SINGAPORE - She almost did not make it to this year's Singapore International Water Week (SIWW 2022).

Last week, the house of Dr Debra Roberts, co-chair of a working group under the United Nations' top climate science body, was flooded when violent storms battered Durban, South Africa.

Ankle-deep floodwaters reached her house, and water supply plunged as the aqueduct was broken.

The floods and mudslides killed more than 440 people, leaving thousands homeless and houses and infrastructure in ruins.

"This is part of the new normal that a city like mine is going to have to deal with," said Dr Roberts in her keynote speech on Monday (April 18) at SIWW on how climate change is affecting water systems.

Scientists believe the south-eastern coast of Africa is becoming more vulnerable to violent storms and floods as greenhouse gases are warming the Indian Ocean.

Dr Roberts, 61, who co-chairs the Intergovernmental Panel on Climate Change's (IPCC) Working Group 2, which released its major report in February, highlighted the sobering implications that rising temperatures, sea-level rise and other indicators will have on humanity.

"Our report shows very clearly that two thirds of all adaptation is in response to water-related hazards... We cannot achieve climate resilient development without the water sector," she said.

Adaptation refers to implementing ways to reduce climate risks, such as building seawalls to keep out rising sea levels.

In an interview with The Straits Times on Tuesday at the sidelines of SIWW 2022, Dr Roberts noted that nature-based solutions play a key role in managing water related impacts - from floods to droughts, and to water quality.

For example, restoring floodplains and wetlands can help to reduce flood risks, as wetlands enable more natural water retention. Restoring mangroves will also help to mitigate climate change impacts with their ability to soak up planet-warming carbon dioxide.

But nature-based solutions will start to fall off the table as the temperature increases beyond the 1.5 deg C threshold, she warned.

Limiting warming to 1.5 deg C above pre-industrial levels is a key goal of the 2015 Paris climate agreement.

"By the time we reach global warming levels of 1.5 deg C, we will probably experience irreversible losses of warm water coral reefs and coastal wetlands, so they won't be able to play that (adaptation) role," she noted.

Moreover, poor planning can cause adaptation measures to backfire and spark other environmental issues, she warned.

For example, sea walls at some coastal sites can cause coastal erosion further down the coastline.

Large-scale reforestation projects that are not thought out fully can lead to water security issues.

Dr Roberts added that current adaptation measures which are in place are not good, adequate or fast enough compared with the rate of changes and impacts humanity will be dealt with.

"You've got this emerging adaptation gap which is unfortunately the largest for the poor and disadvantaged communities."

She also emphasised that scientific know-how and the knowledge of Indigenous people should be brought together to tackle the climate crisis since those local communities know their land well.

Dr Roberts recounted how an Inuit hunter from Canada had noticed that an ice sheet was about to break off. However, satellite images did not spot anything wrong with the glacial ice.

"But that ice sheet broke away. It's that combination of (having) people who understand their environment from the soles of their feet, (and using) sophisticated technology. That brings us to our best state of knowledge of the world."

She said putting together the just over 3,000-page Working Group 2 report was no small feat. Over five years, 270 scientists from around the world assessed more than 34,000 scientific papers, and worked on more than 62,000 review comments from governments and expert reviewers.

The report is the second of three that collectively make up the IPCC's sixth assessment report - detailing the state of the planet over 10,000 pages. The first report, out in August last year, sounded a code red for humanity.

The third report released earlier this month said global greenhouse gas emissions must peak before 2025, and governments must immediately implement deep emission cuts, or the 1.5 deg C warming limit will be out of reach.

"I'm hoping that these three reports tell a story of urgency, the need to rally resources and use them in new ways to think about new development paths, and to increase climate justice and equity across the world," said Dr Roberts.

SIWW 2022 is held at the Sands Expo and Convention Centre till Thursday.