January 6, 2016 | Issue Brief on North Korea
North Korea announced on January 4 that it had conducted a successful H-bomb nuclear test of a miniaturized warhead. Prior to the announcement, sensors had detected a 5.1 magnitude seismic event at the same approximate location as North Korea’s 2013 nuclear test. Nuclear experts are continuing to analyze the data, but preliminary assessments are that North Korea did indeed conduct its fourth nuclear test. South Korea has convened an emergency cabinet meeting to consider its response.
Seismologists can distinguish between natural earthquakes and man-made explosions since each has distinctive characteristics. The South Korean meteorological administration stated, “Considering the waveform and the amplitude of the earthquake, it seems certain that it was an artificial quake. [There is] the high possibility of it being a nuke test.” An estimated size of the explosion has not been determined nor have radioactive isotopes—which would confirm a nuclear explosion—yet been detected.
Satellite imagery had shown excavation and preparatory activity at the Punggye-ri Nuclear Test Site during the past two years. However, no indications of an imminent nuclear test were detected prior to the explosion. North Korean leader Kim Jong-un asserted last month that his country had built a hydrogen nuclear bomb to “defend its sovereignty and the dignity of the nation.” Kim’s initial assertion about hydrogen bombs was met with expert skepticism, and it may be more likely that Pyongyang has achieved a boosted fission rather than a fusion bomb. Such a weapon would be larger than Pyongyang's first three nuclear tests (and the 1945 U.S. atomic weapons) but not of the magnitude of a hydrogen fusion bomb.
If confirmed, North Korea’s fourth nuclear test, particularly of an improved weapon, is a dangerous development. With its ongoing development of several different missile systems, North Korea poses an increasing direct threat to the United States, South Korea, and Japan. Experts estimate that Pyongyang currently has 10–16 nuclear weapons, with the potential to increase that cache to as many as 50–100 by 2020. North Korea has likely already achieved warhead miniaturization, the ability to place nuclear weapons on its medium-range missiles, and a preliminary ability to reach the continental U.S. with a missile.
Washington should be consulting with Seoul and Tokyo to devise a common response to the North Korean nuclear test. The allied response should include:
For its part, South Korea should:
North Korea’s nuclear test is a flagrant violation of numerous U.N. Security Council resolutions. It reflects Pyongyang’s continued pursuit of its prohibited nuclear weapons programs in open defiance of the international community despite countless attempts by the U.S. and its allies to reach a diplomatic resolution. The regime has repeatedly asserted it has no intention of ever abandoning its nuclear weapons, even revising its constitution to enshrine itself as a nuclear weapons state. North Korea’s continuing improvement and augmentation of its nuclear arsenal threatens the U.S. and its allies. It is time for the Obama Administration to abandon its policy of timid incrementalism and fully implement existing U.S. laws by imposing stronger sanctions on North Korea and to work with Congress to determine additional measures.—Bruce Klingner is Senior Research Fellow for Northeast Asia in the Asian Studies Center, of the Kathryn and Shelby Cullom Davis Institute for National Security and Foreign Policy, at The Heritage Foundation.
 Joohee Cho, Luis Martinez, Tom Liddy, and Emily Knapp, “North Korea Says It Has Successfully Tested Hydrogen Bomb,” ABC News, January 6, 2016, http://abcnews.go.com/International/north-korea-successfully-tested-hydrogen-bomb-amid-earthquake/story?id=36109939 (accessed January 6, 2016).
 “S. Korea Says ‘High Possibility’ of Nuke Test by N. Korea,” Yonhap News Agency, January 6, 2016, http://english.yonhapnews.co.kr/news/2016/01/06/0200000000AEN20160106003252315.html?input=www.tweeter.com (accessed January 6, 2016).
 Bruce Klingner, “Why North Korea’s Claim That It Has a Hydrogen Bomb Is Worrisome,” The Daily Signal, December 10, 2015, http://dailysignal.com/2015/12/10/why-north-koreas-claim-that-it-has-a-hydrogen-bomb-is-worrisome/.
 Anna Fifield, “North Korea Hints It Has a Hydrogen Bomb, But Skepticism Abounds,” The Washington Post, December 10, 2015, https://www.washingtonpost.com/world/north-korea-says-its-ready-to-detonate-h-bomb-but-skepticism-abounds/2015/12/10/fe69922e-17ef-4020-8342-1b07fde0a55b_story.html (accessed January 6, 2016).
 Joel S. Wit and Sun Young Ahn, “North Korea’s Nuclear Futures: Technology and Strategy,” Johns Hopkins University, U.S.–Korea Institute at SAIS, February 2015, http://38north.org/wp-content/uploads/2015/02/NKNF-NK-Nuclear-Futures-Wit-0215.pdf (accessed January 6, 2016).
 Bruce Klingner, “Allies Should Confront Imminent North Korean Nuclear Threat,” Heritage Foundation Backgrounder No. 2913, June 3, 2014, http://www.heritage.org/research/reports/2014/06/allies-should-confront-imminent-north-korean-nuclear-threat.
 Bruce Klingner, “Time to Get North Korean Sanctions Right,” Heritage Foundation Backgrounder No. 2850, November 4, 2013, http://www.heritage.org/research/reports/2013/11/time-to-get-north-korean-sanctions-right.
 Bruce Klingner, “Six Myths About North Korean Sanctions,” Korea Chair Platform, Center for Strategic and International Studies, December 19, 2014, http://csis.org/files/publication/141219_Six%20Myths%20About%20North%20Korean%20Sanctions.pdf (accessed January 6, 2016).
 Bruce Klingner, “South Korea Needs THAAD Missile Defense,” Heritage Foundation Backgrounder No. 3024, June 12, 2015, http://www.heritage.org/research/reports/2015/06/south-korea-needs-thaad-missile-defense.