Monthly Archives: November 2010

Gases that warm up the globe reach peak level


By A WMO Spokesperson

Power plant smokestacks

Since 1750, carbon dioxide in the atmosphere has increased by 38%, largely due to fossil fuel burning like in this thermal power plant (Photo: Ian Britton/ Free Foto)

GENEVA: The main greenhouse gases have reached their highest levels recorded since pre-industrial times, according to the World Meteorological Organization’s 2009 Greenhouse Gas Bulletin. The report also highlights concerns that global warming may lead to even greater emissions of methane from Arctic areas.

According to the Bulletin, total radiative forcing of all long-lived greenhouse gases increased by 27.5% from 1990 to 2009 and by 1.0% from 2008 to 2009, reflecting the rising atmospheric burdens of carbon dioxide, methane and nitrous oxide.

“Greenhouse gas concentrations have reached record levels despite the economic slowdown. They would have been even higher without the international action taken to reduce them,” said WMO Secretary-General Mr Michel Jarraud. “In addition, potential methane release from northern permafrost, and wetlands, under future climate change is of great concern and is becoming a focus of intensive research and observations.”

Carbon dioxide (CO2) is the single most important anthropogenic greenhouse gas in the atmosphere and contributes 63.5% to the overall global radiative forcing by long-lived greenhouse gases. Global radiative forcing is the balance between radiation coming into the atmosphere and radiation going out. Positive radiative forcing tends to warm the surface of the Earth and negative forcing tends to cool it.

For about 10,000 years before the start of the industrial era in the mid-18th century, atmospheric carbon dioxide remained almost constant at around 280 ppm (ppm=number of molecules of the gas per million molecules of dry air).  Since 1750, it has increased by 38%, primarily because of emissions from combustion of fossil fuels, deforestation and changes in land-use. During the past 10 years, it has increased by an average annual 1.88%, according to WMO.

Methane (CH4) contributes 18.1% to the overall global radiative forcing and is the second most important greenhouse gas after carbon dioxide.

Before the start of the industrial era, atmospheric methane was about 700 parts per billion. Since 1750, it has increased 158%, mostly because of increasing emissions from human activities such as cattle-rearing, rice planting, fossil fuel exploitation and landfills. Human activities now account for 60% of methane emissions, with the remaining 40% being from natural sources such as wetlands.

After a period of temporary stabilization from 1999 to 2006, atmospheric methane has risen again from 2007-2009. The Greenhouse Gas Bulletin reports that the likely causes were above average wetland methane emissions due to exceptionally warm temperatures at high northern latitudes in 2007 and heavy precipitation in tropical wetlands in 2007 and 2008. However, it cautions that the reasons for the recent increases are not yet fully understood.

Northern permafrost contains large reservoirs of organic carbon and methane clathrates (a form of water ice that contains a large amount of methane within its crystal structure). Rapid warming and melting of the permafrost therefore has the potential to release large quantities of methane into the atmosphere which would contribute further to global warming.

Nitrous oxide (N2O) contributes 6.24% to the overall global radiative forcing. It is emitted into the atmosphere from natural and anthropogenic sources, including the oceans, biomass burning, fertilizer use and various industrial processes. Globally averaged nitrous oxide in 2009 was 19% higher, at 322.5 parts per billion than the pre-industrial era.

Other greenhouse gases: The combined radiative forcing by halocarbons is 12%, nearly double that of nitrous oxide. Some halocarbons such as chlorofluorocarbons (CFCs), previously used as refrigerants, as propellants in spray cans and as solvents, are decreasing slowly as a result of international action to preserve the Earth’s protective ozone layer.

However, concentrations of other gases such as HCFCs and HFCs, which are used to substitute CFCs because they are less damaging to the ozone layer, are increasing rapidly. These two classes of compounds are very potent greenhouse gases and last much longer in the atmosphere than carbon dioxide.

WMO, through its Global Atmosphere Watch (GAW) Programme, coordinates the observations of greenhouse gases in the atmosphere through a network of stations located in more than 50 countries, including high in the Andes and Himalayas. The measurement data are quality controlled, archived and distributed by WMO’s World Data Centre for Greenhouse Gases, hosted by the Japan Meteorological Agency (JMA).

The 2009 Greenhouse Gas Bulletin is the sixth in the series, which began in 2004. The Bulletins report the global consensus of the WMO Global Atmosphere Watch community on the latest changes and atmospheric burdens of the main greenhouse gases.

Mumbai’s climate change blues

By Darryl D’Monte

Mumbai coast

Several crowded spots in Mumbai face the threat of coastal erosion (Photo: Sajpics)

MUMBAI (AlertNet) – Around a third of the coastline north and south of Mumbai, India’s financial capital and most populous city, is vulnerable to severe flooding from extreme weather and rising sea levels, according to a study that has yet to be published.

The number of people living in the Mumbai urban agglomeration will touch 28.5 million by 2020, making it the biggest city in the world, according to the Washington-based Population Institute.

As much as 14 percent of the 720 km (450 miles) coastline – with Mumbai roughly in the centre – is “highly” vulnerable, and 16 percent “moderately” vulnerable, according to the Hyderabad-based Indian National Centre for Ocean Services.

