Why Carbon Emissions Were Down (And Now Up Again)
It looks paradoxical. Carbon emissions (the yellow line) from natural gas have climbed steeply over the past three years. But the overall result (the dotted black line) is that emissions from all fossil fuels are down - at least until last year when the trend reversed slightly.
The explanation, of course, is that the increase in emissions from natural gas has been more than offset by reductions in the emissions from coal and oil. That's why the overall trend has been down. The pattern reversed last year when natural gas prices ticked up 33 percent to $4 per mBTUs and coal registered a slight uptick as utilities switched back to the older fuel. That's the risk of relying too much on natural gas. The plants are cheap to build but fuel makes up 95 percent of the operating costs and prices are extremely volatile.
At the same time, the decline in petroleum-based emissions cannot be attributed to the "dash to gas" but is the result of reduced driving mileage and greater fuel efficiency. The slumping economy has also made a contribution. But if the economy picks up, this may reverse as well.
Overall, the reduction in carbon emissions we've seen over the past four years may have now reached a plateau. If there are to be further reductions, the impetus will probably have to come from somewhere else.