Editor’s note: On August 18, 2015, the Obama administration took a historic step to regulate methane emissions at new and modified oil and gas facilities in the United States. The proposed policy came on the heels of the first-ever final rule to cut carbon dioxide emissions from power plants, known as the Clean Power Plan. As Ilissa writes here, we need a two-pronged strategy to turn the corner on climate change that tackles carbon as well as methane.
Climate change was the last thing on my mind that day when, as a 15-year-old, I was trying to impress a boyfriend with my rollerblading skills – from the top of a steep hill. Before I knew it, I was flying uncontrollably toward traffic with only one thought in my head: “I need to slow down and change course. Or this won’t end well.”
The same urgent mantra is needed for our planet today. We must reduce pollution to slow the rate of global warming – while at the same time limiting maximum warming to change our projected course.
To do so, nations must tackle both short-lived and long-lived climate pollutants – strategically. We need a two-pronged strategy to stay safe, just like I did at 15 when I survived that rollerblading incident.
All emissions are not equal
The way we think and talk about the long and short-term impacts of various greenhouse gases is critical for making smart policy decisions on climate change. The decision today is not, as some suggest, which pollutant to cut first, but how and when to cut both.
The rate of climate change is controlled by short-lived climate pollutants, such as methane. Like carbon dioxide (CO2), methane is a gas that warms the Earth by trapping heat. Methane is 84 times more powerful than CO2 over the first two decades following their release.
But that number changes depending on how far out you look.
Key: Warming potential over time
Comparing emissions of greenhouse gases with vastly different impacts and lifetimes requires a metric that depends on a timeframe. Scientists typically measure the global warming potential of gases over two time periods: 100 years and 20 years.
While methane is 84 times more effective at trapping heat than CO2 over the first 20 years after they are both emitted, it’s “only” 28 times more effective over 100 years. At that point, what’s left of the methane that caused that initial, intense warming is gone.
By contrast, carbon dioxide remains in the atmosphere much longer, some of it for thousands of years after being released. That means CO2 has a greater warming potential over time.
So when discussing what actions to take to slow climate change we must think about these gases’ potency in both timeframes, and guide our policies accordingly.
Our best chance: Tackle CO2 and methane
Since the Industrial Revolution, methane in the atmosphere has increased by a whopping 150 percent. All-in-all, about one-quarter of today’s warming is attributed to human emissions of methane. CO2 accounts for about half.
Reducing CO will limit the overall warming impact the planet will experience for generations to come. This will have a profound impact on limiting sea level rise and other dangerous impacts from climate change.
Reducing warming caused by methane during our lifetime will also reduce the likelihood of extreme weather events and species extinctions.
Overall, it is scientifically clear that a combination of emissions reductions – such as curbing CO2 from coal-fired power plants and methane from oil and gas activities – is our best chance of stabilizing the climate in the long-term while still reducing warming immediately.