“The Indian ocean rim is predisposed to natural disasters,” says the centre’s T. Srinivasa Kumar. “A rise in the sea level due to a storm surge could lead to coastal flooding in a low-lying area or in an open creek or river mouth.”

In July 2005, Mumbai, the capital of Maharashtra state, was hit by an unprecedented cloudburst – 944 mm in 10 hours – which shut down much of the city and took around 400 lives, besides causing millions of dollars of damage to property.

Just over half the population of Greater Mumbai, some 8 million people, live in slums, the highest proportion for any metropolis in the world. They have tended to squat along the coast and estuaries, leaving them exposed to hazards from flooding and sea level rise.

Mumbai residents know only too well that if torrential rain is accompanied by a high tide, the floodwater cannot escape and backs up into the city.

‘NO MORE LAND TO MOVE TO’

Shirish Karlekar, a geographer from SP College in Pune, some 150 km (90 miles) inland from Mumbai, has been monitoring changes along the coast from just north of Mumbai to the southernmost tip of the state’s coast for 20 years. In that period, the average sea level has risen by 5 to 6 cm.

On December 29 last year, the high tide rose by 4 cm near Ratnagiri town, which lies around 200 km (125 miles) south of Mumbai and is the home town of many Mumbai immigrants. Karlekar says the increase on the same day in 2008 was just 2 cm.

“In recent years, the sea level has risen at a much faster pace than in the early years of our study,” he explains.

The ever-higher tides have led to salt water penetrating as much as a kilometre inland, damaging mangroves, eroding beaches and filling creeks with sand.

Sadanand Tandel recalls how the waves first entered his village of Deobagh (meaning God’s garden) in coastal Sindhudurg district during the 1978 monsoon.

Since then, his village has lost 32 hectares (79 acres) of land, mainly valuable coconut groves.

“In the 1980s, the sea was more than 300 metres from my house and more than 1,000 casuarina (pine) trees were planted to protect the coast between my grove and the sea,” Tandel said. Nonetheless, the sea threatens just 40 m from his doorstep today.

Tondawli village, 20 km (12 miles) to the north, has lost 40 hectares (100 acres), including some 500 coconut trees and space for drying fish.

Lakshmi Kochrekar, who tends a coconut plantation and isn’t sure of her age, has had to rebuild her house twice due to the rising tides.

“I have no more land to move to now,” she complains.

Village elders in this region say the sea’s very behaviour is changing. Patterns of erosion and deposition are different.

While tides are eroding the coast more rapidly, debris is being deposited on an unprecedented scale in other areas.

“We have a saying that that the sea brings back whatever it takes,” says Shridhar Wadekar, an elderly villager. “But for the past two years, I have been waiting for it to bring back my rice farm.”

VULNERABLE REAL ESTATE

While poor communities along the coast are the first to have been hit, the super-rich of Mumbai are likely to be affected too. Consultants Jones Lang LaSalle Meghraj recently noted that Mumbai accounts for 40 percent of the $100 billion in Indian construction projects underway.

Property in Mumbai is astronomically expensive because the 100 sq km (39 square mile) island city is located at the southern tip of a peninsula and cannot expand. Coastal multi-storey apartments are in the greatest demand, with high-end apartments now selling for as much as $7 million.

Mumbai also has the highest proportion of land reclaimed from the sea of any old city core in the world. The reclamation was led by rampant speculation during the British Raj in the 18th Century and was only halted by environmentalists in the 1970s. The filling has already caused severe erosion of properties in the northern suburbs as the displaced ocean bites elsewhere along the coast.

After the 2004 Asian tsunami, which impacted only India’s deep south, Mumbai authorities erected three-metre-high walls along shallow-water fishing village coasts to the north of the city, even though the villages had been unaffected.

Environmentalists criticised the Canute-like gesture as both ineffectual and a thinly-disguised attempt by officials to line their pockets from sea wall contracts.

TUBE TECHNOLOGY

The latest protection project being undertaken by the Maharashtra government uses “geo-textile tubes”, which it says are an eco-friendly method of arresting erosion by keeping sand in place. The tubes are already being used in Kerala and Goa.

The tubes – hollow plastic pipes – will be submerged and placed over sand-filled coconut fibre bags to form a semi-circle, creating an artificial bay. It is hoped marine creatures will be able to get a toehold on the resulting reef-like structure.

The state has identified 72 km (45 miles) south of Mumbai – one tenth of the total length of the coast – as subject to high erosion, and it plans to protect the plantations and fish drying grounds of coastal villagers in this area.

The Asian Development Bank is providing loans to cover $104 million of the total project cost of $179 million. The state government will lend $58 million, and the remaining $17 million will come from private investors, who are looking to sell the tubes, particularly if the technique is replicated elsewhere in the state and in the rest of India.

Yet experts warn the technology must be deployed with care. P.K. Das, an architect and activist who has helped “nourish” a strip of eroded beach in midtown Mumbai with Dutch technology that uses partial barriers to stop sand erosion, says that if the geo-textile tubes are too large, they can interfere with the natural movement of sand and tides.

The state should first conduct modeling experiments to establish sand movement patterns, Das says. Otherwise the tubes could act like dams, arresting natural processes.

“Sand is never static,” he explains.