Hurricane Season 2021: the Bad, the Worse, and the Unexpected

Published Jan 18, 2022

Senior Climate Scientist Astrid Caldas elaborates on Ida—and the many other deadly and damaging 2021 storms made worse by climate change.

In this episode

Colleen and Astrid talk about:

  • the specifics of the 2021 hurricane season and how it compared to previous seasons
  • the science behind tracking hurricanes and predicting future trends
  • the emotional toll working on climate change takes and where to find hope
Timing and cues

Opener (0:00-0:30)
Intro (0:30-2:03)
Interview p1 (2:03-11:57)
Break (11:570-13:12)
Interview p2 (13:12-24:47)
Throw (24:47-24:52)
Segment (24:52-27:31)
Outro (27:31-29:00)


This Week in Science History: Katy Love
Editing: Colleen MacDonald
Additional editing and music: Brian Middleton
Research and writing: Pamela Worth and Cana Tagawa
Executive producer: Rich Hayes
Host: Colleen MacDonald

Related content
Full transcript

Colleen: Living near the ocean, I stay on top of weather reports out of necessity. Choppy seas mean the ferry won’t run, and it might be too windy to get outside. Storm surges could mean it’s time to board up the windows. And hurricanes hit different, as they say, when you’re right next to their source.   

But the Northeast is relatively small potatoes compared to the damage hurricanes cause in the Gulf states.  And there was a lot of costly damage. One of my Got Science podcast colleagues was in New Orleans over the holidays and reports that the Big Easy is still deep in recovery from Hurricane Ida in August. A lot of houses still have blue tarps on their roofs and there is much rebuilding to come. 

But many other hurricanes weren’t visible to most of us in the U.S.. In fact, in 2021, more hurricanes went out to sea instead of making landfall, which made last year an unexpected top-ranking hurricane season. The greater intensity of these hurricanes is directly connected to a hotter climate and is only one of many devastating effects of climate change.  

Tracking hurricanes is crucial to ensuring people’s safety. It’s especially crucial for experts as typical, predictable hurricane patterns become less predictable, and deadlier. Joining me on this episode is Senior Climate Scientist, Dr. Astrid Caldas, to discuss key takeaways from the 2021 hurricane season, and what we can expect for the future.

Colleen: Astrid, welcome to the podcast.

Astrid: Thank you, it's a pleasure to be here again.

Colleen: Yeah, it's great to have you back. So, here we are post-hurricane season, and I thought we should check in and do a recap of the 2021 hurricane season. So, what were the key takeaways?

Astrid: In my opinion, there were several takeaways. Some of them unexpected. There was not a lot of hurricanes in the news this year and, of course, we think that it was not as bad. However, it was the third most active season, coming after only 2020 and 2015. We didn't really realize that it was that active because a lot of the hurricanes went out to sea instead of coming and making landfalling. So, that was one of the things that was kind of a surprise to a lot of people.

I think that the United States in particular got lucky, and I'm saying "lucky" in quotation marks, because it could have been a lot worse if we had a lot more landfalling hurricanes. Eight made landfall in the U.S. but only one was terrible, which was Hurricane Ida that hit the Gulf Coast in Louisiana.

So, this kind of contrast about having this horrible hurricane and then not hearing much about other hurricanes was kind of unexpected. But it was the seventh consecutive year that the first storm formed before the official start of the season, which is June 1st. And it was also the fourth costliest hurricane season, since we started tracking the seasons, with more than 70 billion dollars in damages and over 160 fatalities. So, it was a bad season, even though, in our minds, we didn't think much about it.

Colleen: So, before we dig into the specifics of what happened where, I wanna go back to global warming 101. Can you tell us how climate change is making hurricane seasons worse?

Astrid: All this global warming is coming from the burning of fossil fuels since the industrial times. So, all this burning of fossil fuels is increasing the amount of carbon dioxide in the atmosphere, the famous CO2. And that is the main cause of global warming. Global warming, in turn, is behind, what we call, climate change. And climate change includes changes in patterns of hurricanes and changes in intensity of hurricanes, which is one of the main things that we are seeing.

