Climate change: Copenhagen in graphics

Where do greenhouse gas missions come from?

Which countries are most responsible for causing human-induced climate change?

And have governments pledged tough enough cuts so far to keep the global average temperature rise within “safe limits”?

As the UN summit in Copenhagen approaches, we look at the past, present and possible futures of climate change.

Global emissions have risen steadily in recent decades.

Carbon dioxide (CO2) equivalent – Six greenhouse gases are limited by the Kyoto Protocol. Each gas has a different global warming potential.

The overall warming effect of this cocktail of gases is often expressed in terms of carbon dioxide equivalent – the amount of CO2 that would create the same amount of warming.

CO2 equivalent is often measured in kilotonnes (Kt) or thousands of tonnes, and gigatonnes (Gt) or billions of tonnes.

But when trying to assign “responsibility” for causing climate change, how should they be measured?

Populous developing countries such as China and India have relatively high overall emissions – comparable with many developed countries.

But each of their citizens produces a much smaller amount than counterparts in regions such as North America or Western Europe.

Countries that industrialised early and grew rich early because of that industrialisation, such as the UK, Germany and the US, have a higher “historical footprint”.

In some peoples’ eyes, this gives them a higher responsibility for curbing the problem.

Graphic: Carbon emissions

A number of academic teams have calculated how emissions are likely to rise in the next few decades, and what that is likely to mean in terms of rising temperatures.

Their projections are not exact because there are many sources of uncertainty in the calculations, including the exact relationship between greenhouse gas levels and temperature rise.

A number of developed countries and blocs have set targets for cutting their emissions, some of which depend on what other countries do.

The EU, for example, will cut emissions by 20% from 1990 levels – but if there is a global deal, that will rise to 30%.

Some developing nations have also pledged to reduce the rate at which their emissions are growing.

If implemented, are these curbs enough to keep the global average temperature rise below 2C – the target adopted by G8, the EU and a number of major developing countries?

climate change imageAnalysts project that if no further action is taken on emissions, man-made warming will go beyond the relative safety of 2C above pre-industrial levels.

According to the European Climate Foundation analysis – and others – commitments made so far are probably not enough to meet the G8 target.

This shortfall is one of the issues likely to be highlighted during the Copenhagen conference. –BBC News