LONDON (Reuters) - Technologies to remove carbon dioxide from the atmosphere to help tackle global warming only have limited potential and more effort should be made to reduce emissions, European scientists said in a report on Wednesday.

FILE PHOTO - A man wearing a face mask walks on a bridge in front of the financial district of Pudong amid heavy smog in Shanghai, China, December 15, 2015. REUTERS/Aly Song

Proposals to use climate technologies, ranging from spraying sun-dimming chemicals high above the Earth to capturing and storing carbon dioxide underground, have been gaining more attention as the urgency to act on climate change mounts.

Under the 2015 Paris Agreement, world governments have agreed to limit global warming to well below 2 degrees Celsius above pre-industrial levels but a large gap remains between countries’ emissions plans and the reductions needed.

The European Academies’ Science Advisory Council (EASAC), formed from national science academies of EU members, has reviewed scientific evidence about several options for removing carbon dioxide (CO2) from the atmosphere with so-called negative emission technologies.

Examples of such technologies include the direct capture of CO2 and trapping it underground (carbon capture and storage); afforestation and reforestation; land management to increase and fix carbon in soils and ocean fertilisation.

The EASAC, which advises European policymakers, said these technologies have “limited realistic potential to remove carbon from the atmosphere” and not at the scale in some climate forecasts, such as several gigatonnes of carbon each year after 2050.

Their deployment on a large scale would also involve high economic costs and have major impacts on terrestrial or marine ecosystems, the EASAC said in a report.

“Technologies capable of taking out CO2 from the atmosphere are certainly no silver bullet - a point that should drive policymakers to renewed efforts to accelerate emissions reductions,” the report said.

However, the world will need all possible tools to limit warming and some of these technologies can make contributions to remove CO2 from the atmosphere even now, while further research, development and demonstration may allow others to make a limited future contribution,” it added.

Commenting on the report, Andrew Watson, Royal Society Research Professor at the University of Exeter said that while some technologies for removing CO2 from the atmosphere could have a role to play in reducing climate change, all have drawbacks making them difficult to use them on a large scale.

“So our main focus and best hope for avoiding the worst effects of climate change still needs to be reducing our emissions,” he added.

Last week, a leaked draft U.N. report said there is a high chance that the levels of CO2 removal which might be required to meet the Paris goals might not be feasible due to the required scale and speed of technology deployment.