"Together, these two emerging giants are projected to account for around 45 per cent of global carbon emissions from energy by 2050 compared to only around 20 per cent of the global total for the US and EU combined," a consulting and research firm PricewaterhouseCoopers said.

Power generation and transport sectors in these countries would contribute to more carbon emissions than from building and other industries, it unveiled in the report on 'World in 2050'.

The rise in car ownership in these two emerging economies would lead to high growth rate in emissions, it stressed.

With higher projected economic growth in major countries, the CO2 (carbon dioxide) in atmosphere is estimated to rise by 55.8 per cent, from around 385 parts per million (ppm) now to around 600ppm by 2050 globally, it said.

The report suggested that "it would be technologically feasible without excessive economic costs' to bring down global emissions by half the current level by 2050.

Estimating the cost of halving global carbon emissions, it said, "The cost should be no more than around 3 per cent of world GDP. This is broadly equivalent to sacrificing around a year of global GDP growth between now and 2050".

However, the need of the hour is that all governments in major economies demonstrate political will to combat global warming, it said.

PWC Climate Change Services Head Bharti Gupta Ramola said, "The key requirement now is for governments in all of the major economies including the US and developing economies like China and India to send the right economic signals to private sector investors and consumers for delivering the new technologies and changes in behaviour that are required to combat global warming".

For the advanced G7 economies, this requires a reduction in carbon emissions by around 80 per cent relative to current levels by 2050, whereas for the E7 emerging economies led by China and India, it involves mitigating the growth of emissions up to around 2020 and then aiming for reductions in emissions after that date, he said.