In late September, the Global Carbon Project released new statistics on the 'carbon budget' including updated figures for the rate of increase in global carbon dioxide emissions from human sources during the period from 2000-2007. They report that while carbon dioxide emissions worldwide grew at an average rate of 0.9% per year in the 1990's the average rate of growth this decade has been an incredible 3.5% percent per year.
Is this a difference that makes a difference?
It might not sound like a lot at first glance. But, for anything that grows exponentially - from a bank account to the human impact on the planet – a small change in the rate of growth translates into a big difference in the growing entity. Here's a comparison in the form of two outputs from Pangaea - the global climate change simulation tool our team has been using and sharing. The red line shows future emissions in our "business as usual" scenario, at an average rate of growth for global emissions of about 1.5% per year. And the blue line show emissions growing at 3.5% per year, the rate we've just learned more closely fits our current situation.
The baseline run of Pangaea projects future growth rates in emissions based upon estimates provided by the Intergovernmental Panel on Climate Change. These projected rates of growth vary depending upon the region of the world contributing the emissions. They range from 1% to 2% per year for the three regions that Pangaea simulates.
Since global emissions already exceed the rate at which CO2 is removed from the atmosphere that baseline run is not optimistic. It shows a world one-hundred years from now with CO2 levels of almost 900 parts per million - far above the level where several dangerous runaway warming loops could potentially be triggered.
The recent data from the Global Carbon Project mean that what we've been calling 'business as usual' - the scenario when the world doesn't respond to climate change by reducing emissions - is actually conservative. Growth in emissions is happening even faster than expected. The figure below shows the impact on CO2 levels in the atmosphere, if that growth rate holds steady throughout the simulation.
So, is this a difference that makes a difference?
Knowing that a 900 ppm world must be avoided at all costs, does it really mater that business as usual might be taking us there quicker than many had expected?
Isn't the old 'business as usual' trajectory so sobering that it already provides the motivation for individuals and nations to act strongly and decisively?
No one wants a 900 ppm world, so the likely results of what we've been calling 'business as usual' should be enough to motivate the kind of hard work and cooperation need to get emissions onto a downward trajectory. The IPCC scenario has been around, and is familiar, and credible.
On the other hand, an important goal of Pangaea is to allow all of us to ask what if questions.
And the runs I've shown here do ask an important 'what if' question: what if 3.5% per year is the new business as usual? Even if a 900ppm world is bad enough, this faster growth rate means that the degree of emissions reductions need to stabilize the climate might be even bigger than we think. We are racing a faster train than we thought.
It seems to me that all of us, ordinary people, parents, and decision makers, need to look this new reality straight in the face.
For now, I'll keep showing people 'business as usual'.
But I'm also going to start asking people if they'd like to try a 'beyond business as usual' too.