Targets and trust. These are at the heart of a tougher new global climate pact possibly just weeks away.

The bigger the pledged emissions cuts or reductions in growth in carbon dioxide pollution, the greater the need to prove nations meet those targets and curb the pace of climate change. And proof of emissions reductions over time will help unlock billions of dollars in climate funds for poor nations.

The problem, though, is that it is not yet possible to independently monitor a country's greenhouse gas emissions, such as carbon dioxide (CO2) from burning fossil fuels or deforestation.

"Our system is not good enough right now to be able to finger one country versus another. I think the density of observations needs to be cranked up two orders of magnitude," said Pieter Tans of the National Oceanic and Atmospheric Administration (Noaa) in Boulder, Colorado.

Rich nations, he said, are not going to hand over possibly hundreds of billions of dollars to poorer nations to help green their economies purely on trust. Which is why measurement, reporting and auditing of nations' greenhouse gas emissions is a key focus of marathon UN climate talks. The world body hopes the negotiations will lead to agreement on a tougher climate pact from 2013 during a meeting in Copenhagen next month.

Rich nations are under pressure from the developing world to sign up to emissions cuts of 25 to 40 per cent below 1990 levels by 2020 and funnel billions in aid and green technology to the poor. They are also under pressure to curb the pace of their emissions growth. China, India, Indonesia and Brazil are among the world's top carbon polluters.

"If there's no objective system to check lines of success, people are going to claim more than they can deliver. It's natural," said Tans.

Huge variability

Rich nations such as Australia and the United States have developed reliable reporting methods on energy use and fossil fuel emissions, said Pep Canadell of the Global Carbon Project. Accuracy for developing countries is often not as good.

"You have huge variability. And the issue is let's check on some of the developing countries. That's where it gets the most difficult because the reporting is not that accurate," he said.

Noaa runs a global network that tests air samples for a variety of greenhouse gases to build a picture of how their concentrations change over time. CO2 levels are approaching 390 parts per million (ppm) compared with 280 ppm at the start of the Industrial Revolution. If CO2 rises to 450 ppm, the UN climate panel says the planet is likely to warm by at least two degrees Celsius.

Dozens of countries also send greenhouse gas measurement data to the World Meteorological Agency's World Data Centre for Greenhouse Gases. But scientists say we are at least a decade or two away from a monitoring system than can accurately reveal national and regional emissions.

"People have wondered where the CO2 that we're emitting is going and we've been able to tell that in rough numbers that half is staying in the atmosphere. Of the half that is leaving the atmosphere, half of that is going to the terrestrial land plants and the other half is ending up in the oceans," said Britton Stephens of the National Centre for Atmospheric Research in Boulder.

Building a picture

Because CO2 is shifted around by the atmosphere, scientists need powerful computers to simulate the movement of air around the globe and to crunch all the data from an army of CO2 monitoring sites. More accurate measurement and models could give investors more confidence when putting money into large carbon offset schemes. Computer models, though, are years away from proving accurate.

"As everyone knows from complaining about weather forecasts, the atmospheric models are far from perfect," said Stephens.

Current carbon measurement techniques are rather complex, although a new generation of equipment promises much faster and more accurate results and could form the backbone of a greatly enhanced global system. Scientists also need to disentangle natural CO2 from fossil fuel emissions.

Canadell said a future system would need to marry supercomputers and different monitoring tools. And trust is a key driver for investment in the network.


- The writer is Reuter's Climate Change Correspondent for Asia


FACTS OF THE MATTER

HOW MUCH CARBON DOES MANKIND ADD?

Mankind's CO2 emissions total about 30 billion tonnes per year. Of this, about half stays in the atmosphere, while about 7.5 billion tonnes is taken up by the oceans and roughly the same amount by land plants.

HOW IS CO2 MEASURED?

Long-term records starting in the late 1950s involve daily air sampling in remote locations, such as on Mauna Loa in Hawaii and Cape Grim in Tasmania, Australia.

Since the 1970s, many measurements have involved collecting air samples from locations around the globe, either on land, ships or from aircraft. The air in trapped in small flasks and then measured by an infrared absorption analyser to determine the concentration of CO2. A more complicated process is used to measure the radiocarbon content of CO2 to work out how much fossil fuel emissions are contributing to the variations in CO2.

WHO MEASURES CO2?

- Earth Systems Research Laboratory of the National Oceanic and Atmospheric Administration (Noaa). http://www.esrl.noaa.gov/gmd/ccgg/trends/

- Scripps CO2 programme of the Scripps Institution of Oceanography, California, since 1956. http://scrippsco2.ucsd.edu/research/atmospheric_co2.html 

- World Meteorological Agency's Global Atmosphere Watch. http://www.wmo.int/pages/prog/arep/gaw/ghg.html 

- CSIRO Marine and Atmospheric Research Division in Australia. http://www.cmar.csiro.au/research/capegrim_graphs.html 

- National Centre for Atmospheric Research in Boulder, Colorado. http://hippo.ucar.edu/ 

- Carbon Dioxide Information Analysis Centre, of the US Department of Energy. http://cdiac.ornl.gov


Recession forces Japan to meet CO2 goals

TOKYO Japan is expected to report as early as this week that its greenhouse gas emissions sank last year, the first year of its Kyoto Protocol obligations. But the drop is not the good news it may appear to be, as it is mostly due to a recession that has cut the money firms have to spend on green initiatives, and also forced the government to focus more on economic stimulus than its green agenda. This could make it harder for the world's fifth-biggest polluter to prepare for ambitious targets beyond 2012.


Maldives proposes carbon neutral union

Colombo Maldives President Mohamed Nasheed is proposing that developing nations become what he terms carbon neutral ahead of an international conference on climate change. Addressing a meeting in the Maldives for developing countries vulnerable to the effects of climate change, Nasheed said if they committed to carbon neutrality "those opposed to change have nowhere left to hide". The summit aims to forge a common position ahead of talks in Copenhagen.

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