# Why it is a bad idea to burn more coal and reduce car fuel-efficiency standards: Carbon Math 101

The new administration wants society to burn more, not less, fossil fuels in the future. If we are to cap warming at 2° C (or 3.6° F) globally, we need to establish policies that enable us to continue the development and expansion of technologies that will cap atmospheric CO2 levels below 450 parts per million (ppm).

Today the atmosphere contains more than 400 parts per million (ppm) of carbon dioxide; these are values I see at  my field sites in California and are documented worldwide by NOAA. CO2’s ability to absorb and re-radiate thermal or infrared energy explains the physics behind global warming.

An elementary examination of “carbon math” shows how much more carbon we can add to the atmosphere if we want to limit the degree of future climate warming. The current burden of CO2 in the atmosphere translates to a mass of about 876 million-billion grams, or petagrams (1015 g) of carbon in the atmosphere; there are 2.19 petagrams of carbon for each part per million of CO2 in the atmosphere. For perspective, the mass of this carbon is equal to the mass of 5½ times the water in Lake Tahoe.

CO2 in the atmosphere continues to increase because mankind adds about 10 petagrams of carbon into the atmosphere each year through fossil fuel combustion and cement production, according to the report of the Global Carbon Project. If we continue to emit carbon into the atmosphere at this pace for the next 26 years, we will introduce an additional 260 petagrams of carbon into the atmosphere. Luckily, the ocean and land vegetation absorb about half of that CO2, so the net increase in atmospheric carbon will be about 130 petagrams. Nevertheless, this is enough mass to increase atmosphere’s CO2 concentration to 459 ppm. Unfortunately, our current life-style will cause the atmosphere’s CO2 level to exceed the conservative target value (450 ppm) being set by climate scientists to keep future climate warming within 2° C, or 3.6° F.

Here’s the critical point: If we want our planet’s climate system to experience only a modest warming by keeping atmospheric CO2 concentration below 450 ppm, we cannot afford to add more than 110 petagrams of carbon, net, into the atmosphere in the next 100 years, period.  And if we are to remain precautionary, we should emit even less.

Unfortunately, we don’t have the luxury to expect the future emissions of CO2 to remain level at current rates of about 10 petagrams per year. Future carbon emissions are expected to spiral upward towards 20 petagrams per year for a variety of demographic and economic pressures if we continue of a path of “business as usual.” Every dollar spent by every person on the planet is directly related to an expenditure of energy, and ultimately, carbon emissions.

A pessimistic projection is derived from a simple relationship, the Kaya Identity — global carbon emissions are proportional to the product of the population, wealth (gross domestic product per capita), the energy used to create that wealth and the carbon cost of that energy.  At present, several of these factors are increasing. For instance, global population is anticipated to rise from 7 to 9 billion by the next century, China and India are adopting increasingly Western life-styles and their economies are growing at rates exceeding Western economies. We hope pledged reductions that are associated with the Paris treaty will change that trajectory, but with current politics, time will tell.

The Kaya principle informs us about the knobs we can turn to reduce carbon emissions. To stymie this natural of tide towards higher carbon emissions, we must reduce the amount of carbon we emit per unit of energy soon and way below our current levels of 10 petagrams of carbon per year. This can be achieved by adopting and expanding non-carbon based energy sources such as solar, wind, hydrogen, or nuclear power and through increased efficiency (e.g. green buildings, increasing fuel efficiency of autos, redesigning cities, transportation systems and energy distribution systems). While these changes will have upfront costs, they will bring long-term energy and economic savings and make our society more efficient and at the cutting edge of new technology. Already we have ceded top development of wind energy to Spain and Denmark and solar panel production to China.  We need to be forward thinking and innovative to push production, development and wider adoption of electric cars. Here is where California can lead.

The bottom line of doing the “carbon math” is that we cannot continue to treat the atmosphere as a free sewer and society needs to start reducing carbon emissions immediately.  We have many ways to do this that can push our society and economy foward.

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