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Negotiations in Paris are driven by predictions of how unchecked global warming would transform our planet decades and centuries from now. NPR's Nell Greenfieldboyce wanted to know, how can researchers be so sure of what'll happen that far off in the future?
NELL GREENFIELDBOYCE, BYLINE: The Earth is big. Its climate is complicated. To understand it, you need something big and complicated.
PHIL WEBSTER: OK, so it is very noisy in here.
GREENFIELDBOYCE: Phil Webster is taking me into a windowless room full of hulking black monoliths. This is NASA's Center for Climate Simulation in Maryland.
WEBSTER: The computers generate a lot of heat, so there's a lot of fans, a lot of cooling and stuff that's in it.
GREENFIELDBOYCE: Webster runs this supercomputing center with help from a guy nicknamed in the alpha geek, Dan Duffy. Duffy says these huge black boxes are filled with thousands of computers like the one on your desk at work, all connected to create one massive beast. How powerful is it?
DAN DUFFY: If you took everybody on the face of the Earth - all 7.3, 7.4 billion people - and you had them multiply two numbers together every single second for 145 hours total. That's what this entire computing center can do in one second.
GREENFIELDBOYCE: OK. That is a mind-boggling amount of number crunching. And when this thing runs a climate simulation, it takes months for it to spit out an answer. To find out what exactly is going on inside there, I went to New York City.
And if you ever watch the TV show "Seinfeld," you'll know exactly where I am. I'm standing right outside that restaurant, the corner restaurant the gang used to hang out at. Right above this restaurant are the offices of one of the world's foremost climate modelers.
UNIDENTIFIED MAN: Hi.
GREENFIELDBOYCE: Is this Goddard Institute for Space Studies?
UNIDENTIFIED MAN: Yes.
GREENFIELDBOYCE: I'm here to see Gavin Schmidt.
The first thing I see in Gavin Schmidt's office is a black board on the wall that's covered with equations. These scientific scribbles were left by the last guy who worked here, a famous climate change researcher named Jim Hansen. For someone like me, it's totally incomprehensible, but this is the language these folks use to talk about everything that makes up our climate.
What is a climate model, really? Is it just a bunch of equations?
GAVIN SCHMIDT: So the climate model - you're best thinking of it as an encapsulation of all the things that we can go out and measure, right? So we can go and measure how much sunlight reflects off the sea ice. We can go and measure how much water you need to have in the air before you form a cloud. You can go and measure how the winds affect the ocean currents, right? Those are physical processes that we've been observing for hundreds of years. A climate model encapsulates each of those processes, the ones that we think of as being important, and it links them all together.
GREENFIELDBOYCE: Researchers created the first primitive models of Earth's climate back in the 1960s on computers that used punch cards. Schmidt says there's now around 30 different groups worldwide doing climate simulations using supercomputers. And the consensus is, if greenhouse gas emissions keep rising, the world will look different. On his desktop computer screen, Schmidt pulls up one graphic of the globe that's color-coded for temperature. I watch it get redder and redder as the years tick up into the future.
SCHMIDT: So you're looking at a situation where there's very little ice left in the Arctic. You're looking at temperature changes on land that are the equivalent of, you know, moving south by a couple of thousand miles. So you know, climates of New York would have the climates of Miami.
GREENFIELDBOYCE: How confident do you feel about those kinds of predictions?
SCHMIDT: That's a great question.
GREENFIELDBOYCE: He says, well, these simulations are able to basically re-create the Earth's climate as we see it today.
SCHMIDT: What you see are patterns in the models that reflect what you see in the real world. We know that we must be getting something fundamentally correct in order for that to happen.
GREENFIELDBOYCE: He rattles off a bunch of other reasons to feel confident. Can these models re-create past events like the last Ice Age?
SCHMIDT: Yes, they do.
GREENFIELDBOYCE: Do models created independently by different groups show similar patterns?
SCHMIDT: Yes, they do.
GREENFIELDBOYCE: Yes. Do the models make pretty good short-term predictions? Yeah.
SCHMIDT: So models have verifiable skill. They're not perfect, but nonetheless, they make useful predictions.
GREENFIELDBOYCE: Whether or not the world actually will use them - that's what diplomats are hashing out in Paris right now. Nell Greenfieldboyce, NPR News.
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