Climate change has been shown to impact the intensity of hurricanes. In the past 30 years or so, we are seeing more intense hurricanes. We are seeing more hurricanes that are category-3, 4, and 5, which are the stronger hurricanes.

Colleen: And what are the mechanics of how these storms start and become more intense?

Astrid: Hurricanes form when a conjunction of factors occur. One of them is the sea surface temperature and also the temperature below surface of the ocean. Global warming is increasing the temperature of the oceans, and sea surface temperature in particular has been much higher than the average in the past few years. And this is a trend that has started a few years back and is continuing.

So, that higher temperature of the sea surface warms up also the air. And the moisture that comes up of that warm ocean feeds the hurricane. We always say that hurricanes feed on sea moisture because they need moisture to exist among other things-- direction of winds, upper winds and lower winds. But one of the main things about hurricanes is the sea surface temperature. Also because the warmer air, the air is getting warmer with higher temperatures, it can also keep more water vapor. It holds more water vapor. So, that water vapor also can increase the amount of precipitation of rain that comes with the hurricanes. So, these are two of the main ways that global warming is impacting hurricanes.

Colleen: So, Astrid, when comparing hurricane seasons, what variables are you looking at? Is it the intensity? The number of storms? The human toll?

Astrid: Scientifically speaking, we look mostly at the intensity and the number of storms and their patterns. Because the human toll, of course, is relative. It depends on a hurricane making landfall or not, many times. Sometimes a hurricane does not make landfall and there is still bad storm surge and some human toll or some economic and social impact. But, basically, when we compare the seasons, we talk more about the intensity and the number of storms.

The number of storms, even though we have seen lately the 2020 season and the 2021 season all had a record number of hurricanes, 2020 was first in number of performed storms and 2021 was third. That is not a pattern that is scientifically supported as of yet. Even though we are seeing a trend but, at this point, we need more confirmation from the science about the number of storms.

Colleen: So, how long have we been tracking hurricanes?

Astrid: Tracking hurricanes, as we know it now, to actually see and model where the hurricanes are going and where they can make landfall and how can they turn and twist is only since the early 1900s. Before the 1900s, tracking hurricanes was hit and miss. Since the 1800s, early 1800s, a lot of information came from ships that saw storms and told of what was coming and what they had seen. But that didn't allow for forecasting. Forecasting, in the 1800s, was mostly in the Caribbean. And there is a beautiful history about it, about Jesuit father in Cuba, named Benito Vines actually. And he was the one who started really tracking tropical storms and hurricanes from the Caribbean. No wonder he was in the Caribbean, right, it's such a hot spot for hurricanes and tropical storms. But he used a lot of observations and his observations proved true. And a lot of the people who were more science-based, who didn't have his background or were not where he was, many times did not believe his forecasts. But with time, that proved to be very accurate.

Nonetheless, it was only in the mid 1900s that we started having better information because of the methods of communication that came through. There was the underwater cables and there was all kinds of radio communications that allowed people to actually tell other places that the hurricane was going that way. And only in the 1990s actually the resolution of the models that we used for hurricanes, it was only the 1990s that tracking hurricanes became more accurate and we can actually really tell how a hurricane is developing and where it's going. Even though many times they cannot say still how strong it's gonna be. Particularly in this time of climate change when there hurricanes may traverse or not super hot water. So, depending on the track that it takes, it may intensify more or intensify less.

Colleen: So, tell me, what did you see this past year, the 2021 hurricane season, along the East Coast and the Gulf Coast?

Astrid: Well, interestingly, the East Coast was largely spared direct hits from any landfalling storms or hurricanes. But it had a lot of wind and a lot of rain, including tornadoes all the way up to the Northeast and New York, which is a rare occurrence. But a lot of these storms and rain and tornadoes were because storms made landfall in the Gulf and in other areas. And after they made landfall, the storm continued over land and causing all this rain and all this wind and all this...actually, there was a lot of destruction, particularly on the path of Hurricane Ida. Which was very interesting. But the East Coast itself was largely spared a direct hit, a bad hit.

