News

    Greenhouse Gas Speeded Ice Age Melting

    CO2 also plays role in today's warming

    This cross section of an ice core from Antarctica tells scientists the history of the ancient atmosphere.
    This cross section of an ice core from Antarctica tells scientists the history of the ancient atmosphere.

    Multimedia

    Audio
    Rosanne Skirble

    A new study in the Journal Nature provides compelling evidence that carbon dioxide was a major driver of climate change at the end of the last Ice Age.

    That correlation supports the prevailing scientific view that that CO2 is also playing a major role in today’s warming global climate.  

    The study analyzed ice and sediment samples from dozens of locations on every continent to reconstruct variations in global temperature between 20,000 and 10,000 years ago - the end of the last Ice Age.  

    Harvard scientist Jeremy Shakun, the study’s lead author, says climate-change skeptics have long pointed to evidence from Antarctic ice cores that rising levels of C02 in the atmosphere lagged behind the warming climate that marked the end of the Ice Age.

    But Shakun says the new study invalidates that argument by correlating CO2 levels and temperatures all across the prehistoric planet.

    “So you put these two points together, the correlation of global temperature and CO2, the fact that it lags behind the CO2, and it really leaves you thinking that CO2 was the big driver of global warming at the end of the ice age.”

    Other events also helped push the planet out of the ice age. A rare wobble in the Earth’s axis resulted in more sunlight hitting the northern hemisphere. Wind shifted, ice sheets melted, dumping enormous amounts of water into the North Atlantic.

    Shakun says the water flow disrupted global ocean circulation and caused a seesawing of heat between the hemispheres.

    "Antarctica happens to be on the leading end of the warm end of this seesaw, so it warmed first before the CO2 started to rise," he says. “The key thing to realize with this is that this wasn’t associated with the change in global temperature. The south was warming first, but it was at the expense of cooling in the north or just shifting heat around the planet.”  

    Eventually, CO2 released from the deep southern ocean accelerated the warming of the Earth’s atmosphere. Shakun says that ancient story emerges from air bubbles in ice cores, tiny shells in ocean sediment and even pollen at many data points across time.

    “We tried to get records that really are pretty highly resolved so it would have a data point on the order of every several decades out to maybe a few centuries. We didn’t pull in any records that only had data point entry of every thousand or two thousand years. That would just be too fuzzy to really answer what we wanted to answer.”      

    During the end of the last ice age, as the climate warmed, CO2 levels in the atmosphere rose from about 180 parts per million to about 260.

    Shakun says today the CO2 concentration has risen to 392 parts per million - and it’s still climbing.

    “We’ve gone up in the last hundred years about 100 ppm (parts per million). That’s on the same order as the amount we rose at the end of the ice age, which I think puts this in perspective. Clearly it’s not a small amount. Obviously rising CO2 at the end of the ice age had a huge effect on global climate, and so we raised it as much in the last century.”   

    Shakun doesn’t see this trend ending any time soon unless industrial CO2 emissions are reduced at their source: the burning of fossil fuels in power plants, cars and buildings. He says while the research strengthens the link between C02 and the Ice ages, he believes it also reinforces the importance of addressing C02-driven climate change in our own time.

    This forum has been closed.
    Comment Sorting
    Comments
         
    by: Dennis Baker
    April 07, 2012 11:33 AM
    wow 500 characters to share the solution

    no wonder there is a problem

    by: Leslie Graham
    April 06, 2012 9:00 PM
    @ Bunch

    I love your "temps have 'only' risen 0.8C" Yeah - in about a century! And you think it's going to stop now?
    And by what possible stretch of the imagination do you get your absurd "not enough CO2 in the atmosphere to make any difference in temps" meme.
    Did you just make it up on the spur of the moment?

    by: luke
    April 06, 2012 6:45 PM
    In respone to you bunch,
    The increase of CO2 causes the greenhouse effect, this is a long-term change on climate, the increase of temperatures out of the last ice age happened over hundreds, even thousands of years. the current situation with manmade climate change isn't going to increase temperatures over 10 years but over hundres of years. we are putting this earth in a bad place in the future.
    dont think human time, think geological time. earth time.

    by: Bunch
    April 06, 2012 3:51 PM
    the impetus for the warming was the orbit change of planet earth which started the ice melting in the polar regions and the resulting water vapor included with co2 magnified the warming to end the ice age. without the water vapor (clouds), we would still be in the ice age. not enough co2 in the atmosphere to make any difference in temps, today, or then. we now have twice as much as then and temps have only risen .8C. The conclusions that co2 came before warming is not founded in reality.

