As Quartz explained earlier, even a miniature hydrogen bomb is unlikely to be of a similar magnitude to an atomic bomb. So if the calculations are correct, today’s nuclear bomb test was simply too small to be a hydrogen bomb.

Bruce Bennett, an analyst with the Rand Corporation, expressed skepticism to the BBC: “The bang they should have gotten would have been 10 times greater than what they’re claiming. So Kim Jong-un is either lying, saying they did a hydrogen test when they didn’t, they just used a little bit more efficient fission weapon—or the hydrogen part of the test really didn’t work very well or the fission part didn’t work very well.”

There is a chance that the test North Korea conducted today was at a higher depth than the one conducted in 2013. In that case, the calculations will vary and might increase the yield of today’s test. Still, it’s unlikely that the yield would be many times more than 10kT.

One key piece of evidence remains, and we might have to wait a few days before we get it. Radionuclide detectors haven’t yet detected a radioactive fallout. There is a chance that, if the underground explosion was perfectly contained, there will be no radioactive fallout. However, that’s unlikely as all previous nuclear bomb tests in North Korea have released radioactive gases.

Even if the nuclear bomb North Korea tested today wasn’t a hydrogen bomb, just the fact that it tested a nuclear bomb could be cause for worry. The United Nations security council is expected to meet in New York today to discuss North Korea’s claims.

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