Sunstorm by Sir Arthur C. Clarke
Two of the biggest names in SF together again; the sequel to the acclaimed TIME'S EYE
The observatory on the moon has the proof. Life on earth will be incinerated in April 2037 by a massive solar flare. It is building down and it is unstoppable. With only 18 months until doomsday mankind must unite and embark on the most ambitious engineering project ever: the construction, at the La Grange point between the sun and the earth, of a deflecting mirror the diameter of our home planet. The price of failure? Extinction.
One scientist, an expert on the sun, predicted the flare. One person who knew nothing about the sun nevertheless knew the exact date that life on earth would come to an end. She had witnessed the bizarre time dislocations brought by the 'eyes'. She knows who is responsible.
This is hard SF in the grand tradition of the genre.