Saturday, February 15, 2014

Drastic Cuts in Carbon Pollution Needed by 2030

Why We Need to Cut Carbon Emissions by 80% by 2030
Below is an argument that we should aim for an 80% reduction in all carbon pollution in California by 2030.  This is consistent with the Sierra Club resolution calling for 80% reduction in carbon emissions from the electricity generation sector by 2030, but this proposal would apply to all sources of greenhouse gases as well as electricity generation.

Here's why:

The leading scientific study on climate change comes from the Intergovernmental Panel on Climate Change (IPCC).  The IPCC report contends that, in order to have a 66% chance of limiting the warming to 2°C, the total carbon emitted by humans  must be less than 800 gigatonnes (GtC).  (page 20) The report also states that 531 GtC have been emitted since 1880.  This means that the carbon pollution budget is 269 GtC. 

According to the EPA graph below, the world is now emitting about 32 gigatonnes of CO2 per year.  This is equivalent to 8.7 GtC per year.1  Assuming the world emitted at least 8 billion tonnes since the IPCC report was written, and if we continue emitting CO2 and other carbon pollution at the current rate, we will expend our carbon budget in 261/8.7 = 30 years.  Unfortunately, the graph shows that annual emissions are rapidly increasing, so, if that continues, the budget will be used up in less than 30 years.

Fig. 1:  Global CO2 Emissions per Year

So what should our goal be in terms of CO2 reductions?  If the world starts now to cut CO2 and does so continuously, the 261 gigatonnes must be cut to zero in 60 years in order to have a 66% chance of avoiding 2˚ global warming.  A graph of this is shown below:

Figure 2:  Optimistic Carbon Emissions Reduction Plan

If we want to set a global goal for 2050, the graph shows that we earthlings need to lower our current emissions from 8.7 gigatonnes per year to 3.3 gigatonnes by 2050.  This is a 62% reduction.

However, there are several reasons why we in California should aim for bigger cuts than this:

1. The EPA table in Figure 1 shows that carbon pollution is increasing, not decreasing.  So for the next few years, until this can be stopped, we will be using up our carbon pollution budget faster than the above calculations allow.  Therefore, we should aim for bigger cuts than the straight line graph shows.  In fact, if it takes 10 years for the world to begin decreasing carbon pollution, then we will have to completely eliminate carbon emissions by 2050, instead of 2074 as suggested by Figure 2.

2. California should lead the way.  The rest of the world is very likely to move more slowly than California.  We have the technology and the resources to do this much faster, and we should be a model to everyone else.

3.  A 33% chance of climate catastrophe is hardly reassuring.  If you were told that an airplane had a 33% chance of crashing, would you get on board?  We should cut fossil fuels asap!

4.  Plus, we in the advanced industrial societies are the main cause of all this carbon pollution.  In 1970 there were as many cars in Los Angeles as there were on the entire continent of Africa! It is our responsibility to clean up our mess.

Given all this, an 80% cut in CO2 by 2030 would be a much better goal for California than the present goal of 80% below 1990 levels by 2050.  The current state goal needs to be vigorously defended, but it also needs to be improved upon.

As I've argued throughout this blog, we need to convert to 100% electric vehicles running on 100% renewable energy by 2030 if we are to have any chance of avoiding climate catastrophe.

1The molecular weight of carbon is 12, while oxygen is 16.  So when you add two oxygens to a carbon the weight of CO2 is 44.  In other words, burning one pound of carbon creates 44/12 = 3.67 pounds of CO2.  So the annual production of 32 billion tonnes of CO2 equals 32/3.67 = 8.7 GtC.


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