But the fact that the East Coast did not see a direct hit, a bad hit, this year, cannot really be seen as a trend. Because there was a study that, just this year, found that worse hurricane outcomes are likely for the East Coast. That hurricanes coming and getting to the East Coast may be not only more common but they also may bring more rain because there is a pattern that has been observed, the hurricanes stalling when they come to land, when they approach land. So, if they stall, they stay in an area for several days. And that dumps a lot of rain and that can cause a lot of destruction and economic and social damage. So, the East Coast, this year, I'm gonna say in quotation marks again, "got lucky" but still there was quite a bit of impact, even if not direct.

Colleen: Astrid how did the Gulf region make out this last hurricane season?

Astrid: The Gulf was a completely different story because Hurricane Ida was only one of the seven hurricanes in 2021 that tracked somewhere in the Gulf. They were somewhere in the Gulf. And five of them made landfall. Well, in 2020, eight storms made landfall in the Gulf.

So, we kind of can't help but have that feeling that the Gulf is being hit repeatedly. And, in fact, a study, also this year, found that most coastal regions in the United States had an increased [inaudible] for landfalling tropical cyclones that come one after another, sequential tropical cyclones. And tropical cyclones are, what we call, the storms, the tropical storms that lead to hurricanes. So, not always they become hurricanes but they are called tropical cyclones.

They found that Florida and Louisiana are more likely than most regions, in the United States, to experience sequential landfalling tropical cyclones, tropical storms or hurricanes. And not only that but they found that the chance of the time between storms hitting is also smaller, that the likelihood of being 10 days or fewer between storms hitting will be increased in this century. So, that feeling that the Gulf is being hit over and over again and that it's hit and then it's hit again soon after may actually have some scientific basis. And that's not a good thing, right?

Colleen: So, Astrid, can you talk a little bit about the science that is telling us that?

Astrid: The science that tells us that, they evaluate the pattern of the hurricanes and the tracks of the hurricanes and what made them develop and what made them be of a certain intensity. And they use models with characteristics of the atmosphere to determine if those are gonna be more likely in the future, if that was just a one off.

So, by using the models, by using the statistical analysis of probability of certain storms forming under the same circumstances, they can evaluate the likelihood of that happening again. And since the circumstances that they are putting into the models are more likely to continue to happen with global warming, they can tell that certain types of storms or certain periods of occurrence or certain intervals between storms will be more likely also.

For the models, for instance, they use past events to inform what can happen in the future. So, Hurricane Harvey, Hurricane Ida, what were the conditions under which it formed? It formed under this condition of temperature, these conditions of wind, these conditions of sea temperature, and these conditions of water vapor. So, they put all this together and then they have projections to the future of temperature, of temperature of the ocean under different greenhouse-gas emissions scenarios. And they can tell that, under certain projections of global warming, these conditions are gonna be more common or are gonna be more likely to occur. And if they occur, then it's likely that a storm of that with that characteristic of those characteristics will be likely to form.

Colleen: I mean, do you public awareness and belief in climate change increasing as we see more and more devastating storms and impacts of climate change?

Astrid: It is. It is. There is an organization, the Yale Program on Climate Change Communication, they have been polling the United States' population on climate change beliefs and views and perceptions for years now. And just this year, one of their polls, their latest poll showed that the majority of the United States' population, over 50%, say that they have personally experienced the effects of global warming. And this is huge. And three-quarters of the populations, 76%, say that they think global warming is happening. So, this is a big change from a decade ago where a lot of people did not think it was happening or wasn't sure or had not even experienced the effects of global warming.

