Many people living along the coast of cities could find their homes under water with even a moderate sea-level change, former president Mary Robinson has warned.
The United Nations special envoy for climate change said it was predicted 200 million people could be climate displaced people by the end of the century.
“And, if we are not careful, by 2050,” she said.
“We are talking about the fact that an awful lot of people live on the coast in parts of cities will be under water if sea levels rise by even a fairly moderate amount. And the prediction with the 4-degree world will be three times that.”
The former president said although the global goal was stay below 2 degrees, scientists had told her the earth was on course for 4 degrees over this time frame.
Ms Robinson said families in the Pacific Islands were faced with a “real threat to their existence” because of climate change.
“I see communities faced every day with the erosions of their gardens, of their walls,” she said.
“It’s quite incredible that families are faced with a real threat to their existence, in some cases, and certainly to their food production.”
She said a 4-degree rise would be “catastrophic” if it happened.
“It is cyclones beyond belief. It is whole cities like Miami going underwater. And we’re facing that,” she said.
Ms Robinson said there was no plan in place to combat this problem.
“I am actually ashamed as a European that lives are being lost in the Mediterranean, currently. It really is shameful. We are a village, a global village,” she said.
“It cannot be tolerated that the policies of Europe are causing people to cram into boats with awful traffickers, and then lose their lives.”
Ms Robinson said a framework was needed to deal with people displaced by climate.
“We have exploited our earth. We have used up fossil fuels - and if I can put it in a particular way - we are hurting Mother Earth. And she is hurting (us) back by climate disruption that is happening.”
Ms Robinson said climate change was also a gender, human rights, moral, political and development issue.
Ms Robinson said she wanted a legally-binding agreement that would ensure a pathway to stay below a 2 degree rise.
She said some people would be “startled” that she wanted zero carbon emissions by 2050.
“Then I would know, we will have that safe world... It’s time that we thought about how we conserve energy, how we use it. We all have a part to play in this,” she said.
Ms Robinson said India's prime minister Narendra Modi had announced a huge solar project and should be encouraged do double it.
“It’s in the world’s interest that India go solar and not coal,” she said.
Ms Robinson said a commitment needed to be made at the Paris climate change summit later this year.
“I do believe, among the negotiators - and I am with them quite a bit - that there is a realisation that they have to get an agreement in Paris,” she said.
“We all have a part to play in this. But the new economy report makes it very clear that the future is very bright. We just have to make a commitment to get there.”
Ms Robinson, who was speaking in an interview with Al Jazeera America, said all US politicians needed to face reality about climate change.
“The realities of climate change have hit the United States with Katrina, Sandy, with the drought in California - an unprecedented drought - and more wildfires than there have ever been,” she said.
“I don’t think that people are stupid about noting reality. So, I would encourage politicians of every persuasion in this country to be on the side of reality, of climate change.”