Climate policy in the Economist: Why ‘wait and see’ doesn’t cut it
Global surface temperature rise has been slower over the past decade than models have predicted, but does that mean we have time to wait and see before we decide to act on climate change?
In a post in the Economist’s Democracy in America, writer Will Wilkinson argues slower surface warming observed over the last decade is a “reprieve for the planet”, but bad for proponents of climate policies. We take a look at the evidence for his claim.
The Economist blog argues:
“As a rule, climate scientists were previouslyveryconfident that the planet would be warmer than it is by now, and no one knows for sure why it isn’t. This isn’t a crisis for climate science. This is just the way science goes. But itisa crisis for climate-policy advocates who based their arguments on the authority of scientific consensus.”
The hiatus in global surface warming means, the argument follows, that governments should wait a few decades to act on climate change, giving countries the opportunity to grow their economies to the point where they are better able to adapt – not to mention giving climate scientists the time to improve their “callow” discipline.
Slower warming
With greenhouse gases in the atmosphere rising, earth’s surface temperature – that’s the air over the land and ocean – has risen more slowly over the past decade and a half than in previous decades.
As we’ve written before, the slowdown in surface warming is not evidence that global warming has paused – which, in fairness, is a point the Economist blog makes. Surface temperature is, relatively speaking, a small part of climate change. Scientists say the likely reason for the slowdown is natural variability redistributing the sun’s heat into different parts of the climate system, notably the oceans.
While the surface warming slowdown doesn’t call the fundamentals of climate science into question, the blog is not wrong to say that most models have overestimated surface temperatures in the last decade or so, however. Let’s look at that a bit closer.
Model mismatch
The graph below comes from a post on the ‘Climate Lab Book’ blog by Ed Hawkins, a research fellow at the University of Reading. It compares recent global temperatures from the Met Office’s HadCrut4 dataset with projected temperatures from a set of climate models which will be used in the next IPCC report, called CMIP5.
Source: Climate Lab Book
The graph shows global temperatures are tracking the bottom of the range in which 90 per cent of the model simulations lie. In other words, most of the models predict warmer temperatures than we’ve seen in the past decade.
As Hawkins writes in another blog post, there are three possible reasons for the mismatch between climate models and measurements.
Three reasons
The first could be that the climate models aren’t yet fully accounting for the natural variations in the climate that cause more heat to enter the oceans. This means they may overestimate how much of the extra heat stays in the atmosphere.
Some temperature projections might be too high because of assumptions about tiny particles in the atmosphere, known as aerosols. These provide a cooling effect which suppresses greenhouse gas warming.
A third possibility is that climate models projecting the highest temperatures are overestimating how much the climate would warm if carbon dioxide levels doubled – what scientists call climate sensitivity. We’ve written more about all three of these reasons here.
Disentangling
The difficulty is disentangling the different reasons why models might overestimate recent temperature rise – and this isn’t a simple task.
But with plenty of carbon dioxide in the atmosphere trapping heat, the slowdown in surface warming we’re seeing is a temporary situation – atmospheric temperature are likely to continue to rise when natural variability cycles turn in the other direction.
In other words, the slowdown doesn’t necessarily mean we won’t still get a temperature rise within the range the models predict by the end of the century.
So while fine-tuning climate models is an interesting scientific challenge, the mismatch we’re seeing between models and observations isn’t reason to sit back and relax when it comes to efforts to curb emissions.
Does this mean we should wait?
Science aside, the main thrust of the argument is whether it’s worth acting now to try and cut emissions.
Dr Simon Dietz, lecturer in environmental policy at the London School of Economics recently told Carbon Brief that far from giving a more realistic cost-benefit analysis, most discussions that advocate the ‘wait and see’ approach ignore the risks climate scientists have identified. For example, that the Intergovernmental Panel on Climate Change predicts there could be as little as 1.8 degrees warming – or up to as much as six degrees by the end of the century.
Dietz said:
“If warming occurs at the more severe end, this will have significant impacts on the environment, economies and societies. Most people who advocate significantly reducing emissions are looking to avoid that severe outcome. Only by focusing on the most optimistic outcomes and ignoring the element of risk can you come to this kind of conclusion”.
Yale University environmental economist, William Nordhaus, wrote in an article last year:
“My research shows that there are indeed substantial net benefits from acting now rather than waiting fifty years. […] Waiting is not only economically costly, but will also make the transition much more costly when it eventually takes place”.
The Economist blog’s argument is – mostly – political, warning that slower surface warming could discredit attempts to cut emissions. But while Wilkinson sounds like he is advocating caution, experts who weigh up the costs and benefits of acting to curb emissions counter that the ‘wait and see’ argument ignores the full spectrum of risk the world faces when it comes to the effects of climate change. And scientists seem confident that the surface warming slowdown does not significantly alter these risks.