The good news on climate
There’s plenty of bad news around these days, and that’s true of climate policy as of many other things. Turnbull (or Abbott, pulling Turnbull’s strings) has already imposed massive cuts in climate science research in Australia and it seems certain that Trump will do the same in the US.
Happily, it looks as if they have come too late to do real damage. The fact of climate change is now well established. Cutting research will impose all kinds of costs, but it’s not going to change the conclusions of science. Of course, the right will reject inconvenient science as they have done for decades, but more of less research won’t change that.
The big news is that the problem has turned out to be much easier to solve than anyone thought. We’ve long known that, to have a 50-50 chance of limiting warming to 2 degrees C, emissions should peak in 2015, and decline at an annual rate of at least 2.2 per cent thereafter. Hardly anyone thought a peak could happen before 2020 at the earliest, and this would imply a decline so steep (4.6 per cent per year) as to be just about impossible.
It now seems pretty clear, however, that fossil fuel emissions did in fact peak, or at least flatten out in 2015, and have remained stable through 2016.
Of course, stabilization is not enough. Is it possible for emissions to decline at the required rate. We can look at an identity
e = g – t – r
where e is the rate of growth of emissions, g is the rate of growth of output, t is the annual technological improvement in energy efficiency (the ratio of energy use to output, and r is the reduction in emissions per unit of energy, due to renewables).
Currently, these are just about in balance. But installations of renewables (and therefore r) are growing rapidly, while g is declining in the developed world, and probably also in China. It follows that we can expect e to become negative in the near future.
Policy matters, and it is important that the Paris Agreement should go ahead, with or without Trump and Turnbull. But the goals to which governments are willing to commit depend on what they think they can credibly promise. So, the fact that stabilizing the global climate looks to be feasible within the current economic framework is really good news.
UPDATE: A couple of commenters have questioned the math above. So, let’s spell it out. Let
E = Emissions (tonnes CO2)
G = Gross World Product (constant $)
J = Energy used (joules)
T (for technology) = G/J ($/joules)
R (for reduction) = J/E (joules/tonne CO2)
E = G / (T*R)
log (E) = log (G) – log (T) – log (R)
Differentiating with respect to time
e = g – t – r
Anyone wishing to debate this further should do so in the Sandpit