(gentle guitar strumming) - Who doesn't like snow?

It's beautiful, it's fun and it might even mean a day off of school.

But, in a series about natural disasters and climate, (alarm beeps) (car crashes) we definitely need to cover this one.

That's because even a very small amount of ice and snow can really ruin your day if you're not ready for it.

Now, you'd think that our planet's warming climate would mean the end of winter, and scientists used to agree, but then something really unexpected happened.

While warming temperatures do lead to milder winters, on average, many locations in the mid-latitudes started to experience record snowfall events.

Even with Arctic Sea ice extent at record lows, Boston just experienced its snowiest decade since record keeping began.

In this episode, we're gonna explain how average temperatures can be warming while changes in the Arctic might actually be making winters in some areas, more severe, at least for the time being.

And as always, we'll talk to experts about how to prepare, no matter where you live.

(mellow music) (wind whistling) There's a cow right there, but you can't see it (chuckles).

This is just insane.

This is literally the worst I think I've ever seen it and the visibility is just horrendous.

- Extreme cold is, by far, he leading cause of weather-related deaths in the U.S. each year.

According to the CDC, around 1,300 people die each year from cold exposure.

And that doesn't even take into account the over 1,800 traffic fatalities from snow and ice on the roadways.

So, even though snow is fun, winter weather is worth preparing for.

For public health officials and transportation managers, a silver lining of a warming climate seem to be milder winters and hopefully, fewer deaths, but then something happened that surprised even the most astute scientists.

- Go back in the year 90s, the models that we used to try to anticipate climate change were showing a decrease in snowfall.

And there was a very famous New York Times article, "The End of Snow?"

how places like New York City (chuckles) won't snow anymore.

- And in much of the world, that's exactly what happened.

Snowpack in the West has been declining for decades.

Nearly every glacier on earth is receding.

But then in the winter of 2011, a very confusing trend began to take shape.

The new year started out with a historic storm and in the North Eastern U.S., the blizzards kept coming year after year.

The most severe snow storms are given a rating category from one through five.

And looking at the frequency of these storms can give us an idea of climate trends.

- If you look at by decade, since 1958, there were eight or less per decade.

Over the most recent decade, there've been 27 of these disruptive snowstorms.

So, more than a tripling of any other previous decade.

- It will become the snowiest decade for the region.

And within that decade, 2015 exceeded all predictions.

It was Stephanie Pollack's first year as secretary of the Massachusetts Department of Transportation.

- We had 110 inches in a single season which was the we've ever had in Massachusetts.

And it was also cold and it didn't warm up in-between and so it didn't melt, and the piles just got higher and higher.

- 110 inches is more than double the previous average annual snowfall of 48 inches.

And it's not just the Northeast.

Winter storms are getting more severe in the Great Lakes, Northern Europe and Central and East Asia.

- It was really hard to clear the sidewalks.

And then the other big issue was our transit system to the point where we had to shut the system down.

And so we had the people who we now call essential workers, but we didn't even have that word in 2015, we were trying to run buses for them but we couldn't run the subways.

And it took weeks to get back to the point where we could run the entire transit system.

I think of the winter of 2015, as one indication that the climate is changing and we have to be prepared to live in a different world.

- If you're confused about this, that makes sense.

It's why most people use terms like climate change or even global weirding, rather than global warming.

First, let's talk about what conditions you need to get a big snow storm on the East Coast, like a nor'easter or a bomb cyclone.

- To get these big snow storms here in the Northeastern U.S., you really need a confluence of events.

You need a northerly flow to bring in the cold air, you need a southerly flow to bring in the moisture, you need strong high pressure blocking to the North to kinda lock it in along the coast.

- To put it in the simplest way possible, air around an area of low pressure spins counter-clockwise and air around an area of high pressure spins clockwise.

When these two meet along with enough cold air and moisture, they work together like gears to batter the East Coast.

But historically, these systems aren't extremely cold, just a few degrees below freezing.

So you'd think that the two degree Fahrenheit rise in global temperatures would make more of these storms simply turn into rain, but that's not what we're seeing.

Instead, there's been more snow and more outbreaks of cold air dipping down into the U.S. Dr. Cohen told us that a leading theory to explain the increase of cold air from the Arctic, has to do with Arctic amplification.

You might remember from our hurricane episode, that the Arctic is warming much faster than the global average, twice as fast, actually.

That's because dark water and land surfaces absorb more of the sun's energy than white, reflective ice.

So, as ice melts, more of these dark surfaces are exposed which amplifies warming, and a quickly warming Arctic, destabilizes the jet stream.

