News / Science & Technology

Experts Sure Global Warming Manmade, But Predictions Elusive

The Sheldon Glacier with Mount Barre in the background, is seen from Ryder Bay near Rothera Research Station, Adelaide Island, Antarctica, in this NASA/British Antarctic Survey photo, July 15, 2013.
The Sheldon Glacier with Mount Barre in the background, is seen from Ryder Bay near Rothera Research Station, Adelaide Island, Antarctica, in this NASA/British Antarctic Survey photo, July 15, 2013.
Reuters
Climate scientists are surer than ever that human activity is causing global warming, according to leaked drafts of a major U.N. report, but they are finding it harder than expected to predict the impact in specific regions in coming decades.
 
The uncertainty is frustrating for government planners: the report by the Intergovernmental Panel on Climate Change (IPCC) is the main guide for states weighing multi-billion-dollar shifts to renewable energy from fossil fuels, for coastal regions considering extra sea defenses or crop breeders developing heat-resistant strains.
 
Drafts seen by Reuters of the study by the U.N. panel of experts, due to be published next month, say it is at least 95 percent likely that human activities - chiefly the burning of fossil fuels - are the main cause of warming since the 1950s.
 
That is up from at least 90 percent in the last report in 2007, 66 percent in 2001, and just over 50 in 1995, steadily squeezing out the arguments by a small minority of scientists that natural variations in the climate might be to blame.
 
That shifts the debate onto the extent of temperature rises and the likely impacts, from manageable to catastrophic. Governments have agreed to work out an international deal by the end of 2015 to rein in rising emissions.
 
“We have got quite a bit more certain that climate change ... is largely manmade,” said Reto Knutti, a professor at the Swiss Federal Institute of Technology in Zurich. “We're less certain than many would hope about the local impacts.”
 
And gaging how warming would affect nature, from crops to fish stocks, was also proving hard since it goes far beyond physics. “You can't write an equation for a tree,” he said.
 
The IPCC report, the first of three to be released in 2013 and 2014, will face intense scrutiny, particularly after the panel admitted a mistake in the 2007 study which wrongly predicted that all Himalayan glaciers could melt by 2035. Experts say the error far overestimated the melt and might have been based on a misreading of 2350.
 
The new study will state with greater confidence than in 2007 that rising manmade greenhouse gas emissions have already meant more heatwaves. But it is likely to play down some tentative findings from 2007, such as that human activities have contributed to more droughts.
 
Almost 200 governments have agreed to try to limit global warming to below 2 degrees Celsius (3.6 Fahrenheit) above pre-industrial times, seen as a threshold for dangerous changes including more droughts, extinctions, floods and rising seas that could swamp coastal regions and entire island nations.
 
The report will flag a high risk that global temperatures will increase this century by more than that level, and will say that evidence of rising sea levels is now “unequivocal”.
 
For all that, scientists say it is proving harder to pinpoint local impacts in coming decades in a way that would help planners.
 
Drew Shindell, a NASA climate scientist, said the relative lack of progress in regional predictions was the main disappointment of climate science since 2007.
 
“I talk to people in regional power planning. They ask: 'What's the temperature going to be in this region in the next 20-30 years, because that's where our power grid is?”' he said.
 
“We can't really tell. It's a shame,” said Shindell. Like the other scientists interviewed, he was speaking about climate science in general since the last IPCC report, not about the details of the latest drafts.

Warming slowing down

The panel will try to explain why global temperatures, while still increasing, have risen more slowly since about 1998 even though greenhouse gas concentrations have hit repeated record highs in that time, led by industrial emissions by China and other emerging nations.
 
An IPCC draft says there is “medium confidence” that the slowing of the rise is “due in roughly equal measure” to natural variations in the weather and to other factors affecting energy reaching the Earth's surface.
 
Scientists believe causes could include: greater-than-expected quantities of ash from volcanoes, which dims sunlight; a decline in heat from the sun during a current 11-year solar cycle; more heat being absorbed by the deep oceans; or the possibility that the climate may be less sensitive than expected to a build-up of carbon dioxide.
 
“It might be down to minor contributions that all add up,” said Gabriele Hegerl, a professor at Edinburgh University. Or maybe, scientists say, the latest decade is just a blip.
 
The main scenarios in the draft, using more complex computer models than in 2007 and taking account of more factors, show that temperatures could rise anywhere from a fraction of 1 degree Celsius (1.8 Fahrenheit) to almost 5C (9F) this century, a wider range at both ends than in 2007.
 
The low end, however, is because the IPCC has added what diplomats say is an improbable scenario for radical government action - not considered in 2007 - that would require cuts in global greenhouse gasses to zero by about 2070.
 
Temperatures have already risen by 0.8C (1.4F) since the Industrial Revolution in the 19th century.
 
Experts say that the big advance in the report, due for a final edit by governments and scientists in Stockholm from Sept. 23-26, is simply greater confidence about the science of global warming, rather than revolutionary new findings.

Rising sea levels

“Overall our understanding has strengthened,” said Michael Oppenheimer, a professor at Princeton University, pointing to areas including sea level rise.
 
An IPCC draft projects seas will rise by between 29 and 82 cm (11.4 to 32.3 inches) by the late 21st century - above the estimates of 18 to 59 cm in the last report, which did not fully account for changes in Antarctica and Greenland.
 
The report slightly tones down past tentative findings that more intense tropical cyclone are linked to human activities. Warmer air can contain more moisture, however, making downpours more likely in future.
 
“There is widespread agreement among hurricane scientists that rainfall associated with hurricanes will increase noticeably with global warming,” said Kerry Emanuel, of the Massachusetts Institute of Technology.
 
