This is the second half of a speech Australia's chief scientist delivered to the Carbon Market Institute Conference in Melbourne this week. The first is available here.
I know that there are issues of legitimate and continuing debate: the sensitivity of the climate to increases in CO2, the role of the oceans in warming, the extent of warming into the future, the regional impacts of warming to name just a few. All need further work and the soundness of our knowledge will depend on the scientific method: observation, robust scrutiny, peer (or expert) review, skepticism and replication. We will learn more as we do more.
But there are now findings that I think can help us draw conclusions with a high degree of confidence:
At the outset, let me make clear that I accept that work on the ‘climate’ is riddled with complexity. There is more than one variable – and there are some over which we have no control. However, let me say:
– I accept that CO2 is a greenhouse gas – that means that it traps heat and keeps it in the lower atmosphere – simple physics.
– I also accept that the bulk of the atmosphere (Nitrogen and Oxygen) is ‘invisible’ to infrared radiation – so while there are those who point out that the concentration of CO2 is very low and therefore the effect will be marginal, it is the actual amount of CO2 in the atmosphere that is important. A point I’ll come back to later.
– I know that over the last 800,000 years, the CO2 concentration measured using ice-cores varied between 170 and 300 ppm. This makes the present concentration of nearly 400ppm unprecedented over that period.
– During the period of the most rapid rise during the past 800,000 years, the CO2 concentration increased by approximately 90ppm over ~6000 years. The concentration has now increased 100ppm in less than 200 years, and the bulk of that in the last 45.
– I accept that changes in the amount and ratios of isotopes of carbon in the atmosphere all indicate that long-buried fossil fuels have been burned and contributed to the rise in CO2.
– I accept that the planet has warmed, with each of the last three decades warmer on average than any other since 1850; and each warmer than the one before – and that 13 of the 14 hottest years on record have occurred since the late 1990s.
– I accept that sea levels have risen by about 20cm on average over the past 100 years, that the oceans are becoming less alkaline (more acidic), that ice-sheets in Greenland and Antarctica are melting – and that while the temperature of the atmosphere could be in a ‘pause’ the ocean’s heat content has continued to rise.
– I also accept that sea ice cover and thickness in the Arctic is diminishing, while in Antarctica sea ice has increased.
– I know that The US Department of Energy has calculated that human activity has caused some 1.3 trillion tonnes of CO2 to be released into the atmosphere from the burning of fossil fuels;
– And a review by researchers from the Woods Hole Centre calculated that 0.7 trillion tonnes have been released into the atmosphere as a consequence of de-forestation;
– I know that roughly one half the emitted CO2 stays in the atmosphere with ¼ absorbed by each of the oceans (along with 90% of the heat) and the land.
In the light of this, I think that those who doubt that there is significant (or any) anthropogenic contribution to global warming need to answer a few fairly simple questions.
– Why would the addition of some 2 trillion tonnes of a greenhouse gas like CO2 into the atmosphere, to a level unprecedented in the past 800,000 years and at a rate some 30x faster than at any time (or ~120x faster if you look at just the past 50 years), have little if any effect on our planet?
– Is there genuinely science-based evidence that refutes the growing mountain of data that leads to the conclusion that it is highly likely that human activity has had an impact on global warming?
– Is there an explanation (beyond the facile: they’re all flawed) that can explain how models that strip out the additional CO2 show that there would be virtually no warming if it were left to natural causes alone?
No? So sow doubt.
Ask for ‘proof’, even though such a demand shows little understanding of how science works. For a start, what would be the controlled experiment? It would need our world plus a parallel planet the same as ours with all the variables except human beings?
Instead of waiting for the unachievable, scientists look for evidence from multiple sources, then check it, test it, debate it, replicate it and draw conclusions from it. And as the evidence accumulates, they may even notice some convergence – an anthropogenic influence on planetary warming, for example. And we could and should use all the information we accumulate to project ahead.
Instead of constructive discussions about how to get ever more evidence, or ever better models, we have the discussions about whether CO2 is a pollutant; or whether it is a poison; or accusations of group-think. And we are pressed to put the idiosyncratic alongside the expert, individual opinions against the weight of evidence and then to present them as equals, and to give them equal airtime or column inches.
As I said earlier, studies of the climate show just how complex the interactions of the various elements are – and the interpretation of their combined impact needs close and careful study, and modelling.
Modelling is critical. It points out directions like road signs on the freeway – they tell us the direction we are heading, and the distance, but they don’t presume to be accurate to the centimetre. It would be as irrational to ignore the road sign as it would be to ignore the climate models because they give us a range and not a single point.
I note that one Roy Spencer whom Mr Maurice Newman is fond of using to justify his views, was quoted in that great journal of record The Australian as saying I’m not saying that it can be proved that there’s something seriously wrong with these models … They might eventually be shown to be correct in another 30 years if global warming returns with a vengeance.
So there you go. In a nutshell: we can’t show that they are wrong, and we can’t show that they are right, so let’s do nothing, just wait – and I presume hope.
How would we answer the grandchildren when they ask what did you do in the Great Climate Debate, Granddad? Say that we sat on our hands, but uncomfortably because our fingers were crossed?
We live with and use models all the time: from the economy, to interest rates, to the value of the dollar and insurance premiums and health, to name a few. We assess, evaluate and manage risk. And we take prudent steps on the basis of the information we have to hand and that the relevant models provide. So it must be with climate change – the consequences are too significant to ignore. The values and principles of business management bear much in common with climate change management. Both require rationality, evidence and risk analysis.
In a recent speech, Paul Polman, CEO of multinational Unilever, said: “Left unchecked, climate change has the potential to become a significant barrier to our growth strategy, and that of just about every other company…It is only by tackling climate change in a systemic way that we can deliver growth for the global economy in the 21st century”
Corporate managers and investors know that climate change is happening and is, or will, affect their business.
The question is, can this corporate responsibility be used with science to challenge civic indifference or the nay-sayers?
We need more CEOs to show leadership and not just act on climate change inside the company, but to take on the debate outside.
Ian Chubb is the Chief Scientist of Australia.