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A lot of people have been asking me about "swine flu parties"... are they a good idea, or not?

Well at risk of giving credence to what is probably now more than an urban myth, the official line is a resounding "no, no, no - a very bad idea".

But let's look at the logic here.

From parents' point of view, perhaps with a couple of children in local schools, it might make sense that they would prefer their children to catch the virus now, when it is arguably easier to cope with than in the coming autumn and winter when it will certainly be more miserable to be ill; local healthcare resources are more likely to be swamped as numbers of infections rise; and the virus could have changed to become more dangerous.

And many experts agree that even if the virus alters between now and then, those who catch it earlier will develop some immunity to whatever comes later.

But these same experts are having to balance that narrow logic against broader public health concerns.

And on balance, they say, the greater public good still weighs heaviest.

They might concede that most children who catch H1N1 may get over it after just a couple of days of a slight fever, a sore throat and aches and pains - easily sorted out with a few doses of pain killers and some early nights.

But, for vulnerable groups flu is still a killer, and so is this new one.

Friends of those infected at a swine flu party might have asthma, or grandparents unlucky enough to catch the virus - even though their age groups has some immunity from similar viruses circulating a few decades ago.

And asthmatics and older people who DO catch this flu have a higher chance of a severe illness - and complications.

And by seeking out infection, rather than sticking to the wash your hands, "Catch it, Kill it, Bin it" routine, the fear is that the numbers of infections could, as one expert put it to me today "go large" over the summer .

Statistically, having a larger number of infections around raises the likelihood of seeing more really serious cases.

And that is what the government wants to avoid.

In fact Sir Liam Donaldson, the government's chief medical adviser, was candid last week when he said that the whole strategy of containing the spread in areas least affected, and managing it in areas with widespread transmission, is designed to buy time until there is a vaccine in place to boost the immunity of the rest of us - the "herd" - and dampen down the whole bell curve shape of this pandemic.

The driving thought here is that the fewer infections we see overall, the smaller the impact on public services, and the economy as a whole... and an NHS better able to help those with serious complications.

So whilst there is an inarguable internal logic to the position that for some individuals it might be better to catch this new flu now than later, it may not be better for the UK population as a whole.

And as for that logically-minded parent - perhaps it makes sense not to actively seek out infection (even if the mythical swine flu party actually exists), but instead to take news of cases at their child's school with a common sense shrug of the shoulders.

It might also help not to rush around demanding Tamiflu, the anti-viral drug, unless of course they have concerns about asthma or other long term conditions in their offspring.

This was underlined last night with reports that a patient in Denmark has developed resistance to Tamiflu. Though he has now fully recovered, this could mark the start of a significant change in the new H1N1 virus.

What happens in the next few days will be key.

This case could be a one-off, with no further cases in the community. Or, Danish authorities, who will by now no doubt be scrutinising patients closely, could report more cases.

In that situation we could be witnessing the beginning of what many scientists have long described as inevitable - the emergence of a Tamiflu-resistant strain of the 2009 pandemic virus, and the chance that it will become the dominant strain.

Of course this may not happen. Often in the past, viruses that develop resistance to Tamiflu have also been weaker specimens, fizzling out before they become widespread.

But last year a group of H1N1 viruses emerged that were not only resistant to Tamiflu, but showed no compromised abilities.

One interesting concern crossed my radar last night. I hear that Health Protection Agency staff are getting reports of "pack-splitting" of Tamiflu by parents at schools where the drug has been given out to classmates as a prophylaxis.

Hard to guess at the reasoning, but perhaps the aim was to treat two siblings, when only one was given a packet of the drug, or perhaps to treat a child with half the dose now, saving the rest for the winter months.

It is worrying the authorities because it is just the sort of approach that can allow resistance to Tamiflu to develop.

They still hope that we won't see widespread Tamiflu resistance before the autumn, and a vaccine on offer.

If we do, then they will have the alternative drug, Relenza, to hand. Though questions remain about whether we have enough of this drug in the UK stockpile.

My on-air "swine flu" update was trimmed back last night. Reports of Michael Jackson's heart attack and possible death were beginning to filter through the news ether just as Newsnight went on air. So here's the bit I didn't have time to say.

It's about the vaccine against this new flu virus, which the government sees as its most powerful weapon in holding back a potentially overwhelming tide of infections - whether mild or severe. The Health Secretary, Andy Burnham, yesterday confirmed that the Government has contracts with Glaxo SmithKline and Baxter for vaccine for the whole UK population, and that some of this will arrive as early as August.

But in the very next breath we learned that only 60 million of the 120 million doses on order will be ready by this winter. At the estimated two doses apiece to provide protection, that's enough for only half of the UK population. I think many people are expecting a vaccine out there sometime soon with their name on it, should they want it. That will not now be the case for everyone.

It may be that trials show some people gain protection from only one dose, so it's possible there may be more doses to go around. But the Government is clearly going to have to decide who gets the vaccine first, as it comes off the production line. That judgment's a fine balance between the needs of the individual against those of the public at large. High-risk groups such as those with asthma, diabetes or suppressed immune systems, for example, have a strong case for early vaccination. But there's also logic in early vaccination for children, because they're notorious "super spreaders" of influenza.

