If James Webb finds strong signs of intelligent life, we can build a follow-up telescope that uses the Sun as a gravitational lens that will allow us to directly image the planet with high resolution so we could see large scale structures on the planet.
Can you guess how many stars have to be studied to locate
an alien civilization?
Let's use an estimate of one trillion as the total number of galaxies
in the observable universe. 100 billion would seem reasonable to
be the average number of stars in one galaxy. Size of our sun to my
knowledge is slightly above average. A number below 10 should pass
as an intelligent guess of average number of planets and moons
to study in each and every star systems. Saturn has 82 moons
including Titan which has been investigated for signs of life.
So I think 10 is still a conservative estimate.
So out of 1 trillion times 100 billion times 10 planets/moons
how many advanced civilizations are out there awaiting discovery
by James Webb? Assume there are intelligent life in one out
of 1 billion planets/moons there would be no less than 1000 trillion
of planets or moons showing signs of life. That is a huge number.
But still even if we are content with finding just one planet
we will have to scan 1 billion planets/moons around us first.
You have to hope that earth happens to be located in a spot of
the universe where alien civilizations concentrated for James
Webb to find something of interest.