After a fourth night, relatively quiet in London but violent in Manchester and Merseyside, it is too early to say if the riots are on the wane. But the search for answers has only just begun.

Twitter has proved its value for authentic updates from the street, but also its limitations as a forum for serious debate. Mainstream commentators joined the chorus that "something must be done", ignoring the fact that most of the options for "doing something" fail the most important test -- excessive risk of making a bad situation worse.

We should not "send in the Army": they are excellent at what they are trained and equipped to do, but that doesn't include unarmed public order policing. We should also think twice before calling for the Met to issue officers with plastic bullets and water cannon -- not least since these weapons can only be used by specially trained units and it is already clear that getting particular units in the right place at the right time in such a fast-moving situation is one of the things which has proved most difficult.

As for a curfew, this might sound like a good idea, but it brings the risk of an already stretched police force being taunted if they fail to enforce it, further undermining their authority while reinforcing the sense of crisis among ordinary Londoners.

The febrile debate has not been helped by the lack of political leadership. It should have been clear to the politicians by Sunday at the latest that this was not just the annual summer game of journalists trying to drag them back from the beach. But it was another 36 hours before they started to engage, and they have been struggling to catch up ever since.

Not all of their ideas have been wrong: in the short term, the Prime Minister was right to urge the police, prosecutors and courts to work together to impose swift and exemplary sentences; and in the longer term, the Mayor was right to call for the recruitment of more mentors for troubled youngsters, and more black and ethnic minority officers.

However, the main message has been to condemn the behaviour of individual rioters and to promise a greater police presence on the streets. Both are right but neither is enough.

Visible police presence matters but so do their tactics. Public order policing is an art as much as a science, involving inherently difficult judgments about the degree of aggression and force to be used in a particular situation. Sympathetic commentators have noted, rightly, that the police tend to get criticised either way. Two years ago, Her Majesty's Inspector of Policing, Sir Denis O'Connor, was widely praised for his report following the G20 protests when he said that the police "risk losing the battle for the public's consent if they win public order through tactics that appear to be unfair, aggressive or inconsistent."

It is not inconceivable that a more confrontational police response to the initial protest in Tottenham would have elicited a similar reaction.

Two years ago, the BBC were also talking about how public order policing has become even more difficult as "technology is changing protest: flash mobs appear by text message... and all of them download their legal rights from the web - and upload videos of officers who they think are doing wrong".

But whatever the difficulties, there were too many places on Sunday and Monday where the public ended up watching, on television or in person, as the police stood off from trouble rather than confronting it. There is a logic to these tactics, which people are starting to realise: the aim is to avoid inflaming the situation, wait for the worst to pass, and then use CCTV to round up the protagonists. The problem is that in the meantime, the defining moments of the crisis have come and gone.

All this is easy to say this from the comfort and safety of a commentator's desk and with the benefit of hindsight - but it remains true, and something the police will have to bear in mind for the future. Of course, more aggressive tactics bring risks of their own and the police will hope that if those risks materialise, the commentators and politicians who have been urging greater aggression will be equally clear in their support.

In the longer term, the government and the public need to accept that there is a limit to what the police can achieve in the face of such widespread, unfocused disorder. These days people just tend to assume that responding to major threats to public safety is entirely the job of the government, the police, the security services, the Armed Forces, and so on. Some have traced this mindset to the Cold War, when admittedly there was little citizens or communities could do in the face of an existential nuclear threat, and 'national security' became synonymous with authority and secrecy.

The trend has continued with the rise of terrorism, where arguably communities can and should play a greater role, and also with the rise of organised crime, and arguably with events like this week's riots. Politicians need to tread carefully here: suggesting that people take action themselves can invite ridicule, or worse -- especially for a government committed to deep cuts to police numbers.

But regardless of police numbers, we need to start asking ourselves how we can support individuals and communities to do more themselves, either to reduce the risk of events like this week, or to respond better when they happen.

