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Next week I will be in Vienna to hear from . They are the people who detected the blast in North Korea last month. They use the latest technology to pinpoint explosions, analyse them and sample their fallout.

Their executive secretary, Tibor Toth, was in London this week to talk about what his scientists know about the May 25th explosion. North Korea claims it was its second successful nuclear test.

So my ears pricked up when I heard . He spoke of our uniquely interconnected world - from our financial systems, the spread of infections such as a new flu, through the impact of violent extremism and our collective attitude to genocide.

Nuclear weapons, he said, also threaten us all: "When one nation pursues a nuclear weapon, the risk of nuclear attack rises for all nations."

He identified the issue as one of the key sources of tension between the United States and Muslims around the world, mentioning Iran, of course, and what he described as his willingness to move forward on the basis of mutual respect. But nuclear weapons, he said, are an important caveat.

"... it is clear to all concerned that when it comes to nuclear weapons, we have reached a decisive point. This is not simply about America's interests. It is about preventing a nuclear arms race in the Middle East that could lead this region and the world down a hugely dangerous path."

He re-iterated America's commitment to seek a world in which no nations hold nuclear weapons. While recognising Iran's right to have access to peaceful nuclear power, he drew attention to the responsibilities of nations under the nuclear Non-Proliferation Treaty (NPT), to which Iran is a signatory.

The NPT and its sister Comprehensive Nuclear-Test-Ban Treaty (CTBT) are seen as parallel means by which the world holds back nuclear proliferation. Both have flaws, but supporters argue that without these treaties the world would be a less safe place.

America has not yet ratified the CTBT. Attempts 10 years ago failed in the Senate. President Obama has said that he wants America to ratify. But there are still senators suspicious of international treaties, which they say work against America's best interests. And organisations pushing for American ratification fear that if they press too hard, or too fast, their efforts may backfire again. They are wary of opponents, who, they say, will use any excuse to undermine the treaty. This includes picking holes in the technical work of the CTBTO, and its ability to make sense of nuclear tests, and swiftly. This is where the scientific work of the CTBTO comes in.

This week, Tibor Toth proudly talked of the 250 stations now in place of the 340 planned to make up the , and the fact that his organisation was able to send data on the latest North Korean test to 1,100 "secure organisations" around the world within seconds of it happening. This certainly sounds impressive, but the world will want to know why estimates of the magnitude of the blast have differed so widely between Russia, the and the CTBTO.

There are some rational explanations. Russian estimates of the size in kilotonne equivalence of North Korea's nuclear test in 2006 were an order of magnitude higher than most, so might perhaps be expected to be out again this time. And the CTBTO apparently uses a slightly different scale than others to calibrate its measurements. So a difference of a few tenths, say between a magnitude of 4.5 and 4.7 blast, might be down to instrumentation.

And there will be another key test for the CTBTO's network in the next few days. Any nuclear test in North Korea should send radioactive particles, or "radionuclides", through the atmosphere. These should be arriving about now, at monitoring sites in Japan and the Philippines. If they are not picked up then the organisation will be open again to questions from critics.

It may all sound like arcane technical detail, but any disagreement over the reliability of these measurements could be used to undermine the CTBTO, and the nuclear test ban treaty too. Mr Toth described as "a blessing" the fact that North Korea did not warn his organisation of its plans. This, he said, allowed it to prove itself fit-for-purpose in providing what he called "a new Democracy" in data; "We act as an equaliser", he said.

Science is proving increasingly important as a diplomatic tool. But it is valuable only so far as it is reliable. President Obama's words, however eloquent, rely on demonstrably sound science to back them up.