Most of these men and women are suffering from quiet desperation, because they know what is going to happen and they cannot seem to change it. They feel obliged to sound optimistic, but give them a half-hour to talk about it and the sadness and despair start to show.
It was all in service of a book on how to survive global warming (now out) and a video series on the same topic (yet to come), and there were many moments when I shared their despair. Yet after all those interviews I have come away with some hope for the future.
It was a complete fantasy. Global emissions have not fallen in one single year since scientists first sounded the alarm in 1988, but the climate orthodoxy insisted that we could hold the warming down below +1.5°C until the end of the century by emissions cuts alone.
Most climate scientists loyally followed that line for as long as they could — must not discourage the troops — but that time is now past. In fact, the average global temperature has already exceeded that +1.5°C target for an entire year.
It may fall back a bit once the current El Nino warming ends. (That is a natural cycle that dumps some extra heat into the system around once every three to seven years.) But the El Nino peaked last December and is now almost finished, yet the northern hemisphere is having an even hotter spring than last year (the hottest on record).
Even more worrisome is the fact the average sea surface temperature (SST) worldwide has been up by at least one entire degree Celsius for all of the past year, an unprecedented jump. In some parts of the oceans the marine heatwaves are up to two or three degrees higher than normal.
This could mean the ocean currents have reorganised so that they are returning to the surface some of the heat that they previously absorbed. If so we are in deep trouble, because the oceans have buried 90% of the extra heat produced by human activities in their depths.
The climate is chaotic, so this could still be a false alarm: both the air and ocean temperatures might yet return to the "new normal". But that new "normal" was already very high, so our normal emissions will drive us back up to +1.5°C for good by 2030 even if the ocean anomaly disappears.
So what can we do now?
The lost time has not been entirely wasted. Solar and wind power have grown faster than anybody dared hope 10 years ago (though not yet fast enough to start cutting into the 82% share of energy produced from fossil fuels).
But most importantly, a generation of inventors, engineers and entrepreneurs foresaw there would be a big demand for new approaches to curbing the warming once the public realised the urgency of the situation.
A profusion of those new ideas and technologies is now spilling out on to the market, and if enough of them fulfil their promise we might still get through this century without runaway global warming wrecking our future. But only on one condition.
We are already in the danger zone. Somewhere between 1.5 degrees hotter and 3.0 degrees hotter, most climate scientists believe, we will cross various "tipping points" that trigger "feedbacks": extra warming from non-human sources.
For example, parts of the Arctic are warming four times faster than the rest of the planet because the sea ice and the snow cover on land are melting. We caused the warming, so that is our fault, but we could stop the melting if we stopped our emissions.
However, that melting exposes dark rock and open water that absorb sunlight instead of reflecting it back into space. This causes more warming, which is also ultimately our fault — but it is not under our control. We cannot turn it off.
There are about a dozen feedbacks like that. We do not know exactly when they will kick in, but scientists think we will trip them all at various points between here and +3°C.
That is "runaway" territory, so we have to hold the temperature down while we work on our emissions — even if that means doing it artificially.
The good news is there are promising ideas for how to hold it down, because they will probably be needed. It will be a long, hard slog, but we are not yet doomed.
— Gwynne Dyer is an independent London journalist.
