I wonder how a Seattle diagram justifys a statement in the general meaning of 'people became more aware of harming the environment'. Really? I also wonder how 2011 concerns influenced a 1960+ plane. However, thanks for the information on 'most things I have read'.
On a side note, I think one has to be aware of what the term 'emissions' really means as it can be used in different ways, some are more technical. Another interesting one is the actual funding that went into SST projects around the world. You may find out that the Concorde one wasn't the highest, but the only one producing a plane that went into service.
I've read some of Sutter's work. It's really interesting stuff, but I've also read what actual engineers of a working SST thought about the 'unfeasibility concerns' of his. I can tell you that this had nothing to do with carbon emissions, but much with 'how the h... is this thing going to fly?'.
When looking at the target values of the planned SST, nobody was really surprised to see a lot of money going into it, but being held back by technology limits of that time.
As said, Concorde flew and operated right on the edge of things. This does mean that planning a Mach3+ passenger transportation plane with more than two guys in space suits was as ambitious as leaving the Moon out and flying directly to Mars. At least, a lot of tax payer money was lost to find out about the limits of 1960/70s tech in that regard.
Now with the environmental aspects, which sometimes become oh so 'important', I think the threads from Pina and Peter are the ones to look for.
On a large scale, Earth and the environment as we call it does not care if you harm her with a plane or a car using 'much less fuel than others'. It does care for the overall value of harmful things and this one actually grew and grew because, thanks to lower ticket prices, nowadays a vast of amount of people can afford flying and the advertisement of course stresses this 'need' to do spend money it. Depending on the actual country, this 'need' may already be established as common thing to do, regardless of the actual reasons in place.
Shopping trips, cheap holidays in the warm weather, visiting foreign countries to enjoy the tourism industry setup there, giving you a 'typical' impression? Nice! And also a large portion of nowadays passenger volume. In fact, the largest one.
So it's not about doctors trying to reach their patients or certain goods for feeding hungry people, it's about selling tickets for all other sorts of travel interests. Money business. The rest is insignificant when it comes to volume, costs and environmental effects.
Strange matter of fact, this insignificant amount of useful things often gets used as the justification for all the rest. Evil to whom evil thinks.

Environmental awareness? We may remind ourselves about the difference between 'being aware' and 'acting aware' to catch some drift. Only the last part helps the environment, while the first one just calms the conscience and is a major factor with advertising by the way.
So, on the overall numbers, more fuel efficient planes never lead to weaker environmental footprint, but to a much larger one. That's by design since the planes don't get designed fuel efficient to 'take care of the environment', but to counteract higher fuel prices, which prevent selling cheap tickets, which blocks the new markets and the growth of them.
So whenever a company introduces a new 'green' thing, it wants you to look just to the tip of your nose and not beyond. Yes, that one product harms us less (they don't use those words, the turn it into 'it's friendly'), but they plan to build a lot of them. Much more than from its predecessor. So far, a new 'environmental friendly' technology in transportation always had this effect. And, with always I mean .. always.
With air transport markets easily growing in the ranges of 10% per year (much higher in Asia for example), this plan will get fulfilled for some time to go.
Who takes care of the environment when looking at it in
that way?

You can make a lot of money with selling tickets. So much that even expensive new planes justify themselves. This has nothing to do with concerns about Mother Earth, but more with a rather common human character trait. Still, who would want to look at this mess?

Approx 1 billion people travelling by plane in 1990 and, 20 years later, 2.3 billion are flying. No current technology in the world can counteract
that environmental impact. Think they are all flying to their patients or transporting vital goods? Well ..
And what about a SST? Well, it's not blocked by anything else than its market value. So as soon as some clever financial guy comes up and can explain that even the nice values of business and first class subsonic tickets can be beaten by a supersonic service, you will see them starting to work on it right away. Environmental concerns? Well, we couldn't care less, do we?