First the good news: According to government sources, U.S. greenhouse gas emissions have dropped to a 20-year low. Recent data released by the Energy Information Administration suggests that U.S. energy-related greenhouse gas emissions–roughly 98% of all U.S. greenhouse gas emissions–have dropped from a high of 6 billion tons in 2007 to roughly 5.2 billion tons today. This decline in emissions constitutes a drop of 14% below 2005 levels–very close to the target of 17% below 2005 levels set by the Obama Administration at climate negotiations in Copenhagen, Denmark, in 2009.  However, instead of reaching that goal by 2020, the U.S. is close to reaching it today, virtually without effort.

Government and industry officials are quick to attribute the drop in emissions to a corollary drop in the price of natural gas. This, they claim,  has encouraged a rapid switch from coal to gas at power plants in the U.S.

If  true, it would be ironic that the U.S., the number one naysayer at climate talks  is actually the one country to have reduced overall emissions more than any other nation.

But hang on a minute. Just how accurate is our assessment of the climate impact of the extraction and combustion of natural gas? This is a critical question, since the switch to gas is apparently the primary reason for a decline in U.S. emissions. It turns out when it comes to assessing the climate impact of fracking, there are a lot of unknowns. According to a recent Cornell study, the process of hydraulic fracturing for natural gas–or “fracking”–may be worse than coal, from a climate perspective.  The reason: Roughly 4-8% of methane leaks over the lifetime of a fracked well. Methane is roughly 22% more potent than CO2 as a global warming agent, if compared on a 100-year timeline. However, on a shorter time frame, which is actually more appropriate, Cornell study author and Professor Robert Howarth argues, given that methane attenuates and breaks down over 20 years, methane is even more potent. Depending on whether one assesses methane’s potency on a 100-year time span or on a 20-year time span,  its climate impact can actually by 33 times and as much as 100 times more potent than CO2.

If Howarth is correct, all of the fracking that has replaced the coal–which used to supply us with roughly 50% of our energy needs, and now supplies us with roughly 34%–a 16% increase, could mean we are back to where we were before switching to coal from a climate perspective. Or, sadly, we could be far worse off. Clearly, more study is needed.

Nevertheless, let’s assume the EIA numbers are accurate, and we have indeed reduced overall emissions back down to 1992 levels in a matter of 5 years. What does this tell us? The good news: It suggests we can make system changes quickly and seamlessly, if the incentives are correct.

In this case, the incentive was financial, which is one reason  placing a price on carbon at the wellhead would both discourage a return to coal burning should the price of gas rise back above the price of coal any time soon. And, done well, it would also make renewable energy like wind more cost-competitive with gas and coal for electricity.

A price on carbon could also be used to ensure that coal that is now being subsidized by the U.S. taxpayer for profitable export by Peabody Coal and others to China and India from Appalachia’s flattened mountains and Wyoming’s Powder River Basin has a price tag that returns some of the wealth back to the American people, while making it more expensive for other countries to burn it as well. After all, we will only come out ahead, climate-wise, if we can discourage other fossil fuels from being consumed elsewhere, too. A carbon tax does not have to be regressive; it could come with a monthly dividend, just like social security, to ensure only the over-consumers paid more.

Until a tax on carbon comes online, if we are to address true climate and energy security, we need a continued subsidy or, better yet, a national feed-in tariff for renewable energy, similar to that being deployed successfully in Germany and other countries, to encourage the widespread investment in and proliferation of renewable energy systems.

In the immediate future, we need to make sure the climate impact of fracking is fully accounted for, environmental laws are upheld and all of the externalized costs that are now borne by communities near fracking wells and coal mines are borne instead by the companies. Cheap energy should not be delivered to us at the cost of our health or the health and wellbeing of future generations.