Arsenal are top of the Premier League table after winning eight of their opening nine matches, including big ones over Tottenham Hotspurs and Liverpool.
The Gunners are also flying high in the Europa League with two wins out of two so far.
It has been an incredible turnaround from the Arsenal of yesteryears, especially last season, when they started badly and ended up losing the final Champions League spot to Tottenham Hotspurs in the final weeks of the season.
Asked about the atmosphere around the club, Tierney told Arsenal's website: "I'd say it's the best since I've been here and I think that's a credit to all the fans, and the players and the staff.
"It just feels like it has clicked – everybody has come together. You hear reactions after we concede goals, you very rarely hear that in football.
"Our fans ended up drowning out the Liverpool fans after they scored, just to try and cheer us on, go again and try and get another goal. I think you need that.
"It's been building, even last season you could see it's been getting better and better between the players, the staff and the fans, and this season it's all just come together and we're one club, one unit."
"It's only been nine games and you can't say anyone is anything after nine games," the Scotland international added. "If you look at last year, we were down in the table and we climbed our way up, so there's a long way to go and there's no point in even thinking like that.
"You want to stay [at the top] of course. I've got a bit of experience at Celtic when we were expected to be at the top and stay on the top as well, so it is familiar in that way for me that the pressure is on you to stay there.
"The other teams are chasing you, and we want to keep that going as long as we can. Progress is the main thing. We've progressed every year, so we want to keep progressing well.
"You just want to finish up as high as possible, and we know what we want and we'll keep working towards it."
