North Korea's claim that it had tested a hydrogen bomb on Wednesday caused concern all around the world. While it was North Korea's fourth test of a nuclear weapon, the use of a hydrogen bomb would suggest a step up from the countries' nuclear program.

However, multiple experts have cast doubt on North Korea's claim that they were testing an h-bomb. Why? Because the explosion it appears to produce was far too weak.

To put it in a historical perspective, the chart below shows how it compares to some of the most powerful nuclear tests from other nations below:


However, this second chart is perhaps a better indication of why this test causes so much concern.

North Korea's nuclear program may be nascent and Pyongyang could well be lying about its capabilities – but North Korea is the only country in the world currently carrying out nuclear tests. It has continued to pursue nuclear weapons, despite considerable international politics and economic pressure.


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Map: The countries believed to have tested hydrogen bombs