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

For Lebanon-based Refugees, Desperation Fuels Perilous Passage

In a war that has caused an estimated three million people to flee Syria, efforts to make perilous sea journey in search of asylum expected to increase More

South African Brewer Tackles Climate Change

Mega-brewer SAB Miller sent delegates to climate summit in Peru, says it is one of many private companies taking their own steps to fight climate change More

Indonesia Reports Increase in Citizens Joining Islamic State

Officials say more than 350 of its citizens are now in Syria or Iraq to fight with Islamic State - 50 more than last month 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.
Will Pakistan School Shooting Galvanize Pakistan Against Extremism?i
X
Ayesha Tanzeem
December 17, 2014 11:54 AM
The attack on a military school in Pakistan’s northwest city of Peshawar left 141 dead, including 132 children. Strong statements of condemnation poured in from across the world. The country announced three days of mourning, and the leadership, both political and military, promised retribution. VOA's Ayesha Tanzeem looks at how likely the Pakistani government is to clamp down on all extremist groups.
Video

Video Will Pakistan School Shooting Galvanize Pakistan Against Extremism?

The attack on a military school in Pakistan’s northwest city of Peshawar left 141 dead, including 132 children. Strong statements of condemnation poured in from across the world. The country announced three days of mourning, and the leadership, both political and military, promised retribution. VOA's Ayesha Tanzeem looks at how likely the Pakistani government is to clamp down on all extremist groups.
Video

Video ‘Anti-Islamization’ Marches Increase Tensions In Germany

Anti-immigrant rallies in Germany have been building in recent weeks, peaking Monday night in the city of Dresden where tens of thousands of people turned out to demonstrate against what they call the ‘Islamization’ of the West. Germany has offered asylum to more Syrian refugees than any other country, and this appears to have set off the protests. Henry Ridgwell reports from London.
Video

Video Aceh Rebuilt Decade After Tsunami, But Scars Remain

On December 26, 2004 there was an earthquake in the Indian Ocean so powerful it caused the Earth’s axis to wobble a few centimeters. Onshore on the island of Sumatra, the resulting tsunami was devastating. A decade later, VOA Correspondent Steve Herman reports from Banda Aceh, Indonesia, where although there is little remaining evidence of the physical devastation, the psychological scars among survivors remain.
Video

Video Refugees Living in Kenya Long for Peace in the Home Countries

Kenya is host to numerous refugees seeking safe haven from conflict. Immigrants from Somalia face challenges in their new lives in Kenya. Ahead of International Migrants Day (December 18) Lenny Ruvaga has more for VOA News from the Kenyan capital.
Video

Video Turkey's Authoritarianism Dismays Western Allies

The Turkish government has been defiant in the face of criticism at home and abroad for its raids targeting opposition media. The European Union on Monday expressed dismay after President Recep Tayyip Erdogan lashed out at Brussels for criticizing his government's action. Turkey's bid to be considered for EU membership has been on hold while critics accuse the NATO ally of increasingly authoritarian rule. Zlatica Hoke reports.
Video

Video US-China Year in Review: Hong Kong to Climate Change

The United States is pushing for a code of conduct to resolve territorial disputes in the South China Sea as it works to improve commercial ties with Beijing. VOA State Department correspondent Scott Stearns reports on a year of U.S. policy toward China from Hong Kong to climate change.
Video

Video Japanese Leader’s Election Win Raises Potential for Conflict with Neighbors

Japan’s Prime Minister Shinzo Abe and his allies easily won a two-thirds majority in parliament Sunday, even though the country has slipped into recession under his conservative policies. VOA’s Brian Padden reports from Seoul, that the prime minister’s victory will empower him to continue economic reforms but also pursue a nationalist agenda that will likely increase tensions with Japan’s neighbors.
Video

Video Nuba Mountain Families Hide in Caves to Escape Aerial Bombings

Despite ongoing peace talks between Sudan's government and the rebel Sudan People’s Liberation Movement-North, or SPLM-N, daily aerial attacks continue in South Kordofan province’s Nuba Mountains. Adam Bailes was there and reports for VOA that government forces are targeting civilian areas, rather than military positions, with their daily bombardments.

All About America

AppleAndroid