Is it too late for us to maintain our comfortable western lifestyles AND avert catastrophic climate change?
Despite all of the lobbying from climate sceptics, the absolute vast majority of scientists have, for years, agreed that release of CO₂ into the atmosphere by humans (both from burning fossil fuels and from cutting down forests for farmland) is the main cause of global warming, and that YES, planet Earth is warming much faster than it would without all that extra CO₂ in the atmosphere.
For years there has been a general agreement in the scientific community that we need to keep CO₂ concentrations in the atmosphere at less than 500 ppm (parts per million – that is the equivalent of 0.05%) if we want to avoid raising the average surface temperature of the earth by 2 °C, which is the maximum temperature rise the Earth can tolerate without irreversible, catastrophic (for our way of life and economy) climate change.
Back in 2004, when atmospheric CO₂ levels were ~375 ppm and global CO₂ emissions were ~ 7 billion tonnes of carbon per year, a paper published in Science by Pacala and Socolow looked at our current global CO₂ emissions, the rate they have been increasing and how this affects the concentration of CO₂ in the atmosphere. They calculated that, if we are going to keep the atmospheric concentration of CO₂ below 500 ppm over the next 50 years, annual carbon emissions cannot increase above 7 billion tons per year – i.e. they had to stay the same as in 2004. They also calculated what our carbon emissions would be in 50 years’ time if the rate of emission increased “business as usual” – i.e. if we continued generating more power and emitting more CO₂ without making any effort to reduce emissions. They calculated that, in 2054, our carbon emissions would double to around 14 billion tons per year. That meant, we needed to find a way to reduce carbon emissions by 7 billion tonnes over the next 5 years, and we needed to start doing it quickly.
This graph (after Pacala and Socolow, 2004) compares the maximum amount of CO₂ we can emit per year whilst avoiding raising the atmospheric CO₂ concentration above 500 ppm (blue line) and an estimate of how much CO₂ we will be emitting if we carry on as normal (red line). In short, CO₂ emissions needed to stay the same as they were in 2004 to avoid major climate change. Unfortunately, as the world population increases, and developing countries gain a better quality of life, more energy is consumed and more CO₂ is produced.
But there was hope! Pacala and Socolow pointed out that, even back in 2004, there were plenty of options for reducing our CO₂ emissions – they just needed scaling up. They identified 15 different ways that we could start to reduce our CO₂ emissions by increasing energy efficiency, decreasing energy use, changing land-use, switching to lower carbon power generation and capturing and storing CO₂ from power plants.
To make the task even less daunting, Pacala and Socolow came up with the concept of “stabilisation wedges” (if you look at the space between the red and blue lines on the above diagram, it is kind of wedge shaped). This means that all we needed to do in the short term was to make small changes to reduce our CO₂ emissions, and gradually scale them up to make bigger changes in the long term. To make things even easier, this wedge was split up into 7 separate wedges that were each the equivalent of saving 1 billion tonnes of carbon per year after 50 years. All we needed to do was pick 7 existing CO₂ reduction methods from the list and scale them up so that in 50 years time, each of them would be reducing our carbon emissions by 1 billion tonnes every year. If we include these 7 wedges on the above diagram, it starts to look something like this:
This was brilliant! Pacala and Socolow identified a very real and dangerous problem, but importantly they gave an achievable solution. We could avert catastrophic climate change, if we just started using and investing, NOW, in low-carbon technology.
So what happened?
Fast forward to 2013 when Davis and others published a paper in Environmental Research Letters. They looked at recent CO₂ emissions and worked out whether the wedge system would still work. They showed that in 2010, just 6 years later, worldwide carbon emissions were already more than 9 billion tonnes – that is much higher than Pacala and Socolow predicted for “business as usual”. Not only had the world failed to stabilise CO₂ emissions, it had increased emissions much faster than predicted. Davis et al worked out what would happen to atmospheric CO₂ concentrations if we started implementing the stabilisation wedge NOW. First of all, they worked out that at least 9 wedges would be needed to just *stabilise* carbon emissions over 50 years (i.e. keep emissions at 9 billion tonnes per year). Then they looked at how this would affect the total amount of CO₂ in the atmosphere and calculated that there would still be more than 500 ppm CO₂ by the year 2049;
If, today, we were able to stabilise CO₂ emissions at the same level as they were in 2010, we would reach that scary threshold of 500 ppm CO₂, or a 2 °C global temperature rise in less than 40 years!
