Bluntest warning delivered on climate

Intergovernmental panel says extreme sea level rises will become annual events

Humanity has been given its starkest warning yet that the planet is in serious trouble.

Extreme sea level rises that used to be a "once in a lifetime event" will become annual events by the middle of the century, affecting the lives of billions of people living along the world's coasts.

The warning was contained in the Intergovernmental Panel on Climate Change (IPCC) Special Report on the Oceans and Cryosphere released on Sept 26.

"We have never had such clear and almost real-time information on the state of climate and of the planet," said Pep Canadell, chief research scientist at the Commonwealth Scientific and Industrial Research Organisation, or CSIRO, an independent Australian federal government agency responsible for scientific research.

"Report after report, including this latest IPCC special report, shows a consistent picture of climate change coming fast and at an accelerating pace," he said in a note to China Daily.

"Some of the impacts are as expected and previously projected. For others, they are coming faster and punching harder than we had anticipated.

"There is absolutely no doubt that we are at a critical point in time of intensification of climate change impacts."

Hundreds of scientists from around the world, including China, worked on the report. It gives the bluntest warning yet that the planet's climate is facing an uncertain future as temperatures get warmer. And decarbonate actions by all on the planet are in dire need.

"The report in my mind is perhaps the most comprehensive assessment of the impacts of climate change, caused by humans - on oceans in particular but also high mountains and polar regions and on sea level and extreme events - that we've ever had," said Nathan Bindoff, professor of physical oceanography at the University of Tasmania.

Professor Bindoff was one of the scientists who worked on chapter five of the report - Changing Ocean, Marine Ecosystems, and Dependent Communities.

The report said extreme sea level events that used to occur once a century will strike every year on many coasts by 2050.

This could be disastrous considering that half the world's megacities, and almost 2 billion people, live on coasts, the report said.

It said that even if heating is restricted to just 2 C, the impact of the sea level rise will cause several trillion dollars of damage a year and result in many millions of migrants. And a number of advanced economies have not taken sufficient actions against it.

The report concludes that many serious effects are already inevitable, from more intense storms to melting permafrost and dwindling marine life.

But far worse impacts will hit without urgent action to cut fossil fuel emissions, including an eventual sea level rise of about 4 meters in the worst case, an outcome that would redraw the map of the world and harm billions of people.

The report, approved by the IPCC's 193 member nations, said that "all people on Earth depend directly or indirectly on the ocean" and ice caps and glaciers to regulate the climate and provide water and oxygen. But it finds unprecedented and dangerous changes being driven by global heating.

The rise in sea levels is accelerating and the ocean is getting hotter, more acidic and less oxygenated. All these trends will continue to the end of the century, the report said.

"Ocean and ice environments around the world are changing at an unprecedented rate and will accelerate into the future," said Jess Melbourne-Thomas, a transdisciplinary research and knowledge broker with the CSIRO's Oceans and Atmosphere unit.

She was an author on chapter three of the report on polar regions.

"Changes in these environments - which include sea level rise, ocean warming, melting ice and snow, and loss of oxygen in the surface ocean - have profound consequences for ecosystems and for human communities globally," she said.

"The oceans and cryosphere (ice covered surface) support services ranging from food supply and cultural values, through to tourism and coastal carbon sequestration.

"Findings from the report show that climate-driven changes in the physical environment are negatively impacting these services in all regions of the ocean, with the exception of the polar regions where there are mixed positive and negative impacts.

"The polar regions are important on a global scale. The Southern Ocean in particular plays a key role in the Earth's energy budget, and about 90 percent of all the ice on Earth is found in Antarctica."

She said the report includes "even stronger evidence than before" that ice sheets can change rapidly enough to contribute to a sea-level rise on time scales of decades to centuries. Researchers used to think it would take many centuries or thousands of years.

"Ocean warming is also driving large-scale redistribution of marine species in the world's oceans," she said.

"In general, these species are moving away from the tropics, toward the poles.

"This means that the Arctic region and the Southern Ocean are gaining species, but also means that species which are highly adapted to cold, polar environments have little space to migrate to. We are already seeing very significant changes to ice and ocean ecosystems due to climate change."