Most of the discussion of global warming is about the wrong questions. Much of the argument is about the scientific evidence that global warming is occurring (overwhelming) and the scientific evidence that human activities are the dominant cause (very strong evidence). The latter is sometimes termed Anthropogenic Global Warming (AGW). The “sceptic” arguments are about the remaining scientific uncertainty, but this confuses the scientific debate with the policy debate. The policy implications can be clear even while the (legitimate) scientific debate continues.
Anyway the productive debate is about the level of risk, the consequences of inaction and the cost of action. So as to minimise the continuing spurious discussions here and elsewhere, I’ll set it out as I see it.
There is always uncertainty in science. There is uncertainty in the accuracy of measurements, in the completeness of measurements and in the adequacy of our understanding. For a system as complex as the climate system there will always be uncertainty. Nevertheless climate science is a lot stronger than is claimed by sceptics. The main conclusions are supported by multiple independent lines of evidence, so nit-picking one line like “models” does not invalidate it.
Uncertainty cuts both ways
It’s true that global warming might not turn out as bad as we thought. It’s also true that it might turn out worse than we thought. In significant ways it is turning out worse than projections from 5 or 10 years ago.
Given the uncertainty combined with the indications of human-caused warming, we need to estimate risks.
• What is the risk that global warming will continue?
• What is the risk that we are causing global warming?
• What is the risk that global warming will have bad or catastrophic consequences?
How do we evaluate the risks?
These risks are not quantifiable. The best we can hope for is to make well-informed judgements.
Who is best-place to make these judgements?
The judgements obviously require a good grasp of the evidence and a good grasp of our current understanding of how the climate system works. The people who know these things best are climate scientists.
Who else might make such judgements? Certainly not politicians, attack-dog journalists and shock jocks, who don’t have the beginning of an understanding of the subject. Certainly not those whose vested interest is to deny any human-caused global warming. If you would trust any of them ahead of the scientists who spend their lives working to understand the climate system, then you subscribe to a highly implausible conspiracy theory and ignore a very obvious conspiracy (to spread confusion), and I have nothing more to say to you.
Have such judgements been made?
Yes, and they have been stated clearly. The most comprehensive have been by the IPCC (Inter-governmental Panel on Climate Change).
The IPCC in 2007 stated that global warming is occurring, and it is highly likely (90% probability) that humans are causing it. (Here I will not go into the science behind these judgements, because this is precisely where the debate gets deflected from the one we should be having.)
Can the IPCC judgements be trusted?
Not entirely. Their conclusions were vetted by politicians and some of the more challenging conclusions were removed at the insistence of China, the US and other countries with big vested interests in fossil fuels – that’s why it’s called an inter-governmental panel. Their process was also rather slow and conservative, so even the un-vetted conclusions may have been dated and too conservative.
Many climate scientists soon pointed out that the situation is likely to be worse than portrayed in the 2007 IPCC report, though that is not the bias climate sceptics usually mention. Also some sceptics challenge the IPCC’s use of probabilities, without making clear that they are an attempt to clarify the meaning of qualitative terms like “likely” and “highly likely”. They are attempts to convey the reliability of the judgements, not the science.
Nevertheless the IPCC message is clear and alarming (the news is alarming, not the messengers).
How certain should we be before we act?
The response of the climate system to greenhouse gas emissions is delayed by two or three decades. By the time we agree the uncertainty is acceptably low, it will be too late. We must, if we are to avoid disaster, act before we have reasonably complete knowledge.
Our politicians do that all the time, and with far less evidence, on many important topics.
What are the costs of reducing greenhouse gas emissions?
If we are causing global warming through our emissions of greenhouse gases, which of the following options best conveys the cost of reducing and eventually eliminating those emissions?
a) it would wreck most countries’ economies
b) it would be a substantial but bearable cost
c) it would be a minor cost
d) it would save more money than it would cost
You may be surprised to learn that many economists these days would say (c), though some diehards cling to (b). Many environmentalists say (b), and point to the moral imperative to sacrifice, but they could be better informed. Many fossil fuel companies and other vested interests promote the myth of (a). (Well, you could wreck economies by going about it the wrong way, like relying on “clean coal” and other such distant, expensive, risky and uncertain fantasies.)
However most economists are not actually very knowledgable about technology or business (or many other things you’d think they ought to know about).
A minority of economists, business people, technologists, town planners, etc. point out that many better designs, technologies and ways of organising our societies already exist that dramatically cut greenhouse gas emissions while saving money, or at a cost that is a very sensible investment. People who assess the prospects of this approach argue that emissions could be reduced to near zero by 2050 at small or negative cost (eg. RMI, Circular, and many other studies). They assume only present technology or modest and plausible developments of it – technology is not the limitation.
So the best answer is
no more than (c, a minor cost), but (d, a saving), if we do it right.
What if we do nothing, or not enough?
At some point global warming is likely to run out of control and ramp up to 4, 6 or more degrees Celsius (at present it is about 0.8°C), because natural processes like release of gases from warming tundra kick in and tip it into runaway warming.
We don’t really know where the tipping point might be. New science is suggesting it might be below 2°C of warming. It could conceivably be happening now, for all we know (those uncertainties again). James Hanson thinks we should limit warming to no more than 1°C, and bring it down quickly even from that. That would, by now, be a big but not impossible challenge.
What are the consequences of doing nothing, or not enough?
I did not ask what are the costs, because the consequences go far beyond any meaningful dollar values. The consequences go far beyond a few extra heat waves, fires, storms and floods. The Earth would become an unfamiliar place, unlike anything since our fragile civilisation began around 10,000 years ago. Here are a few plausible possibilities.
The Great Barrier Reef an early casualty (it may already be too late).
The present global industrial system another early casualty (victim of severe weather, disrupted supply lines, peak oil, political disruptions, and its own internal fragility among other factors). Real hardship for many people, with rising death rates.
Half the world’s cities flooded within 100-200 years, and continuing sea level rise for centuries.
Food production dramatically disrupted, resulting in millions, possibly hundreds of millions, conceivably billions of deaths.
Up to half of the world’s species extinct.
On the way to those extinctions, severe disruption of ecosystems resulting in plagues and pandemics.
Wars over territory and dwindling resources.
A dark time for humanity.
What would be left?
Life on Earth would certainly survive, though diminished by a significant mass extinction. Humans would survive, though in an impoverished world. Settled communities would be challenged by continuing climate instability, probably for thousands of years. A much diminished form of civilisation might survive, though not with certainty. Global inter-dependence would be severely weakened, local economies would be necessary. Of the current richness of human culture and knowledge, who knows?
So, the risk is high and the consequences potentially catastrophic or apocalyptic. That is the best judgement of those best-placed to know.
The cost of avoiding disaster is not large, but we have to act soon. We just have to be willing to change many of our current habits. The good news is that we can solve all the other global crises at the same time (peak oil, peak water, depleting soil, depleting forests etc.) if we do it right. The further good news is that our health would improve, and we can focus on living more satisfying lives than just accumulating stuff.
The best news is we would avoid catastrophe and pass a still-rich and wondrous world to our grandchildren.