The past decade has seen years hotter than all but the most extreme outliers in the past 11,000 years, according to a climate study led by UW researchers and recently published in “Nature.”

Paleoclimatologist Bryan Shuman of UW’s Department of Geology and Geophysics said the study found temperatures in recent decades were hotter than the average temperature of any century since the last ice age.

“Our research shows that climate is always changing,” Shuman said. “It is something we have to prepare for. Whether it’s going to get warmer or colder in the future, we should always plan that climate’s not going to be the same as it was in the past. At the same time, this highlights the fact that there is a real risk that we’re moving rapidly to conditions that are very different from the ones we’ve experienced.”

Shuman and his colleagues — among them, fellow UW paleoclimatologist Jeremiah Marsicek — examined fossil pollen from 642 bodies of water across Europe and North America, including some locations in Wyoming. The researchers could use this data to extrapolate the climate of given places and times, Shuman said, because plants require different temperatures to grow.

“You can do this today,” he said. “If you took pollen data from plants growing in an area and knew something about the temperature requirements for those plants, you could make a reasonably accurate estimate about what the temperature is where you are. So, we’re just doing that back through time, using ancient samples.”

Drawing this data from hundreds of separate locations, researchers were able to create an average temperature estimate for North America and Europe every century going back 11,000 years.

“This provides a really interesting context for where our current temperatures are,” Shuman said. “The data suggests that we really are pretty rapidly moving outside the range of temperatures we have experienced over the last 11,000 years.”

Recent average temperatures are .5 degrees Fahrenheit warmer than the hottest averages assessed for the last 11 millennia, according to the study — which is more significant than it might at first seem, Shuman said.

The last ice age — during which a massive ice sheet covered most of Canada and large portions of the northern United States — had an average temperature just 3.5 degrees colder than today, Shuman said.

“And the model projections for the end of the century have 4 degrees of warming,” Shuman said. “So, if those forecasts pan out to be true, by the end of the century, we will be as different from today as the ice age is from today, except we will be moving in a warmer direction. When we talk about a .5-degree temperature change, it doesn’t sounds like very much, but it’s a substantial fraction of the difference between modern conditions and the ice age.”

He added .5-degree changes are significant in climate research — compared to the relative unimportance of a .5-degree change in weather — because climate is more predictable.

“When we talk about climate, of course, it is fundamentally different from what we mean by weather, because weather can change minute-to-minute, hour-to-hour,” Shuman said. “The climate is the average of all those conditions over, say, 30 years or longer and so when we talk about climate change, we’re not talking about, ‘Is there going to be a storm tomorrow?’ We’re talking about, ‘Is the average going to be different in the future?’”

The study closely matches climate simulations run by the National Center for Atmospheric Research, which was conducted independently, according to a UW news release.

Shuman said he was motivated to study fossil pollen by a desire to understand how the climate varies from age to age, but the research does encourage discussion about possible solutions.

“The point of the study was really just to understand the process of the climate change in a general way,” he said. “But to the degree that those results show that we are rapidly moving toward a warmer climate than we’ve had through all of human civilization, I think it raises the point that we should really seriously be discussing this.”

The study offers no prescriptions, but rather a diagnosis, Shuman said.

“I feel like a doctor who’s studying cancer and recognizes that a patient has cancer,” he said. “It’s hard for me to tell that patient exactly what they should do, but I need to make them aware that there’s a problem.”

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