A World in Flames - Climate fantasy from Sweden

Magic crystals and two brave children fight environmental threats together with the guardians of the elements in new climate fantasy series!

Best friends Leah and Erik each have a leather necklace with a crystal hanging around their neck. A crystal given to them by a mysterious woman many years ago. When the crystals suddenly begin to glow, they soon learn that they are are filled with magical powers, and after that, nothing will ever be the same...
Together with the guardians of the elements they embark on breathtaking adventures in four books full of excitement and magic. And they are prepared to do anything and everything to save the world. 

In 'An Invisible Enemy', the first part of the series, Leah, Erik and the guardians take on air pollution. But this is easier said than done as people refuse to see that the environment is in danger! A plan takes shape, a plan as risky as it is ingenious - by taking some of the most influential deniers to the future and showing them the potential consequences of their actions they hope to change their minds. Sera, the guardian of the air element, and Erik go with them, but the deniers are hard to convince, and the mission takes a dangerous turn when Erik falls to the ground. Leah and Erik find themselves years apart when the plan is quickly failing and Erik is at the brink of taking his last breath...