For ages, the world’s oceans have helped to stave off climate change by absorbing heat and carbon dioxide from the atmosphere. But that is now changing, with devastating consequences for humanity in the approaching decades, leading researchers have warned in a high-level IPCC report commissioned by the United Nations.
Since the early 1990s, the rate at which the oceans are warming has more than doubled, and marine heatwaves are becoming more frequent and intense, furthermore, these trends are reshaping ocean ecosystems and fueling more powerful storms. And as the oceans continue to absorb CO2, they are becoming more acidic, thereby threatening the survival of coral reefs and fisheries.
The final special report on oceans and ice by the Intergovernmental Panel on Climate Change (IPCC) ominously warns that without steep cuts to greenhouse gas emissions, fisheries will falter, the average strength of hurricanes will rise, and increasing seas will intensify the risk of flooding in low-lying areas around the globe.
According to Ko Barrett, vice-chair of the IPCC and a deputy administrator at the US National Oceanic and Atmospheric Administration, “ The oceans can’t keep up with humanity’s greenhouse-gas output. The consequences for nature and humanity are sweeping and severe.”
Over 100 scientists from 30 countries contributed to the 42-page summary of the analysis on 25 September at the IPCC meeting in Monaco.
The report projects that sea levels could surge by up to 1.1 meters by 2100 if greenhouse gas emissions continue to rise. This level is 10 centimeters more than the estimate projected in IPCC’s last comprehensive report on the global climate released in 2013.
Richard Alley, a geoscientist at Pennsylvania State University in University Park, feels that the new report’s sea-level rise projections are conservative primarily because scientists still aren’t certain about when rising temperatures might trigger a rapid collapse of ice sheets, mainly in western Antarctica. If that transpires, ocean levels will rise much faster than the IPCC’s latest estimate.
Alley says, “Sea level rise could be a little less, a little more, or a lot more than the latest report predicts. But it’s not going to be a lot less.”
The report says that the rising seas will increase the risk of flooding during storms and high tides will turn out to be more frequent and severe. By 2050, flooding events that nowadays occur once per century are likely to happen annually in many coastal cities and islands—even after sharp emissions cuts.
But the report is emphatically clear that humanity can blunt the worst effects of climate change over the very long term. It conjectures that the sea level in 2300 could range from 0.6-5.5 meters above present day’s, depending majorly on whether and how swiftly countries move to curb greenhouse gas emissions.
Michael Oppenheimer, a climate scientist at Princeton University in New Jersey and coordinating lead author on the report’s chapter on sea-level rise, said, “We’re going to get sea-level rise for centuries. The question is whether it’s going to be manageable or not.”
A draft version of this report estimated that rising seas could displace about 280 million people worldwide by 2100. But the IPCC eventually removed that figure from the final analysis after scientists conceded that they had misinterpreted the findings of an earlier study, Oppenheimer says.”
The IPCC report also studies the fate of the planet’s ice which it predicts will continue to shrink in the coming decades. In the Arctic sea, ice melts each summer and freezes each winter but the annual summer minimum extent has lessened by approximately 13% per decade since 1979. That rate of change is prospectively unprecedented in at least 1,000 years, the IPCC says. Around 20% of the Arctic’s permafrost is vulnerable to abrupt thaw, followed by the sinking of the soil left behind. By the end of the century, this could increase by half the area of the Arctic protected by small lakes.
Even the mountainous regions with small glaciers ranging from the Andes to Indonesia are expected to lose 80% of their ice by 2100.
Barrett says that the report’s overarching message is that, “ Climate change is affecting water from the tops of Earth’s highest peaks to the depths of its oceans, and ecosystems are responding. Without steep emissions cuts, the total biomass of marine animals could decrease by 15% by 2100, and commercial fisheries could see their maximum catch decrease by around 10-24% over the same time period”.
According to Kathy Mills, a fisheries ecologist with the Gulf of Maine Research Institute in Portland, such changes are already playing out in many locations like in the North Atlantic Ocean where rising temperatures have sent right whales further north in search of cooler waters. And this movement increases the animals’ risk of getting caught up in lobster-trap lines.
“These ocean changes mean big problems for the future of people,” remarks Jane Lubchenco, a marine ecologist at Oregon State University in Corvallis and former head of the US National Oceanic and Atmospheric Administration, also an advisor to the High Level Panel for a Sustainable Ocean Economy. They released its own report 23 September regarding climate change and the world’s oceans. The analysis recognizes a range of actions such as promoting renewable energy and sustainable fisheries, curbing marine shipping emissions and protecting coastal ecosystems , to potentially reduce global carbon emissions and limit the effects of climate change.
Lubchenco says these actions would also boost coastal economies and help lift people out of poverty.
She says, “The reality is that the ocean is central to solving many problems. The situation is quite dire and quite gloomy, but it is not hopeless.”