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

US, Brazil's Climate-Change Plan: More Renewables, Less Deforestation

Officials say joint initiative on climate change will allow Brazil, United States to strengthen and accelerate cooperation on issues ranging from land use to clean energy More

Video Blind Somali Journalist Defies Odds in Mogadishu

Reporting from Somali capital for past decade, Abdifatah Hassan Kalgacal has been working at one of Mogadishu's leading radio stations covering parliament More

After Nearly a Century, Voodoo Opera Rises Again

Opera centers on character named Lolo, a Louisiana plantation worker and Voodoo priestess 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.
Blind Somali Journalist Defies Odds in Mogadishui
X
Abdulaziz Billow
June 30, 2015 2:16 PM
Despite improving security in the last few years, Somalia remains one of the most dangerous countries to be a journalist – even more so for someone who cannot see. Abdulaziz Billow has the story of journalist Abdifatah Hassan Kalgacal, who has been reporting from the Somali capital for the last decade despite being blind.
Video

Video Blind Somali Journalist Defies Odds in Mogadishu

Despite improving security in the last few years, Somalia remains one of the most dangerous countries to be a journalist – even more so for someone who cannot see. Abdulaziz Billow has the story of journalist Abdifatah Hassan Kalgacal, who has been reporting from the Somali capital for the last decade despite being blind.
Video

Video Texas Defies Same-Sex Marriage Ruling

Texas state officials have criticized the US Supreme Court decision giving same-sex couples the right to marry nationwide. The attorney general of Texas says last week's decision did not overrule constitutional "rights of religious liberty," and therefore officials performing wedding services can refuse to perform them for same-sex couples if it is against their religious beliefs. Zlatica Hoke reports on the controversy.
Video

Video US Gay Marriage Ruling Yields Real-life Impact

Friday’s landmark Supreme Court decision legalizing same-sex marriage throughout the United States is an outcome few thought possible just years ago, and shows a nation that increasingly tolerates and even celebrates the hopes and aspirations of gay people. VOA’s Michael Bowman spoke to a same-sex couple that will benefit from the high court ruling, and to a Christian scholar who is apprehensive about its potential consequences for America’s faith community.
Video

Video Syrians Flee IS Advance in Hasaka

The Syrian government said Monday it has taken back one of several districts in Hasaka overrun by Islamic State militants. But continued fighting elsewhere in the northern city has forced thousands of civilians from their homes. In this report narrated by Bill Rodgers, VOA Kurdish Service reporter Zana Omer describes the scene in Amouda, where some of the displaced are taking refuge.
Video

Video Rabbi Hits Road to Heal Jewish-Muslim Relations in France

France is on high alert after last week's terrorist attack near the city Lyon, just six months after deadly Paris shootings. The attack have added new tensions to relations between French Jews and Muslims. France’s Jewish and Muslim communities also share a common heritage, though, and as far as one French rabbi is concerned, they are destined to be friends. From the Paris suburb of La Courneuve, Lisa Bryant reports about Rabbi Michel Serfaty and his friendship bus.
Video

Video S. Korea Christians Protest Gay Rights Festival

The U.S. Supreme Court decision mandating marriage equality nationwide has energized gay rights supporters around the world. Gay rights remain a highly contentious issue in a key U.S. ally, South Korea, where police did a deft job Sunday of preventing potential clashes between Christian protesters and gay activists. Kurt Achin reports from Seoul.
Video

Video Saudi Leaks Expose ‘Checkbook Diplomacy’ In Battle With Iran

Saudi Arabia’s willingness to wield its oil money on the global diplomatic stage appears to have been laid bare, after the website WikiLeaks published tens of thousands of leaked cables from Riyadh’s Ministry of Foreign Affairs. VOA's Henry Ridgwell reports.
Video

Video Nubians in Kenya Face Land Challenges

East Africa's ethnic Nubians have a rich cultural history that dates back thousands of years, but in Kenya they are facing hardships, including the loss of lands they have lived on for generations. They say the government has reneged on its pledge to award them title deeds for the plots. VOA's Lenny Ruvaga reports.
Video

Video Syrian Refugees Return to Tal Abyad

Syrian refugees in Turkey confirm they left their hometown of Tal Abyad because of intense fighting and coalition airstrikes, not because Kurdish fighters were engaged in ethnic cleansing, as some Turkish officials charged. VOA Kurdish Service reporter Zana Omer, in Tal Abyad, finds that civilians coming back to the town agree, as we hear in this report narrated by Roger Wilkison.
Video

Video Military Experts Question New Russian Tank Capabilities

Russia has been showing off its new tank design – the Armata T-14. Designers claim it is 20 years ahead of current Western designs - and driving it feels like playing a computer game. But military analysts question those assertions, and warn the cost could be too heavy a burden for Russia’s struggling economy. Henry Ridgwell reports.
Video

Video In Kenya, Police Said to Shoot First, Ask Questions Later

An organization that documents torture and extrajudicial killings says Kenyan police were responsible for 1,252 shooting deaths in five cities, including Nairobi, between 2009 and 2014, representing 67 percent of all gun deaths in the areas reviewed. Gabe Joselow has more from Nairobi.
Video

Video In Syrian Crisis, Social Media Offer Small Comforts

Za’atari, a makeshift city in Jordan, may be the only Syrian refugee camp to tweet its activities, in an effort to keep donors motivated as the war in Syria intensifies and the humanitarian crisis deepens. Inside the camp, families say mobile phone applications help hold together families that are physically torn apart. VOA’s Heather Murdock reports.

VOA Blogs