As for condemning the rioters, it goes without saying that their behaviour is immoral, destructive, and counter-productive for the areas in which they live. But is it really "criminality pure and simple", as the Prime Minister said yesterday? Yes, in the sense that it has long since detached itself from the original trigger, of local discontent at the shooting of a man by the police. As one woman in Hackney famously put it, confronting the looters: "we're meant to be fighting for a cause, not thieving from Foot Locker" -- a sentiment and soundbite that community leaders would struggle to improve on.

But while it is clearly criminal as opposed to political, it cannot be criminality "pure and simple", as the Prime Minister suggests, because the pattern is clearly not random nor indeed typical of ordinary criminality. This week's riots are different in many ways from the riots in the 1980s but in other ways they are very similar, including many of the same locations, in Tottenham, Brixton, Toxteth, and Birmingham. And while of course economic hardship doesn't justify looting -- to say it does is an insult to the many young people in these areas and elsewhere who strive to overcome that hardship without resorting to crime -- it is a mistake to think that condemning the rioters is an alternative to trying to understand them.

This is not about "moral relativism", as Michael Gove would have us believe: it is about evidence-based policy and the responsibilities of government. Unless the authorities are confident that a crime is a one-off, it is their duty to try to understand. This was one of the key questions raised by the recent killings in Norway: was this a one-off tragedy committed by a uniquely disturbed individual or was it a sign of a new trend of similar attacks -- and if so, what could be done to try to pre-empt this?

In relation to everyday crime, the same question was posed by David Cameron himself in his early incarnation as Conservative leader when he argued that "understanding the background, the reasons, the causes... doesn't mean excusing crime but it will help us tackle it... This behaviour is wrong, but simply blaming the kids who get involved in it doesn't really get us much further."

"Understanding the background, the reasons, the causes" is a complex task involving psychological, social, and cultural factors. Take something as mundane as boredom: clearly it is not an excuse but does anyone believe it is not a factor? Many of the rioters are far younger than their counterparts in the 1980s. Surveys of young people find 8 in 10 saying they have little to do outside school, and no one is surprised when youth anti-social behaviour and petty crime increase during the long summer holidays -- so how surprised can we be when the same young people provide the footsoldiers for a riot? This is not a new problem but it is likely to get worse with the cuts to youth services, as the Guardian reported long before the riots struck.

It is economic factors, however, which are the most significant. Again, youth unemployment is not an excuse for criminality but does anyone believe it is not a factor? Youth unemployment fell slightly in the most recent figures but remains historically high at around 20 per cent. IPPR analysis last year showed that unemployment was even higher among young black people, close to 50 per cent.

More recent research by IPPR last month highlighted the particularly worrying trend in long term youth unemployment. Again, this is not a new problem: after significant falls through the late 1990s and early 2000s, long term youth unemployment began to rise from 2002. But it rose far more steeply after 2009. Around ten years ago, roughly one in ten of 18-24 year olds had been unemployed for a year; according to the latest figures it is now one in four, and higher still among young men.

The rise in long-term youth unemployment
(% unemployed over 12 months, by sex)

Along with others, IPPR has been warning about the lifelong costs of long term youth unemployment -- a generation suffering for the rest of their working lives from poor job prospects, low skills and repeated spells out of work -- based on the experience of the 1980s. In this context it is not "opportunistic", or "political", to note that the riots bring another, more acute reminder of that same decade.

The government's plan for tackling youth unemployment is a range of apprenticeship and work experience programmes, underpinned by private sector economic growth. That growth looks ever more fragile, and at the same time tuition fees are being increased, funding for colleges and skills training has been cut, and the Education Maintenance Allowance has been abolished. The young person's job guarantee -- a temporary measure aimed at mitigating the scarring effects of long term unemployment -- has also been scrapped. Long before this week's riots, IPPR has been urging the government to think again and act urgently to open up education and job opportunities for young people.

Unemployment is not an excuse, but ministers looking for something to say as they tour the trouble spots should consider -- alongside a U-turn on cutting police numbers -- the powerful message it would send if they announced a guaranteed job at the minimum wage for all young people who have been out of work for a year.

Matt Cavanagh is Associate Director at IPPR www.ippr.org
Follow him on Twitter @matt_cav_