JOHN YANG: The Paris Olympics opening ceremony is a little less than four weeks away, organizers have set a lofty goal generate less than half the greenhouse gas emissions of the last two Summer Games.

And it's not just the Olympics.

Across the sports world, there's a new opponent climate change.

Jeffrey Brown reports on how the changing climate is changing the game.

JEFFREY BROWN (voice-over): The crack of the bat throw from the outfield on hallowed ground in American sports and Yankee Stadium in the Bronx, New York.

It's time for that great baseball tradition, the pregame warmup.

But these days here is everywhere.

Warm up means something much more.

DR. ALLEN HERSHKOWITZ, NY Yankees Environment Advisor: Every professional sports community in the United States is being affected by climate change.

JEFFREY BROWN (voice-over): Allen Hershkowitz is the environmental science and sustainability adviser for the New York Yankees, the first environmental scientists hired by a pro team across all sports.

At his urging, the Yankees became the first North American pro team to sign a United Nations pledge to bring down greenhouse gas emissions, because he says the stakes are too high.

ALLEN HERSHKOWITZ: So there is an urgency because guess what?

Children are not going to be able to play baseball outside people are not going to be able to play tennis outside.

Something's got to give.

JEFFREY BROWN (voice-over): The last 10 years have been the warmest ever recorded.

It's pushed the globe into new and uncharted territory, and it's pushing sports to its limits.

MADELEINE ORR, Assistant Professor of Sport Ecology, University of Toronto: The big issue with climate change, the one that's at the top of every sport scientists mind right now is heat.

JEFFREY BROWN (voice-over): metal and or as a sports ecologist and author of a new book, "Warming Up: How Climate Change is Changing Sport."

She use baseball to highlight how rising temperatures have fueled the weather disasters that affect sports bottom line.

The powerful thunderstorms that cause rain delays, the churning hurricanes that have completely swamped ballparks, and massive wildfires to bring dystopian scenes and sometimes game postponements.

MADELEINE ORR: You'd be hard pressed to find a facility manager who's not worried about storms and wildfire and heat and all these things they know about it for a very long time, though, the assumption has been Oh, it's a one off.

And that's really a dangerous assumption because you'll clean up that mess and not necessarily put in place the adaptations that are going to help reduce the risks next time.

DANIIL MEDVEDEV, Tennis Player: One player is going to die.

And they're going to see.

JEFFREY BROWN: Indeed sports are trying to adapt from implementing rest periods at the U.S. Open to help players cope with extreme heat to holding the 2019 World Championship marathon in Qatar at midnight to avoid unsafe temperatures.

For baseball, one adaptation roofs taking fans not out to the ballgame but in.

But experts including Madeline or note that adaptations only go so far.

MADELEINE ORR: On the winter side, it's essentially are we going to have a season at all that's the question and it's because we're not getting as much snow and where we are getting snow.

It's just melting too fast.

So the solution for 50 years has been we will make snow artificially and blow it out of these guns.

But you can make snow all you want and if it's not cold enough outside for the snow to stick on the ground, it's going to mountain.

JEFFREY BROWN (voice-over): On the trails of Mount Bachelor in Bend, Oregon Olympian cross country skier Gus Schumacher is living that reality.

He's not able to rely on snow It's been there in the past.

GUS SCHUMACHER, Cross Country Skier: We've shifted our camp a little bit earlier just so we make sure we get on good snow.

JEFFREY BROWN (voice-over): We read Schumacher as he trained for the Alpine Skiing World Cup and the next Winter Olympics.

Conditions on this day, not bad.

But that wasn't the case back in February, when he raised in the American Birkebeiner in northern Wisconsin.

GUS SCHUMACHER: This year was my first year and there was not a drop of snow on the entire length of trail from cable to Hayward like the actual trail was totally dry.

JEFFREY BROWN (voice-over): The warmest winter in 130 years reduce the 50 kilometer race to a manmade loop of entirely artificial snow.

GUS SCHUMACHER: Climate change has dramatically altered the conditions for winter sports including Nordic skiing.

JEFFREY BROWN: Schumacher has grown so concerned that earlier this year, he traded his ski gear for a suit and appeared on Capitol Hill with the advocacy group protect our winters to share his experience.

GUS SCHUMACHER: Rising temperatures have led to shorter and more erratic winter seasons.

With snow cover becoming increasingly unreliable.

DOUG BEHAR, Senior Vice President, Stadium Operations, New York Yankees: We took the opportunity to say these are the things that we continue to try to stay ahead of reducing our carbon footprint.

So big or small, we're turning over every stone.

JEFFREY BROWN (voice-over): Back at the ballpark.

We met Doug Behar, Yankee Senior Vice President of Stadium Operations.

DOUG BEHAR: Natural cooling you can feel the breeze come through.

JEFFREY BROWN (voice-over): He showed us some of the ways the Yankees are trying to mitigate climate change, not just adapt to it.

Starting at the cavernous great hall where fans enter the stadium constructed in an eco-friendly manner.

It doesn't require air conditioning with cooling is required.

JEFFREY BROWN: A little bit like being in the bottom of a ship or something.

JEFFREY BROWN (voice-over): A new water based cooling system is much more energy efficient.

Recycling and compost bins and every concourse packaged food given away to shelters after every game.

All of it leads to a less electricity use and less food waste, which means fewer greenhouse gases that warm the planet.

ALLEN HERSHKOWITZ: 90 percent of our environmental work the fans don't see because they relate to our equipment.

They don't know that we're using LED lights that reduced our lighting emission by 60 percent.

You know a lot of it is invisible.

JEFFREY BROWN (voice-over): What's much more visible Allen Hershkowitz says is the influence sports and athletes have unmilled use.

ALLEN HERSHKOWITZ: Guess what they learned from their sports organization, sports loyalty is handed down generation to Generation, less than 20 percent of Americans regularly follow science, over 80 percent regularly follow sports.

The most influential role models are athletes.

If athletes are selling cars, if they're endorsing banks, if they're selling pizza, why can't they sell environmental literacy?

JEFFREY BROWN (voice-over): The Yankees haven't won a championship since 2009.

But they're off to a great start this year.

They'll be hard sees plenty more to do on and off the field.

DOUG BEHAR: The Yankees are doing our best to try to stay ahead of the curve lead where we can and certainly do all the things that are necessary to be productive and responsible.

JEFFREY BROWN: While winning championships.

DOUG BEHAR: Absolutely.

JEFFREY BROWN (voice-over): For PBS News Weekend.

I'm Jeffrey Brown at Yankee Stadium in the Bronx.