    Featured Videos

    Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
    Uganda Unveils its First Solar-powered Busi
    X
    July 28, 2016 4:16 AM
    A solar-powered bus described by its Ugandan makers as the first in Africa has made its public debut. Kiira Motors' electric bus, Kayoola, displayed recently at a stadium in Uganda's capital. From Kampala, Maurice Magorane filed this report narrated by Salem Solomon.
    Video

    Video Uganda Unveils its First Solar-powered Bus

    A solar-powered bus described by its Ugandan makers as the first in Africa has made its public debut. Kiira Motors' electric bus, Kayoola, displayed recently at a stadium in Uganda's capital. From Kampala, Maurice Magorane filed this report narrated by Salem Solomon.
    Video

    Video Silicon Valley: More Than A Place, It's a Culture

    Silicon Valley is a technology powerhouse and a place that companies such as Google, Facebook and Apple call home. It is a region in northern California that stretches from San Francisco to San Jose. But, more than that, it's known for its startup culture. VOA's Elizabeth Lee went inside one company to find out what it's like to work in a startup.
    Video

    Video Immigrant Delegate Marvels at Democratic Process

    It’s been a bitter and divisive election season – but first time Indian-American delegate Dr. Shashi Gupta headed to the Democratic National Convention with a sense of hope. VOA’s Katherine Gypson followed this immigrant with the love of U.S. politics all the way to Philadelphia.
    Video

    Video Philadelphia Uses DNC Spotlight to Profile Historic Role in Founding of United States

    The slogan of the Democratic National Convention now underway in Philadelphia is “Let’s Make History Again” which recognizes the role the city played in the foundation of the United States in the 18th century. As VOA’s Kane Farabaugh reports, local institutions are opening their doors in an effort to capitalize on the convention spotlight to draw visitors, and to offer more than just a history lesson.
    Video

    Video A Life of Fighting Back: Hillary Clinton Shatters Glass Ceiling

    Hillary Clinton made history Thursday, overcoming personal and political setbacks to become the first woman to win the presidential nomination of a major U.S. political party. If she wins in November, she will go from “first lady” to U.S. Senator from New York, to Secretary of State, to “Madam President.” Polls show Clinton is both beloved and despised. White House Correspondent Cindy Saine takes a look at the life of the woman both supporters and detractors agree is a fighter for the ages.
    Video

    Video Dutch Entrepreneurs Turn Rainwater Into Beer

    June has been recorded as one of the wettest months in more than a century in many parts of Europe. To a group of entrepreneurs in Amsterdam the rain came as a blessing, as they used the extra water to brew beer. Serginho Roosblad has more to the story.
    Video

    Video First Time Delegate’s First Day Frustrations

    With thousands of people filling the streets of Philadelphia, Pennsylvania for the 2016 Democratic National Convention, VOA’s Kane Farabaugh narrowed in on one delegate as she made her first trip to a national party convention. It was a day that was anything but routine for this United States military veteran.
    Video

    Video Commerce Thrives on US-Mexico Border

    At the Democratic Convention in Philadelphia this week, the party’s presumptive presidential nominee, Hillary Clinton, is expected to attack proposals made by her opponent, Republican presidential nominee Donald Trump, to build a wall along the U.S.-Mexico border. Last Friday, President Barack Obama hosted his Mexican counterpart, President Enrique Peña Nieto, to underscore the good relations between the two countries. VOA’s Greg Flakus reports from Tucson.
    Video

    Video Film Helps Save Ethiopian Children Thought to be Cursed

    'Omo Child' looks at effort of African man to stop killings of ‘mingi’ children
    Video

    Video London’s Financial Crown at Risk as Rivals Eye Brexit Opportunities

    By most measures, London rivals New York as the only true global financial center. But Britain’s vote to leave the European Union – so-called ‘Brexit’ – means the city could lose its right to sell services tariff-free across the bloc, risking its position as Europe’s financial headquarters. Already some banks have said they may shift operations to the mainland. Henry Ridgwell reports from London.
    Video

    Video Recycling Lifeline for Lebanon’s Last Glassblowers

    In a small Lebanese coastal town, one family is preserving a craft that stretches back millennia. The art of glass blowing was developed by Phoenicians in the region, and the Khalifehs say they are the only ones keeping the skill alive in Lebanon. But despite teaming up with an eco-entrepreneur and receiving an unexpected boost from the country’s recent trash crisis the future remains uncertain. John Owens reports from Sarafand.
    Video

    Video Migrants Continue to Risk Lives Crossing US Border from Mexico

    In his speech Thursday before the Republican National Convention, the party’s presidential candidate, Donald Trump, reiterated his proposal to build a wall along the U.S.-Mexico border if elected. Polls show a large percentage of Americans support better control of the nation's southwestern border, but as VOA’s Greg Flakus reports from the border town of Nogales in the Mexican state of Sonora, the situation faced by people trying to cross the border is already daunting.

    Special Report

    Adrift The Invisible African Diaspora