The nation's attention has been focused on the recent riots in Baltimore, but the harsh truth is that they could have happened in any major city. Indeed, we could see a long hot summer of urban (and, as in places like Ferguson, suburban) riots that would make the two-day disturbances in Baltimore seem trivial in comparison. 

We can surely expect more turmoil next year, too, if social and economic conditions continue to deteriorate, and if candidates for president and Congress fail to make specific suggestions for addressing the suffering and hardship facing the nation.

But promises can only quell riots for so long. Hope soon turns to frustration, and then anger, unless there's real action to change conditions.

The turmoil in Baltimore followed the trajectory of the urban riots of the 1960s (in Detroit, Newark, Los Angeles, and 161 other cities) and subsequent civil disorders in Miami (1980), Los Angeles (1992) and elsewhere. It typically begins with an incident of police abuse against an African-American resident. Outraged members of the black community organize nonviolent protests, the police over-react and the protests become violent and threatening. 

In Baltimore, the death of Freddie Gray, a 25-year-old unarmed black man, at the hands of the police, triggered the demonstrations, but the city was already a powder keg of economic and racial grievances. The same is true in cities across America.

Fixing racist police practices and bias in our criminal justice system is important. But the underlying cause of riots is the hopelessness that comes with persistent poverty, unemployment, slum housing, widespread sickness, underfunded schools and lack of opportunity to escape such intolerable conditions. 

Since Baltimore exploded, many pundits have taken to quoting Martin Luther King, who once said that "a riot is the language of the unheard." But few pundits have discovered another one of King's profound insights: "There is no noise as powerful as the sound of the marching feet of a determined people."

Riots are not truly political protests. They are expressions of hot anger -- outrage about social conditions. They do not have a clear objective, a policy agenda or a strategy for bringing about change. They are a wake-up call to those in power. 

In contrast, social movements reflect cold anger. They are intentional and strategic. They take place when people are hopeful -- when people believe not only that things should be different, but also that they can be different. 

Riots tell us what desperate people are against. Social movements tell us what hopeful people are for. 

To avoid a long hot summer this year and in the future, but also to address the underlying causes and tensions in our communities, we need to do two things. First, strengthen and invest in the social movements -- grassroots organizing and coalition building -- that have emerged in cities across the country. Second, engage the country in a policy conversation about full employment, and then take action to guarantee every American a good job. ...