In fact, just two years ago, one of their polls showed that a lot of people said, "Oh, I believe global warming is happening but I don't think it's going to affect me personally." Which was kind of amazing, right? I mean, "It's happening but I'm not gonna feel the effect, it's for other people, it's for vulnerable people, it's for people in other continents, in other countries." So, this awareness of climate change and the awareness of the impact of climate change on weather, in the United States, is really good. It's happening, it's

So, if we do everything now that we possibly can, what will future hurricane seasons look like? Is there any dialing back the severity that we see now?

Astrid: Oh, yes, it's possible to dial back. It's gonna take time and it's gonna take a lot of efforts to reduce emissions. There's models that show that a reversal of trends that we are seeing now is possible if we achieve zero emissions. Now, achieving zero emissions is not an easy thing to do, right? Because there will be no emissions from anything. And we know that there are lots of emissions from forests, from burning, from all kinds of things. Most of the efforts these days are focusing on net zero, which means emissions that go into the atmosphere are counter balanced with emissions that go out, in some manner. Or a lot of the efforts are focusing only on reducing that emissions that go in.

So, achieving zero emissions is something that is not likely. But if we achieved zero emissions, if emissions stopped completely and went down to zero, actually global warming could be reversed and could start slowing down significantly. And a lot of these trends that are fueled by global warming could be reversed. However, if the trends we are seeing now of "business as usual" and continuing to pump greenhouse-gas emissions into the atmosphere, not only future hurricane seasons will likely be worse in terms of the intensity of the hurricanes at least, which is what we know is connected with these human-caused global warming, but other things also, you know, may continue to happen. So, it's important and essential that we reduce emissions and we don't go on "business as usual."

Colleen: Right. And, so, what you were saying before was we can't stop emitting everything but we could get to a point where we are only putting in what we can take out so there's sort of a zero sum?

Astrid: Yes, net zero. Yeah. And the focus currently is to reach net zero by mid-century to try to contain global warming to below 2 degrees Celsius. Which is in accordance to the Paris Agreement, which is to keep it well below 2 degrees Celsius, preferably at 1.5 degrees.

Colleen: Astrid, climate change is really heavy and hard to work on. What gives you hope in the work that you do?

Astrid: I am a very optimistic person in everything in my life, in general. When it comes to climate change, there is a lot of instances where I think, "We're doomed. There's no way anything's gonna happen." But then some things happen and you draw hope from them. I draw hope from the Youth Movement. I draw hope from the increased awareness of climate change and the polls that we see. I draw hope from small steps, which should be bigger but they are still small. But I draw hope from the small steps on things like the conference of parties, the COP meetings on climate change that happen every year where they make decisions, like they did this year. This year, they met and they decided to reduce methane emissions, they talked about reducing fossil-fuel emissions. For the first time actually, they never mentioned of fossil fuels in the official proceedings of these meetings. And for the first time they mentioned it.

There is a lot of things that, put together, gives me hope. But specifically, it's a hard call to be hopeful. You know, it's not a Pollyanna-type thing, you have to really dig for good reasons. And you have to give into grief also many times. You have to give into your feelings. You cannot be above all because, if you try to not feel it as a human being, the part of your work that impacts humanity, you are likely to really break apart. You know, so, it's a roller coaster.

Colleen: I just, I want to thank you so much for the work that you do but also for your honesty and talking about the difficulties of working on climate change. It is really hard but I hope your hopeful message will really resonate with people.

Astrid: I hope so too. I talk with a lot of people and I give a lot of talks and I communicate climate change and climate science to a lot of people in a lot of different audiences. And thankfully, I usually get feedback such as, "Your hope is contagious. You are really into this," you know, "your excitement about working with this and getting things done is really good and impactful." And I think, I hope, I like to think that it makes a difference.

Colleen: I think it definitely makes a difference. Well, Astrid, thank you so much for joining me on the podcast, it's been great talking to you.

Astrid: Thank you so much for having me. And we're gonna keep the fight, we're not giving up. Never give up, never surrender.

Colleen: Absolutely not.

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