As reported by Spaceweather.com, the stratospheric balloons they've been flying together with the students of Earth to Sky Calculus since the spring of 2015 show that radiation levels are indeed increasing. This has also been observed on numerous ground-based cosmic ray monitors.
The reason why they are increasing is the solar cycle. Solar activity rises and falls with a period of about 11 years. It rises as we approach Solar Maximum, making it harder for cosmic rays to reach Earth, and falls as we head into Solar Minimum, allowing them to reach and affect our planet and everything on it.
Since we are now on the way toward Solar Minimum, the Sun is becoming increasingly spotless, solar activity is low and the cosmic ray intensity is high and rising. On 3rd September a huge sunspot appeared and in the week that followed, it unleashed the strongest solar flare in more than a decade, hurled a powerful CME toward Earth, and sparked a severe geomagnetic storm (G4-class) with Northern Lights appearing much farther south than usual.
To show just how much solar activity can affect cosmic radiation on Earth, Earth to Sky Calculus students provided the graph above. Notice a sharp drop at the beginning of September 2017. That's when the Sun surprised observers with its sudden outburst of explosive activity. Radiation dropped to levels not seen since 2015
After the Sun's outburst, radiation levels in the stratosphere took more than 2 months to fully rebound. Now they are back on track, increasing steadily as the quiet Sun resumes its progress toward Solar Minimum. The solar cycle is not expected to hit rock bottom until 2019 or 2020, so cosmic rays should continue to increase significantly in the months and years ahead.
Credit for Featured image: Spaceweather.com and Earth to Sky Calculus