That's the critical CO2 concentration leading to irreversible damage
Goh Sui Noi, Straits Times 24 Nov 09;
LAST month on Oct 24, United Nations Day, people around the world had the number '350' thrown at them.
Activists - from skateboarders in Australia to farmers in Bangladesh, and from divers in the Maldives to herders on the Mongolian steppes - formed the number with their bodies or held placards and banners bearing it. In Singapore, more than 300 volunteers formed the number for an aerial photograph.
They wanted to etch the number deep in the minds of as many human beings as possible. They wanted citizens to push their leaders to negotiate a strong treaty next month in Copenhagen to reduce carbon dioxide emissions and thereby prevent irreversible climate change.
This number - 350 - refers to the concentration of carbon dioxide in the earth's atmosphere by volume: 350 parts per million (ppm). It is the low end of a range of 350 ppm to 550 ppm that scientists believe will trigger irreversible climate change. We are now at 387 ppm, and the last time we saw 350 ppm was in 1987. The figure of 350 ppm is what scientists believe is the safe upper limit for carbon dioxide in our atmosphere.
Another figure to remember is 2 deg C. This is a European Union target - to limit the increase in global temperature to a maximum of 2 deg C over pre-industrial levels (or 1.2 deg C over today's level). A rise above 2 deg C is likely to trigger dangerous irreversible climate change.
To achieve this target would require the world to stabilise carbon dioxide levels in the atmosphere at about 400 ppm and greenhouse gas concentrations - carbon dioxide plus other greenhouse gases - at about 445-490 ppm. Based on the current growth trajectory, greenhouse gas levels could hit 550-700 ppm in 2050.
So what do we do with the knowledge of the possible danger we and our children face? Take the bus or cycle to work or school, use reusable shopping bags, remember to switch off lights not in use, buy fewer clothes, recycle our waste? For how long? A week? A month?
The world needs a more concerted effort than what we as individuals can do on our own - although individual actions are important - to cut emissions to meet the 2deg C target. Emissions must peak by 2020 and then be more than halved by 2050 relative to 1990 levels for global warming to fall below the 2 deg C limit. Developed countries will have to cut their emissions by 25 per cent to 40per cent and developing countries, which emit far less carbon dioxide per capita than rich nations, will have to slow their emissions growth.
A powerful mechanism for reducing emissions would be establishing a carbon price - that is, impose a cost on carbon emissions. Having to pay a price for spewing carbon into the atmosphere would motivate countries, businesses and individuals to reduce their carbon emissions. It would discourage the use of fossil fuels and encourage the development of renewable sources of energy and low-carbon emission, energy-efficient consumer technologies.
'We need more energy, less carbon and price signals to unleash the energy to take us forward,' said Mr Jeremy Benthem, vice-president of Shell Global Business Environment, at a recent conference in Copenhagen, Denmark.
Two ways to price carbon have been proposed: an outright tax on fossil fuels and a cap-and-trade system. In the latter instance, caps on emissions would be set and power generators, industries and other emitters of carbon would have to purchase permits to emit more carbon than their mandated limits. A market would be established for the trading of permits.
The carbon tax is favoured by some, such as former Mexican president Ernesto Zedillo. It would be simpler to implement and less open to corruption than cap-and-trade. It would also set a clear price, something that would be easier for industries to plan around than the fluctuating price that a cap-and-trade system would entail. A tax would also raise a clear amount of revenue, which could be used for the research and development of renewable energy sources or as rebates to the public - for example, to offset higher energy prices.
Proponents of cap-and-trade argue that it has a clear advantage over a carbon tax in that a cap would effectively place a legally binding limit on emissions which a tax would not. While a tax would penalise all indiscriminately, a cap-and-trade system would penalise those who failed to keep within their caps but would reward those who did and who would thus be able to sell their permits in the market. A cap-and-trade system would encourage growth in new green sectors.
The cap-and-trade system was first used successfully in the United States in the 1980s to eliminate the use of leaded petrol in cars. A cap was placed on the production of leaded fuels, and refiners were allowed to buy and sell permits among themselves. Refiners producing unleaded fuels could sell their unused permits to leaded fuel producers. The latter, in order to compete in the market, were incentivised to turn to producing unleaded fuel. Within five years, nearly all leaded petrol was eliminated.
The Kyoto Protocol, the global climate pact now in force, provides for a cap-and-trade system in which 37 developed countries agreed to reduce their greenhouse gas emissions by 5.2per cent from 1990 levels. These countries could trade emission reduction credits among themselves, as well as offset their emissions by financing projects that reduce emissions in developing countries.
However, the Kyoto Protocol will end in 2012 and the world is in the midst of negotiating a new treaty. As the time for sealing a deal nears - set for next month at the 15th annual United Nations conference on climate change - several countries are beginning to warm to the idea of a carbon tax or a combination of a tax and emissions trading.
Whichever path is adopted, the emissions cuts must be deep enough to ensure that the 2 deg C limit is maintained. There is no sign yet that the nations of the world are close to agreeing on cuts that will meet that target.
