Director, Earth Institute, Columbia University, United States.
The Financial Times
In 1992, the United Nations Framework Convention on Climate Change rightly called for a stabilisation of greenhouse gas concentrations at a level that would prevent dangerous climate change. The UN climate talks that have just begun in Paris can and should underpin the decarbonisation of the global economy needed to meet that goal.
Signatories to the convention have agreed to limit global warming to no more than 2 deg C, or 1.5 deg C if the emerging science justifies it.
To have a two-thirds probability of meeting the 2 deg C target, total CO2 emissions between 2011 and 2100 have to be less than about 950 billion tonnes. Emissions from energy need to fall from about 35 billion tonnes this year to 10-15 billion tonnes by 2050, and to zero by about 2070.
Such decarbonisation is achievable with current technologies. The cost will be modest, assuming significant technological improvements that are within reach, through a combination of targeted research and learning by doing.
If a consumption-based approach to carbon accounting is taken, Britain's national carbon emissions would be twice as high as officially reported.
A global collaboration of energy research teams has identified the steps that need to be taken by 16 countries that are major emitters.
The proposals all involve better energy efficiency through smart buildings, power grids and transport.
They rely on low-carbon power such as wind, solar, nuclear, geo-thermal or hydroelectric. They entail eliminating carbon-based fuels: vehicles and planes must switch to electricity, hydrogen fuel cells or advanced biofuels; buildings and industry mustswop heating oil for electricity and fuel cells.
As for the technology, one priority is improved batteries for home appliances, electric vehicles and electricity grids. Another is carbon capture and storage, and a way to reuse carbon dioxide as synthetic fuel. A third is "smart" electricity grids, based on metering and feedback. Finally, safer and publicly accepted nuclear power.
An agreement is needed to prevent countries from free-riding on the efforts of others, to facilitate cooperation on technology and to provide public goods such as climate financing for poor countries. Yet the multilateral system has failed repeatedly; success is not assured.
The UN convention required rich countries to move first, but until now the US Senate has insisted that China move together with America. Last year China agreed, even committing to provide climate finance for poor countries. For the first time since 1992, the US, China and the European Union are aligned.
In Paris, leaders must reaffirm the 2 deg C limit, and agree to check every five years whether a tougher one is needed. They should commit to decarbonisation this century and explain by 2018 how they intend to pursue it to 2050. Major economies must spend more on research and development and say how they will pay for at least US$100 billion (S$141 billion) a year in additional climate financing for low-income countries by 2020. The deal they strike should be reviewed every five years.
For years, sceptics have attacked climate science. Now they attack the Paris conference itself - wrongly alleging that the needed technologies do not yet exist or arguing, illogically, that climate change is a low priority or that adaptation is better than prevention. They quibble absurdly with specific reduction pledges made in advance of Paris, pretending that these would be the final word until the end of this century.
This is word play, not serious analysis of what can be done, should be done and what may well emerge from Paris. The governments there will pay little attention to such scepticism.