Unless world agrees upon new climate deal that would oblige countries to massive CO2 emissions cuts we are very likely to see that negative side of climate change that scientists are constantly talking about. Many experts believe that world still isn't ready for massive CO2 cuts, and that world would require backup plan to solve climate change problem. Some scientists believe that this backup plan should be geoengineering.
Geoengineering includes all techniques that aim to deliberately manipulate the Earth's climate to counteract the effects of global warming from greenhouse gas emissions. Official geoengineering definition issued by the National Academy of Sciences defines geoengineering as "options that would involve large-scale engineering of our environment in order to combat or counteract the effects of changes in atmospheric chemistry."
Geoengineering techniques such as capturing CO2 from the atmosphere using artificial trees or shooting tiny particles (sulfate aerosols) into the upper atmosphere to reflect away sunlight have potential but science can still only guess and predict their environmental impact.
Most promising geoengineering technique is definitely using artificial trees to capture CO2 from the atmosphere but this technology is still far away from being cost-effective to be used on global level. Shooting tiny particles of sulfate aerosols into the stratosphere could also do the trick but many believe this would have extremely negative effect that could even destroy ozone layer. This technique wouldn't cost much and would be acceptable from economic point of view but its environmental impact is still connected with huge risks.
Geoengineering techniques are still only a theory and are in need of further research to determine the risk of their use, as well as their advantages and disadvantages. Any interference in our planet carries huge risk because nature is the one that knows best what is needed to do. However the environmental mess we have created over the years is making nature's job very difficult, forcing science to come up with alternative solutions such as geoengineering, if in the worst scenario everything else backfires.
We have to accept the fact that fossil fuel lobbies are still extremely powerful and that they will use their power to affect new climate deal that could result in insufficient CO2 cuts which would open the door for global climate catastrophe.
Therefore alternative techniques such as geoengineering are definitely worthy to consider in case everything else fails. Of course these techniques can't guarantee success in fight against climate change but their potential and necessity of backup plan gives them more than sufficient justification for further research. This is why we should ensure enough funds for further research of these techniques and hope in science to find the right answer. We should be aware that science is really our only chance against climate change because politics is unlikely to do anything positive for our planet, except perhaps giving us more false promises so we can live in denial.