Mark Carney, the Governer of the Bank of England, gave a pretty impressive speech a couple of days ago. You can read the speech yourself, but I thought I would use it to highlight more of what I was getting at in my post about Emission Reductions.

Mark Carney says the following in his speech:

The challenges currently posed by climate change pale in significance compared with what might come. The far-sighted amongst you are anticipating broader global impacts on property, migration and political stability, as well as food and water security. So why isn’t more being done to address it? ……… We don’t need an army of actuaries to tell us that the catastrophic impacts of climate change will be felt beyond the traditional horizons of most actors – imposing a cost on future generations that the current generation has no direct incentive to fix. That means beyond: the business cycle;

the political cycle; and

the horizon of technocratic authorities, like central banks, who are bound by their mandates. The horizon for monetary policy extends out to 2-3 years. For financial stability it is a bit longer, but typically only to the outer boundaries of the credit cycle – about a decade. In other words, once climate change becomes a defining issue for financial stability, it may already be too late.

The basic point that he seems to be making is that we live in a society where, at most, we think a decade ahead. The problem with climate change is that its timescale is longer than that; what we do now will likely have little obvious effect in the next decade, but will impact what happens in the decades beyond that. However, if it appears as though things are okay now, and we can’t see any reason to do anything unless we’ll see impacts in the next decade, then our general tendency will be to simply wait until it’s more obvious that we should be doing something.

The issue, however, is related to the figure on the right, that I discussed in my earlier post on Emission reductions. The figure is based on a basic calculation that assumes a mid-range Equilibrium Sensitivity (about 2.5oC per doubling of CO 2 ), that we increase emissions at a rate similar to that for RCP6.0 (for the next few decades anyway) and that we then reduce emissions at the rate shown on the y-axis, starting in the year shown on the x-axis.

For these assumptions, the figure shows that if we started today to reduce emissions by 1%/year, we could keep peak warming below 2.5oC. If we wait till 2040, 1% per year would only be likely to keep warming below 4oC. Keeping warming below 2.5oC would then probably require emission reductions of 5% per year. The longer we wait, the more extreme the reductions will need to be if we wish to have a reasonable chance of keeping peak warming below some level. Of course, we could follow a different emission pathway, and climate sensitivity could be (probably is) different to what’s been assumed. However, the basic picture doesn’t change; the longer we wait before acting to reduce emissions, the more extreme they are likely to have to be.

There is something else to bear in mind. If you spend some time talking to climate scientists, you will probably discover that most would agree that 4oC or more would be pretty catastrophic. As it stands (and as should be pretty clear from the figure above) keeping peak warming below 2oC is going to be extremely difficult, if not impossible; to have a reasonable chance of doing so would require emission reductions of 3%/year, starting now. If we keep increasing emissions till 2030, 3%/year would only give us a reasonable chance of keeping peak warming below 3oC. Keep going a couple more decades and that’s what we’d need to do to just have a chance of staying below 4oC. If we want to be virtually certain of staying below 4oC, we may need even more drastic emission reductions.

So, if starting emission reductions now is potentially economically risky, what will the impact be if we end up being forced to reduce emissions drastically, simply to avoid levels of warming that could have extremely severe impacts? Similarly, for those concerned about risks to democracy, how risky is it to wait and then discover that keeping warming below levels that could have severe impacts, would require doing things that today would be regarded as unpalatable. Of course, we could be lucky, but that doesn’t change that if we aren’t, we could end up being forced to undertake drastic measures.

This post has got slightly longer and more convoluted than I had intended, but I’ll make one further point. None of the above is policy prescriptive; it’s simply what the scientific evidence is indicating; it tells us what level of emission reductions would be required if we want to have some chance of keeping peak warming below some level. It doesn’t tell us that we must do this, but it does tell us what we will probably have to do, if we do recognise that there is a level of warming beyond which the impacts would be so severe that we should avoid it at all costs. Whether emissions reductions are inconvenient, or not, is irrelevant. How our climate responds to increasing anthropogenic forcings depends only on basic physics, not on our values or wishes. We certainly have control over what decisions we make, but we can’t complain if our climate does what we’d rather it hadn’t; it doesn’t care.