UN Secretary-General Ban Ki-moon has called on global leaders to find "seeds of hope" in the turmoil and despair of a world that may seem like it is falling apart.
In his state of the world address at the opening of the UN General Assembly's annual ministerial meeting, Mr Ban pointed to crises piling up, disease spreading, Cold War ghosts returning and so much of the Arab spring going violently wrong.
"But leadership is precisely about finding the seeds of hope and nurturing them into something bigger," the UN chief told presidents, prime ministers, monarchs and ministers from the UN's 193 member states.
"That is our duty," Mr Ban said. "That is my call to you today."
He cited many crises - from beheadings and the use of barrel bombs in Syria to the volatile situation in Ukraine and Boko Haram's "murderous onslaught" in Nigeria.
The issue certain to top the agenda at the ministerial session is the threat from Islamic terrorists intent on erasing borders, with the first US and Arab air strikes in Syria taking place on Monday night in response.
Many diplomats hope that the crisis will not drown out the plight of millions of civilians caught in conflicts in Syria, Iraq, the Central African Republic, South Sudan, Ukraine and Gaza; the misery of the largest number of refugees since the Second World War; and global support for new UN goals to fight poverty and address climate change.
Looking at the array of complex challenges, Norway's foreign minister, Borge Brende, said: "It's unprecedented in decades, that's for sure."
He pointed to the situation confronting the UN and international donors: four top-level humanitarian crises at the same time in Iraq, the Central African Republic, South Sudan and Syria and a relentlessly escalating death toll from Ebola in West Africa.
He singled out the UN Security Council's failure to address the Syrian civil war, now in the fourth year, which the UN says has killed more than 190,000 people.
In a preview of his speech last week, Mr Ban said the "multiple crises" all feature attacks on civilians and having dangerous sectarian, ethnic or tribal dimensions.
In addition to the major conflicts, Mr Ban said the world must not forget the continuing violence in Mali, the volatile situation in and around Ukraine, the chaos in Libya, the greater polarisation between Israelis and Palestinians following the recent devastating war, and the advances of Boko Haram in Nigeria which "grow more alarming every day".
The opening of the annual UN meeting, which ends on September 30, follows the highest-level meeting ever on climate change, with some 120 world leaders responding to the secretary-general's call for increased political momentum to address the warming planet.
"For all the immediate challenges that we gather to address this week - terrorism, instability, inequality, disease - there's one issue that will define the contours of this century more dramatically than any other, and that is the urgent and growing threat of a changing climate," US President Barack Obama said.
But Mr Obama, along with China, the world's largest greenhouse gas emitter, said he would not propose targets to reduce carbon pollution beyond 2020 until early next year.