I am scared! I am angry!
10 years ago (I am writing in August 2014), the problem of greenhouse gases and climate change was a big scary problem, but it might have been possible to avoid the worst of the damage by starting to make relatively small changes and investing in the right kind of technology and development.
Today, it is too late for that. To prevent 500 ppm of CO₂ in the atmosphere, we need to not only stabilise CO₂ emissions, we need to drastically reduce them. This is because the concentration of CO₂ in the atmosphere responds to the absolute amount of CO₂ we pump out, rather than just the rate we pump it out at – yes, if we pump it out faster, we increase the concentration faster, but if we keep emission rates the same, we are still increasing the concentration and eventually it will become too high; all of the CO₂ we have pumped out since the Industrial Revolution won’t just magically disappear overnight, especially while we continue to cut down forests to make way for farmland. Pacala and Socolow recognised this in 2004, but hoped that new technology would be developed in the next 50 years to not just stabilise, but reduce and maybe eliminate CO₂ emissions. The wedges concept was supposed to be a kickstarter – a way to start taking action to protect our climate NOW. It wasn’t supposed to be a magic wand that can be waved whenever we feel like it – it was a way of buying us time (50 years) to develop ways to stop emitting CO₂ completely.
Here is what the CO₂ wedges diagram looks like today, adapted from Davis et al, 2013:
I have left on the 2004 “business as usual” prediction line so you can see just how much extra CO₂ we are emitting, compared to what was expected. The red stars show the annual global emissions from 2006 – 2013.
Davis et al worked out that now we might need to use as many as 31 wedges just to delay the 2 °C temperature rise until 2060. They also calculated that 1 wedge is the equivalent of creating ~ 1 TW (terrawatt – 1 TW = 1 billion kW) of carbon-free energy. For comparison, the London Array, which is a wind farm of 175 wind turbines and one of the largest wind farms in the world, has a peak-capacity output of 630 megawatts – that is 0.00063 TW. You would need 1600 London Array windfarms, all operating at maximum capacity all of the time, to create just 1 carbon wedge (also consider that most windfarms operate at ~one third efficiency, so 4800 London Array windfarms per C-wedge is more likely).
10 years ago we had an opportunity to prevent long-term damage to our infrastructure and quality of life by making small, gradual changes and small sacrifices to our quality of life and by investing in and developing low-C technologies.
We may have missed that opportunity. Why? Because we all sat back and ignored the problem. We elected governments who give jobs such as “Secretary of State for Environment, Food and Rural Affairs” to climate sceptics. We are more concerned about paying less money for our energy than investing in renewable and low-C energy. We are more concerned about how a wind-farm will alter the view in the British countryside than sea-level rise swallowing entire island-nations. We allow our governments to give in to lobbying from industry when they should be implementing measures that force us all to adopt low-C technology, not just so we can reduce our own emissions, but so that we can fully develop and share this technology with the developing world who can’t yet afford to develop it themselves.
As you can see from the title, I initially addressed this blog to the World Leaders who have failed to take appropriate action on preventing man-made climate change. However, we are all responsible. Each-and-every-one-of-us! The threat of climate change is real and it is scary! Please remember that when you are voting / switching energy provider / buying stuff.
Footnotes and references:
 This is actually much higher than the “safe” concentration recommended in a 2008 paper by James Hansen and others published in the Open Atmospheric Science Journal (http://benthamopen.com/openaccess.php?toascj/articles/V002/217TOASCJ.htm). They noted that the last time there was more than 450 ppm CO₂ in the atmosphere was around 50 million years ago, back when Antarctica was completely ice free! and they suggested that we need to limit CO₂ concentrations to a maximum of 350 ppm to avoid catastrophic, irreversible climate change over the next few decades.
 Pacala, S. and Socolow, R., 2004. Stabilization Wedges: Solving the Climate Problem for the Next 50 Years with Current Technologies. Science 305: 968-972 DOI: 10.1126/science.1100103
 Davis, S. J., Cao, L., Caldeira, K., Hoffert, M. I., 2013. Rethinking Wedges. Environmental Research Letters 8: DOI: 10.1088/1748-9326/8/1/011001