We've recently been witnessing the worst refugee crisis since World War II, with several million Syrians having fled their country.
It has rightly gripped Australians' attention and moved us deeply. But it coincides with a more obscure event that's potentially just as ominous.
In New Zealand, a man named Ioane Teitiota recently applied, and failed, to be accepted as the world's first climate-change refugee.
The 38-year-old arrived in New Zealand from Kiribati in 2007.
When his visa expired, he sought refugee status to avoid deportation.
He argued his family would be unsafe in Kiribati, which is threatened by rising seas and storm surges. Unfortunately for Teitiota, the world's courts do not yet formally recognise climate-change refugees.
Whatever the legal realities, Teitiota's case is a timely symbol of two looming, and interconnected, global crises.
One is the ecological crisis of climate change, which threatens human existence as we know it.
The second is the human crisis of refugees fleeing trauma and violence to reach peaceful nations that represent paradise by comparison.
These two great challenges are gradually merging into one great crisis of cause and effect, because climate change will ultimately create a further refugee crisis.
On current trends, the United Nations' Intergovernmental Panel on Climate Change predicts sea levels will rise by up to 60 centimetres by 2100, putting vast areas under water.
We must start preparing now, with strong and ethical leadership.
And we must harness the determination and compassion inspired by the Syrian crisis. Closed hearts and borders will not yield a solution.
The response of most Australians to the Syrian refugee crisis shows that compassion, sacrifice and mutual responsibility are alive and well in our community, and offers hope for a less toxic debate about refugees.
Attitudes to climate change are also changing.
Recent polling showed 70 per cent of Australians now believe climate change is happening (up from 64 per cent in 2012), with 89 per cent of those accepting humans are at least partly the cause. So the deniers are now fewer than a third.
So, what to do about the looming challenge of climate change refugees?
The answers are obviously complex, but, fundamentally, we will need a more co-operative and generous approach between nations – with far more shared responsibility and genuine resettlement options than now exist.
We will need less emphasis on borders of separation, and more emphasis on the equal value and equal rights of every living person, regardless of race, religion or wealth.
And we will need to defeat the toxic demonising of vulnerable people trying to cross borders in search of survival and security.
When the number of climate refugees starts to swell, it will take courage and compassion to cope.
There's a fight under way to inspire those values in our communities.
And there's an ongoing fight to limit the damage of climate change and prepare for its consequences.
I believe we are up for it, if we open our hearts and minds.