“But measuring rainfall is very tricky,” he said.

You May Like

Jihadist Assassin says Goal of Tunisia Murders Was Chaos

Abu Muqatil at-Tunusi’s remarks in a propaganda interview also cast light on attack on Bardo Museum More

Russia Denies License to Tatar-Language TV Station in Crimea

OSCE official says denial shows 'politically selective censorship of free and independent voices in Crimea is continuing' More

Kenyan Startups Tackle Expensive Remittances Through Bitcoin

Some think services could give Western Union a run for its money, though others say it’s still got a long way to go More

This forum has been closed.
Comment Sorting
Comments
     
by: Kitagawa Keikoh from: Daikanyama, JPN
August 17, 2013 7:13 PM
Is the amount of CO2 reducing from the 1990's when scientists started to say we need to reduce it ?
Have our effort to reduce CO2 been effective since then ?

The answer is NO, because reducing CO2 means reducing the production of total amount of oil, and there is no incentive to oil producing countries to do so.

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
For Obama, It's More Business Than Friendships With World Leadersi
X
Aru Pande
April 01, 2015 9:09 PM
The rift between President Barack Obama and Israeli Prime Minister Benjamin Netanyahu has put a spotlight on the importance of the American leader’s personal relationships with other world leaders and what role such friendships play in foreign policy. VOA's Aru Pande reports.
Video

Video For Obama, It's More Business Than Friendships With World Leaders

The rift between President Barack Obama and Israeli Prime Minister Benjamin Netanyahu has put a spotlight on the importance of the American leader’s personal relationships with other world leaders and what role such friendships play in foreign policy. VOA's Aru Pande reports.
Video

Video Buhari: Nigeria Has ‘Embraced Democracy’

Nigeria woke up to a new president-elect Wednesday, Muhammadu Buhari. But people say democracy is the real winner as the country embarks on its first peaceful handover of power since the end of military rule in 1999. VOA’s Anne Look reports from Abuja.
Video

Video Tiny Camera Sees Inside Blood Vessels

Ahead of any surgical procedure, doctors try to learn as much as possible about the state of the organs they plan to operate on. A new camera developed in the Netherlands can now make that easier - giving surgeons an incredibly detailed look inside blood vessels, all the way to the patient’s heart. VOA’s George Putic has more.
Video

Video Latin American Groups Seek Fans at Texas Music Festival

Latin American music groups played all over Austin, Texas, during the recent South by Southwest festival, and some made fans out of locals as well as people from around the world who had come to hear music. Such exposure can boost such groups' image back home. VOA’s Greg Flakus reports.
Video

Video Stockton Community, Police, Work to Improve Relations

Relations are tense between minority communities and police departments around the United States following police shootings that have generated widely-publicized protests. VOA's Mike O’Sullivan reports from Stockton, California, where police and community groups are working toward solutions, with backing from Washington.
Video

Video Indiana Controversy Highlights Divergent Meanings of Religious Freedom

Indiana’s state government has triggered a nationwide controversy by approving a law that critics say is aimed at allowing discrimination against gays and lesbians. The controversy stems from divergent notions of religious freedom in America. VOA's Jerome Socolovsky reports.
Video

Video Report: State of Black America a 'Tale of Two Nations'

The National Urban League has described this year's "State of Black America" report as a "tale of two nations." The group's annual report, released earlier this month (March), found that under an equality index African Americans had only 72% parity compared to whites in areas such as education, economics, health, social justice and civic engagement. It’s a gap that educators and students at Brooklyn’s Medgar Evers College are looking to close. VOA's Daniela Schrier reports from the school.
Video

Video Film Tells Story of Musicians in Mali Threatened by Jihadists

At this year's annual South by Southwest film and music festival in Austin, Texas, some musicians from Mali were on hand to promote a film about how their lives were upturned by jihadists who destroyed ancient treasures in the city of Timbuktu and prohibited anyone from playing music under threat of death. As VOA’s Greg Flakus reports from Austin, some are afraid to return to their hometowns even though the jihadists are no longer in control there.
Video

Video Ebola Vaccine Trials Underway in West Africa

Ebola has claimed the lives of more than 10,000 people in West Africa. Since last summer, researchers have rushed to get anti-Ebola vaccines into clinical trials. While it's too early to say that any of the potential vaccines work, some scientists say they are seeing strong results from some of the studies. VOA's Carol Pearson reports.
Video

Video Philippines Wants Tourists Spending Money at New Casinos

Tourism is a multi-billion dollar industry in the Philippines. Close to five million foreign visitors traveled there last year, perhaps lured by the country’s tropical beaches. But Jason Strother reports from Manila that the country hopes to entice more travelers to stay indoors and spend money inside new casinos.
Video

Video Civilian Casualties Push Men to Join Rebels in Ukraine

The continued fighting in eastern Ukraine and the shelling of civilian neighborhoods seem to be pushing more men to join the separatist fighters. Many of the new recruits are residents of Ukraine made bitter by new grievances, as well as old. VOA's Patrick Wells reports.
Video

Video Cambodian Land Grabs Threaten Traditional Communities

Indigenous communities in Cambodia's Ratanakiri province say the government’s economic land concession policy is taking away their land and traditional way of life, making many fear that their identity will soon be lost. Local authorities, though, have denied this is the case. VOA's Say Mony went to investigate and filed this report, narrated by Colin Lovett.

VOA Blogs

Circumventing Censorship

An Internet Primer for Healthy Web Habits

As surveillance and censoring technologies advance, so, too, do new tools for your computer or mobile device that help protect your privacy and break through Internet censorship.
More