Sir Liam Donaldson, the Chief Medical Officer for England, made it sound as if this was all part of the master plan, pointing out that pandemics typically last two to three years, so we're going to need vaccine stock in subsequent years. The public may not see it like that if we really do reach the tens of thousands of cases a week he's predicting for this autumn and winter, especially if the virus changes in a way that makes it more dangerous.

As , reminded us at the start of all this, flu viruses are notoriously unpredictable, and can change rapidly. One piece of news I was told last night is typically ambiguous. Flu specialists in the US now estimate that as many as 30 to 40 per cent of infections may be completely symptom-free. Good news if you happen to be one of those with such a mild response, but tricky for scientists trying to track and model the spread of infections to help officials who are planning ahead.

Scientists learn more about this virus every day, and plans put in place assuming the pandemic virus would resemble H5N1 "Bird flu", with its 60% mortality, are having to evolve. So what may appear to many of us to be policy-making on the hoof, could turn out to be common-sense tweaking as the world tries to make sense of who's getting infected, and how badly.

There is a big government launch on Thursday of research showing the possible impacts of climate change here in the UK, looking out towards the end of the century.

It is Environment Secretary Hilary Benn's day. His aim is to show us all what might lay ahead for our children, depending on how successful we are at cutting back greenhouse gas emissions.

Some might say to "worry" us into changing our behaviour.

This is an update on similar research from seven years ago, both spearheaded by the Hadley Centre's climate change team.

This time round there will be an interactive website for consumers, so we can all find out about the likely warmer, wetter winters or hotter, drier summers where we live.

The scientists have apparently divided up the UK into a grid of 25km (16 mile) squares.

The only trouble is that by offering up such a fine grid as this, instead of the region-by-region break down of 2002, there is necessarily less certainty about the changes that might be felt in each square.

The head of climate change at the Hadley Centre, Vicky Pope, tells me this larger uncertainty is "reflected" in the results.

She may find she struggles to get this across later on Thursday.

She told me the grid is designed to help satisfy "users", such as insurers who deal in say the risk of extra flooding, or local planners deciding where to build schools and hospitals.

But she also concedes that using climate models in this way necessarily stretches them as far as they can: "so there will be some unease", she says.

There may be even more unease tomorrow, when the Environment Agency publishes its strategy on current flood risks, and what it is going to cost to cope with climate change.

As the huge hall at Vienna's began to fill with 800 scientists, diplomats and journalists this morning, a line of children wove its way to the stage. Looking slightly nervous and each in some form of national dress, they opened this scientific conference on nuclear testing with touching songs about world peace.

Officially the conference aims to sum up how well science is doing in detecting, understanding and warning the world's politicians about an explosion anywhere in the world - and the likelihood that such an explosion might be a nuclear test.

Its tool is a scientific network that underpins the (CTBT), which proponents argue has a key role in creating a world free of nuclear tests, and possibly, one day, a world free of nuclear weapons.

But there was one thing everybody in the room wanted to know. Had the network of sensors picked up radionuclides from the North Korean explosion two weeks ago? Seismologists here today say they are comfortable that explosion was a nuclear test, but detecting radionuclide evidence in the form of radioactive gas is the "smoking gun". And the big news here is that they have not found that signal.

What's more, scientists don't really seem to know why. One delegate, an expert on radionuclide detection from Sweden, told the conference how well the network performed after North Korea's nuclear test in 2006. Twelve days after that event the network picked up just a few hundreds of atoms of the noble gas Xenon 133 in Canada. He confessed to being "surprised" that this time round, so far, there has been nothing. He said he is sure the sensors are working properly. So why might there be no signal, and does it matter?

The eminent seismologist implied it didn't matter so much. The network includes a range of technologies - using seismic, infrasound, hydroacoustic and radionuclide technologies precisely to give the world what he described as a "a quiver of arrows". Thus if one arrow doesn't hit the target, then others will; if one detection set-up sees no nuclear signature, others will. And his personal view is that this was most likely a nuclear test.

So was there a deliberate attempt by the North Koreans to contain the explosion? Or was the explosion contained by accident? Some larger yield nuclear explosions can apparently "melt" the rock around them, so less noble gas seeps out. Attempts to explain the lack of a noble gas signal remain educated guesses at the moment. The official line here is that all this highlights the need for more countries to ratify the Treaty, so that it can come into force, thus allowing on-site inspection teams to move in to check out such tests.

In the meantime, scientists here might be keeping their fingers crossed that something shows up soon, but they seem already to be resigned to the possibility that it may not.

Those in Washington and elsewhere who see no value in treaties such as the CTBT may view this differently, perhaps as a vulnerability. The window of opportunity to detect noble gases from the May blast is closing. One more week and it will be too late. The material will be too widely dispersed or no longer radioactive enough to pick up.

The children who sang this morning invited the audience to join their "circle of friends", and they imagined a Magic Song that might bring peace to the world. It would be easy to be cynical. But it is a message pretty much echoed by the Austrian foreign minister who, perhaps optimistically, described the monitoring network as "a promise of peace to our children".

In the end, the scientists here say their goal is to give the world the best data they have, and let politicians decide what to do about it. At least the data from this second north Korean blast reached key people soon enough that they were able to convene the Security Council on the same day. But the world waits to see what, if anything, will happen next.

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.