Sophisticated geo-engineering programmes - including mirrors to reflect the sun's radiation or plans to "fertilise" oceans - have already been imagined to try and manipulate the Earth's climate in case global warming gets out of hand.
But Raes dismissed what he described as "hard engineering," such as launching rockets to release dust particles into the stratosphere to create a cooling effect by blocking sunlight from entering the atmosphere.
"It's a temporary cure and doesn't solve anything, and the second thing is that we don't know the earth system enough to start playing with it," he said.
Moreover, he warned that some countries have already started to influence the climate by considering large-scale reforestation programmes in desert areas.
Dark tree coverage absorbs sunlight previously reflected by sandy deserts, heating up the system, he explained. The climate benefits of removing CO2 from the atmosphere only kick in years later when the trees have grown, he added.
"We have to stay very careful about how to use afforestation and deforestation so that we really have a benefit for the climate," Raes said.
As international climate negotiators are now considering how to introduce a mechanism to reduce emissions from deforestation and forest degradation, called REDD, EU researchers are working closely with policymakers to evaluate the climate impact of different mechanisms and to create reliable methods to monitor deforestation via satellites, he added.
As an example of a "win-win" soft geo-engineering approach, Raes singled out biochar technology, which turns agricultural waste into charcoal to enhance soil, while the gases can be used as fuel. The process thus avoids releasing the methane which would be freed if the waste were left to rot naturally in the fields, as well as CO2 emissions which result from burning it, he explained.
"That's something that is certainly of interest for developing countries that still live from agriculture and have a lot of agricultural waste," Raes said.
Nevertheless, the researcher said it was the job of scientists to research even the most extreme ideas around, even if to show that they are in reality too expensive or risky. The EU is also doing earth modelling to test how different geo-engineering approaches would impact upon the entire earth system: not just the atmosphere, but the oceans and the biosphere as well, he said.
"We'd rather go with what I call geo-renovating," Raes argued. "It is about discussing very sophisticated ways of solving the problems of climate change and air pollution rather than resorting to hard geo-engineering," he explained.
The scientist argued that climate policymakers are currently ignoring the impact of regular pollutants like ozone and black carbon particles. He pointed out that action to reduce their emissions could bring immediate benefits for the climate, whereas CO2 remains in the atmosphere for a long time.
"They have a strong impact on the climate and they are discussed in another forum, by air pollution policymakers, whereas the climate change people talk about CO2 emissions and the energy system," Raes stated, calling for the two agendas to be integrated.
Nevertheless, the researcher said that the climate negotiations are now finally being informed by science. He said recommendations from the UN's scientific body (IPCC) that we should not overstep CO2 concentrations above 450 ppm to keep global warming at a maximum 2°C were now widely used, "at least by the European negotiators".
Frank Raes was speaking to Susanna Ala-Kurikka.