SCOTT SIMON, host: This week, it's wilting heat. But recent months have brought other weather extremes.
SUSAN STAMBERG: The Souris River is cresting today in the flood-battered town of Minot, North Dakota.
UNIDENTIFIED WOMAN: I've never seen so many storms come through our state at one time.
STEVE INSKEEP: Let's go next to Texas, which is suffering from a drought, and the word drought doesn't really capture it. The last nine months...
SIMON: Climate scientists have predicted that global warming will cause more extreme weather events. Has the future arrived? We've called Dr. Martin Hoerling, who's a meteorologist with the National Oceanic and Atmospheric Administration. Dr. Hoerling, thanks for being with us.
Dr. MARTIN HOERLING: Thank you for having me.
SIMON: Hot out there.
(SOUNDBITE OF LAUGHTER)
SIMON: You've heard?
HOERLING: I have felt it.
SIMON: How certain are you that global warming is a contributing factor?
HOERLING: If we look at the planet as a whole, the whole average of all months of the year, we can say with great confidence that the warming of the climate system is pretty much unequivocal, and that's based on observations. The temperature has risen. It's risen beyond what you would expect from chance. When we start looking at smaller scales, so tornadoes for instance, or the flooding rains in the Ohio Valley, there the science has a great challenge in front of it, and that is to understand how climate change would manifest itself either in sign or in magnitude at those small scales.
SIMON: As I don't have to tell you Dr. Hoerling, there are people who wonder how can you talk about global warming when we had what was called snowmageddon last year?
HOERLING: Hmm. Well, you know, I'm going to take us back a little bit. While the heat wave and drought have been going on in the south-central U.S., it has been very wet and very cool, if not cold, in the Pacific Northwest. And so that contrast makes it very confusing to speak about global warming. On the one, hand how can both be happening of opposite signs in such close proximity? And here the story is probably less about global warming in terms of that pattern than it is about another climate phenomenon that has been in place for hundreds of years, perhaps thousands of years as far as one can tell from the data, and that is called La Nina.
SIMON: And does global warming affect this?
HOERLING: Yes. Absolutely. When you ask the question does global warming, the increasing carbon dioxide in the atmosphere, affect weather systems? Yes, the answer would be it does. How does it affect it is the question that we're challenged with. That's where the research challenge is right now. Rather than an event such as the heat wave, I want point to something that's more longer in its time scale and bring it into the current, and that's the Arctic sea ice.
As we speak, the latest update, which came from the National Snow and Ice Data Center, located here in Boulder, indicates that the sea ice extent in the Arctic as of the middle of July was at its historical low, breaking the record that was set in 2007. And temperatures near the Pole are running between 11 and 14 degrees Fahrenheit warmer than normal. Now no one probably complains about that if you're at the Pole. But it's the canary in the coal mine.
In the Arctic we're really looking at climate change and we're looking at very significant impacts of the changing chemistry of our atmosphere.
SIMON: Help us understand Dr. Hoerling, how someone living in Southern Illinois or Missouri, which seems an awful long way, which is an awful long way from the polar ice cap, how might they be affected by the melting that's going on in the Arctic?
HOERLING: In many ways, it's useful to think about this heat wave that we're having - if we can go back to the heat wave...
SIMON: Mm-hmm.
HOERLING: Let's think about that, not necessarily worry about exactly the cause in this instant. But let's think about this as to what would climate look like in about 50 to 100 years in that region, Southern Illinois? The experiments that are used to project climate into the future are indicating that an event, a heat wave of let's say one in 100-year recurrence in the 20th century type of frequency, would happen perhaps once every 10 years, maybe once every five years.
Conditions that are so uncomfortable today - the reason that you're talking to me about this today is people are uncomfortable. If were not adapted to the situation that we're experiencing today, we almost certainly will not be adapted to the temperature conditions that are on the horizon as we go deeper into the 21st century. So it's a good wake-up call for us as to what climate may become as we continue to increase our emissions of carbon dioxide.
SIMON: So what you're suggesting is instead of just putting up with this for a week or two, this might become summer.
HOERLING: The extremes that we are experiencing today may become the normals of the latter half of the 21st century.
SIMON: Dr. Martin Hoerling specializes in climate dynamics at the National Oceanic and Atmospheric Administration in Boulder, Colorado. Thanks so much.
HOERLING: Thank you. Transcript provided by NPR, Copyright NPR.