produced extreme rainfall totals, amounts that overwhelmed
• 9:24
  drainage systems, flood neighborhoods, and linger longer after winds have died down.
• 9:30
  And another variable to consider is speed.
• 9:33
  Not the wind speed in the storm, but how fast the storm is moving.
• 9:38
  In some cases, storms are slowing down as they approach land or move inland.
• 9:44
  And when a storm slows down, it spends more time over the same area.
• 9:50
  That means that any given area gets much more rain than it would if the storm was moving
• 9:56
  faster.
• 9:58
  Rain keeps falling, hour after hour, sometimes day after day.
• 10:03
  So now you have a system that can hold more moisture, which releases more rain, and it
• 10:09
  does it over a longer period of time.
• 10:12
  That combination is what turns a storm from a wind event into a flooding event.
• 10:18
  You can also think of the atmosphere like a sponge.
• 10:21
  A warmer atmosphere is a larger sponge.
• 10:25
  It can hold more water.
• 10:27
  And when a hurricane squeezes that sponge, more water comes out.
• 10:33
  But if you hold that sponge over the same spot and keep squeezing, the ground below doesn't
• 10:37
  get a chance to recover.
• 10:39
  That's when flooding becomes a dominant risk.
• 10:43
  So when we ask about climate change and how it's affecting hurricanes, the most clear
• 10:48
  answer we can get is it's increasing the amount of water available to the system.
• 10:54
  And that's changing what these storms can do once they reach land.
• 10:59
  So what are scientists actually seeing in the data?
• 11:03
  This is where the story becomes more complicated.
• 11:06
  But more interesting at the same time, when researchers look at the long-term record of
• 11:11
  hurricanes, especially in the Atlantic, one of the first challenges is the data itself.
• 11:18
  Before satellites became widely available in the 1970s, we didn't see every storm.
• 11:25
  Some systems just stayed out to see.
• 11:28
  Some were never recorded.
• 11:30
  So when scientists try to answer whether hurricane numbers are increasing or if the intensities
• 11:36
  are going up, they have to account for what they may have missed.
• 11:41
  And when they do that, there are different approaches that can lead to different answers.
• 11:47
  Some studies that correct for missing storms suggest that over the historical record, going
• 11:53
  back to the 1800s, there really isn't a long-term increase in the total number of hurricanes.
• 12:01
  But other approaches look at the problem differently.
• 12:04
  Instead of counting individual storms, they look at the environmental conditions that
• 12:10
  produce hurricanes, ocean temperatures, atmospheric moisture, instability.
• 12:17
  Those studies show conditions that favor hurricane development have become more favorable
• 12:22
  over time and that leads to stronger storms.
• 12:27
  In fact, some research has found what it describes as unequivocal increases in Atlantic
• 12:35
  tropical cyclone activity when looking at those underlying conditions rather than just
• 12:41
  the raw storm counts.
• 12:44
  So now we have two independent ideas side by side.
• 12:49
  The total number of storms may be uncertain, partly because of the limits of historical
• 12:54
  data.
• 12:55
  But the environment those storms are forming in is clearly changing.
• 13:01
  And there's another layer to consider.
• 13:03
  Since the 1970s, when we had more reliable satellite observations, many key hurricane metrics
• 13:10
  have increased.
• 13:12
  The number of named storms, the number of major hurricanes, and something scientists call
• 13:17
  Accumulated Cyclone Energy, which is a measure of the total energy produced by storms over
• 13:25
  a season.
• 13:27
  Researchers point to a combination of factors behind that increase.
• 13:32
  Cleaner air, for instance, has reduced certain types of pollution that used to reflect sunlight
• 13:37
  and cool the oceans slightly.
• 13:40
  The fewer of those particles in the atmosphere, more sunlight reaches the ocean's surface,
• 13:46
  and that contributes to warming.
• 13:48
  Obviously, warmer oceans are more favorable for hurricane development, too.
• 13:54
  So when we ask, are there more hurricanes?
• 13:57
  The most honest answer is, we're still working that out.
• 14:01
  But if you ask, are the conditions for hurricanes becoming more favorable, and will the storms
• 14:06
  that do form be likely stronger, the data is pointing to, yeah.
• 14:13
  So where does that leave us?
• 14:15
  When it comes to hurricanes, climate change isn't giving us a simple answer.
• 14:19
  It's not a straightforward, more storms or fewer storms.
• 14:23
  Instead, we're seeing a shift in behavior.
• 14:27
  Storms that can strengthen more quickly and carry more water.
• 14:31
  Things that in some cases can linger over the same area for days at a time.
• 14:37
  And all of that comes back to something we've talked about throughout this episode.
• 14:41
  Energy.
• 14:42
  Hurricanes don't operate in isolation.
• 14:45
  They respond to the environment around them, and the environment is changing.
• 14:51
  The oceans are warmer.
• 14:53
  The atmosphere is holding more moisture, and the system as a whole has more energy to
• 14:59
  work with.
• 15:01
  That doesn't change what any single storm will do.
• 15:04
  But when you look at the whole system, it does change the range of what's possible.
• 15:19
  The story of climate change isn't just about temperature.
• 15:23
  It's about how energy moves through the system, and what happens when that flows shifts.
• 15:28
  For hurricanes, that means we're not just watching how many storms form, we're watching
• 15:33
  how they behave.
• 15:35
  It's an active area research, and we're still continuing to study how these patterns
• 15:40
  are evolving.
• 15:42
  What signals are strongest, and what the uncertainties mean.
• 15:46
  So for now, the next step is just to pay attention and see where the trend lines are heading,
• 15:51
  but to prepare for surprises that may come in a warmer world.
• 15:56
  I'm Dr. Mac, and this has been the Climate Translation.
• 16:00
  If you have a question about the climate you've been too afraid to ask, or if you have
• 16:04
  a differing opinion, I want to hear from you.
• 16:07
  I can use your viewpoints in future episodes.
• 16:10
  You can reach me at theclimatetranslation at gmail.com.
• 16:16
  I'll see you next time.