The Paris climate change conference, COP21, officially starts tomorrow, but negotiators already started today as more than 190 nations try to define a new international charter that will cut greenhouse gas emissions by enough to keep the increase in global warming under 2 degrees above pre-industrial levels.

There is substantial urgency on this as 2015 will be the warmest year on record and the global average surface temperature will already be 1 degree above the pre-industrial levels, according to recent data from the World Meteorological Organisation.

The most serious clash at COP21 will be between developing countries that cannot afford to slow down their economic growth as they seek greater prosperity for their people and developed countries that have burnt fossil fuels for centuries to build their current prosperity but can now afford to change to less-polluting technologies.

An area of tense argument will be how much the world’s richer nations are prepared to pay for the poorer nations to change to technologies that have reduced carbon emissions.

A problem with COP21 is a global target of 2 degrees is too vague for any one country to commit to. It is a valuable overall target as this is what scientists agree is the highest rise in temperature the world can afford before triggering truly calamitous extreme weather such as heatwaves, droughts and flooding.

But it will be important for individual states to commit to measurable carbon emission targets, like the European Union, which has made a pledge to cut Europe-wide emissions by at least 40 per cent on 1990 levels by 2030. This target can be measured and the EU can be held to its promise.

The UAE has stated that it sees the Paris conference as a vital milestone on a long and continuing journey, so it is keen to welcome flexibility in the final deal so that all countries can commit to the targets, and at the very least move in the same direction.