Some say storing carbon underground as a way to curb greenhouse gas emissions is risky. The container has to last essentially forever, and what if an earthquake rips through the seal? But new research is showing that pumping CO2 underground could itself trigger earthquakes.

Stanford University geophysicist Mark Zoback looked at saline aquifers, one of the main types of geologic formations under assessment for carbon sequestration. He found that adding CO2 gas could increase the geologic pressure underground and set off a quake. Not a big one, mind you. Most likely you’d feel some shaking on the surface at a magnitude three or four. But underground the scenario would be a different story.

“At depth those earthquakes represent slip-on faults and if those earthquakes threaten the integrity of the geologic seal that’s keeping the CO2 in place, then they pose the hazard of inducing long-term leakage of the CO2 out of the repository,” said Zoback. “And of course that’s why it’s being injected in the first place, to keep it out of the atmosphere.”

The Earth’s crust is brittle because of shifting continental plates and just a bit more pressure can set off a quake in otherwise seismically safe areas. Never mind quake-prone California,” he said. “Even quiet places that have been eyeballed for carbon storage like the Midwest still have fault lines.”

To make a dent in global warming using carbon sequestration, about a billion tons of CO2 per year needs to be pumped underground by mid century – equivalent to the volume produced by burning oil and gas. Zoback figures that represents about 3,500 storage sites, or 75 new projects per year by 2050. He’s skeptical that all those sites can be found: “Are we going to invest the huge sums, we’re talking about many tens of billions of dollars only to find that when the earthquakes start occurring we’re going to have to stop the injection and find alternative strategies?”

Zoback presented his findings at the American Geophysical Union’s Fall Meeting in San Francisco.

Alison Hawkes is a freelance journalist in San Francisco and co-founder of Way Out West News.

The scientists analyzed 100 years of temperature data collected in downtown Los Angeles  and found that between 1906 and 2006 the average number of extreme heat days – those over 90 degrees – increased from 2 per year to more than 25 per year.  In that time, the average maximum daytime temperature for the city climbed 5 degrees.  Heat waves have also increased, from 2-day events to sweltering stretches that last for 1-2 weeks. The scientists predict that in the coming decades, 10-14 day heat waves will be the norm. 

The bottom line? Even though this summer was a cool one, Southern California is going to get warmer, for longer periods of time. ”Our snow pack will be less, our fire seasons will be longer, and unhealthy air alerts will be a summer staple” said study co-author Bill Patzert, a NASA climatologist and oceanographer.

The scientists assert that the main cause of this increase in temperature and heat days in Los Angeles is due the “urban heat island effect,” which makes urban areas 2-10 degrees Fahrenheit warmer than the surrounding rural areas.

Check out a historical temperature chart for downtown Los Angeles and a full report on the study here.