The jet stream is a fast-moving, high altitude wind current that forms where cold and warm air meet.

The greater the temperature difference between these air masses, the stronger the jet stream becomes.

But, when that difference decreases, the jet stream can slow dramatically and dip further South.

There's also a giant mass of swirling cold air high over the Arctic called the polar vortex.

When everything's stable, we don't really notice it.

But, destabilize the jet stream, and the polar vortex becomes wobbly like a top as its rotation slows.

- Instead of just sitting there spinning quietly on the top of the globe over the Northern Pole, now it starts to meander, starts to wander around.

When you have these disruptions of the polar vortex, feels like it's like a dam breaking and the cold air just rushes out into the lower latitudes and mid-latitudes.

You get more amplified flow and more opportunities for snowstorms.

(vehicles humming) - None of this is new, but it's happening more frequently.

And a growing number of scientists like Judah, believe our warming climate is driving the process that provides Boston with enough cold air and moisture to set snowfall records.

("Miro - Hina" by The New Dawn Collective) Boston is relatively well-prepared to deal with harsh winters and there are very few cold exposure deaths each year, but these polar vortex events can push cold and even snow into cities that aren't accustomed to it, which is actually more dangerous.

And in January of 2014, the polar vortex was a major catalyst in the winter weather event that brought just 2.6 inches of snow to Atlanta, crippling one of the nation's largest cities for days.

Children were stuck at school, interstates were clogged, thousands were stuck in their cars for hours.

One mother even gave birth on the side of the highway.

This was a true disaster, all because the lack of timely preparation.

But, who could blame them, right?

The South just isn't accustomed to dealing with winter weather so it doesn't take much for it to become disruptive.

To get some tips on how to stay safe in big snow events, we talked to Peter Murphy from the Oregon Department of Transportation.

- You can go from dry, bare pavement to black ice in a matter of feet, here.

And if you're not prepared for that, you really can end up in a sideways situation and in some cases it can be fatal.

(alarm beeps) (car crashes) And so consciousness of the direction the vehicle's going in, the conditions that we're driving in, is critical, whether you're in New York City, whether you're in Atlanta, whether you're in San Diego or in Portland, Oregon.

Be ready with the right equipment, the right gear.

Just make sure your car is equipped with the right kind of tires.

We like to know that you've done what you can to get a full tank of gas before you've headed out on the road.

Make sure you have that extra stopping distance between yourself and the other car in front of you.

- If you're traveling during winter weather it makes sure to have food and water in your car.

It's also smart to prepare a kit that includes things like an ice scraper, a shovel, gloves, warm clothing, a blanket or sleeping bag, a flashlight, chains for your tires and even a spare cell phone battery.

- But by and large, we're a society that has learned how to stay in place.

COVID has taught us many things; that's one of them.

So, it is always in our power to not go someplace.

(plow blade scraping) - Extreme weather is more than just a traffic problem.

So I'm calling Dr. Stuart Harris to chat with him about what he sees as an emergency physician at Massachusetts General Hospital in Boston.

Hi, Dr. Harris.

What are the most common things you see as an emergency doctor when winter weather gets extreme?

- So, you can think about cold injury in a number of different ways.

One is if your whole body gets cold, what we call hypothermia.

As you get a little bit colder, our brains just don't work very well and people can do crazy things, we call it paradoxical undressing.

They can start taking off layers that they desperately need, people become sluggish and then just aren't able to move.

- [Maiya] Warning signs of hypothermia include shivering, exhaustion, confusion, fumbling hands, memory loss, slurred speech and drowsiness.

Hypothermia is a medical emergency so take action quickly to get warm and get medical help.

- Other types of injury are sometimes very superficial, what we call frostnip or even frostbite, where tissues actually start to freeze.

- [Maiya] Signs of frostbite include white or greyish/yellow skin, skin that feels firm or waxy, and numbness.

The best way to warm up frostbitten skin is with warm water or with body heat, if that's not available.

- [Stuart] We see a lot of falls, people on black ice going down, breaking an ankle, breaking a leg, breaking a wrist.

- As our climate continues to shift, I'm in Atlanta, so we're seeing a lot more of these extreme cold events dip further down to the South.

- Yeah.

- What can people do to best prepare themselves for extreme cold weather?

- So, you're exactly right, as the climate changes, what you thought was normal in Atlanta, or Texas, or Virginia, is not gonna be.

It's critical that we're prepared, the appropriate clothing, that you're being thoughtful about how you travel, that you're adequately hydrated and have access to food.

These are things that we need to be mindful of.

- Lastly, make sure to check out our upcoming episode on creating an emergency pantry for when extreme weather comes your way.