By Gwynne Dyer

At the opening of the COP28 global climate summit, here are some thoughts about the state of climate science.

I have interviewed at least sixty leading climate scientists in a dozen countries over the past three years. They are unanimously terrified by the speed at which things are moving, but also relieved that the crisis is finally getting some serious attention from both the public and the governments.

What might be useful at this point is a review of how the science has developed, because it can be seen as a play in three acts. In the first, beginning in the 1980s, warming was identified as a potentially serious problem, but not one that required an emergency response.

Yes, greenhouse gases of human origin were warming the atmosphere, but it could be dealt with by modest reductions in emissions (5%) by the biggest emitting countries. Developing countries could emit as much as they liked: it wouldn’t be enough to do any harm.

That was the 1990s. Twenty years on, in 2015, things had changed a lot. The early support for the notion that ‘something must be done’ had been undermined by a powerful campaign of climate change denial largely funded by the oil, gas and coal industries.

At the same time, the emissions of the ‘developing countries’ had soared as their economies shifted into high-speed growth. The biggest emitter is now China, not the United States, and India holds third place. Scientific understanding of how the atmosphere will react to a huge influx of carbon dioxide and other warming gases had expanded enormously.

It has also become clear that the climate does not only change gradually.

As it warmed up when we emerged from the last Ice Age, it made sudden leaps when various ‘tipping points’ were crossed.

We had to avoid them at all costs, because we would have no way of turning them off once they got going. Johan Rockström, the director of the Potsdam Institute for Climate Change Research that did most of the work on tipping points, sees it as a kind of journey.

Thirty years of climate science has given us so much understanding, and what I now see very clearly as a red thread during that entire journey is that the more we learn about the Earth system, the more reason for concern we have….

In 2001, you see the best assessment of the risk of crossing catastrophic tipping points, of destabilising the biosphere, is estimated to be somewhere between +5°C and +6°C of warming.

Then for every new assessment the level (of average global temperature at which the risk of crossing tipping points gets serious) just goes down, down, down – until 2018, where the assessment is somewhere between +2°C and +3°C .

People think we raise the alarm because human pressures are increasing, but that’s not the case at all. It’s just that we are learning how the planet works, and the more we learn the more vulnerable she is.

So here we are in 2023, and Jim Hansen, the climate scientist who originally delivered the wake-up message to the US congress in 1988, returns to tell us that we are currently set for five degrees Celsius of global warming, not the three degrees we thought we were facing.

At that level, large parts of the planet would become uninhabitable for people who must work outdoors (like farmers).

It may be time to start taking this climate stuff seriously.