It’s a well-worn joke to question the validity of global warming from the depths of an extreme winter.
But the understanding of climate change continued to grow this week, as new research published in the journal Nature described two more ways the Earth’s weather has abruptly changed in the last half-century.
In one paper, scientists found that the timing of seasons has crept forward around the world, meaning early relief from winter’s chill but also disruptions of the planet’s ecosystems.
In the other, researchers discovered that temperatures are rising in more of Antarctica than previously thought, countering a favorite argument of climate-change skeptics.
Taken together, the new research adds weight to the argument that the Earth’s climate has changed in dramatic, startling and worrisome ways over the last 50 years, implicating humans and their technology in the shift.
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If temperatures continue to rise in Antarctica, the continent’s ice sheet could begin melting, causing sea levels to rise around the world, scientists warn.
For a decade, climate researchers have argued about temperature change in Antarctica, the coldest place on Earth.
The thin peninsula stretching from the northwest corner of the continent is one of the fastest-warming locations in the world. But scientists also found that the rest of the continent had cooled during the 20th Century, a fact seized upon by climate-change skeptics.
Now new research has clarified the picture, showing that western Antarctica has warmed at a rapid rate over the last 50 years and eastern Antarctica has also warmed, but more slowly. The study, published Thursday, used satellites to expand upon temperature information measured at Antarctic weather stations.
In western Antarctica, temperatures are rising at a rate of 0.17 degrees Celsius each decade, almost double the average warming rate around the globe for the last century, the study found. Most of the warming was found to occur in winter and spring.
Should the warming continue, the millions of miles of ice covering Antarctica could begin to melt, causing sea levels around the world to rise in the long term, said lead author Eric Steig, a climatologist at the University of Washington.
“This warming means we can’t be complacent about thinking the West Antarctica ice sheet is invulnerable,” Steig said.
“It will eventually melt if warming like this continues.”
Scientists who had previously documented cooling across Antarctica’s interior applauded the research as providing valuable data that could help predict the impact of further Antarctic warming on the Earth’s climate.
Among them is Peter Doran, a climatologist at the University of Illinois at Chicago, who said his research has been falsely distorted by those who doubt climate change is happening.
The key issue, he said, is not whether Antarctica as a whole is warming or cooling, because even partial warming is enough to cause alarm.
“Really what’s important is how does this feed into models as far as sea-level rise,” Doran said. “The parts that are warming are contributing to sea rise regardless of what’s happening on the rest of the continent.”
Doran said he hopes the new research will help convince the public of the scientific consensus on climate change.
According to a survey of Earth scientists he conducted with fellow UIC researcher Maggie Kendall Zimmerman, 90 percent believe that mean global temperatures have risen since 1800, and 82 percent say human activity has been a significant contributing factor.
The survey went to more than 10,000 scientists, and more than 3,000 responded. The results appeared this week in the science newspaper EOS.
“There are a handful of doubters you see on the news all the time that keep saying it’s not real, but really, the vast majority of the climate scientists say it’s real,” Doran said. “I think that’s a powerful conclusion.”
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Over the last 50 years, spring has inched earlier by almost two days, a new study finds. Scientists warn such seasonal drift could have dire ecological results.
In the throes of a severe winter, an earlier spring may seem welcome. But be careful what you wish for.
Though researchers reported Wednesday that spring indeed has inched earlier by almost two days over the last 50 years, scientists warn that such seasonal drift could have catastrophic ecological consequences.
To measure the seasons, the study looked at temperatures in locations around the world and compared them to the Earth’s exposure to sunlight at different times of the year.
How much exposure the Earth receives from the sun as it travels on its orbit mediates the planet’s cyclical warming and cooling. Though that pattern never changes, the timing of seasons has moved forward 1.7 days since 1957, the authors calculated.
Why? Alexander Stine, a University of California at Berkeley graduate student who led the study, suspects the Earth’s solar exposure now affects the planet more quickly, leading to earlier springs and falls.
Normally, changes in the Earth’s surface temperature take about a month to kick in — for example, the hottest day of the year occurs about 30 days after the summer solstice, the longest day of the year.
But various factors may have shortened that lag time, Stine said. Reduced moisture in the soil, for instance, could mean faster changes in temperature because drier soil heats and cools faster, as seen in the desert. More man-made aerosols in the atmosphere may also have an effect by altering how much of the sun’s energy reaches Earth.
Stine said the seasonal change appears to be accelerating, noting that the majority of the drift has occurred since 1981. “Really the last 27 years stand out as being different from anywhere previous in the record,” he said.
The team’s analysis also found a decrease in the difference between average temperatures in summer and winter, predominantly because of higher temperatures during winter.
While warmer winters and earlier springs may sound nice in January, scientists have already observed that changing seasonal patterns are affecting Earth’s plant and animal populations.
Some think the seasons are shifting even more rapidly than the new study suggests.
Mark Schwartz, a University of Wisconsin-Milwaukee climatologist, said his own research on the blooming of lilacs indicates spring is moving earlier by slightly more than a day each decade.
“When these kinds of changes are happening, you start to create a ripple effect,” Schwartz said. “That begins to have ecological implications from the point of view of survival of species.”
“If we’re trying to make projections for how the planet will respond as it warms, one of the things we’re all concerned about is whether there are some surprises that will change the Earth in unexpected ways,” Stine said.
“Most of the surprises we can think of are not real good.”
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“There are a handful of doubters you see on the news all the time that keep saying it’s not real, but really, the vast majority of the climate scientists say it’s real.”
— Peter Doran, a climatologist at the University of Illinois at Chicago
Opinions on climate change
In response to public skepticism of global climate change, UIC researchers polled the experts– earth scientists–to learn their opinions on the phenomenon.
Question: When compared with pre-1800s levels, do you think that mean global temperatures have generally risen, fallen, or remained relatively constant?
90% answered “risen.”
A March 2008 Gallup poll found that just 61% of the general public believes that global warming has already begun.
Question: Do you think human activity is a significant contributing factor in changing mean global temperatures?
82% answered “yes.”
The Gallup poll found only 58% of the general public believes this.
SOURCES: UIC online poll of 10,257 earth scientists, with 3,146 respondents, conducted in late 2008; Gallup poll of 1,012 U.S. adults conducted March 6-9, 2008.
TRIBUNE
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Antarctica: Signs of the Great Thaw
At the end of the Earth, scientists measure the toll of global warming. Read the Tribune series at chicagotribune.com/antarctica
