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

FIFA Indictments Put Gold Cup Tournament Under Cloud

Experts say US indictments could lead to charges of other world soccer officials, and lead to major shakeup in sport's governance More

Video Seoul Sponsors Korean Unification Fair

At a recent even in Seoul, border communities promoted benefits of increased cooperation and North Korean defectors shared stories of life since the war More

Video VOA EXCLUSIVE: Iraq President Vows to Fight IS 'Until They Are Killed or We Die'

In wide-ranging interview with VOA Persian service reporter, Fuad Masum describes conflict as new type of fight that will take time to win 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.
Expelled from Pakistan, Afghan Refugees Return to Increased Hardshipi
X
Ayesha Tanzeem
May 28, 2015 6:48 PM
Undocumented refugees returning to Afghanistan from Pakistan have no jobs, no support system, and no home return to, and international aid agencies say they and the government are overwhelmed and under-resourced. Ayesha Tanzeem has more from Kabul.
Video

Video Expelled from Pakistan, Afghan Refugees Return to Increased Hardship

Undocumented refugees returning to Afghanistan from Pakistan have no jobs, no support system, and no home return to, and international aid agencies say they and the government are overwhelmed and under-resourced. Ayesha Tanzeem has more from Kabul.
Video

Video Britain Makes Controversial Move to Crack Down on Extremism

Britain is moving to tighten controls on extremist rhetoric, even when it does not incite violence or hatred -- a move that some are concerned might unduly restrict basic freedoms. It is an issue many countries are grappling with as extremist groups gain power in the Middle East, fueled in part by donations and fighters from the West. VOA’s Al Pessin reports from London.
Video

Video Floodwaters Recede in Houston, but Rain Continues

Many parts of Texas are recovering from one of the worst natural disasters to hit the southwestern state. Heavy rains on Monday and early Tuesday caused rivers to swell in eastern and central Texas, washing away homes and killing at least 13 people. As VOA’s Greg Flakus reports from Houston, floodwaters are receding slowly in the country's fourth-largest city, and there likely is to be more rain in the coming days.
Video

Video 3D Printer Makes Replica of Iconic Sports Car

Cars with parts made by 3D printers are already on the road, but engineers are still learning about this new technology. While testing the possibility of printing an entire car, researchers at the U.S. Department of Energy recently created an electric-powered replica of an iconic sports roadster. VOA’s George Putic has more.
Video

Video Al-Shabab Recruitment Drive Still on In Kenya

The al-Shabab militants that have long battled for control of Somalia also have recruited thousands of young people in Kenya, leaving many families disconsolate. Mohammed Yusuf recently visited the Kenyan town of Isiolo, and met with relatives of those recruited, as well as a many who have helped with the recruiting.
Video

Video US Voters Seek Answers From Presidential Candidates on IS Gains

The growth of the Islamic State militant group in Iraq and Syria comes as the 2016 U.S. presidential campaign kicks off in the Midwest state of Iowa.   As VOA’s Kane Farabaugh reports, voters want to know how the candidates would handle recent militant gains in the Middle East.
Video

Video A Small Oasis on Kabul's Outskirts Provides Relief From Security Tensions

When people in Kabul want to get away from the city and relax, many choose Qargha Lake, a small resort on the outskirts of Kabul. Ayesha Tanzeem visited and talked with people about the precious oasis.
Video

Video Film Festival Looks at Indigenous Peoples, Culture Conflict

A recent Los Angeles film festival highlighted the plight of people caught between two cultures. Mike O'Sullivan has more on the the Garifuna International Film Festival, a Los Angeles forum created by a woman from Central America who wants the world to know more about her culture.
Video

Video Kenyans Lament Losing Sons to al-Shabab

There is agony, fear and lost hope in the Kenyan town of Isiolo, a key target of a new al-Shabab recruitment drive. VOA's Mohammed Yusuf visits Isiolo to speak with families and at least one man who says he was a recruiter.
Video

Video Scientists Say Plankton More Important Than Previously Thought

Tiny ocean creatures called plankton are mostly thought of as food for whales and other large marine animals, but a four-year global study discovered, among other things, that plankton are a major source of oxygen on our planet. VOA’s George Putic reports.
Video

Video Kenya’s Capital Sees Rise in Shisha Parlors

In Kenya, the smoking of shisha, a type of flavored tobacco, is the latest craze. Patrons are flocking to shisha parlors to smoke and socialize. But the practice can be addictive and harmful, though many dabblers may not realize the dangers, according to a new review. Lenny Ruvaga has more on the story for VOA from Nairobi, Kenya.
Video

Video Iowa Family's Sacrifice Shaped US Military Service for Generations

Few places in America have experienced war like Waterloo. This small town in the Midwest state of Iowa became famous during World War II not for what it accomplished, but what it lost. As VOA’s Kane Farabaugh reports, the legacy of one family’s sacrifice is still a reminder today of the real cost of war for all families on the homefront.

VOA Blogs