Professor Kevin Anderson says we're heading towards a future in which floods regularly swamp our properties and farmers battle with severe weather and new pests.
He says that by 2050, much of the lower-lying parts of Belfast could be under water – "from Short Strand to Shore Road".
He came to Stormont yesterday to issue a stark warning – that it is more than likely too late now to limit global temperature to a rise of 2C, the level at which the vast majority of scientists have said is the maximum tolerable level of temperature increase above pre-industrial levels.
Prof Anderson warned that emissions would need to be cut by 70% in a decade to avoid dangerous climate change.
He said that even to keep the increase to 4C will require a major push to cut emissions, yet that will mean a very different world from the one we live in now – increases of 10-12C on the hottest days in New York, 40% reduction in maize and rice crops in lower latitudes and a global temperature rise that is "incompatible with an organised global community".
Despite the importance of his message, just four MLAs out of an invited 108 turned up to the Friends of the Earth-organised event – and only UKIP's David McNarry and the Alliance Party's Anna Lo stayed for the talk.
Professor Anderson painted a shocking picture of a future in which heatwaves in Europe would be 8-10C hotter than they are now, with underground trains unable to run and tarmac melting.
"If Northern Ireland and the rest of the world continue to do nothing about climate change, NI will be severely impacted by it with floods, changes in weather, significant impacts on agriculture such as changes in temperatures and pests. Flooding will be a big one here," he said.
"By 2050 we are heading towards a half metre to a metre sea level rise.
"From Short Strand to the Shore Road may be inundated and places like City Hall and the Titanic Quarter will really struggle.
"Despite what we might think, Northern Ireland is one of the wealthier parts of the world and the wealthy produce high emissions, have a good quality of life and a high consumption.
"Those people who consume a lot of energy will have to make the lion's share of the carbon reductions," he added.
James Orr, Director of Friends of the Earth Northern Ireland said: "If ever there was a wake-up call to what we are doing to the planet this should be it.
"The truth and urgency behind Professor Anderson's message may be uncomfortable listening.
"At most it requires us to rethink the future in very different terms, but at the least it requires us to drive down emissions through strong climate legislation," he added.
Environment Minister Alex Attwood said: "We must play our part and live up to our ethical and political responsibilities to help tackle the climatic changes that are affecting us all.
"The message from Professor Anderson confirms where we need to go.
"Bold steps... are needed.
"Northern Ireland should have the ambition to make renewables our biggest industry, be a world class leader in carbon reduction, protect and positively develop our heritage," he added.
"This should be the measure of what we should do – climate change is part of the driver."
6 things Northern Ireland must do...
Six things Professor Kevin Anderson says Northern Ireland needs to do to combat climate change
1. Reject fracking.
2. Put in place structures to rapidly switch to renewables. Northern Ireland is one of the most fortunate countries in the world when it comes to renewable potential.
3. Bring together high levels of unemployment with the desperate need to retrofit poor housing stock to become low carbon and resilient to future climate.
4. Use innovative thinking to reduce carbon footprint of agriculture, a major source of emissions, while maintaining its position as one of the bedrocks of NI's economy.
5. Instead of expanding aviation, invest in very high quality fast internet capabilities.
6. MLAs must show courage and leadership to realise the opportunity for NI to make the most of the potential it has to build a good renewables regime, retrofit homes and ensure new infrastructure is low carbon and suitable for dealing with climate impacts.